Fri·Dec 21, 2018Friday·December 21, 2018

1. 01*

   Natural Seesaw and Leptogenesis from Hybrid of High-Scale Type I and TeV-Scale Inverse

   Kaustubh Agashe🇺🇸 · Peizhi Du🇺🇸 · Majid Ekhterachian🇺🇸 · Chee Sheng Fong🇧🇷 · Sungwoo Hong🇺🇸 · Luca Vecchi🇨🇭

   We develop an extension of the basic inverse seesaw model which addresses simultaneously two of its drawbacks, namely, the lack of explanation of the tiny Majorana mass term $\mu$ for the TeV-scale singlet fermions and the difficulty in achieving successful leptogenesis. Firstly, we investigate systematically leptogenesis within the inverse (and the related linear) seesaw models and show that a successful scenario requires either small Yukawa couplings, implying loss of experimental signals, and/or quasi-degeneracy among singlets mass of different generations, suggesting extra structure must be invoked. Then we move to the analysis of our new framework, which we refer to as hybrid seesaw. This combines the TeV degrees of freedom of the inverse seesaw with those of a high-scale ($M_N\gg$ TeV) seesaw module in such a way as to retain the main features of both pictures: naturally small neutrino masses, successful leptogenesis, and accessible experimental signatures. We show how the required structure can arise from a more fundamental theory with a gauge symmetry or from warped extra dimensions/composite Higgs. We provide a detailed derivation of all the analytical formulae necessary to analyze leptogenesis in this new framework, and discuss the entire gamut of possibilities our scenario encompasses: including scenarios with singlet masses in the enlarged range $M_N\sim 10^6-10^{16}$ GeV. The idea of hybrid seesaw was proposed by us in arXiv:1804.06847; here, we substantially elaborate upon and extend earlier results.

   hep-phJHEP(2019)·29 citations
2. 02*

   QCD Sum Rules Approach to the $X,Y$ and $Z$ States

   Raphael M. Albuquerque🇧🇷 · Jorgivan M. Dias🇧🇷 · K. P. Khemchandani🇧🇷 · A. Martinez Torres🇧🇷 · Fernando S. Navarra🇧🇷 · Marina Nielsen🇧🇷 · Carina M. Zanetti🇧🇷

   In the past decade, due to the experimental observation of many charmonium-like states, there has been a revival of hadron spectroscopy. In particular, the experimental observation of charged charmonium-like, $Z_c$ states, and bottomonium-like, $Z_b$ states, represents a challenge since they can not be accommodated within the naive quark model. These charged states are good candidates of either tetraquark or molecular states and their observation motivated a vigorous theoretical activity. This is a rapidly evolving field with enormous amount of new experimental information. In this work, we review the current experimental progress and investigate various theoretical interpretations of these candidates of the multiquark states. The present review is written from the perspective of the QCD sum rules approach, where we present the main steps of concrete calculations and compare the results with other approaches and with experimental data.

   hep-phnucl-thJ.Phys.G(2019)·152 citations
3. 03*

   Slow neutron production as a probe of hadron formation in high-energy ${\gamma }^{\ast }A$ reactions

   A.B. Larionov🇩🇪 · M. Strikman🇺🇸

   Deep Inelastic Scattering (DIS) experiments at the planned Electron-Ion Collider will be affected by details of the hadron formation inside the nuclear volume. Besides semi-inclusive particle production experiments decays of the target nucleus via emission of neutrons provide an additional opportunity to probe this domain. This paper reports on the hybrid dynamical+statistical calculations of low-energy neutron production in muon- and virtual photon-induced collisions with nuclei. We confirm the conclusion that the E665 data on neutron production in ${\mu }^{-}$ + Pb DIS at 470 GeV indicate a strong suppression of the final state interaction for hadrons with momenta above $\sim 1$ GeV/c. Ultraperipheral heavy-ion collisions at the Large Hadron Collider (LHC) and the Relativistic Heavy Ion Collider (RHIC) can be used to test this suppression. The calculations of the neutron multiplicity distributions and $p_t$-spectra in photon - nucleus collisions at the energies accessible at the LHC and RHIC are presented for several models of hadron formation. We argue that studies of neutron production in ultraperipheral heavy ion collisions open a new window on the small-$x$ dynamics and hadron component of the photon wave function.

   hep-phhep-exnucl-exnucl-thPRC(2020)·13 citations
4. 04*

   Assessing the sensitivity of PINGU to effective dark matter-nucleon interactions

   Anton Bäckström🇸🇪 · Riccardo Catena🇸🇪 · Carlos Pérez de los Heros🇸🇪

   We calculate the sensitivity of next generation neutrino telescopes to the 28 (isoscalar and isovector) coupling constants defining the non-relativistic effective theory of (spin 1/2) dark matter (DM)-nucleon interactions. We take as a benchmark detector the proposed Precision IceCube Next Generation Upgrade (PINGU), although our results are valid for any other neutrino telescope of similar effective volume. We express PINGU's sensitivity in terms of $5\sigma$ sensitivity contours in the DM-mass - coupling constant plane, and compare our sensitivity contours with the 90% C.L. exclusion limits on the same coupling constants that we obtain from a reanalysis of the null result of current DM searches at IceCube/DeepCore. We find that PINGU can effectively probe not only the canonical spin-independent and spin-dependent DM-nucleon interactions, but also velocity-dependent or momentum-dependent interactions that generate coherently enhanced DM-nucleus scattering cross sections. We also find that PINGU's $5\sigma$ sensitivity contours are significantly below current IceCube/DeepCore 90% C.L. exclusion limits when $b\bar{b}$ is the leading DM annihilation channel. This result shows the importance of lowering the experimental energy threshold when probing models that generate soft neutrino energy spectra, and holds true independently of the assumed DM-nucleon interaction and for all DM masses tested here. When DM primarily annihilates into $\tau \bar{\tau }$, a PINGU-like detector will improve upon current exclusion limits for DM masses below $35$ GeV, independently of the assumed DM-nucleon interaction.

   hep-phJCAP(2019)·4 citations
5. 05*

   Precision Inclusive Higgs Physics at $e^{+}{e}^{-}$ Colliders With Tracking Detectors and Without Calorimetry

   Patrick Draper🇺🇸 · Jonathan Kozaczuk🇺🇸 · Scott Thomas🇺🇸

   A primary goal of a future $e^{+}{e}^{-}$ collider program will be the precision measurement of Higgs boson properties. For practical reasons it is of interest to determine the minimal set of detector specifications required to reach this and other scientific goals. Such information could be useful in developing a staged approach to the full collider project with an initial lower-cost version focused on achieving some of the primary scientific objectives. Here we investigate the precision obtainable for the $e^{+}{e}^{-}\to Zh\to {\mu }^{+}{\mu }^{-}X$ inclusive cross section and the Higgs boson mass using the di-muon recoil method, considering a detector that has only an inner tracking system within a solenoidal magnetic field, surrounded by many nuclear interaction lengths of absorbing material, and an outer muon identification system. We find that the sensitivity achievable in these measurements with such a tracking detector is only marginally reduced compared to that expected for a general purpose detector with additional electromagnetic and hadronic calorimeter systems. The difference results mainly from multi-photon backgrounds that are not as easily rejected with tracking detectors. We also comment on the prospects for an analogous measurement of the inclusive cross section $\sigma (e^{+}{e}^{-}\to Zh\to e^{+}{e}^{-}X)$. Finally, we study searches for light scalars utilizing the di-muon recoil method, estimating the projected reach with a tracking and general purpose detector.

   hep-phhep-exphysics.ins-detJHEP(2020)·7 citations
6. 06*

   Multistep Strongly First Order Phase Transitions from New Fermions at the TeV Scale

   Andrei Angelescu🇺🇸 · Peisi Huang🇺🇸

   In spite of the vast literature on the subject of first order Electroweak Phase Transitions (EWPTs), which can provide the necessary conditions for generating the Baryon Asymmetry in the Universe, fermion-induced EWPTs still remain a rather uncharted territory. In this paper, we consider a simple fermionic extension of the Standard Model involving one $SU(2{)}_L$ doublet and two $SU(2{)}_L$ singlet Vector-Like Leptons, strongly coupled to the Higgs boson and with masses close to the TeV scale. We show how such a simple scenario can give rise to a non-trivial thermal history of the Universe, involving strongly first order multistep phase transitions occurring at temperatures close to the electroweak scale. Finally, we investigate the distinct Gravitational Wave (GW) signatures of these phase transitions at future space--based GW detectors, such as LISA, DECIGO, and BBO, and briefly discuss the possible LHC signatures of the Vector-Like Leptons.

   hep-phastro-ph.COPRD(2019)·67 citations
7. 07*

   Probing new physics in semileptonic ${\Lambda }_b$ decays

   Atasi Ray🇮🇳 · Suchismita Sahoo🇮🇳 · Rukmani Mohanta🇮🇳

   In recent times, several hints of lepton non-universality have been observed in semileptonic $B$ meson decays, both in the charged-current ($b\to cl{\bar{\nu }}_l$) and neutral-current ($b\to sll$) transitions. Motivated by these intriguing results, we perform a model independent analysis of the semileptonic ${\Lambda }_b$ decays involving the quark level transitions $b\to (u,c)l{\nu }_l$, in order to scrutinize the nature of new physics. We constrain the new parameter space by using the measured branching ratios of $B_{c,u}^{+}\to {\tau }^{+}{\nu }_{\tau }$, $B\to \pi \tau {\nu }_{\tau }$ processes and the existing experimental results on $R_{D^{(\ast )}}$, $R_{J/\psi }$ and $R_{\pi }^l$ parameters. Using the constrained parameters, we estimate the branching ratios, forward backward asymmetries, hadron and lepton polarization asymmetries of the ${\Lambda }_b\to ({\Lambda }_c,p)l{\nu }_l$ processes. Moreover, we also examine whether there could be any lepton universality violation in these decay modes.

