Tue·Jul 31, 2018Tuesday·July 31, 2018

1. 01*

   Mass and structure of the nucleon: Gluon trace anomaly versus spontaneous symmetry breaking

   Martin Schumacher🇩🇪

   Two different approaches to mass and structure of the nucleon are discussed in recent works, $viz.$ (case 1) the QCD lagrangian evaluated via lattice calculations and (case ii) spontaneous symmetry breaking mediated by the $\sigma$ field. These approaches are complementary in the sense that the QCD lagrangian makes use of the gluon content of the nucleon entering in terms of the gluon trace-anomaly and ignores the effects of $q\bar{q}$ vacuum polarization, whereas in spontaneous symmetry breaking masses are formed by attaching $q\bar{q}$ pairs to the valence quarks, thus giving them a definite mass which is named the constituent mass. By the same process the $q\bar{q}$ pairs of the vacuum polarization acquire mass and in this form are the elements of the quark condensate, having an up-quark and a down-quark component. A linear combination of these two components in the form $\sigma =1/\sqrt{2}(u\bar{u}+d\bar{d})$ shows up as the $\sigma$ field. It is shown that (case i) corresponds to an unstable nucleon configuration whereas (case ii) corresponds to a stable nucleon configuration as observed in low-energy photo-nuclear and pion-nuclear reactions.

   hep-ph4 citations
2. 02*

   Electroweak vacuum lifetime in two Higgs doublet models

   V. Branchina🇮🇹 · F. Contino🇮🇹 · P.M. Ferreira🇵🇹

   We study the stability of neutral electroweak vacua in two Higgs doublet models, and calculate the lifetime of these states when the parameters are such that they are false vacua. As the two Higgs doublet model is invariant under a sign change of both doublets, degenerate true vacua exist. It is shown that this degeneracy, despite the fact that each of these minima locally describes the same physics, can immensely affect their lifetime. We apply these calculations to the parameter space of the models which is allowed by recent LHC searches, and infer combinations of parameters which should be excluded on grounds of a tunneling time inferior to the age of the universe.

   hep-phJHEP(2018)·42 citations
3. 03*

   Cosmic QCD Epoch at Nonvanishing Lepton Asymmetry

   Mandy M. Wygas🇩🇪 · Isabel M. Oldengott🇪🇸 · Dietrich Bodeker🇩🇪 · Dominik J. Schwarz🇩🇪

   We investigate how a lepton asymmetry impacts the cosmic trajectory in the QCD phase diagram. We study the evolution of chemical potentials during the QCD epoch of the early Universe using susceptibilities from lattice QCD to interpolate between an ideal quark gas and an ideal hadron resonance gas. The lepton asymmetry affects the evolution of all chemical potentials. The standard cosmic trajectory is obtained assuming tiny lepton and baryon asymmetries. For larger lepton asymmetry, the charge chemical potential exceeds the baryon chemical potential before pion annihilation.

   hep-phastro-ph.COhep-latPRL(2018)·53 citations
4. 04*

   Coarse graining $\pi \pi$ scattering

   Jacobo Ruiz de Elvira🇨🇭 · Enrique Ruiz Arriola🇪🇸

   We carry out an analysis of $\pi \pi$ scattering in the $IJ=00$, $11$ and $20$ channels in configuration space up to a maximal center-of-mass energy $\sqrt{s}=1.4$ GeV. We separate the interaction into two regions marked by an elementarity radius of the system; namely, a long distance region above which pions can be assumed to interact as elementary particles and a short distance region where many physical effects cannot be disentangled. The long distance interaction is described by chiral dynamics, where a two-pion-exchange potential is identified, computed and compared to lattice calculations. The short distance piece corresponds to a coarse grained description exemplified by a superposition of delta-shell potentials sampling the interaction with the minimal wavelength. We show how the so constructed non-perturbative scattering amplitude complies with the proper analytic structure, allowing for an explicit N/D type decomposition in terms of the corresponding Jost functions and fulfilling dispersion relations without subtractions. We also address renormalization issues in coordinate space and investigate the role of crossing when fitting the scattering amplitudes above and below threshold to Roy-equation results. At higher energies, we show how inelasticities can be described by one single complex and energy dependent parameter. A successful description of the data can be achieved with a minimal number of fitting parameters, suggesting that coarse graining is a viable approach to analyze hadronic processes.

   hep-phnucl-thEPJC(2018)·14 citations
5. 05*

   Relaxion and light (pseudo)scalars at the HL-LHC and lepton colliders

   Claudia Frugiuele🇮🇱 · Elina Fuchs🇮🇱 · Gilad Perez🇮🇱 · Matthias Schlaffer🇮🇱

   We study the potential of future lepton colliders, running at the Z-pole and above, and the High-Luminosity LHC to search for the relaxion and other light scalars $\varphi$. We investigate the interplay of direct searches and precision observables for both CP-even and -odd couplings. In particular, precision measurements of exotic Z-decays, Higgs couplings, the exotic Higgs decay into a relaxion pair and associated $Z\varphi$ and $\gamma \varphi$ production are promising channels to yield strong bounds.

   hep-phJHEP(2018)·59 citations
6. 06*

   Comparing AdS/QCD and Sum Rules predictions for $B\to K^{\ast }\nu \bar{\nu }$

   Mohammad Ahmady🇨🇦 · Alexandre Leger🇨🇦 · Zoe McIntyre🇨🇦 · Alexander Morrison🇨🇦 · Ruben Sandapen🇨🇦

   Using the form factors obtained from holographic AdS/QCD and QCD sum rules, we predict the differential branching ratio and longitudinal polarization fraction for the rare $B\to K^{\ast }\nu \bar{\nu }$ decay. This is an interesting decay channel as it does not suffer from hadronic uncertainties beyond the form factors. We point out that the future measurement of the $B\to K^{\ast }\nu \bar{\nu }$ with around 30% accuracy can discriminate between the two models.

