Tue·Dec 17, 2019Tuesday·December 17, 2019

1. 01*

   Determining the lifetime of long-lived particles at the HL-LHC

   Shankha Banerjee🇬🇧 · Biplob Bhattacherjee🇮🇳 · Andreas Goudelis🇫🇷 · Björn Herrmann🇫🇷 · Dipan Sengupta🇺🇸 · Rhitaja Sengupta🇮🇳

   We examine the capacity of the Large Hadron Collider to determine the mean proper lifetime of long-lived particles assuming different decay final states. We mostly concentrate on the high luminosity runs of the LHC, and therefore, develop our discussion in light of the high amount of pile-up and the various upgrades for the HL-LHC runs. We employ model-dependent and model-independent methods in order to reconstruct the proper lifetime of neutral long-lived particles decaying into displaced leptons, potentially accompanied by missing energy, as well as charged long-lived particles decaying ihnto leptons and missing energy. We also present a discussion for lifetime estimation of neutral long-lived particles decaying into displaced jets, along with the challenges in the high PU environment of HL-LHC. After a general discussion, we illustrate and discuss these methods using several new physics models. We conclude that the lifetime can indeed be reconstructed in many concrete cases. Finally, we discuss to which extent including timing information, which is an important addition in the Phase-II upgrade of CMS, can improve such an analysis.

   hep-phEPJC(2021)·23 citations
2. 02*

   The leading jet transverse momentum in inclusive jet production and with a loose jet veto

   Darren J. Scott🇳🇱 · Wouter J. Waalewijn🇳🇱

   We study the transverse momentum of the leading jet in the limit where the jet radius is small, $R\ll 1$. We introduce the leading-jet function to calculate this cross section for an inclusive jet sample, and the subleading-jet function when a loose veto on additional jets is imposed, i.e. $p_{T,J}\gtrsim p_T^{\mathrm{veto}}$. These jet functions are calculated at next-to-leading order in QCD and the resummation of jet radius logarithms is explored. We present phenomenological results for Higgs + 1 jet production, for both the jet and Higgs transverse momentum distribution. We find that, while the $R\ll 1$ limit of the cross section provides a good description of the full NLO result, even for values as large as $R=0.8$, simply retaining the leading logarithm at this order does not. Indeed, the NLO contribution to the hard function and, to a lesser extent, non-logarithmic corrections to the jet function are sizable and must be included to obtain the correct cross section. In the inclusive cross section we find that the ${\alpha }_s^2{\ln }^{2}R$ corrections are several precent, while in exclusive cross sections at large $p_{T,J}$ and small $R$ they can reach 20%. However, it is not clear how important the resummation of these logarithms is, given the presence of other large corrections at NNLO.

   hep-phJHEP(2020)·12 citations
3. 03*

   Self-interacting dark matter without prejudice

   Nicolás Bernal🇨🇴 · Xiaoyong Chu🇦🇹 · Suchita Kulkarni🇦🇹 · Josef Pradler🇦🇹

   The existence of dark matter particles that carry phenomenologically relevant self-interaction cross sections mediated by light dark sector states is considered to be severely constrained through a combination of experimental and observational data. The conclusion is based on the assumption of specific dark matter production mechanisms such as thermal freeze-out together with an extrapolation of a standard cosmological history beyond the epoch of primordial nucleosynthesis. In this work, we drop these assumptions and examine the scenario from the perspective of the current firm knowledge we have: results from direct and indirect dark matter searches and cosmological and astrophysical observations, without additional assumptions on dark matter genesis or the thermal state of the very early universe. We show that even in the minimal set-up, where dark matter particles self-interact via a kinetically mixed vector mediator, a significant amount of parameter space remains allowed. Interestingly, however, these parameter regions imply a meta-stable, light mediator, which in turn calls for modified search strategies.

   hep-phastro-ph.HEPRD(2020)·45 citations
4. 04*

   A new approach to search for free neutron-antineutron oscillations using coherent neutron propagation in gas