   hep-phPRD(2019)·45 citations
8. 08*

   Scalar Non-Standard Interactions in Neutrino Oscillation

   Shao-Feng Ge🇯🇵 · Stephen J. Parke🇺🇸

   The scalar nonstandard interactions (NSI) can also introduce matter effect for neutrino oscillation in a medium. Especially the recent Borexino data prefers nonzero scalar NSI, ${\eta }_{ee}=-0.16$. In contrast to the conventional vector NSI, the scalar type contributes as a correction to the neutrino mass matrix rather than the matter potential. Consequently, the scalar matter effect is energy independent while the vector one scales linearly with neutrino energy. This leads to significantly different phenomenological consequences in reactor, solar, atmospheric, and accelerator neutrino oscillations. A synergy of different types of experiments, especially those with matter density variation, is necessary to identify the scalar NSI and guarantee the measurement of CP violation at accelerator experiments.

   hep-phhep-exPRL(2019)·107 citations
9. 09*

   Increasing the Discovery Potential Using Rare SUSY Scenarios Part I: Gluinos

   Linda M. Carpenter🇺🇸 · Khalida Hendricks🇺🇸

   In this work we consider the HL-LHC discovery potential in the 3 inverse ab data set for gluinos in the gluino-weakino associated production channel. We propose a search in the jets plus missing energy channel which exploits kinematic edge features in the reconstructed transverse mass of the gluino. We find that for squark masses in the 2 TeV range we have 5 sigma discovery potential for gluino masses in the range of 2.4 to 3 TeV, competitive with the projections for discovery potential in the gluino pair production channel.

   hep-ph1 citation
10. 10*

    A theoretical analysis of the doubly radiative decays ${\eta }^{(\prime )}\to {\pi }^0\gamma \gamma$ and ${\eta }^{\prime }\to \eta \gamma \gamma$

    Rafel Escribano🇪🇸 · Sergi Gonzàlez-Solís🇺🇸 · Renata Jora🇷🇴 · Emilio Royo🇪🇸

    The scalar and vector meson exchange contributions to the doubly radiative decays ${\eta }^{(\prime )}\to {\pi }^0\gamma \gamma$ and ${\eta }^{\prime }\to \eta \gamma \gamma$ are analysed within the Linear Sigma Model and Vector Meson Dominance frameworks, respectively. Predictions for the diphoton invariant mass spectra and the associated integrated branching ratios are given and compared with current available experimental data. Whilst a satisfactory description of the shape of the $\eta \to {\pi }^0\gamma \gamma$ and ${\eta }^{\prime }\to {\pi }^0\gamma \gamma$ decay spectra is obtained, thus supporting the validity of the approach, the corresponding branching ratios cannot be reproduced simultaneously. A first theoretical prediction for the recently measured ${\eta }^{\prime }\to \eta \gamma \gamma$ by the BESIII collaboration is also presented.

    hep-phhep-exnucl-thPRD(2020)·42 citations
11. 11*

    Seesaw model with hidden $SU(2{)}_H\times U(1{)}_X$ gauge symmetry

    Takaaki Nomura🇰🇷 · Hiroshi Okada🇰🇷

    We propose a seesaw model with a hidden gauge symmetry $SU(2{)}_H\times U(1{)}_X$ where two types of standard model singlet fermions in realizing a seesaw mechanism are organized into $SU(2{)}_H$ doublet. Then we formulate scalar and gauge sector, neutrino mass matrix and lepton flavor violations. In our gauge sector, $Z$-$Z^{\prime }$ mixing appears after spontaneous symmetry breaking and we investigate constraint from $\rho$-parameter. In addition we discuss $Z^{\prime }$ production at the large hadron collider via $Z$-$Z^{\prime }$ mixing, where $Z^{\prime }$ tends to dominantly decay into heavy neutrinos.

    hep-phPRD(2019)·5 citations
12. 12*

    Correlation between $R_{D^{(\ast )}}$ and top quark FCNC decays in leptoquark models

    Tae Jeong Kim🇰🇷 · Pyungwon Ko🇰🇷 · Jinmian Li🇰🇷 · Jiwon Park🇰🇷 · Peiwen Wu🇰🇷

    Some interpretations of $R_{D^{(\ast )}}$ anomaly in $B$ meson decay using leptoquark (LQ) models can also generate top quark decays through Flavor Changing Neutral Current (FCNC). In this work we focus on two LQs, i.e. scalar $S_1$ and vector $U_1$ which are both singlet under the $SU(2{)}_L$ gauge group in the Standard Model (SM). We investigate their implications on the 3-body top FCNC decays $t\to c{\ell }_i{\ell }_j$ at tree level and the 2-body $t\to cV$ at one-loop level, with $\ell$ being the SM leptons and $V=\gamma ,Z,g$ being the SM gauge bosons. We utilize the $2\sigma$ parameter fitting ranges of the LQ models and find that $Br(t\to c{\ell }_i{\ell }_j)$ at tree level can reach $\mathcal{O}(10^{-6})$ and $Br(t\to cV)$ at one-loop level can reach $\mathcal{O}(10^{-10})$. Some quick collider search prospects are also analyzed.

    hep-phhep-exJHEP(2019)·46 citations
13. 13*

    Dark photon searches with atomic transitions

    C. Álvarez-Luna🇪🇸 · J. A. R. Cembranos🇪🇸

    Dark matter could be made up of dark photons, massive but very light particles whose interactions with matter resemble those of usual photons but suppressed by a small mixing parameter. We analyze the main approaches to dark photon interactions and how they can be applied to direct detection experiments which test different ranges of masses and mixings. A new experiment based on counting dark photons from induced atomic transitions in a target material is proposed. This approach appears to be particularly appropriate for dark photon detection in the meV mass range, extending the constraints in the mixing parameter by up to eight orders of magnitude with respect to previous experiments.

    hep-phJHEP(2019)·8 citations
14. 14*

    Singly Cabibbo suppressed decays of ${\Lambda }_c^{+}$ with SU(3) flavor symmetry

    Chao-Qiang Geng🇨🇳 · Chia-Wei Liu🇹🇼 · Tien-Hsueh Tsai🇹🇼

    We analyze the weak processes of anti-triplet charmed baryons decaying to octet baryons and mesons with the SU(3) flavor symmetry and topological quark diagram scheme. We study the decay branching ratios without neglecting the contributions from $\mathcal{O}(\overline{15})$ for the first time in the SU(3) flavor symmetry approach. The fitting results for the Cabibbo allowed and suppressed decays of ${\Lambda }_c^{+}$ are all consistent with the experimental data. We predict all singly Cabibbo suppressed decays. In particular, we find that $\mathcal{B}({\Lambda }_c^{+}\to p{\pi }^0)=(1.3\pm 0.7)\times 10^{-4}$, which is slightly below the current experimental upper limit of $2.7\times 10^{-4}$ and can be tested by the ongoing experiment at BESIII as well as the future one at Belle-II.

    hep-phhep-exPLB(2019)·48 citations
15. 15*

    Chemical potentials of light hadrons and quarks from yield ratios of negative to positive particles in high energy $pp$ collisions

    Xing-Wei He🇨🇳 · Hua-Rong Wei🇨🇳 · Fu-Hu Liu🇨🇳

    We describe the transverse momentum spectra of ${\pi }^{\pm }$, $K^{\pm }$, $p$, and $\bar{p}$ produced in proton-proton ($pp$) collisions at different collision energies by using a Tsallis-Pareto-type function, and obtain the yield ratios, $k_{\pi }$, $k_K$, and $k_p$, of negative to positive particles from the fitting results of transverse momentum spectra and the extracted normalization constants. The transverse momentum dependent and energy dependent chemical potentials of light hadrons ($\pi$, $K$, and $p$) and quarks ($u$, $d$, and $s$) in $pp$ collisions are then extracted successively from the yield ratios. The six types of transverse momentum dependent chemical potentials show the trend of being close to zero in low-$p_T$ region and away from zero in high-$p_T$ region. Meanwhile, the energy dependent chemical potentials seem to decrease slightly with the increase of the collision energy, and the limiting values of the six types of chemical potentials are zero at very high energy in $pp$ collisions, which confirms that the partonic interactions possibly play an important role at RHIC and LHC, especially at LHC.

    hep-phnucl-thJ.Phys.G(2019)·7 citations
16. 16*

    Proton Lifetime Upper Bound in Non-SUSY SU(5) GUT

    Naoyuki Haba🇯🇵 · Yukihiro Mimura🇯🇵 · Toshifumi Yamada🇯🇵

    In preparation for upcoming nucleon decay searches at Hyper-Kamiokande, it is important to derive a theoretical upper bound on the proton lifetime in a general class of grand unified theory (GUT) models. In this paper, we make an attempt along this direction for non-SUSY SU(5) models, under the mild restrictions that only one or two SM-decomposed multiplets are singularly light, and that the SU(5) gauge theory is asymptotically free and thus there are no too large representations in the model. We derive criteria for SM-decomposed multiplets that potentially enhance the proton lifetime when they are singularly light. We perform a numerical analysis on the proton lifetime and show that some choices of singularly light multiplets can provide a testable upper bound on the proton lifetime.

    hep-phPRD(2019)·7 citations
17. 17*

    Virtual contributions from $D^{\ast }(2007{)}^0$ and $D^{\ast }(2010{)}^{\pm }$ in the $B\to D\pi h$ decays