   hep-phPoS(2018)·0 citations
7. 07*

   Family Unification in Special Grand Unification

   Naoki Yamatsu🇯🇵

   We discuss family unification in grand unified theory (GUT) based on an $SU(19)$ GUT gauge group broken to its subgroups including a special subgroup. In the $SU(19)$ GUT on the six-dimensional (6D) orbifold space $M^4\times T^2/{\mathbb{Z}}_2$, three generations of the 4D SM Weyl fermions can be embedded into a 6D bulk Weyl fermions in an $SU(19)$ second-rank anti-symmetric tensor representation. 6D and 4D gauge anomalies can be canceled out by considering proper matter content without 4D exotic chiral fermions at low energies.

   hep-phhep-thPTEP(2018)·16 citations
8. 08*

   Exclusive diffractive vector meson production: A comparison between the dipole model and the leading twist shadowing approach

   Shashank Anand🇮🇳 · Tobias Toll🇮🇳

   With the imminent construction of an electron-ion collider in the USA, both saturation physics and nuclear shadowing physics will be important for the same processes for the first time. In particular for exclusive production of vector mesons, such as the J/$\psi$. In this paper we investigate the underlying assumptions commonly made when phenomenologically investigating this process from a shadowing and saturation perspective respectively. We use the bSat model which is commonly used to describe saturation physics, and a calculation by M.G. Ryskin which is commonly used when describing nuclear shadowing at leading twist. It is expected that the bSat model is equivalent to Ryskin's result in the hard scattering and non-relativistic limits. By explicitly taking these limits we show that the bSat model does indeed become equivalent to Ryskin's result. However, two more approximations are needed for this result. Firstly, the factorisation and renormalisation scales in the bSat model has to be independent of the dipole radius, and secondly, we need to omit a term in the overlap between the vector meson and virtual photon wave functions. We show that for the typical dipole radius of the J/$\psi$, the different approximations off-set each other and the bSat model agrees very well with Ryskin's calculation in hard-scattering and non-relativistic limits.

   hep-phPRC(2019)·4 citations
9. 09*

   Generalized linear sigma model with two glueballs

   Amir H. Fariborz🇺🇸 · Renata Jora🇷🇴

   We present a generalized linear sigma model that includes both scalar and pseudoscalar glueballs in addition to a quark-antiquark as well as a four-quark chiral nonet. Utilizing the axial and trace anomalies of QCD (at the effective mesonic level), we aim to develope the most general structure of the Lagrangian which can be used to study the interaction of quarkonia with glueballs. We then study the effect of scalar glueball on the vacuum of the model by considering a decoupling limit in which the glueball fields are decoupled from quarkonia. This determines the properties of the pure scalar glueball and builds a practical foundation for determining the model parameters when the interactions are turned on.

   hep-phnucl-thPRD(2018)·11 citations
10. 10*

    Comment on scalar glueball mass

    Amir H. Fariborz🇺🇸 · Renata Jora🇷🇴

    We study the interaction of scalar glueball with quark-antiquark and four-quark spinless meson fields within the framework of a generalized linear sigma model in which the trace anomaly of QCD is exactly realized. To determine the pure scalar glueball mass ($m_h$), we consider the decoupling limit in which the scalar glueball decouples from the meson fields. We find the exact relationship $m_h=2h_0$ where $h_0$ is the vacuum expectation value of the scalar glueball field independent of the properties of the framework used.

    hep-phhep-latnucl-thPLB(2019)·9 citations
11. 11*

    Neutrino Trident Scattering at Near Detectors

    Peter Ballett🇬🇧 · Matheus Hostert🇬🇧 · Silvia Pascoli🇬🇧 · Yuber F. Perez-Gonzalez🇧🇷 · Zahra Tabrizi🇧🇷 · Renata Zukanovich Funchal🇧🇷

    Neutrino trident scattering is a rare Standard Model process where a charged-lepton pair is produced in neutrino-nucleus scattering. To date, only the dimuon final-state has been observed, with around 100 total events, while the other channels are as yet unexplored. In this work, we compute the trident production cross section by performing a complete four-body phase space calculation for different hadronic targets. This provides a correct estimate both of the coherent and the diffractive contributions to these cross sections, but also allows us to address certain inconsistencies in the literature related to the use of the Equivalent Photon Approximation in this context. We show that this approximation can give a reasonable estimate only for the production of dimuon final-states in coherent scattering, being inadmissible for all other cases considered. We provide estimates of the number and distribution of trident events at several current and future near detector facilities subjected to intense neutrino beams from accelerators: five liquid-argon detectors (SBND, $\mu$BooNE, ICARUS, DUNE and $\nu$STORM), the iron detector of T2K (INGRID) and three detectors made of composite material (MINOS, NO$\nu$A and MINER$\nu$A). We find that for many experiments, trident measurements are an attainable goal and a valuable addition to their near detector physics programme.

    hep-phJHEP(2019)·80 citations
12. 12*

    Concavity of the meson Regge trajectories

    Jiao-Kai Chen🇨🇳

    It is illustrated by the fitted Regge trajectories for a large majority of mesons that both the radial and orbital Regge trajectories for mesons prefer being concave. The concavity of the meson Regge trajectories is model-independent. If the convex Regge trajectories or the Regge trajectories having the inflection points do not exist, the concavity can act as a criterion to choose a newly observed meson or to assign a particle to the unwell-established state. The curvature of the meson Regge trajectories can be taken as a guide in constructing models. The appropriate models should yield the spectra which can produce the concave Regge trajectories according to the concavity of the meson Regge trajectories. If the large majority of the meson Regge trajectories are concave while a few meson Regge trajectories are convex which neither have been confirmed nor have been completely excluded at present, many existing models should be corrected or even be reconstructed, which will lead to the further understanding of the meson dynamics.