   V. Gudkov🇺🇸 · V. V. Nesvizhevsky🇫🇷 · K. V. Protasov🇫🇷 · W. M. Snow🇺🇸 · A. Yu. Voronin🇷🇺

   Coherent forward neutron propagation in gas is discussed as a new approach to search for neutron-antineutron oscillations ($n-\bar{n}$), which violate both $B$ and $B-L$ conservation. We show that one can increase the probability of neutron - antineutron transitions to essentially the free neutron oscillation rate in the presence of a nonzero external magnetic field by tuning the density of an appropriate mixture of gases so that the neutron optical potential of the gas cancels that from an external magnetic field.

   hep-phnucl-thPLB(2020)·21 citations
5. 05*

   Implication of $b\to c\tau \nu$ flavor anomalies on $B_s\to D_s^{\ast }\tau \nu$ decay observables

   Nilakshi Das🇮🇳 · Rupak Dutta🇮🇳

   The experimental predictions of $R_D$, $R_{D^{\ast }}$, $R_{J/\psi }$, $P_{\tau }^{D^{\ast }}$ and $F_L^{D^{\ast }}$ in $B$ decays mediated via $b\to cl\nu$ quark level transition deviate significantly from the standard model expectations. The current world average of the ratio of branching ratios $R_D$ and $R_{D^{\ast }}$ in $B\to D^{(\ast )}l\nu$ ($l\in e,\tau$) show $1.4\sigma$ and $2.5\sigma$ deviation from the SM expectations. Similarly, the $\tau$ polarization fraction $P_{\tau }^{D^{\ast }}$ and the longitudinal polarization fraction of the $D^{\ast }$ meson $F_L^{D^{\ast }}$ in $B\to D^{\ast }\tau \nu$ are found to deviate from the standard model expectations at $1.6\sigma$ and $1.5\sigma$ level, respectively. In addition, the ratio of branching ratio $R_{J/\psi }$ in $B_c\to J/\psi l\nu$ deviates from the standard model prediction at $2\sigma$ level. In this regard, we study the implication of $R_D$, $R_{D^{\ast }}$, $R_{J/\psi }$, $P_{\tau }^{D^{\ast }}$, and $F_L^{D^{\ast }}$ anomalies on $B_s\to D_s^{\ast }\tau \nu$ decay observables in a model independent effective field theory formalism. We give predictions of several physical observables in the standard model and in the presence of various $1D$ and $2D$ new physics scenarios.

   hep-phJ.Phys.G(2020)·15 citations
6. 06*

   Electroweak Radiative Corrections for Collider Physics

   Ansgar Denner🇩🇪 · Stefan Dittmaier🇩🇪

   Current particle phenomenology is characterized by the spectacular agreement of the predictions of the Standard Model of particle physics (SM) with all results from collider experiments and by the absence of significant signals of non-standard physics, despite the fact that we know that the SM cannot be the ultimate theory of nature. In this situation, confronting theory and experiment with high precision is a promising direction to look for potential traces of physics beyond the SM. On the theory side, the calculation of radiative corrections of the strong and electroweak interactions is at the heart of this task, a field that has seen tremendous conceptual and technical progress in the last decades. This review aims at a coherent introduction to the field of electroweak corrections and tries to fill gaps in the literature between standard textbook knowledge and the current state of the art. The SM and the machinery for its perturbative evaluation are reviewed in detail, putting particular emphasis on renormalization, on one-loop techniques, on modern amplitude methods and tools, on the separation of infrared singularities in real-emission corrections, on electroweak issues connected with hadronic initial or final states in collisions, and on the issue of unstable particles in quantum field theory together with corresponding practical solutions.