    Wen-Fei Wang🇨🇳 · Jian Chai🇨🇳

    We study the quasi-two-body decays $B\to D^{\ast }h\to D\pi h$ with $h=(\pi ,K)$ in the perturbative QCD approach and focus on the virtual contributions from the off-shell $D^{\ast }(2007{)}^0$ and $D^{\ast }(2010{)}^{\pm }$ in the four measured decays ${\bar{B}}^0\to D^0{\pi }^{+}{\pi }^{-}$, ${\bar{B}}^0\to D^0{\pi }^{+}{K}^{-}$, $B^{-}\to D^{+}{\pi }^{-}{\pi }^{-}$ and $B^{-}\to D^{+}{\pi }^{-}{K}^{-}$. For the ${\bar{B}}^0\to D^{\ast +}{\pi }^{-}\to D^0{\pi }^{+}{\pi }^{-}$ and ${\bar{B}}^0\to D^{\ast +}{K}^{-}\to D^0{\pi }^{+}{K}^{-}$ decays, their branching fractions concentrate in a very small region of $m_{D^0{\pi }^{+}}$ near $D^{\ast +}$ pole mass, and the virtual contributions from $D^{\ast +}$, in the region $m_{D^0{\pi }^{+}}>2.1$ GeV, are about $5\%$ of the corresponding quasi-two-body results. We define two ratios $R_{D^{\ast +}}$ and $R_{D^{\ast 0}}$, from which we conclude that the flavor-$SU(3)$ symmetry will be maintained for the $B\to D^{\ast }h\to D\pi h$ decays with very small breaking at any physical value of the $m_{D\pi }$. The $B^{-}\to D^{\ast 0}{\pi }^{-}\to D^0{\pi }^0{\pi }^{-}$ and $B^{-}\to D^{\ast 0}{K}^{-}\to D^0{\pi }^0{K}^{-}$ decays can be employed as a constraint for the $D^{\ast 0}$ decay width, with preferred values consistent with previous theoretical predictions for this quantity.

    hep-phPLB(2019)·24 citations
18. 18*

    Photoproduction of the double $J/\psi$ (${\rm Y}$) at the LHC with forward proton tagging

    Pan Xue-An🇨🇳 · Li Gang🇨🇳 · Song Mao🇨🇳 · Zhang Yu🇨🇳 · Sun Hao🇨🇳 · Guo Jian-You🇨🇳

    We calculate the photoproduction of double $J/\psi$ (${\rm Y}$) to leading order based on the nonrelativistic quantum chromodynamics factorization framework at the Large Hadron Collider with forward proton tagging. The numerical results of double $J/\psi$ photoproduction pp $\to$ p$\gamma$p $\to$ $J/\psi$ + $J/\psi$ with different forward detector acceptances ($\xi$) are presented. The total cross section of double $J/\psi$ photoproduction is less than 200 fb with 0.1 $<$ $\xi$ $<$ 0.5, but can reach about 1.37(1.27) pb with 0.0015 $<$ $\xi$ $<$ 0.5 ( 0.0015 $<$ $\xi$ $<$ 0.15 ). The double $J/\psi$ photoproduction may have the potential to be detected and provide an interesting signature, thus is useful for studying the mechanism of heavy quarkonium production. We also predict the double ${\rm Y}$ photoproduction and find they are, unfortunately, small (with less than 10 fb).

    hep-phPRD(2019)·9 citations
19. 19*

    Associated production of a top quark pair with a heavy electroweak gauge boson at NLO+NNLL accuracy

    Anna Kulesza🇩🇪 · Leszek Motyka🇵🇱 · Daniel Schwartländer🇩🇪 · Tomasz Stebel🇵🇱 · Vincent Theeuwes🇩🇪

    We perform threshold resummation of soft gluon corrections to the total cross sections and the invariant mass distributions for production of a top-antitop quark pair associated with a heavy electroweak boson $V=W^{+}$, $W^{-}$ or $Z$ in $pp$ collisions at the Large Hadron Collider. The resummation is carried out at next-to-next-to-leading-logarithmic (NNLL) accuracy using the direct QCD Mellin space technique in the three-particle invariant mass kinematics. It is found that for the $t\bar{t}Z$ process the soft gluon resummation introduces significant corrections to the next-to-leading order (NLO) results. For the central scale equal to the $t\bar{t}Z$ invariant mass the corrections reach nearly 30%. For this process, the dominant theoretical uncertainty of the cross section due to the scale choice is significantly reduced at the NLO+NNLL level with respect to the NLO results. The effects of resummation are found to be less pronounced in the $t\bar{t}{W}^{\pm }$ case. The obtained results are compared to recent measurements performed by CMS and ATLAS collaborations at the LHC.

    hep-phEPJC(2019)·129 citations
20. 20*

    Signatures of the Type-I 2HDM at the LHC

    Rikard Enberg🇸🇪 · William Klemm🇸🇪 · Stefano Moretti🇬🇧 · Shoaib Munir🇰🇷

    One of the simplest extensions of the Standard Model (SM) is the two-Higgs-doublet model (2HDM), which contains two neutral Higgs bosons, in addition to a 125 GeV one, and a charged pair. At the Large Hadron Collider (LHC), gluon-induced processes are generally the most important modes for the resonant production of the SM-like Higgs boson as well as its pair-production, and it is generally considered to be the case also for an additional neutral Higgs boson possibly existing in nature. We show that for certain parameter configurations in the Type-I 2HDM, electroweak pair-production of the neutral Higgs states can dominate over the QCD-initiated production. Moreover, it is possible for the pair-production of the charged Higgs state along with a neutral one, which can only take place electroweakly, to have a substantial cross section. We delineate such 2HDM parameter space regions through its comprehensive numerical scanning, requiring their consistency with the most relevant theoretical and experimental constraints. We also highlight some specific di-Higgs signatures that can be probed at the LHC in order to establish the Type-I 2HDM as the underlying new physics model.

    hep-phPoS(2018)·6 citations
21. 21*

    Indirect and monojet constraints on scalar leptoquarks

    Alexandre Alves🇧🇷 · Oscar J. P. Eboli🇧🇷 · Giovanni Grilli di Cortona🇧🇷 · Roberto R. Moreira🇧🇷

    We obtain constraints on first- and second-generation scalar leptoquarks using the available data on dilepton (Drell-Yan) and monojet searches at the CERN Large Hadron Collider. Assuming that the leptoquark interactions respect the Standard Model gauge symmetries as well as lepton and baryon numbers, we show that the study of dilepton production enlarges the exclusion region on the mass and coupling plane with respect to the pair production searches for first-generation leptoquarks. Moreover, the monojet channel leads to a larger excluded parameter region for moderate to large values of the leptoquark Yukawa coupling than the presently available experimental results.

    hep-phPRD(2019)·35 citations
22. 22*

    Neutrino spin oscillations in polarized matter

    A. Grigoriev🇷🇺 · E. Kupcheva🇷🇺 · A. Ternov🇷🇺

    We study the neutrino spin oscillations, i.e., neutrino spin precession caused by the neutrino interaction with matter polarized by external magnetic field (or, equivalently, by the interaction of the induced magnetic moment (IMM) of a neutrino with the magnetic field). In the analysis, we consider realistic conditions inside supernovae and discuss both the Dirac and Majorana cases. We show that due to the interaction with the polarized matter a neutrino flux from a supernova suffers additional attenuation at low neutrino energies. Another possible effect is that when taken together the effects of conventional magnetic moment and polarized matter can cancel each other so that under certain condition the oscillations disappear. We note that this can lead to the appearance of a characteristic maximum in the spectrum of electron neutrinos from supernovae. Accounting for neutrino mixing (in the two-flavor approximation) can significantly increase (almost twice) the effective value of the IMM of the electron neutrino. As a result, electron neutrinos with twice as high energy will be able to participate in the processes of spin conversion. Various feedback mechanisms accompanying the considered phenomena are also discussed.

    hep-phastro-ph.HEPLB(2019)·17 citations
23. 23*

    Constraining heavy neutral gauge boson $Z^{\prime }$ in the 3 - 3 - 1 models by weak charge data of Cesium and proton

    H. N. Long🇻🇳 · N. V. Hop🇻🇳 · L. T. Hue🇻🇳 · N. T. T. Van🇻🇳

    The recent experimental data of the weak charges of Cesium and proton is analyzed in the framework of the models based on the $\text{mbox}SU(3{)}_C\times \text{mbox}SU(3{)}_L\times \text{mbox}U(1{)}_X$ (3-3-1) gauge group, including the 3-3-1 model with CKS mechanism (3-3-1CKS) and the general 3-3-1 models with arbitrary $\beta$ (3-3-1$\beta$) with three Higgs triplets. We will show that at the TeV scale, the mixing among neutral gauge bosons plays significant effect. Within the present values of the weak charges of Cesium and proton we get the lowest mass bound of the extra heavy neutral gauge boson to be 1.27 TeV. The results derived from the weak charge data, perturbative limit of Yukawa coupling of the top quark, and the relevant Landau poles favor the models with $\beta =\pm 1/\sqrt{3}$ and $\beta =0$ while ruling out the ones with $\beta =\pm \sqrt{3}$. In addition, there are some hints showing that in the 3-3-1 models, the third quark family should be treated differently from the first twos.

    hep-phNPB(2019)·19 citations
24. 24*

    High-energy behavior of strong-field QED in an intense plane wave

    T. Podszus🇩🇪 · A. Di Piazza🇩🇪

    Analytical calculations of radiative corrections in strong-field QED have hinted that in the presence of an intense plane wave the effective coupling of the theory in the high-energy sector may increase as the $(2/3)$-power of the energy scale. These findings have raised the question of their compatibility with the corresponding logarithmic increase of radiative corrections in QED in vacuum. However, all these analytical results in strong-field QED have been obtained within the limiting case of a background constant crossed field. Starting from the polarization operator and the mass operator in a general plane wave, we show that the constant-crossed-field limit and the high-energy limit do not commute with each other and identify the physical parameter discriminating between the two alternative limits orders. As a result, we find that the power-law scaling at asymptotically large energy scales pertains strictly speaking only to the case of a constant crossed background field, whereas high-energy radiative corrections in a general plane wave depend logarithmically on the energy scale as in vacuum. However, we also confirm the possibility of testing the ``power-law'' regime experimentally by means of realistic setups involving, e.g., high-power lasers or high-density electron-positron bunches.