    hep-phPLB(2018)·33 citations
13. 13*

    Linking infrared and ultraviolet parameters of pion-like states in strongly coupled gauge theories

    Sergey Troitsky🇷🇺 · Vadim Troitsky🇷🇺

    It has been shown previously that in a relativistic constituent-quark model, predictions for the electromagnetic form factor of the pi meson match not only experimental data but also, in the limit of large momentum transfers, the asymptotics derived from Quantum Chromodynamics (QCD). This is remarkable since no parameters are introduced to provide for this infrared-ultraviolet link. Here, we follow this approach, going beyond QCD. We obtain numerical relations between the gauge coupling constant, the decay constant and the charge radius of the pion-like meson in general strongly-coupled theories. These relations are compared to published lattice results for SU(2) gauge theory with two fermion flavours, and a good agreement is demonstrated. Further applications of the approach, to be explored elsewhere, include composite Higgs and dark-matter models.

    hep-phEPJC(2018)·1 citation
14. 14*

    Extending the Predictive Power of Perturbative QCD

    Bo-Lun Du🇨🇳 · Xing-Gang Wu🇨🇳 · Jian-Ming Shen🇨🇳 · Stanley J. Brodsky🇺🇸

    The predictive power of perturbative QCD (pQCD) depends on two important issues: (1) how to eliminate the renormalization scheme-and-scale ambiguities at fixed order, and (2) how to reliably estimate the contributions of unknown higher-order terms using information from the known pQCD series. The Principle of Maximum Conformality (PMC) satisfies all of the principles of the renormalization group and eliminates the scheme-and-scale ambiguities by the recursive use of the renormalization group equation to determine the scale of the QCD running coupling ${\alpha }_s$ at each order. Moreover, the resulting PMC predictions are independent of the choice of the renormalization scheme, satisfying the key principle of renormalization group invariance. In this letter, we show that by using the conformal series derived using the PMC single-scale procedure, in combination with the Padé Approximation Approach (PAA), one can achieve quantitatively useful estimates for the unknown higher-order terms from the known perturbative series. We illustrate this procedure for three hadronic observables $R_{e^{+}{e}^{-}}$, $R_{\tau }$, and $\Gamma (H\to b\bar{b})$ which are each known to 4 loops in pQCD. We show that if the PMC prediction for the conformal series for an observable (of leading order ${\alpha }_s^p$) has been determined at order ${\alpha }_s^n$, then the $[N/M]=[0/n-p]$ Padé series provides quantitatively useful predictions for the higher-order terms. We also show that the PMC + PAA predictions agree at all orders with the fundamental, scheme-independent Generalized Crewther relations which connect observables, such as deep inelastic neutrino-nucleon scattering, to hadronic $e^{+}{e}^{-}$ annihilation. Thus, by using the combination of the PMC series and the Padé method, the predictive power of pQCD theory can be greatly improved.

    hep-phhep-thEPJC(2019)·38 citations
15. 15*

    Photoproduction of $f_0(980)$ and $f_0(1500)$ resonances off a proton target

    Hanyang Xing🇨🇳 · Chun-Sheng An🇨🇳 · Ju-Jun Xie🇨🇳 · Gang Li🇨🇳

    We study the $\gamma p\to p{f}_0$ [$f_0(980)$ and $f_0(1500)$] reaction close to threshold within an effective Lagrangian approach. The production process is described by $s$-channel nucleon pole or $t$-channel $\rho$ and $\omega$ exchange. The $K^0{\bar{K}}^0$ invariant mass distributions of the $\gamma p\to f_0(980)p\to K^0{\bar{K}}^0$ and $\gamma p\to f_0(1500)p\to K^0{\bar{K}}^{0}p$ reactions are investigated, where the two kaons have been separated in $S$ wave decaying from $f_0(980)$ and $f_0(1500)$. It is shown that the $s$-channel process is favored for the production of $f_0(980)$, while for the $f_0(1500)$ production, the experimental measurements can be described quite well by the $t$-channel process. It is expected that the theoretical results can be tested by further experiments at CLAS.

    hep-phhep-exPRD(2018)·5 citations
16. 16*

    Model independent top quark width measurement using a combination of resonant and non resonant cross sections

    Alexey Baskakov🇷🇺 · Eduard Boos🇷🇺 · Lev Dudko🇷🇺

    Though top quark was discovered more than twenty years ago, measurement of its width is still challenging task. Most measurements either have rather low precision or they are done in assumption of the SM top quark interactions. We consider model independent parametrization of the top quark width and provide estimations on achievable accuracy using a combination of fiducial cross sections in double, single and non-resonant regions.

    hep-phPRD(2018)·20 citations
17. 17*

    Adding vacuum branching to jet evolution in a dense medium

    P. Caucal🇫🇷 · E. Iancu🇫🇷 · A.H. Mueller🇺🇸 · G. Soyez🇫🇷

    We study the fragmentation of a jet propagating in a dense quark-gluon plasma. We show that the "vacuum-like" emissions triggered by the parton virtualities can be factorized from the medium-induced radiation responsible for the energy loss within a controlled, "double-logarithmic", approximation in perturbative QCD. We show that the collisions with the plasma constituents modify the vacuum-like parton shower already at leading twist, in two ways: the radiation phase-space is reduced and the first emission outside the medium can violate angular ordering. We compute the jet fragmentation function and find results in qualitative agreement with measurements at the LHC.