   hep-phPhys.Rept.(2020)·291 citations
7. 07*

   Q-ball decay through A-term in the gauge-mediated SUSY breaking scenario

   Masahiro Kawasaki🇯🇵 · Hiromasa Nakatsuka🇯🇵

   Q-balls are non-topological solitons whose classical stability is ensured by a global $U(1)$ charge. In particular, Q-balls are produced in the framework of the Affleck-Dine baryogenesis where $U(1)$ charge is the baryon number. Since some type of Q-balls is stable against quantum decay into nucleons, it can work as the dark matter. When the dark matter Q-balls are captured into the neutron star, they absorb the surrounding neutrons and grow to consume all the neutrons, which leads to a stringent constraint on the Q-ball dark matter. However, the Q-ball growth stops due to the $U(1)$ breaking A-term. We revisit the constraint by the neutron star for the gauge-mediation type and the new type Q-ball, and find the allowed parameter space, in which Q-balls work as the dark matter.

   hep-phastro-ph.COJCAP(2020)·15 citations
8. 08*

   Finite temperature properties of a modified Polyakov$-$Nambu$-$Jona-Lasinio model

   Abhijit Bhattacharyya🇮🇳 · Paramita Deb🇮🇳 · Sanjay K. Ghosh🇮🇳 · Soumitra Maity🇮🇳 · Sibaji Raha🇮🇳 · Rajarshi Ray🇮🇳 · Kinkar Saha🇮🇳 · Sudipa Upadhaya🇮🇳

   Thermodynamic properties of strongly interacting matter are investigated using the Polyakov loop enhanced Nambu$-$Jona-Lasinio model along with some modifications to include the hadrons. Various observables are shown to have a close agreement with the numerical data of QCD on lattice. The advantage of the present scheme over a similar study using a switching function is that here no extra parameters are to be fitted. As a result the present scheme can be easily extended for finite chemical potentials.

   hep-phPRD(2020)·10 citations
9. 09*

   Threshold cusps and triangle singularities in hadronic reactions

   Feng-Kun Guo🇨🇳 · Xiao-Hai Liu🇨🇳 · Shuntaro Sakai🇨🇳

   The spectrum of hadrons is the manifestation of color confinement of quantum chromodynamics. Hadronic resonances correspond to poles of the S-matrix. Since 2003, lots of new hadron resonant structures were discovered in the mass regions from light mesons to hadrons containing a pair of a heavy quark and an antiquark. Many of them are candidates of exotic hadrons, and they are usually observed as peaks in invariant mass distributions. However, the S-matrix also has kinematical singularities due to the on-shellness of intermediate particles for a process, such as two-body thresholds and triangle singularities, and they can produce peaks as well. On the one hand, such singularities may be misidentified as resonances; on the other hand, they can be used as tools for precision measurements. In this paper, we review the threshold cusps and various triangle singularities in hadronic reactions, paying attention to their manifestations in phenomena related to exotic hadron candidates.

   hep-phhep-exnucl-thPPNP(2020)·381 citations
10. 10*

    Quantum evolution of quarkonia with correlated and uncorrelated noise

    Rishi Sharma🇮🇳 · Anurag Tiwari🇮🇳

    In the quark-gluon plasma (QGP), it is well known that the evolution of quarkonia is affected by the screening of the interaction between the quark and the anti-quark. In addition, exchange of energy and color with the surrounding medium can be included via the incorporation of noise terms in the evolution Hamiltonian. For noise correlated locally in time, these dynamics have been studied in a simple setting by Kajimoto et al.[PHYS. REV. D 97, 014003(2018)]. We extend this calculation by considering non-Abelian dynamics for a three-dimensional wavefunction. We also propose a modification of the noise correlation, allowing it to have a finite correlation in time with the motivation to include long-lived gluonic correlations. We find that in both cases the results differ significantly from solutions of rate equations.