    hep-phPRD(2019)·91 citations
25. 25*

    Composite Higgs and leptoquarks from a simple group

    Leandro Da Rold🇦🇷 · Federico Lamagna🇦🇷

    We propose a composite grand unified theory to study the anomalies in the semileptonic $B$ decays. We show a simple group containing the custodial and Standard Model gauge symmetries, that can deliver a set of composite pseudo Nambu-Goldstone bosons: the Higgs, a colorless SU(2)${}_L$-fourplet and three leptoquarks: a triplet and two doublets. We give a description in terms of an effective theory of resonances. By assuming anarchic partial compositeness of the Standard Model fermions, we find representations for the composite fermions that allow to obtain the Higgs Yukawa couplings, as well as leptoquark interactions explaining the deviations in $R_{K^{(\ast )}}^{\mu e}$. We calculate the one-loop potential, we show that it can trigger electroweak symmetry breaking and we find a region of the parameter space that can reproduce the Standard Model spectrum. The model predicts leptoquark masses of order $0.4-1.3$ TeV, corrections to some electroweak observables, with $Z{b}_L{\bar{b}}_L$ saturating the current bounds, and a very reach phenomenology at LHC. We also study the possibility of explaining $R_{D^{(\ast )}}^{\tau \ell }$.

    hep-phJHEP(2019)·19 citations
26. 26*

    Generic dijet soft functions at two-loop order: correlated emissions

    Guido Bell🇩🇪 · Rudi Rahn🇨🇭 · Jim Talbert🇩🇪

    We present a systematic algorithm for the perturbative computation of soft functions that are defined in terms of two light-like Wilson lines. Our method is based on a universal parametrisation of the phase-space integrals, which we use to isolate the singularities in Laplace space. The observable-dependent integrations can then be performed numerically, and they are implemented in the new, publicly available package SoftSERVE that we use to derive all of our numerical results. Our algorithm applies to both SCET-1 and SCET-2 soft functions, and in the current version it can be used to compute two out of three NNLO colour structures associated with the so-called correlated-emission contribution. We confirm existing two-loop results for about a dozen $e^{+}{e}^{-}$ and hadron-collider soft functions, and we obtain new predictions for the C-parameter as well as thrust-axis and broadening-axis angularities.

    hep-phJHEP(2019)·51 citations
27. 27*

    Top-quark effects in diphoton production through gluon fusion at NLO in QCD

    Fabio Maltoni🇧🇪 · Manoj K. Mandal🇮🇹 · Xiaoran Zhao🇧🇪

    At hadron colliders, the leading production mechanism for a pair of photons is from quark-anti-quark annihilation at the tree level. However, due to large gluon-gluon luminosity, the loop-induced process $gg\to \gamma \gamma$ provides a substantial contribution. In particular, the amplitudes mediated by the top quark become important at the $t\bar{t}$ threshold and above. In this letter we present the first complete computation of the next-to-leading order (NLO) corrections (up to ${\alpha }_S^3$) to this process, including contributions from the top quark. These entail two-loop diagrams with massive propagators whose analytic expressions are unknown and have been evaluated numerically. We find that the NLO corrections to the top-quark induced terms are very large at low diphoton invariant mass $m(\gamma \gamma )$ and close to the $t\bar{t}$ threshold. The full result including five massless quarks and top quark contributions at NLO displays a much more pronounced change of slope in the $m(\gamma \gamma )$ distribution at $t\bar{t}$ threshold than at LO and an enhancement at high invariant mass with respect to the massless calculation.

    hep-phhep-exPRD(2019)·37 citations
28. 28*

    Dark matter pair production in the MSSM and in simplified dark matter models at the LHC

    Christoph Borschensky🇩🇪 · Gabriele Coniglio🇩🇪 · Barbara Jäger🇩🇪

    We study the collider phenomenology of dark matter pair production at the LHC in simplified dark matter models and in the MSSM. Among the large space of dark matter models, we focus on two particular models where a fermionic dark matter candidate interacts with the Standard Model via the exchange of either a vector mediator in the s-channel or coloured scalar mediators in the t-channel. We find that the simplified models are capable of reproducing the predictions of the MSSM to some extent in simplified supersymmetric scenarios, but lack the complexity to descibe the complete theory over the full supersymmetric parameter space.

    hep-phhep-exEPJC(2019)·7 citations
29. 29*

    Asymptotic Scale Invariance and its Consequences

    Mikhail Shaposhnikov🇨🇭 · Kengo Shimada🇨🇭

    Scale invariance supplemented by the requirement of the absence of new heavy particles may play an important role in addressing the hierarchy problem. We discuss how the Standard Model may become scale invariant at the quantum level above a certain value of the Higgs field value without addition of new degrees of freedom and analyze phenomenological and cosmological consequences of this setup, in particular, possible metastability of the electroweak vacuum and Higgs inflation.

    hep-phhep-thPRD(2019)·30 citations
30. 30*

    Heavy Neutrinos with Dynamic Jet Vetoes: Multilepton Searches at $\sqrt{s}=14,27,$ and $100$ TeV

    Silvia Pascoli🇬🇧 · Richard Ruiz🇧🇪 · Cedric Weiland🇬🇧

    Heavy neutrinos $(N)$ remain one of most promising explanations for the origin of neutrinos' tiny masses and large mixing angles. In light of broad advances in understanding and modeling of hadron collisions at large momentum transfer, we revisit the long-standard search strategy for heavy $N$ decaying to multiple charged leptons $(\ell )$, $pp\to N\ell X\to 3\ell \nu X$. For electroweak and TeV-scale $N$, we propose a qualitatively new collider analysis premised on a dynamic jet veto and discriminating, on an event-by-event basis, according to the relative amount of hadronic and leptonic activity. We report that the sensitivity to $N$ at the Large Hadron Collider (LHC) can be improved by roughly an order of magnitude over the collider's lifetime. At $\sqrt{s}=14$ TeV with $\mathcal{L}=3{\mathrm{ab}}^{-1}$, active-sterile mixing as small as $|V_{\ell N}{|}^2=10^{-2}(10^{-3})[5\times 10^{-4}]$ can be probed at $95\%$ CL for Dirac neutrinos masses $m_N\lesssim 1200(300)[200]$ GeV, well beyond present constraints for such heavy states. The improvement holds also for Majorana $N$, and is largely independent of whether charged lepton flavor is conserved or violated. The analysis, built almost entirely from inclusive, transverse observables, is designed to be robust across increasing collider energies, and hence serves as a basis for searches at future colliders: With $\mathcal{L}=15{\mathrm{ab}}^{-1}$ at $\sqrt{s}=27$ TeV, one can probe mixing below $|V_{\ell N}{|}^2=10^{-2}(10^{-3})[2\times 10^{-4}]$ for $m_N\lesssim 3500(700)[200]$ GeV. At a hypothetical 100 TeV $pp$ collider with $\mathcal{L}=30{\mathrm{ab}}^{-1}$, one can probe below $|V_{\ell N}{|}^2=9\times 10^{-5}(10^{-3})[10^{-2}]$ for $m_N\lesssim 200$ GeV ($4$ TeV) [$15$ TeV]. We anticipate these results can be further improved with detector-specific tuning and application of machines learning techniques.

    hep-phhep-exJHEP(2019)·158 citations
31. 31*

    Testing New Physics Explanations of MiniBooNE Anomaly at Neutrino Scattering Experiments

    Carlos A. Argüelles🇺🇸 · Matheus Hostert🇬🇧 · Yu-Dai Tsai🇺🇸

    Heavy neutrinos with additional interactions have recently been proposed as an explanation to the MiniBooNE excess. These scenarios often rely on marginally boosted particles to explain the excess angular spectrum, thus predicting large rates at higher-energy neutrino-electron scattering experiments. We place new constraints on this class of models based on neutrino-electron scattering sideband measurements performed at MINER$\nu$A and CHARM-II. A simultaneous explanation of the angular and energy distributions of the MiniBooNE excess in terms of heavy neutrinos with light mediators is severely constrained by our analysis. In general, high-energy neutrino-electron scattering experiments provide strong constraints on explanations of the MiniBooNE observation involving light mediators.

    hep-phhep-exPRL(2019)·89 citations
32. 32*

    New Analysis of Neutron Star Constraints on Asymmetric Dark Matter

    Raghuveer Garani🇧🇪 · Yoann Genolini🇧🇪 · Thomas Hambye🇧🇪

    Due to their extreme density and low temperature, neutron stars (NS) are efficient probes to unveil interactions between standard model and dark matter (DM) particles. From elastic scatterings on NS material, DM can get gravitationally trapped by the star. The cooling of DM through further collisions may lead to the formation of a dense core which could collapse into a black hole, thus destroying the whole NS. From the observation of old NS, such a scenario leads to very stringent constraints on the parameter space of asymmetric DM. In this work we reexamine this possibility in detail. This includes: (a) a new detailed determination of the number of DM particles captured, properly taking into account the fact that neutrons form a highly degenerate Fermi material; (b) the determination of the time evolution of the DM density and energy profiles inside the NS, which allows us to understand how, as a function of time, DM thermalizes with NS material; (c) the determination of the corresponding constraints which hold on the DM-neutron cross section, including for the case where a large fraction of DM particles have not thermalized; (d) the first determination of the stringent constraints which also hold in a similar way on the DM-muon cross section, particularly relevant for leptophilic DM models; and (e) the use of realistic NS equations of state in determining these constraints.