    hep-phnucl-thNPA(2019)·0 citations
18. 18*

    Angular distributions in electroweak pion production off nucleons: odd parity hadron terms, strong relative phases and model dependence

    J.E. Sobczyk🇪🇸 · E. Hernández🇪🇸 · S.X. Nakamura🇧🇷 · J. Nieves🇪🇸 · T. Sato🇯🇵

    The study of pion production in nuclei is important for signal and background determinations in current and future neutrino oscillation experiments. The first step, however, is to understand the pion production reactions at the free nucleon level. We present an exhaustive study of the charged-current and neutral-current neutrino and antineutrino pion production off nucleons, paying a special attention to the angular distributions of the outgoing pion. We show, using general arguments, that parity violation and time-reversal odd correlations in the weak differential cross sections are generated from the interference between different contributions to the hadronic current that are not relatively real. Next, we present a detailed comparison of three, state of the art, microscopic models for electroweak pion production off nucleons, and we also confront their predictions with polarized electron data, as a test of the vector content of these models. We also illustrate the importance of carrying out a comprehensive test at the level of outgoing pion angular distributions, going beyond comparisons done for partially integrated cross sections, where model differences cancel to a certain extent. Finally, we observe that all charged and neutral current distributions show sizable anisotropies, and identify channels for which parity violating effects are clearly visible. Based on the above results, we conclude that the use of isotropic distributions for the pions in the center of mass of the final pion-nucleon system, as assumed by some of the Monte Carlo event generators, needs to be improved by incorporating the findings of microscopic calculations.

    hep-phhep-exnucl-exnucl-thPRD(2018)·40 citations
19. 19*

    Analyzing lepton flavor universality in the decays ${\Lambda }_b\to {\Lambda }_c^{(\ast )}({\frac{1}{2}}^{\pm },{\frac{3}{2}}^{-})+\ell {\bar{\nu }}_{\ell }$

    Thomas Gutsche🇩🇪 · Mikhail A. Ivanov🇷🇺 · Jürgen G. Körner🇩🇪 · Valery E. Lyubovitskij🇩🇪 · Pietro Santorelli🇮🇹 · Chien-Thang Tran🇮🇹

    Lepton flavor universality can be tested in the semileptonic decays ${\Lambda }_b\to {\Lambda }_c^{(\ast )}$ where ${\Lambda }_c^{(\ast )}$ denotes either the ground state ${\Lambda }_c(2286)$ (with $J^P=1/2^{+}$) or its orbital excitations ${\Lambda }_c(2595)$ (with $J^P=1/2^{-}$) and ${\Lambda }_c(2625)$ (with $J^P=3/2^{-}$). We calculate the differential decay rates as well as the branching fractions of these decays for both tauonic and muonic modes with form factors obtained from a covariant confined quark model previously developed by us. We present results for the rate ratios of the tauonic and muonic modes which provide important tests of lepton flavor universality in forthcoming experiments.

    hep-phhep-exPRD(2018)·38 citations
20. 20*

    Top quark polarization as a probe of charged Higgs bosons

    Abdesslam Arhrib🇲🇦 · Adil Jueid🇨🇳 · Stefano Moretti🇬🇧

    We study the production and decay of a heavy charged Higgs boson in the $bg\to t{H}^{-}$ and $H^{-}\to b\bar{t}$ processes at the Large Hadron Collider (LHC). We show that the chiral structure of the $H^{-}t\bar{b}$ vertex entering both stages is sensitive to the underlying Higgs mechanism of Electro-Weak Symmetry Breaking (EWSB) and we specifically demonstrate that one could distinguish between two popular realizations of a 2-Higgs Double Model (2HDM) embedding a new $H^{\pm }$ state, i.e., those with Type-I and -Y Yukawa couplings. The chiral structure of such a vertex, which is different in the two cases, in turn triggers a particular spin state of the top quark which is then transmitted to its decay products. Hence, both inclusive rates and exclusive observables can be used to extract the presence of such a charged Higgs boson state in LHC data.

    hep-phPRD(2018)·16 citations
21. 21*

    Effects of a non-zero strangeness-chemical potential in strong interaction models

    Ayon Mukherjee🇩🇪 · Abhijit Bhattacharyya🇮🇳 · Stefan Schramm🇩🇪

    The effect of a non-zero strangeness chemical potential on the strong interaction phase diagram has been studied within the framework of the SU(3) quark-hadron chiral parity-doublet model. Both, the nuclear liquid-gas and the chiral/deconfinement phase transitions are modified. The first-order line in the chiral phase transition is observed to vanish completely, with the entire phase boundary becoming a crossover. These changes in the nature of the phase transitions are expected to modify various susceptibilities, the effects of which might be detectable in particle-number distributions resulting from moderate-temperature and high-density heavy-ion collision experiments.

    hep-phPLB(2019)·8 citations
22. 22*

    Scrutinizing a massless dark photon: basis independence

    Jun-Xing Pan🇨🇳 · Min He🇨🇳 · Xiao-Gang He🇹🇼 · Gang Li🇹🇼

    A new $U(1{)}_X$ gauge boson field $X$ can have renormalizable kinetic mixing with the standard model (SM) $U(1{)}_Y$ gauge boson field $Y$. This mixing induces interactions of $X$ with SM particles even though $X$ starts as a dark photon without such interactions. If the $U(1{)}_X$ is not broken, both the dark photon field $X$ and the photon field $A$ are massless. One cannot determine which one of them is the physical dark photon or the photon by just looking at kinetic terms in the Lagrangian. We revisit this issue and show explicitly that when all contributions are included, all physical processes do not depend on which basis is used and the kinetic mixing effects do not show up in electromagnetic and weak interactions if only SM particles are involved in the calculations. On the other hand, the kinetic mixing provides a portal for probing the dark sector beyond the SM. We update constraints on the millicharged dark sector particles from the Lamb shift and lepton $g-2$ measurements.