    hep-phPRD(2020)·44 citations
11. 11*

    Shape analysis in Higgs boson pair production

    Matteo Capozi🇩🇪 · Gudrun Heinrich🇩🇪

    We study the impact of anomalous couplings in the Higgs sector on the shape of the Higgs boson pair invariant mass distribution at NLO. Our analysis is based on a five-dimensional coupling parameter space relevant for Higgs boson pair production in gluon fusion, in the framework of a non-linear Effective Field Theory. In particular, we present a clustering procedure into certain shape types based on unsupervised machine learning, with the aim to infer information about the underlying parameter space from a given shape type.

    hep-phPoS(2019)·0 citations
12. 12*

    Systematic study on production of hidden-bottom pentaquark via $\gamma p$ and ${\pi }^{-}p$ scatterings

    Xiao-Yun Wang🇨🇳 · Jun He🇨🇳 · Xurong Chen🇨🇳

    The production of hidden-bottom pentaquark $P_b$ states via $\gamma p$ and ${\pi }^{-}p$ scatterings is studied within an effective Lagrangian approach and the vector-meson-dominance mechnism. For the $P_b$ production in the process $\gamma p\to {\rm Y}p$, the dipole Pomeron model is employed to calculate the background contribution, and the experimental data can be well described. For the process ${\pi }^{-}p\to {\rm Y}n$, the Reggeized $t$-channel with $\pi$ exchange is considered as the main background for the $P_b$ production. Near the threshold, two-peak structure from the states P_{b (11080) and $P_b(11125)$ can be observed if energy bin width is chosen as 0.01 GeV, and the same result is obtained in the ${\pi }^{-}p$ scattering. Moreover, by taking the branching ratio of Br$[P_b\to \pi N]\simeq 0.05\%$, the numerical result shows that the average value of cross section from the $P_b(11080)$ state produced in the $\gamma p$ or ${\pi }^{-}p$ scattering reaches at least 0.1 nb with a bin of 0.1 GeV. Even if we reduce the branching ratio of the $P_b$ state into $\pi N$ channel by one order, the theoretical average of the cross section from $P_b(11080)$ production in ${\pi }^{-}p$ scattering can reach the order of 0.01 nb with a bin of 0.1 GeV, which means that the signal can still be clearly distinguished from the background. The experimental measurements and studies on the hidden-bottom pentaquark $P_b$ state production in the $\gamma p$ or ${\pi }^{-}p$ scattering near-threshold energy region around $W\simeq 11$ GeV are strongly suggested, which are accessible at COMPASS and JPARC. Particularly, the result of the photoproduction suggests that it is very promising to observe the hidden-bottom pentaquark at proposed EicC facility in China.

    hep-phhep-exnucl-exnucl-thPRD(2020)·21 citations
13. 13*

    Can the state $Y(4626)$ be a $P$-wave tetraquark state $[cs][\bar{c}\bar{s}]$?

    Chengrong Deng🇨🇳 · Hong Chen🇨🇳 · Jialun Ping🇨🇳

    Stimulated by the state $Y(4626)$ recently reported by Belle Collaboration, we utilize a multiquark color flux-tube model with a multibody confinement potential and one-glue-exchange interaction to make an exhaustive investigation on the diquark-antidiquark state $[cs][\bar{c}\bar{s}]$. Numerical results indicate that the appearance of the states $[cs][\bar{c}\bar{s}]$ like a dumb-bell, the larger the orbital excitation $L$, the more distinguished the shape. The mixing of the color configurations ${\left[[cs{]}_{{\bar{3}}_c}[\bar{c}\bar{s}{]}_{3_c}\right]}_1$ and ${\left[[cs{]}_{6_c}[\bar{c}\bar{s}{]}_{{\bar{6}}_c}\right]}_1$ in the ground states is strong while the color configuration ${\left[[cs{]}_{{\bar{3}}_c}[\bar{c}\bar{s}{]}_{3_c}\right]}_1$ is absolutely predominant in the excited states. The main component of the state $Y(4626)$ can be interpreted as a $P$-wave state $[cs][\bar{c}\bar{s}]$. Its hidden-bottom partner is predicted in the model calculation. The states $X(4140)$, $X(4274)$, $X(4350)$, $X(4500)$ and $X(4700)$ are also discussed.