    hep-phastro-ph.COastro-ph.HEJCAP(2019)·153 citations
33. 33*

    Supersymmetry, direct and indirect constraints

    F. Mahmoudi🇫🇷

    We present an overview of direct and indirect constraints in the MSSM, in CP-conserving and CP-violating MSSM scenarios, with some emphasis on the importance of combining the constraints from different sectors, namely SUSY and Higgs direct searches at the LHC, flavour physics, dark matter and electric dipole moments.

    hep-phNucl.Part.Phys.Proc.(2018)·2 citations
34. 34*

    Cosmological Production of Dark Nuclei

    Michele Redi🇮🇹 · Andrea Tesi🇮🇹

    We study the formation of Dark Matter nuclei in scenarios where DM particles are baryons of a new confining gauge force. The dark nucleosynthesis is analogous to the formation of light elements in the SM and requires as a first step the formation of dark deuterium. We compute this process from first principles, using the formalism of pion-less effective theory for nucleon-nucleon interactions. This controlled effective field theory expansion allows us to systematically compute the cross sections for generic SM representations under the assumption of shallow bound states. In the context of vector-like confinement models we find that, for nucleon masses in the TeV range, baryonic DM made of electro-weak constituents can form a significant fraction of dark deuterium and a much smaller fraction of dark tritium. Formation of dark nuclei can also lead to monochromatic photon lines in indirect detection. Models with singlets do not undergo nucleosynthesis unless a dark photon is added to the theory.

    hep-phastro-ph.COnucl-thJHEP(2019)·31 citations
35. 35*

    Dark matter amnesia in out-of-equilibrium scenarios

    Joshua Berger🇺🇸 · Djuna Croon🇨🇦 · Sonia El Hedri🇳🇱 · Karsten Jedamzik🇫🇷 · Ashley Perko🇺🇸 · Devin G. E. Walker🇺🇸

    Models in which the dark matter is produced at extremely low rates from the annihilation of Standard Model particles in the early Universe allow us to explain the current dark matter relic density while easily evading the traditional experimental constraints. In scenarios where the dark matter interacts with the Standard Model via a new physics mediator, the early Universe dynamics of the dark sector can be particularly complex, as the dark matter and the mediator could be in thermal and chemical equilibrium with each other. This equilibration takes place via number-changing processes such as double Compton scattering and bremsstrahlung, whose amplitudes are cumbersome to calculate. In this paper, we show that in large regions of the parameter space, these equilibration mechanisms do not significantly affect the final dark matter relic density. In particular, for a model with a light dark photon mediator, the relic density can be reasonably estimated by considering that the dark matter is solely produced through the annihilation of Standard Model particles. This result considerably simplifies the treatment of a large class of dark matter theories, facilitating in particular the superimposition of the relic density constraints on the current and future experimental bounds.

    hep-phastro-ph.COJCAP(2019)·11 citations
36. 36*

    The least squares method: application to analysis of the flavor dependence of the QCD relation between pole and $\overline{\mathrm{MS}}$-scheme running heavy quark masses

    A.L. Kataev🇷🇺 · V.S. Molokoedov🇷🇺

    The features of the ordinary least squares method, which gives a possible way to a solution of the overdetermined systems of algebraic equations and allows to estimate the uncertainties of the obtained solutions, are considered. As the important physical example we define four-loop QCD coefficients in the dependence of the relation between pole and running heavy quarks masses on the number of light flavors, using the existing results of numerical supercomputer based calculations of the corresponding four-loop contributions at different fixed numbers of light flavors. Stability of the found solutions to the number of the considered equations and unknowns is demonstrated and supported by the Pearsons's $\chi$-squared test.

    hep-phhep-thTheor.Math.Phys.(2019)·8 citations
37. 37*

    Composite gravity from a metric-independent theory of fermions

    Christopher D. Carone🇺🇸 · Joshua Erlich🇺🇸 · Diana Vaman🇺🇸

    We present a metric-independent, diffeomorphism-invariant model with interacting fermions that contains a massless composite graviton in its spectrum. The model is motivated by the supersymmetric D-brane action, modulated by a fermion potential. The gravitational coupling is related to new physics at the cutoff scale that regularizes UV divergences. We also speculate on possible extensions of the model.

    ↳ hep-thgr-qchep-phClass.Quant.Grav.(2019)·9 citations
38. 38*

    Numerical study of inflationary preheating with arbitrary power-law potential and a realization of curvaton mechanism

    Jie Jiang🇨🇳 · Qiuyue Liang🇨🇳 · Yi-Fu Cai🇨🇳 · Damien A. Easson🇺🇸 · Yang Zhang🇨🇳

    During inflationary preheating, the energy stored in the inflaton field is rapidly converted into excitations of other entropy fields. This stage is characterized by exponential particle production due to parametric resonance and is notoriously difficult to analyze using analytic methods. We develop a detailed numerical simulation to investigate inflationary preheating when the potential of the inflaton is a power-law function with arbitrary power index. To achieve a successful graceful exit from a primordial inflationary phase to a smooth, oscillatory phase during preheating, we assume the inflaton potential reduces to a quadratic function in the infrared regime, which may be regarded as a mass term at low energy scales. With this simplification, our numerical method may be applied to unconventional chaotic inflation models. To demonstrate its validity, we numerically analyze the preheating stage of axion-monodromy inflation which is inspired by string theory. By performing perturbation analyses, our result shows that the power spectrum of primordial curvature perturbation can be dominated by fluctuations of entropy field rather than those of inflaton, which can be regarded as a particular realization of the curvaton mechanism through a preheating process.

    ↳ astro-ph.COgr-qchep-phhep-thApJ(2019)·14 citations
39. 39*

    Chiral crossover in QCD at zero and non-zero chemical potentials

    A. Bazavov🇺🇸 · H.-T. Ding🇨🇳 · P. Hegde🇮🇳 · O. Kaczmarek🇩🇪 · F. Karsch🇩🇪 · N. Karthik🇺🇸 · E. Laermann🇩🇪 · Anirban Lahiri🇩🇪 · R. Larsen🇺🇸 · S.-T. Li🇨🇳 · Swagato Mukherjee🇺🇸 · H. Ohno🇯🇵 and 5 other authors

    We present results for pseudo-critical temperatures of QCD chiral crossovers at zero and non-zero values of baryon ($B$), strangeness ($S$), electric charge ($Q$), and isospin ($I$) chemical potentials ${\mu }_{X=B,Q,S,I}$. The results were obtained using lattice QCD calculations carried out with two degenerate up and down dynamical quarks and a dynamical strange quark, with quark masses corresponding to physical values of pion and kaon masses in the continuum limit. By parameterizing pseudo-critical temperatures as $T_c({\mu }_X)=T_c(0)\left[1-{\kappa }_2^X({\mu }_X/T_c(0){)}^2-{\kappa }_4^X({\mu }_X/T_c(0){)}^4\right]$, we determined ${\kappa }_2^X$ and ${\kappa }_4^X$ from Taylor expansions of chiral observables in ${\mu }_X$. We obtained a precise result for $T_c(0)=(156.5\pm 1.5)\mathrm{MeV}$. For analogous thermal conditions at the chemical freeze-out of relativistic heavy-ion collisions, i.e., ${\mu }_S(T,{\mu }_B)$ and ${\mu }_Q(T,{\mu }_B)$ fixed from strangeness-neutrality and isospin-imbalance, we found ${\kappa }_2^B=0.012(4)$ and ${\kappa }_4^B=0.000(4)$. For ${\mu }_B\lesssim 300\mathrm{MeV}$, the chemical freeze-out takes place in the vicinity of the QCD phase boundary, which coincides with the lines of constant energy density of $0.42(6){GeV/fm}^3$ and constant entropy density of $3.7(5){\mathrm{fm}}^{-3}$.

    ↳ hep-lathep-phhep-thnucl-ex+1PLB(2019)·878 citations
40. 40*

    Experiment to detect dark energy forces using atom interferometry

    Dylan Sabulsky🇬🇧 · Indranil Dutta🇬🇧 · E. A. Hinds🇬🇧 · Benjamin Elder🇬🇧 · Clare Burrage🇬🇧 · Edmund J. Copeland🇬🇧

    The accelerated expansion of the universe motivates a wide class of scalar field theories that modify gravity on large scales. In regions where the weak field limit of General Relativity has been confirmed by experiment, such theories need a screening mechanism to suppress the new force. We have measured the acceleration of an atom toward a macroscopic test mass inside a high vacuum chamber, where the new force is unscreened in some theories. Our measurement, made using atom interferometry, shows that the attraction between atoms and the test mass does not differ appreciably from Newtonian gravity. This result places stringent limits on the free parameters in chameleon and symmetron theories of modified gravity.

    ↳ physics.atom-phastro-ph.COgr-qchep-phPRL(2019)·145 citations
41. 41*

    Nucleon generalized form factors from two-flavor lattice QCD

    Gunnar S. Bali🇩🇪 · Sara Collins🇩🇪 · Meinulf Göckeler🇩🇪 · Rudolf Rödl🇩🇪 · Andreas Schäfer🇩🇪 · André Sternbeck🇩🇪

    We determine the generalized form factors, which correspond to the second Mellin moment (i.e., the first $x$-moment) of the generalized parton distributions of the nucleon at leading twist. The results are obtained using lattice QCD with $N_f=2$ nonperturbatively improved Wilson fermions, employing a range of quark masses down to an almost physical value with a pion mass of about 150 MeV. We also present results for the isovector quark angular momentum and for the first $x$-moment of the transverse quark spin density. We compare two different fit strategies and find that directly fitting the ground state matrix elements to the functional form expected from Lorentz invariance and parametrized in terms of form factors yields comparable, and usually more stable results than the traditional approach where the form factors are determined from an overdetermined linear system based on the fitted matrix elements.