    hep-phNPB(2020)·32 citations
23. 23*

    Sub-eikonal corrections to scattering amplitudes at high energy

    Giovanni Antonio Chirilli🇩🇪

    Most of the progress in high-energy Quantum Chromodynamics has been obtained within the eikonal approximation and infinite Wilson-line operators. Evolution equations of Wilson lines with respect to the rapidity parameter encode the dynamics of the hadronic processes at high energy. However, even at high energy many interesting aspects of hadron dynamics are not accessible within the eikonal approximation, the spin physics being an obvious example. The higher precision reached by the experiments and the possibility to probe spin dynamics at future Electron Ion Colliders make the study of deviations from eikonal approximation especially timely. In this paper I derive the sub-eikonal quark and gluon propagators which can serve as a starting point of studies of these effects.

    hep-phhep-thJHEP(2019)·100 citations
24. 24*

    Simplest Scoto-Seesaw Mechanism

    Nicolás Rojas🇨🇱 · Rahul Srivastava🇪🇸 · José W. F. Valle🇪🇸

    By combining the simplest (3,1) version of the seesaw mechanism containing a single heavy "right-handed" neutrino with the minimal scotogenic approach to dark matter, we propose a theory for neutrino oscillations. The "atmospheric" mass scale arises at tree level from the seesaw, while the "solar" oscillation scale emerges radiatively, through a loop involving the "dark sector" exchange. Such simple setup gives a clear interpretation of the neutrino oscillation lengths, has a viable WIMP dark matter candidate, and implies a lower bound on the neutrinoless double beta decay rate.

    hep-phPLB(2019)·71 citations
25. 25*

    Soft-drop event shapes in electron-positron annihilation at next-to-next-to-leading order accuracy

    Adam Kardos🇭🇺 · Gábor Somogyi🇭🇺 · Zoltán Trócsányi🇭🇺

    We present predictions for soft-drop event shapes of hadronic final states in electron-positron annihilation at next-to-next-to-leading order accuracy in perturbation theory obtained using the CoLoRFulNNLO subtraction method. We study the impact of the soft drop on the convergence of the perturbative expansion for the distributions of three event shape variables, the soft-drop thrust, the hemisphere jet and narrow jet invariant masses. We find that grooming generally improves perturbative convergence for these event shapes. This better perturbative stability, in conjunction with a reduced sensitivity to non-perturbative hadronization corrections makes soft-drop event shapes promising observables for the precise determination of the strong coupling at lepton colliders.

    hep-phPLB(2018)·37 citations
26. 26*

    Combined explanations of $(g-2{)}_{\mu ,e}$ and implications for a large muon EDM

    Andreas Crivellin🇨🇭 · Martin Hoferichter🇺🇸 · Philipp Schmidt-Wellenburg🇨🇭

    With the long-standing tension between experiment and Standard-Model (SM) prediction in the anomalous magnetic moment of the muon, $a_{\mu }=(g-2{)}_{\mu }/2$, at the level of 3-4$\sigma$, it is natural to ask if there could be a sizable effect in the electric dipole moment (EDM) $d_{\mu }$ as well. In this context it has often been argued that in UV complete models the electron EDM, which is very precisely measured, excludes a large effect in $d_{\mu }$. However, the recently observed 2.5$\sigma$ tension in $a_e=(g-2{)}_e/2$, if confirmed, requires that the muon and electron sectors effectively decouple to avoid constraints from $\mu \to e\gamma$. We briefly discuss UV complete models that possess such a decoupling, which can be enforced by an Abelian flavor symmetry $L_{\mu }-L_{\tau }$. We show that, in such scenarios, there is no reason to expect a correlation between the electron and muon EDM, so that the latter can be sizable. New limits on $d_{\mu }$ improved by up to two orders of magnitude are expected from the upcoming $(g-2{)}_{\mu }$ experiments at Fermilab and J-PARC. Beyond, a proposed dedicated muon EDM experiment at PSI could further advance the limit. In this way, future improved measurements of $a_e$, $a_{\mu }$, as well as the fine-structure constant $\alpha$ are not only set to provide exciting precision tests of the SM, but, in combination with EDMs, to reveal crucial insights into the flavor structure of physics beyond the SM.

    hep-phhep-exPRD(2018)·320 citations
27. 27*

    Accessing quark helicity in $e^{+}{e}^{-}$ and SIDIS via dihadron correlations

    Hrayr H. Matevosyan🇦🇺

    The correlation between the longitudinal polarization of a fragmenting quark and the transverse momenta of the produced hadrons was predicted over two decades ago. Nevertheless, experimental searches in the electron-positron annihilation process, both through the so-called jet handedness measurements by the {\tt SLD} Collaboration and more recently via the measurements of the azimuthal asymmetry containing the helicity-dependent dihadron fragmentation function (DiFF) by the $\text{BELLE}$ Collaboration, did not yield a signal. We will first discuss our recent explanation of the zero result at $\text{BELLE}$, and the two new methods for accessing the helicity-dependent DiFFs both in the electron-positron annihilation experiments, and in the semi-inclusive deep inelastic scattering (SIDIS) experiments with a longitudinally polarized target. We will also for the first time describe yet another, new method for accessing the helicity-dependent DiFFs in SIDIS using polarized beam asymmetry. Finally, we will present a new Monte Carlo calculation of the specific Fourier moments of the helicity-dependent DiFF entering in to the new asymmetries, performed within the extended quark-jet model, and compare the results to those for the interference DiFF.