    hep-phPRD(2020)·24 citations
14. 14*

    Leptogenesis in fast expanding Universe

    Shao-Long Chen🇨🇳 · Amit Dutta Banik🇨🇳 · Ze-Kun Liu (CCNU, Wuhan, Inst. Part. Phys.)🇨🇳

    With the consideration of a fast expanding Universe in effect due to an additional scalar field, we present a study of leptogenesis in non-standard cosmology. The Hubble expansion rate is modified by the new added scalar field $\phi$, which can change the abundance of lepton asymmetry resulted by the leptogenesis mechanism. We report a significant deviation from the standard unflavored leptogenesis scenario can be achieved in presence of the scalar field $\phi$ that dominates the energy budget of the early Universe. We present our results for leptogenesis from type-I seesaw with heavy right-handed Majorana neutrinos. The results are based on Boltzmann equations and effects of the scalar field are similar for other kinds of leptogenesis framework.

    hep-phJCAP(2020)·31 citations
15. 15*

    The Electroweak Phase Transition: A Collider Target

    Michael J. Ramsey-Musolf🇨🇳

    Determining the thermal history of electroweak symmetry breaking (EWSB) is an important challenge for particle physics and cosmology. Lattice simulations indicate that EWSB in the Standard Model (SM) occurs through a crossover transition, while the presence of new physics beyond the SM could alter this thermal history. The occurrence of a first order EWSB transition would be particularly interesting, providing the needed pre-conditions for generation of the cosmic matter-antimatter asymmetry and sources for potentially observable gravitational radiation. I provide simple, generic arguments that if such an alternate thermal history exists, the new particles involved cannot be too heavy with respect to the SM electroweak temperature, nor can they interact too feebly with the SM Higgs boson. These arguments do not rely on the decoupling limit. I derive corresponding quantitative expectations for masses and interaction strengths which imply that their effects could in principle be observed (or ruled out) by prospective next generation high energy colliders. The simple, generic arguments provide a quantitative, parametric understanding of results obtained in a wide range of explicit model studies; relate them explicitly to the electroweak temperature; and delineate broad contours of collider phenomenology pertaining to a non-standard history of EWSB.

    hep-phJHEP(2020)·140 citations
16. 16*

    Triply-charmed dibaryon states or two-baryon scattering states from the QCD sum rules?

    Zhi-Gang Wang🇨🇳

    In this article, we construct the color-singlet-color-singlet type currents to study the scalar and axialvector ${\Xi }_{cc}{\Sigma }_c$ dibaryon states with QCD sum rules in details by taking into account both the dibaryon states and two-baryon scattering sates at the hadron side, and examine the existence of the ${\Xi }_{cc}{\Sigma }_c$ dibaryon states. Our calculations indicate that the two-baryon scattering states cannot saturate the QCD sum rules, it is necessary to introduce the dibaryon states, the color-singlet-color-singlet type currents couple potentially to the molecular states, not to the two-particle scattering states, the molecular states begin to receive contributions at the order $\mathcal{O}({\alpha }_s^0)$, not at the order $\mathcal{O}({\alpha }_s^2)$.

    hep-phPRD(2020)·25 citations
17. 17*

    Signatures of ${\tilde{R}}_2$ class of Leptoquarks at the upcoming $ep$ colliders