    ↳ hep-lathep-phPRD(2019)·64 citations
42. 42*

    Elastic differential cross-section measurement at $\sqrt{s}=13$ TeV by TOTEM

    TOTEM Collaboration: G. Antchev🇧🇬 · P. Aspell🇨🇭 · I. Atanassov🇧🇬 · V. Avati🇵🇱 · J. Baechler🇨🇭 · C. Baldenegro Barrera🇺🇸 · V. Berardi🇮🇹 · M. Berretti🇫🇮 · E. Bossini🇮🇹 · U. Bottigli🇮🇹 · M. Bozzo🇮🇹 · H. Burkhardt🇨🇭 and 64 other authors

    The TOTEM collaboration has measured the elastic proton-proton differential cross section $\mathrm{d}\sigma /\mathrm{d}t$ at $\sqrt{s}=13$ TeV LHC energy using dedicated ${\beta }^{\ast }=90$ m beam optics. The Roman Pot detectors were inserted to 10$\sigma$ distance from the LHC beam, which allowed the measurement of the range $[0.04$ GeV${}^2$$;4$GeV${}^2$$]$ in four-momentum transfer squared $|t|$. The efficient data acquisition allowed to collect about 10${}^9$ elastic events to precisely measure the differential cross-section including the diffractive minimum (dip), the subsequent maximum (bump) and the large-$|t|$ tail. The average nuclear slope has been found to be $B=(20.40\pm 0.002^{\mathrm{stat}}\pm 0.01^{\mathrm{syst}})$GeV${}^{-2}$ in the $|t|$-range $0.04$GeV${}^2$ to $0.2$GeV${}^2$. The dip position is $|t_{\mathrm{dip}}|=(0.47\pm 0.004^{\mathrm{stat}}\pm 0.01^{\mathrm{syst}})$GeV${}^2$. The differential cross section ratio at the bump vs. at the dip $R=1.77\pm 0.01^{\mathrm{stat}}$ has been measured with high precision. The series of TOTEM elastic pp measurements show that the dip is a permanent feature of the pp differential cross-section at the TeV scale.

    ↳ hep-exhep-phnucl-exEPJC(2019)·130 citations
43. 43*

    Three-loop Euler-Heisenberg Lagrangian in 1+1 QED, part 1: single fermion-loop part

    Idrish Huet🇲🇽 · Michel Rausch de Traubenberg🇫🇷 · Christian Schubert🇲🇽

    We study the three-loop Euler-Heisenberg Lagrangian in spinor quantum electrodynamics in 1+1 dimensions. In this first part we calculate the one-fermion-loop contribution, applying both standard Feynman diagrams and the worldline formalism which leads to two different representations in terms of fourfold Schwinger-parameter integrals. Unlike the diagram calculation, the worldline approach allows one to combine the planar and the non-planar contributions to the Lagrangian. Our main interest is in the asymptotic behaviour of the weak-field expansion coefficients of this Lagrangian, for which a non-perturbative prediction has been obtained in previous work using worldline instantons and Borel analysis. We develop algorithms for the calculation of the weak-field expansions coefficients that, in principle, allow their calculation to arbitrary order. Here for the non-planar contribution we make essential use of the polynomial invariants of the dihedral group D4 in Schwinger parameter space to keep the expressions manageable. As expected on general grounds, the coefficients are of the form r1+r2*zeta(3) with rational numbers r1, r2. We compute the first two coefficients analytically, and four more by numerical integration.

    ↳ hep-thhep-phJHEP(2019)·27 citations
44. 44*

    Dilute Fermi gas at fourth order in effective field theory

    C. Wellenhofer🇩🇪 · C. Drischler🇺🇸 · A. Schwenk🇩🇪

    Using effective field theory methods, we calculate for the first time the complete fourth-order term in the Fermi-momentum or $k_{\mathrm{F}}{a}_s$ expansion for the ground-state energy of a dilute Fermi gas. The convergence behavior of the expansion is examined for the case of spin one-half fermions and compared against quantum Monte-Carlo results, showing that the Fermi-momentum expansion is well-converged at this order for $|k_{\mathrm{F}}{a}_s|\lesssim 0.5$.

    ↳ nucl-thcond-mat.quant-gashep-phPLB(2020)·20 citations
45. 45*

    Reconstruction of $\text{t}\bar{\text{t}}$H, H $\to \text{b}\bar{\text{b}}$ events using the matrix element method and substructure techniques

    Maren Meinhard🇨🇭

    This contribution outlines the implementation of the matrix element method (MEM) in the search for $\text{t}\bar{\text{t}}$H, H $\to \text{b}\bar{\text{b}}$ events. In particular, the evaluation of the transfer functions, which relate detector level to parton level quantities in the computation of the MEM, is described. In addition, it is presented how jet substructure reconstruction can be combined with the MEM. The combination of these techniques leads to a decrease in computation time by up to 90% and an increase in event selection efficiency of 30% in the high Higgs boson and top quark p${}_T$ phase space.

    ↳ hep-exhep-ph0 citations
46. 46*

    Towards distinguishing variants of non-minimal inflation

    Tomo Takahashi🇯🇵 · Tommi Tenkanen🇬🇧

    We study models of inflation where the scalar field $\varphi$ that drives inflation is coupled non-minimally to gravity via $\xi {\varphi }^{2}R$, or where the gravity sector is enlarged by an $R^2$ term. We consider the original Higgs inflation, Starobinsky inflation, and two different versions of a scenario where the inflaton is a scalar field other than the Higgs, and discuss if they can be distinguished from each other by measuring the tensor-to-scalar ratio and runnings of the spectral index of primordial curvature perturbations, on top of the amplitude and spectral index of the perturbations. We consider both metric and Palatini theories of gravity, showing how detailed studies of non-minimally coupled models can help to identify the inflaton field and how they may provide for a way to also distinguish between different theories of gravity in the present context.

    ↳ astro-ph.COgr-qchep-phJCAP(2019)·58 citations
47. 47*

    Weighted transverse spin asymmetries in 2015 COMPASS Drell-Yan data

    Jan Matousek (on behalf of the COMPASS Collaboration)🇮🇹

    Muon pairs created in the Drell-Yan process of a negative pion beam of 190 GeV/c momentum impinging on a transversely polarised NH${}_3$ target were detected with the COMPASS spectrometer at CERN in 2015. In addition to the extraction of the transverse spin asymmetries (TSAs) from these data, a complementary analysis of the TSAs weighted by powers of the dimuon momentum $q_T$ has been performed and is presented in this paper. In the transverse momentum dependent parton distribution functions (TMD PDFs) formalism, the $q_T$-weighted TSAs can be interpreted in terms of products of the TMD PDFs of the beam pion and of the transversely polarised target proton, unlike the conventional TSAs, which are interpreted as their convolutions. This allowed us to make a straightforward comparison with the expectation based on the weighted Sivers asymmetry measured in the SIDIS process. In a similar way, the Boer-Mulders function of the pion and proton can be obtained as well.

    ↳ hep-exhep-phPoS(2018)·3 citations
48. 48*

    Finite-density gauge correlation functions in QC2D

    Tamer Boz🇮🇪 · Ouraman Hajizadeh🇦🇹 · Axel Maas🇦🇹 · Jon-Ivar Skullerud🇮🇪

    2-color QCD is the simplest QCD-like theory which is accessible to lattice simulations at finite density. It therefore plays an important role to test qualitative features and to provide benchmarks to other methods and models, which do not suffer from a sign problem. To this end, we determine the minimal-Landau-gauge propagators and 3-point vertices in this theory over a wide range of densities, the vacuum, and at both finite temperature and density. The results show that there is essentially no modification of the gauge sector in the low-temperature, low-density phase. Even outside this phase only mild modifications appear, mostly in the chromoelectric sector.

    ↳ hep-lathep-phnucl-thPRD(2019)·40 citations
49. 49*

    Consistency between Lüscher's finite volume method and HAL QCD method for two-baryon systems in lattice QCD

    Takumi Iritani🇯🇵 · Sinya Aoki🇯🇵 · Takumi Doi🇯🇵 · Tetsuo Hatsuda🇯🇵 · Yoichi Ikeda🇯🇵 · Takashi Inoue🇯🇵 · Noriyoshi Ishii🇯🇵 · Hidekatsu Nemura🇯🇵 · Kenji Sasaki🇯🇵

    There exist two methods to study two-baryon systems in lattice QCD: the direct method which extracts eigenenergies from the plateaux of the temporal correlator and the HAL QCD method which extracts observables from the non-local potential associated with the tempo-spatial correlator. Although the two methods should give the same results theoretically, qualitatively different results have been reported. Recently, we pointed out that the separation of the ground state from the excited states is crucial to obtain sensible results in the former, while both states provide useful signals in the latter. In this paper, we identify the contribution of each state in the direct method by decomposing the two-baryon correlators into the finite-volume eigenmodes obtained from the HAL QCD method. We consider the $\Xi \Xi$ system in the ${}^1$S${}_0$ channel at $m_{\pi }=0.51$ GeV in 2+1 flavor lattice QCD using the wall and smeared quark sources. We demonstrate that the "pseudo-plateau" at early time slices (t = 1~2 fm) from the smeared source in the direct method indeed originates from the contamination of the excited states, and the true plateau with the ground state saturation is realized only at t > 5~15 fm corresponding to the inverse of the lowest excitation energy. We also demonstrate that the two-baryon operator can be optimized by utilizing the finite-volume eigenmodes, so that (i) the finite-volume energy spectra from the HAL QCD method agree with those from the optimized temporal correlator and (ii) the correct spectra would be accessed in the direct method only if highly optimized operators are employed. Thus we conclude that the long-standing issue on the consistency between the Lüscher's finite volume method and the HAL QCD method for two baryons is now resolved: They are consistent with each other quantitatively only if the excited contamination is properly removed in the former.