    hep-phhep-exnucl-thPoS(2018)·4 citations
28. 28*

    The Sudakov radiator for jet observables and the soft physical coupling

    Andrea Banfi🇬🇧 · Basem Kamal El-Menoufi🇬🇧 · Pier Francesco Monni🇨🇭

    We present a procedure to calculate the Sudakov radiator for a generic recursive infrared and collinear (rIRC) safe observable in two-scale problems. We give closed formulae for the radiator at next-to-next-to-leading-logarithmic (NNLL) accuracy, which completes the general NNLL resummation for this class of observables in the {\tt ARES} method for processes with two emitters at the Born level. As a byproduct, we define a physical coupling in the soft limit, and we provide an explicit expression for its relation to the $\overline{\mathrm{MS}}$ coupling up to $\mathcal{O}({\alpha }_s^3)$. This physical coupling constitutes one of the ingredients for a NNLL accurate parton shower algorithm. As an application we obtain analytic NNLL results, of which several are new, for all angularities ${\tau }_x$ defined with respect to both the thrust axis and the winner-take-all axis, and for the moments of energy-energy correlation $F{C}_x$ in $e^{+}{e}^{-}$ annihilation. For the latter observables we find that, for some values of $x$, an accurate prediction of the peak of the differential distribution requires a simultaneous resummation of the logarithmic terms originating from the two-jet limit and at the Sudakov shoulder.

    hep-phJHEP(2019)·69 citations
29. 29*

    Conformal Realization of the Neutrino Option

    Vedran Brdar🇩🇪 · Yannick Emonds🇩🇪 · Alexander J. Helmboldt🇩🇪 · Manfred Lindner (MPIK Heidelberg)🇩🇪

    It was recently proposed that the electroweak hierarchy problem is absent if the generation of the Higgs potential stems exclusively from quantum effects of heavy right-handed neutrinos which can also generate active neutrino masses via the type-I seesaw mechanism. Hence, in this framework dubbed the "neutrino option", the tree-level scalar potential is assumed to vanish at high energies. Such a scenario therefore lends itself particularly well to be embedded in a classically scale-invariant theory. In this paper we perform a survey of models featuring conformal symmetry at the high scale. We find that the minimal framework compatible with the "neutrino option" requires the Standard Model to be extended by two real scalar singlet fields in addition to right-handed neutrinos. The spontaneous breaking of scale invariance, which induces the dynamical generation of Majorana masses for the right-handed neutrinos, is triggered by renormalization group effects. We identify the parameter space of the model for which a phenomenologically viable Higgs potential and neutrino masses are generated, and for which all coupling constants remain in the perturbative regime up to the Planck scale.

    hep-phhep-thPRD(2019)·43 citations
30. 30*

    Probing the Triple Higgs Self-Interaction at the Large Hadron Collider

    Jeong Han Kim🇺🇸 · Kyoungchul Kong🇺🇸 · Konstantin T. Matchev🇺🇸 · Myeonghun Park🇰🇷

    We propose a novel kinematic method to expedite the discovery of the double Higgs ($hh$) production in the ${\ell }^{+}{\ell }^{-}b\bar{b}+E_T/$ final state. We make full use of recently developed kinematic variables, as well as the variables $Topness$ for the dominant background (top quark pair production) and $Higgsness$ for the signal. We obtain a significant increase in sensitivity compared to the previous analyses which used sophisticated algorithms like boosted decision trees or neutral networks. The method can be easily generalized to resonant $hh$ production as well as other non-resonant channels.

    hep-phPRL(2019)·46 citations
31. 31*

    Higgs boson production at the LHC using the $q_T$ subtraction formalism at N${}^3$LO QCD

    Leandro Cieri🇮🇹 · Xuan Chen🇨🇭 · Thomas Gehrmann🇨🇭 · E.W.N. Glover🇬🇧 · Alexander Huss🇨🇭

    We consider higher-order QCD corrections to Higgs boson production through gluon-gluon fusion in the large top quark mass limit in hadron collisions. We extend the transverse-momentum ($q_T$) subtraction method to next-to-next-to-next-to-leading order (N${}^3$LO) and combine it with the NNLO Higgs-plus-jet calculation to numerically compute differential infrared-safe observables at N${}^3$LO for Higgs boson production in gluon fusion. To cancel the infrared divergences, we exploit the universal behaviour of the associated $q_T$ distributions in the small-$q_T$ region. We document all the necessary ingredients of the transverse-momentum subtraction method up to N${}^3$LO. The missing third order collinear functions, which contribute only at $q_T$ =0, are approximated using a prescription which uses the known result for the total Higgs boson cross section at this order. As a first application of the third-order $q_T$ subtraction method, we present the N${}^3$LO rapidity distribution of the Higgs boson at the LHC.

    hep-phJHEP(2019)·138 citations
32. 32*

    Direct $CP$ violation from isospin symmetry breaking effects in PQCD

    Gang Lü🇨🇳 · Qin-Qin Zhi🇨🇳

    We investigate the direct $CP$ violation for the decay process of ${\bar{B}}_s\to P(V){\pi }^0$ (P,V refer to the pseudoscalar meson and vector meson, respectively) via isospin symmetry breaking effects from the ${\pi }^0-\eta -{\eta }^{\prime }$ mixing mechanism in PQCD factorization approach. Isospin symmetry breaking arises from the electroweak interaction and the u-d quark mass difference by the strong interaction which are known to be tiny. However, we find that isospin symmetry breaking at the leading order shifts the $CP$ violation due to the new strong phases.