    Rojalin Padhan🇮🇳 · Sanjoy Mandal🇮🇳 · Manimala Mitra🇮🇳 · Nita Sinha🇮🇳

    We explore the signatures of the ${\tilde{R}}_2$ class of leptoquark (LQ) models at the proposed $e^{-}p$ and $e^{+}p$ colliders. We carry out an analysis for the proposed colliders LHeC and FCC-eh with center of mass (c.m.) energy 1.3 TeV and 3.46 TeV, respectively. For ${\tilde{R}}_2$ class of LQ models, there are a number of final states that can arise from LQ production and its subsequent decay. In this report we do a detailed cut-based analysis for the $l^{\pm }j$ final state. We also discuss the effect of polarized electron and positron beams on LQ production and in turn on $l^{\pm }j$ production. At LHeC, the final state $l^{+}j$ has very good discovery prospect. We find that, only 100 ${\text{fb}}^{-1}$ of data can probe LQ mass upto 1.2 TeV with $5\sigma$ significance, even with a generic set of cuts. On the contrary, at FCC-eh, one can probe LQ masses upto 2.2 TeV (for $e^{-}$ beam) and 3 TeV (for $e^{+}$ beam), at more than $5\sigma$ significance with luminosity $1000{\text{fb}}^{-1}$ and $500{\text{fb}}^{-1}$, respectively.

    hep-phPRD(2020)·26 citations
18. 18*

    Strong decays of the lowest bottomonium hybrid within an extended Born-Oppenheimer framework

    Roberto Bruschini🇪🇸 · Pedro González🇪🇸

    We analyze the decays of the theoretically predicted lowest bottomonium hybrid $H(1P)$ to open bottom two-meson states. We do it by embedding a quark pair creation model into the Born-Oppenheimer framework which allows for a unified, QCD-motivated description of bottomonium hybrids as well as bottomonium. A new ${}^1{P}_1$ decay model for $H(1P)$ comes out. The same analysis applied to bottomonium leads naturally to the well-known ${}^3{P}_0$ decay model. We show that $H(1P)$ and the theoretically predicted bottomonium state ${\rm Y}(5S)$, whose calculated masses are close to each other, have very different widths for such decays. A comparison with data from ${\rm Y}(10860)$, an experimental resonance whose mass is similar to that of ${\rm Y}(5S)$ and $H(1P)$, is carried out. Neither a ${\rm Y}(5S)$ nor a $H(1P)$ assignment can explain the measured decay widths. However, a ${\rm Y}(5S)$-$H(1P)$ mixing may give account of them supporting previous analyses of dipion decays of ${\rm Y}(10860)$ and suggesting a possible experimental evidence of $H(1P)$.

    hep-phEPJC(2021)·4 citations
19. 19*

    Possible molecular states in $B^{(\ast )}{B}^{(\ast )}$ scatterings

    Meng-Ting Yu🇨🇳 · Zhi-Yong Zhou🇨🇳 · Dian-Yong Chen🇨🇳 · Zhiguang Xiao🇨🇳

    We present that, if unitarizing the $B^{(\ast )}{B}^{(\ast )}$ scattering amplitudes in the constituent interchange model, one can find two bound state poles for $(I_{tot},S_{tot})=(0,1)$ $B{B}^{\ast }$ and $B^{\ast }{B}^{\ast }$ system, which corresponds to two $I(J^P)=0(1^{+})$ doubly bottomed molecular states. Furthermore, it is noticed that the virtual states in $(1,0)$ $BB$, $(1,1)$ $B{B}^{\ast }$, $(1,0)$ $B^{\ast }{B}^{\ast }$, and $(1,2)$ $B^{\ast }{B}^{\ast }$ systems could produce enhancements of the module squares of the scattering $T$-matrix just above the related thresholds, which might correspond to $I(J^P)=1(0^{+})$, $1(1^{+})$, and $1(2^{+})$ doubly bottomed molecular states, respectively. The calculation may be helpful for searching for the doubly bottomed molecular state in future experiments.

    hep-phhep-exPRD(2020)·14 citations
20. 20*

    Doubly Charged Lepton Search Potential of the FCC-Based Energy-Frontier Electron-Proton Colliders