    ↳ hep-lathep-phnucl-thJHEP(2019)·57 citations
50. 50*

    Bi-directional universal dynamics in a spinor Bose gas close to a non-thermal fixed point

    Christian-Marcel Schmied🇩🇪 · Maximilian Prüfer🇩🇪 · Markus K. Oberthaler🇩🇪 · Thomas Gasenzer🇩🇪

    We numerically study the universal scaling dynamics of an isolated one-dimensional ferromagnetic spin-1 Bose gas. Preparing the system in a far-from-equilibrium initial state, simultaneous coarsening and refining is found to enable and characterize the approach to a non-thermal fixed point. A macroscopic length scale which scales in time according to $L_{\Lambda }(t)\sim t^{\beta }$, with $\beta \simeq 1/4$, quantifies the coarsening of the size of spin textures. At the same time kink-like defects populating these textures undergo a refining process measured by a shrinking microscopic length scale $L_{\lambda }\sim t^{{\beta }^{\prime }}$, with ${\beta }^{\prime }\simeq -0.17$. The combination of these scaling evolutions enables particle and energy conservation in the isolated system and constitutes a bi-directional transport in momentum space. The value of the coarsening exponent $\beta$ suggests the dynamics to belong to the universality class of diffusive coarsening of the one-dimensional XY-model. However, the universal momentum distribution function exhibiting non-linear transport marks the distinction between diffusive coarsening and the approach of a non-thermal fixed point in the isolated system considered here. This underlines the importance of the universal scaling function in classifying non-thermal fixed points. Present-day experiments with quantum gases are expected to have access to the predicted bi-directional scaling.

    ↳ cond-mat.quant-gashep-phnlin.PSPRA(2019)·28 citations
51. 51*

    Elastic differential cross-section $\mathrm{d}\sigma /\mathrm{d}t$ at $\sqrt{s}=$2.76 TeV and implications on the existence of a colourless 3-gluon bound state

    TOTEM Collaboration: G. Antchev🇧🇬 · P. Aspell🇨🇭 · I. Atanassov🇧🇬 · V. Avati🇵🇱 · J. Baechler🇨🇭 · C. Baldenegro Barrera🇺🇸 · V. Berardi🇮🇹 · M. Berretti🇫🇮 · E. Bossini🇮🇹 · U. Bottigli🇮🇹 · M. Bozzo🇮🇹 · H. Burkhardt🇨🇭 and 63 other authors

    The proton-proton elastic differential cross section $\mathrm{d}\sigma /\mathrm{d}t$ has been measured by the TOTEM experiment at $\sqrt{s}=2.76$ TeV energy with ${\beta }^{\ast }=11$ m beam optics. The Roman Pots were inserted to 13 times the transverse beam size from the beam, which allowed to measure the differential cross-section of elastic scattering in a range of the squared four-momentum transfer ($|t|$) from $0.36$ GeV${}^2$ to $0.74$ GeV${}^2$. The differential cross-section can be described with an exponential in the $|t|$-range between $0.36$ GeV${}^2$ and $0.54$ GeV${}^2$, followed by a diffractive minimum (dip) at $|t_{\mathrm{dip}}|=0.61\pm 0.03$ GeV${}^2$ and a subsequent maximum (bump). The ratio of the $\mathrm{d}\sigma /\mathrm{d}t$ at the bump and at the dip is $1.7\pm 0.2$. When compared to the $\mathrm{p}\bar{\mathrm{p}}$ measurement of the D0 experiment at $\sqrt{s}=1.96$ TeV, a significant difference can be observed. Under the condition that the effects due to the energy difference between TOTEM and D0 can be neglected, the result provides evidence for a colourless 3-gluon bound state exchange in the $t$-channel of the proton-proton elastic scattering.

    ↳ hep-exhep-phnucl-exEPJC(2020)·122 citations
52. 52*

    Spontaneous breaking of Weyl quadratic gravity to Einstein action and Higgs potential

    D. M. Ghilencea🇷🇴

    We consider the (gauged) Weyl gravity action, quadratic in the scalar curvature ($\tilde{R}$) and in the Weyl tensor (${\tilde{C}}_{\mu \nu \rho \sigma }$) of the Weyl conformal geometry. In the absence of matter fields, this action has spontaneous breaking in which the Weyl gauge field ${\omega }_{\mu }$ becomes massive (mass $m_{\omega }\sim$ Planck scale) after "eating" the dilaton in the ${\tilde{R}}^2$ term, in a Stueckelberg mechanism. As a result, one recovers the Einstein-Hilbert action with a positive cosmological constant and the Proca action for the massive Weyl gauge field ${\omega }_{\mu }$. Below $m_{\omega }$ this field decouples and Weyl geometry becomes Riemannian. The Einstein-Hilbert action is then just a "low-energy" limit of Weyl quadratic gravity which thus avoids its previous, long-held criticisms. In the presence of matter scalar field ${\varphi }_1$ (Higgs-like), with couplings allowed by Weyl gauge symmetry, after its spontaneous breaking one obtains in addition, at low scales, a Higgs potential with spontaneous electroweak symmetry breaking. This is induced by the non-minimal coupling ${\xi }_1{\varphi }_1^2\tilde{R}$ to Weyl geometry, with Higgs mass $\propto {\xi }_1/{\xi }_0$ (${\xi }_0$ is the coefficient of the ${\tilde{R}}^2$ term). In realistic models ${\xi }_1$ must be classically tuned ${\xi }_1\ll {\xi }_0$. We comment on the quantum stability of this value.

    ↳ hep-thgr-qchep-phJHEP(2019)·111 citations
53. 53*

    Type I Abelian Higgs strings: evolution and Cosmic Microwave Background constraints

    Mark Hindmarsh🇫🇮 · Joanes Lizarraga🇪🇸 · Jon Urrestilla🇪🇸 · David Daverio🇬🇧 · Martin Kunz🇨🇭

    We present results from the first simulations of networks of Type I Abelian Higgs cosmic strings to include both matter and radiation eras and Cosmic Microwave Background (CMB) constraints. In Type I strings, the string tension is a slowly decreasing function of the ratio of the scalar and gauge mass-squared, $\beta$. We find that the mean string separation shows no dependence on $\beta$, and that the energy-momentum tensor correlators decrease approximately in proportion to the square of the string tension, with additional O(1) correction factors which asymptote to constants below $\beta \lesssim 0.01$. Strings in models with low self-couplings can therefore satisfy current CMB bounds at higher symmetry-breaking scales. This is particularly relevant for models where the gauge symmetry is broken in a supersymmetric flat direction, for which the effective self-coupling can be extremely small. If our results can be extrapolated to $\beta \simeq 10^{-15}$, even strings formed at $10^{16}$ GeV (approximately the grand unification scale in supersymmetric extensions of the Standard Model) can be compatible with CMB constraints.

    ↳ astro-ph.COhep-phhep-thPRD(2019)·31 citations
54. 54*

    Measuring the atmospheric neutrino oscillation parameters and constraining the 3+1 neutrino model with ten years of ANTARES data

    ANTARES Collaboration: A. Albert (1)🇫🇷 · M. André (2)🇪🇸 · M. Anghinolfi (3)🇮🇹 · G. Anton (4)🇩🇪 · M. Ardid (5)🇪🇸 · J.-J. Aubert (6)🇫🇷 · J. Aublin (7)🇫🇷 · T. Avgitas (7)🇫🇷 · B. Baret (7)🇫🇷 · J. Barrios-Martí (8)🇪🇸 · S. Basa (9)🇫🇷 · B. Belhorma (10)🇲🇦 and 123 other authors

    The ANTARES neutrino telescope has an energy threshold of a few tens of GeV. This allows to study the phenomenon of atmospheric muon neutrino disappearance due to neutrino oscillations. In a similar way, constraints on the 3+1 neutrino model, which foresees the existence of one sterile neutrino, can be inferred. Using data collected by the ANTARES neutrino telescope from 2007 to 2016, a new measurement of $\Delta m_{32}^2$ and ${\theta }_{23}$ has been performed - which is consistent with world best-fit values - and constraints on the 3+1 neutrino model have been derived.

    ↳ hep-exhep-phJHEP(2019)·94 citations
55. 55*

    Bottom Production in $pp$ Collisions at Large Hadron Collider Energies using Parton Cascade Model

    Rupa Chatterjee🇮🇳 · Dinesh K. Srivastava🇮🇳

    We study the production of bottom quarks in $pp$ collisions at Large Hadron Collider energies using previously developed parton cascade model to explore the impact of Landau Pomeranchuk Midgal (LPM) effect on their dynamics. In contrast to the case for charm quarks reported recently, we find only a marginal impact of the suppression of multiple scatterings of partons due to the LPM effect on their production. It is felt that this happens as they are only produced in very hard collisions.