    hep-phAdv.High Energy Phys.(2019)·2 citations
33. 33*

    Heavy $P$-wave quarkonium production via Higgs decays

    Qi-Li Liao🇨🇳 · Ya Deng🇨🇳 · Yan Yu🇨🇳 · Guang-Chuan Wang🇨🇳 · Guo-Ya Xie🇨🇳

    The production of the heavy quarkonium, i.e., $|(c\bar{b})[n]⟩$ (or $|(b\bar{c})[n]⟩$), $|(c\bar{c})[n]⟩$, and $|(b\bar{b})[n]⟩$- quarkonium [$|(Q\overline{Q^{\prime }})[n]⟩$-quarkonium for short], through Higgs $H^0$ boson semiexclusive decays is evaluated within the NRQCD framework, where $[n]$ stands for the production of the two color-singlet $S$-wave states, $|(Q\overline{Q^{\prime }}){[}^1{S}_0{]}_{\text{1}}⟩$ and $|(Q\overline{Q^{\prime }}){[}^3{S}_1{]}_{\text{1}}⟩$, the production of the four color-singlet $P$-wave states, i.e., $|(Q\overline{Q^{\prime }}){[}^1{P}_0{]}_{\text{1}}⟩$, $|(Q\overline{Q^{\prime }}){[}^3{P}_J{]}_{\text{1}}⟩$ (with $J=[0,1,2]$). Moreover, according to the velocity scaling rule of the NRQCD, the production of the two color-octet components, $|(Q\overline{Q^{\prime }})g{[}^1{S}_0{]}_{\text{8}}⟩$ and $|(Q\overline{Q^{\prime }})g{[}^3{S}_1{]}_{\text{8}}⟩$, are also taken into account. The "improved trace technology" to derive the simplified analytic expressions at the amplitude level is adopted, which shall be useful for dealing with these decay channels. If all higher heavy quarkonium states decay completely to the ground states, it should be obtained $\Gamma (H^0\to |(c\bar{b}){[}^1{S}_0{]}_{\text{1}}⟩)=15.14$ KeV, $\Gamma (H^0\to |(c\bar{c}){[}^1{S}_0{]}_{\text{1}}⟩)=1.547$ KeV, and $\Gamma (H^0\to |(b\bar{b}){[}^1{S}_0{]}_{\text{1}}⟩)=1.311$ KeV. The production of $5.6\times 10^5$ Bc meson, $4.7\times 10^4$ charmonium meson, and $4.9\times 10^4$ bottomonium meson per year in Higgs decays at the HE/HL-LHC can be obtained.

    hep-phPRD(2018)·19 citations
34. 34*

    Entropic Leggett-Garg inequality in neutrinos and B (K) meson systems

    Javid Naikoo🇮🇳 · Subhashish Banerjee🇮🇳

    Entropic Leggett-Garg inequality is studied in systems like neutrinos in the context of two and three flavor neutrino oscillations and in neutral $B_d$, $B_s$ and $K$ mesons. The neutrino dynamics is described with the matter effect taken into consideration. For the decohering $B/K$ meson systems, the effect of decoherence and CP violation have also been taken into account, using the techniques of open quantum systems. Enhancement in the violation with increase in the number of measurements has been found, in consistency with findings in spin-$s$ systems. The effect of decoherence is found to bring the deficit parameter ${\mathcal{D}}^{[n]}$ closer to its classical value zero, as expected. The violation of entropic Leggett-Garg inequality lasts for a much longer time in $K$ meson system than in $B_d$ and $B_s$ systems.

    hep-phEPJC(2018)·12 citations
35. 35*

    Moments of Ioffe time parton distribution functions from non-local matrix elements

    Joseph Karpie🇺🇸 · Kostas Orginos🇺🇸 · Savvas Zafeiropoulos🇩🇪

    We examine the relation of moments of parton distribution functions to matrix elements of non-local operators computed in lattice quantum chromodynamics. We argue that after the continuum limit is taken, these non-local matrix elements give access to moments that are finite and can be matched to those defined in the $\overline{MS}$ scheme. We demonstrate this fact with a numerical computation of moments through non-local matrix elements in the quenched approximation and we find that these moments are in excellent agreement with the moments obtained from direct computations of local twist-2 matrix elements in the quenched approximation.

    ↳ hep-lathep-phJHEP(2018)·126 citations
36. 36*

    Flavour anomalies: a review

    Elena Graverini🇨🇭

    The concept of lepton flavour universality (LFU), according to which the three lepton families are equivalent except for their masses, is a cornerstone prediction of the Standard Model (SM). LFU can be violated in models beyond the SM by new physics particles that couple preferentially to certain generations of leptons. In the last few years, hints of LFU violation have been observed in both tree-level $b\to c\ell \nu$ and loop-level $b\to s\ell \ell$ transitions. These measurements, combined with the tensions observed in angular observables and branching fractions of rare semileptonic $b$ decays, point to a coherent pattern of anomalies that could soon turn into the first observation of physics beyond the SM. These proceedings review the anomalies seen by the LHC experiments and the $B$ factories, and give an outlook for the near future.