    ↳ nucl-thhep-ph1 citation
56. 56*

    Wobbly Dark Matter Signals at Cherenkov Telescopes from Long Lived Mediator Decays

    Stefania Gori🇺🇸 · Stefano Profumo🇺🇸 · Bibhushan Shakya🇺🇸

    Imaging Atmospheric Cherenkov Telescope (IACT) searches for dark matter often perform observations in "wobble mode", i.e. collecting data from the signal region and from a corresponding background control region at the same time, enabling efficient simultaneous determination and subtraction of background. This observation strategy is possibly compromised in scenarios where dark matter annihilates to long-lived mediators that can traverse astrophysical distances before decaying to produce the gamma rays observed by the IACTs. In this paper, we show that this challenge comes with several interesting features and opportunities: in addition to signal contamination in the background control region, the gamma-ray spectrum changes with the observing direction angle and typically exhibits a hard excess at high energies. This affects signal reconstruction via subtraction of the background control region measurements in non-trivial ways. Such features represent a significant departure from the canonical picture, and offer novel handles to identify a dark matter signal and to extract underlying dark matter parameters.

    ↳ astro-ph.HEhep-phPRL(2019)·12 citations
57. 57*

    Universe's Primordial Quantum Memories

    Gia Dvali🇩🇪 · Lukas Eisemann🇩🇪 · Marco Michel🇩🇪 · Sebastian Zell🇩🇪

    We provide a very general argument showing that the Universe must have kept its quantum memories from an epoch much earlier than $60$ e-foldings before the end of inflation. The point is that a generic system of enhanced memory storage capacity exhibits a phenomenon of memory burden. Due to its universal nature this effect must be applicable to de Sitter since the latter has a maximal memory storage capacity thanks to its Gibbons-Hawking entropy. The primordial information pattern encoded in de Sitter memory initially costs very little energy. However, because of Gibbons-Hawking evaporation, the memory burden of the pattern grows in time and increasingly back reacts on the evaporation process. After a finite time the memory burden becomes unbearable and de Sitter quantum breaks. If inflation ended not long before its quantum break-time, the imprints of the primordial memory pattern can be observable. This provides a qualitatively new type of window in the Universe's beginning, a sort of cosmic quantum hair.

    ↳ hep-thastro-ph.COgr-qchep-ph+1JCAP(2019)·54 citations
58. 58*

    Higgs-$R^2$ inflation -- full slow-roll study at tree-level

    Vera-Maria Enckell🇫🇮 · Kari Enqvist🇫🇮 · Syksy Rasanen🇵🇸 · Lumi-Pyry Wahlman🇫🇮

    We consider Higgs inflation with an $\alpha R^2$ term. It adds a new scalar degree of freedom, which leads to a two-field model of inflation. We do a complete slow-roll analysis of the three-dimensional parameter space of the $R^2$ coefficient $\alpha$, the non-minimal coupling $\xi$ and the Higgs self-coupling $\lambda$. We find three classes of inflationary solutions, but only pure $R^2$ and attractor solutions fit observations. We find that pure Higgs inflation is impossible when the $R^2$ term is present regardless of how small $\alpha$ is. However, we can have Higgs-like inflation, where the amplitude of the perturbations does not depend on $\alpha$ and the predictions as a function of e-folds are the same as in Higgs inflation, although the inflationary trajectory is curved in field space. The spectral index is $0.939<n_R<0.967$, and constraining it to the observed range, the tensor-to-scalar ratio varies from $3.8\times 10^{-3}$ to the maximum allowed by observations, $0.079$. Observational constraints on isocurvature perturbations contribute to these limits, whereas non-Gaussianity is automatically in the range allowed by observations.

    ↳ astro-ph.COgr-qchep-phJCAP(2020)·49 citations
59. 59*

    Open quantum dynamics induced by light scalar fields

    Clare Burrage🇬🇧 · Christian Käding🇬🇧 · Peter Millington🇬🇧 · Jiří Minář🇳🇱

    We consider the impact of a weakly coupled environment comprising a light scalar field on the open dynamics of a quantum probe field, resulting in a master equation for the probe field that features corrections to the coherent dynamics, as well as decoherence and momentum diffusion. The light scalar is assumed to couple to matter either through a nonminimal coupling to gravity or, equivalently, through a Higgs portal. Motivated by applications to experiments such as atom interferometry, we assume that the probe field can be initialized, by means of external driving, in a state that is not an eigenstate of the light scalar-field--probe system, and we derive the master equation for single-particle matrix elements of the reduced density operator of a toy model. We comment on the possibilities for experimental detection and the related challenges, and highlight possible pathways for further improvements. This derivation of the master equation requires techniques of non-equilibrium quantum field theory, including the Feynman-Vernon influence functional and thermo field dynamics, used to motivate a method of Lehmann-Symanzik-Zimmermann-like reduction. In order to obtain cutoff-independent results for the probe-field dynamics, we find that it is necessary to use a time-dependent renormalization procedure. Specifically, we show that non-Markovian effects following a quench, namely the violation of time-translational invariance due to finite-time effects, lead to a time-dependent modulation of the usual vacuum counterterms.

    ↳ hep-thastro-ph.COgr-qchep-ph+1PRD(2019)·59 citations
60. 60*

    SU(3)-breaking ratios for $D_{(s)}$ and $B_{(s)}$ mesons

    Peter A Boyle🇬🇧 · Luigi Del Debbio🇬🇧 · Nicolas Garron🇬🇧 · Andreas Juttner🇬🇧 · Amarjit Soni🇺🇸 · Justus Tobias Tsang🇬🇧 · Oliver Witzel (RBC/UKQCD collaboration)🇺🇸

    We present results for the $SU(3)$ breaking ratios of decay constants $f_{D_s}/f_D$ and $f_{B_s}/f_B$ and - for the first time with physical pion masses - the ratio of bag parameters $B_{B_s}/B_{B_d}$, as well as the ratio $\xi$, forming the ratio of the nonpeturbative contributions to neutral $B_{(s)}$ meson mixing. Our results are based on Lattice QCD simulations with chirally symmetric 2+1 dynamical flavors of domain wall fermions. Eight ensembles at three different lattice spacing in the range $a=0.11-0.07\mathrm{fm}$ enter the analysis two of which feature physical light quark masses. Multiple heavy quark masses are simulated ranging from below the charm quark mass to half the bottom quark mass. The $SU(3)$ breaking ratios display a very benign heavy mass behaviour allowing for extrapolation to the physical bottom quark mass. The results in the continuum limit including all sources of systematic errors are $f_{D_s}/f_D=1.1740(51{)}_{\mathrm{stat}}{(}_{-68}^{+68}{)}_{\mathrm{sys}}$, $f_{B_s}/f_B=1.1949(60{)}_{\mathrm{stat}}{(}_{-175}^{+95}{)}_{\mathrm{sys}}$, $B_{B_s}/B_{B_d}=0.9984(45{)}_{\mathrm{stat}}{(}_{-63}^{+80}{)}_{\mathrm{sys}}$ and $\xi =1.1939(67{)}_{\mathrm{stat}}{(}_{-177}^{+95}{)}_{\mathrm{sys}}$. Combining these with experimentally measured values we extract the ratios of CKM matrix elements $|V_{cd}/V_{cs}|=0.2164(57{)}_{\exp }{(}_{-12}^{+12}{)}_{\mathrm{lat}}$ and $|V_{td}/V_{ts}|=0.20329(41{)}_{\exp }{(}_{-301}^{+162}{)}_{\mathrm{lat}}$.

    ↳ hep-lathep-ph101 citations
61. 61*

    Gravitational wave production after inflation with cuspy potentials

    Jing Liu🇨🇳 · Zong-Kuan Guo🇨🇳 · Rong-Gen Cai🇨🇳 · Gary Shiu🇺🇸

    We investigate the effect of the cuspiness of scalar potentials on the production of gravitational waves during oscillon formation after inflation. We consider a more general form of potentials with a mass parameter $M$, which repoduce cuspy potentials for fields much larger than $M$, and smooth potentials in the opposite limit. For cuspy potentials, nonsmooth oscillations of the inflaton induce an amplification of the inflaton fluctuations at the bottom of the potential, so that oscillons copiously form, which leads to a significant stochastic gravitational wave background with a double-peak spectrum. By varying the parameter $M$, we find that cuspy potentials yield stronger signals of gravitational waves and the generation of gravitational waves disappears for smooth potentials. Moreover, we calculate the equation of state after inflation and find the presence of a quasi matter-dominated stage right before the transition to the radiation-dominated stage.

    ↳ astro-ph.COgr-qchep-phPRD(2019)·41 citations
62. 62*

    Pion Interactions and the Standard Model at High Precision

    B. Ananthanarayan🇮🇳 · Shayan Ghosh🇮🇳

    Pions were predicted by H. Yukawa as force carriers of the inter-nucleon forces, and were detected in 1947. Today they are known to be bound states of quarks and anti-quarks of the two lightest flavours. They satisfy Bose statistics, and are the lightest particles of the strong interaction spectrum. Determination of the parameters of the Standard Model, including the masses of the lightest quarks, has only recently reached high precision on the lattice. Pions are also known to be pseudo-Goldstone bosons of spontaneously broken approximate axial-vector symmetries, and a probe of their properties and interactions at high precision tests our knowledge of the strong interactions. While also being a probe of the solution of the strong interactions on the computer, which is known as lattice gauge theory. Despite their long history, there are significant experimental and theoretical challenges in determining their properties at high precision. Examples include the lifetime of the neutral pion, and the status of their masses and decay widths in effective field theories. Pion-pion scattering has been studied for several decades using general methods of field theory such as dispersion relations based on analyticity, unitarity and crossing. Knowledge from these theoretical methods are used to confront high precision experimental data, and to analyze them to extract information on their scattering and phase shift parameters. This knowledge is crucial for estimating the Standard Model contributions to the anomalous magnetic moment of the muon, which is being probed at Fermilab in ongoing experiments. Other sensitive tests include the rare decay of the eta meson into three pions, which represents an isospin violating decay. The present article briefly reviews these important developments.

    ↳ physics.hist-phhep-ph1 citation

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.