    ↳ hep-exhep-phJ.Phys.Conf.Ser.(2019)·51 citations
37. 37*

    Tighter Limits on Dark Matter Explanations of the Anomalous EDGES 21cm Signal

    Ely D. Kovetz🇺🇸 · Vivian Poulin🇺🇸 · Vera Gluscevic🇺🇸 · Kimberly K. Boddy🇺🇸 · Rennan Barkana🇮🇱 · Marc Kamionkowski🇺🇸

    We investigate the hypothesis that Coulomb-type interactions between dark matter (DM) and baryons explain the anomalously low 21cm brightness-temperature minimum at redshift z ~ 17 that was recently measured by the EDGES experiment. In particular, we reassess the validity of the scenario where a small fraction of the total DM is millicharged, focusing on newly derived constraints from Planck 2015 cosmic microwave background (CMB) data. Crucially, the CMB power spectrum is sensitive to DM-baryon scattering if the fraction of interacting DM is larger than (or comparable to) the fractional uncertainty in the baryon energy density. Meanwhile, there is a mass-dependent lower limit on the fraction for which the required interaction to cool the baryons sufficiently is so strong that it drives the interacting-DM temperature to the baryon temperature prior to their decoupling from the CMB. If this occurs as early as recombination, the cooling saturates. We precisely determine the viable parameter space for millicharged DM, and find that only a fraction (m_chi/MeV) 0.0115% <~ f <~ 0.4% of the entire DM content, and only for DM-particle masses between 0.5 MeV - 35 MeV, can be charged at the level needed to marginally explain the anomaly, without violating limits from SLAC, CMB, Big-Bang nucleosynthesis (BBN), or stellar and SN1987A cooling. In reality, though, we demonstrate that at least moderate fine tuning is required to both agree with the measured absorption profile and overcome various astrophysical sources of heating. Finally, we point out that a ~0.4% millicharged DM component which is tightly coupled to the baryons at recombination may resolve the current 2-sigma tension between the BBN and CMB determinations of the baryon energy density. Future CMB-S4 measurements will be able to probe this scenario directly.

    ↳ astro-ph.COhep-phhep-thPRD(2018)·199 citations
38. 38*

    Femtolensing by Dark Matter Revisited

    Andrey Katz🇨🇭 · Joachim Kopp🇩🇪 · Sergey Sibiryakov🇨🇭 · Wei Xue🇨🇭

    Femtolensing of gamma ray bursts (GRBs) has been put forward as an exciting possibility to probe exotic astrophysical objects with masses below $10^{-13}$ solar masses such as small primordial black holes or ultra-compact dark matter minihalos, made up for instance of QCD axions. In this paper we critically review this idea, properly taking into account the extended nature of the source as well as wave optics effects. We demonstrate that most GRBs are inappropriate for femtolensing searches due to their large sizes. This removes the previous femtolensing bounds on primordial black holes, implying that vast regions of parameter space for primordial black hole dark matter are not robustly constrained. Still, we entertain the possibility that a small fraction of GRBs, characterized by fast variability can have smaller sizes and be useful. However, a large number of such bursts would need to be observed to achieve meaningful constraints. We study the sensitivity of future observations as a function of the number of detected GRBs and of the size of the emission region.

    ↳ astro-ph.COastro-ph.HEhep-phJCAP(2018)·307 citations
39. 39*

    Gradient resummation for nonlinear chiral transport: an insight from holography

    Yanyan Bu🇨🇳 · Tuna Demircik🇮🇱 · Michael Lublinsky🇮🇱

    Nonlinear transport phenomena induced by chiral anomaly are explored within a 4D field theory defined holographically as $U(1{)}_V\times U(1{)}_A$ Maxwell-Chern-Simons theory in Schwarzschild-$Ad{S}_5$. In presence of weak constant background electromagnetic fields, the constitutive relations for vector and axial currents, resummed to all orders in the gradients of charge densities, are encoded in nine momenta-dependent transport coefficient functions (TCFs). These TCFs are first calculated analytically up to third order in gradient expansion, and then evaluated numerically beyond the hydrodynamic limit. Fourier transformed, the TCFs become memory functions. The memory function of the chiral magnetic effect (CME) is found to differ dramatically from the instantaneous response form of the original CME. Beyond hydrodynamic limit and when external magnetic field is larger than some critical value, the chiral magnetic wave (CMW) is discovered to possess a discrete spectrum of non-dissipative modes.

    ↳ hep-thhep-phnucl-thEPJC(2019)·10 citations
40. 40*

    A Critical Assessment of CMB Limits on Dark Matter-Baryon Scattering: New Treatment of the Relative Bulk Velocity

    Kimberly K. Boddy🇺🇸 · Vera Gluscevic🇺🇸 · Vivian Poulin🇺🇸 · Ely D. Kovetz🇺🇸 · Marc Kamionkowski🇺🇸 · Rennan Barkana🇮🇱

    We perform an improved cosmic microwave background (CMB) analysis to search for dark matter-proton scattering with a momentum-transfer cross section of the form ${\sigma }_0{v}^n$ for $n=-2$ and $n=-4$. In particular, we present a new and robust prescription for incorporating the relative bulk velocity between the dark matter and baryon fluids into the standard linear Boltzmann calculation. Using an iterative procedure, we self-consistently include the effects of the bulk velocities in a cosmology in which dark matter interacts with baryons. With this prescription, we derive CMB bounds on the cross section, excluding ${\sigma }_0>2.3\times 10^{-33}{\mathrm{cm}}^2$ for $n=-2$ and ${\sigma }_0>1.7\times 10^{-41}{\mathrm{cm}}^2$ for $n=-4$ at $95\%$ confidence, for dark matter masses below 10 MeV. Furthermore, we investigate how these constraints change when only a subcomponent of dark matter is interacting. We show that Planck limits vanish if $\lesssim 0.4\%$ of dark matter is tightly coupled to baryons. We discuss the implications of our results for present and future cosmological observations.

    ↳ astro-ph.COhep-phPRD(2018)·189 citations
41. 41*

    A vector meson dominance model for pions

    G. B. Tupper🇿🇦

    A renormalizable non-abelian vector meson dominance model coupled to pions is constructed which exhibits a $\mathrm{SO}\left(4,3\right)$ vacuum symmetry. Tree-level predictions for $p$-$p$ scattering lengths and slopes at leading order are in reasonable agreement with experiment.

    ↳ physics.gen-phhep-ph0 citations

* 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.