    A. Ozansoy🇹🇷

    We search for the doubly charged leptons ($L^{--}$) predicted in composite models including extended weak isospin multiplets namely, $I_W=1$ and $I_W=3/2$ at the Future Circular Collider (FCC)-based energy-frontier electron-proton colliders with the center-of-mass energies of $\sqrt{s}=3.46$ TeV, $\sqrt{s}=10$ TeV, and $\sqrt{s}=31.6$ TeV, respectively. We deal with the $e^{-}p\to L^{--}X\to e^{-}{W}^{-}X$ process, calculate the production cross sections and give the normalized transverse momentum and pseudorapiditiy distributions of final state electron to obtain the kinematical cuts for the discovery. We show the statistical significance ($SS$) of the expected signal yield as a function of doubly charged lepton mass ($SS-M_L$ plots) to attain the doubly charged lepton discovery mass limits both for the $I_W=1$ and $I_W=3/2$. It is obtained that discovery mass limits on the mass of doubly charged lepton for $I_W=1$ ($I_W=3/2$) are, $2.21(2.73)$ TeV, $5.46(8.47)$ TeV, and $12.9(20.0)$ TeV for $\sqrt{s}=3.46$ TeV, $\sqrt{s}=10$ TeV, and $\sqrt{s}=31.6$ TeV, respectively.

    hep-phAdv.High Energy Phys.(2020)·6 citations
21. 21*

    Pion observables with the Minkowski Space Pion Model

    J. P. B. C. de Melo (Laboratório de Física Teórica e Computacional, LFTC/Universidade Cruzeiro do Sul/Universidade Cidade de São Paulo)🇧🇷 · Rômulo M. Moita🇧🇷 · Tobias Frederico (Instituto Tecnológico de Aeronáutica, DCTA 12.228-900 São José dos Campos, SP, Brazil)🇧🇷

    The pion structure in Minkowski space is described in terms of an analytic model of the Bethe-Salpeter amplitude combined with Euclidean Lattice QCD results for the running quark mass. In the present work, a pion model previously proposed, which allows for a Nakanishi integral representation, is studied in order to verify the sensitivity of the pion electromagnetic form factor to small variations of the quark self-energy. In addition, we extend the previous work, providing the Nakanishi integral representation for the invariants associated with a decomposition of the pion Bethe-Salpeter amplitude.

    hep-phnucl-thPoS(2019)·2 citations
22. 22*

    Efficient High-Energy Photon Production in the Supercritical QED Regime

    Matteo Tamburini🇩🇪 · Sebastian Meuren🇺🇸

    When dense high-energy lepton bunches collide, the beam particles can experience rest-frame electromagnetic fields which greatly exceed the QED critical one. Here it is demonstrated that beamstrahlung efficiently converts lepton energy to high-energy photons in this so-called supercritical QED regime, as the single-photon emission spectrum exhibits a pronounced peak close to the initial lepton energy. It is also shown that the observation of this high-energy peak in the photon spectrum requires one to mitigate multiple photon emissions during the interaction. Otherwise, the photon recoil induces strong correlations between subsequent emissions which soften the photon spectrum and suppress the peak. The high-energy peak in the photon spectrum constitutes a unique observable of photon emission in the supercritical QED regime, and provides decisive advantages for the realization of an efficient multi-TeV laserless gamma-gamma collider based on electron-electron collisions.

    hep-phphysics.acc-phPRD(2021)·40 citations
23. 23*

    Top-quark hadroproduction in NNLO QCD

    Simone Devoto🇨🇭

    The study of top-quark production and decay is central in the LHC physics programme, allowing precise tests of the Standard Model and offering a window on possible new physics. Accurate theoretical predictions for this process are therefore crucial. We report on a new calculation of the next-to-next-to-leading order QCD radiative corrections to the production of top-quark pairs at hadron colliders. The calculation is performed by using the $q_T$-subtraction method to handle and cancel infrared singular contributions at intermediate stages of the computation, and it represents its first complete application to the hadroproduction of a colourful high-mass system at next-to-next-to-leading order. We discuss the calculation of the additional soft contributions needed to implement $q_T$ subtraction for this process, and we show first numerical results.

    hep-phPoS(2019)·0 citations
24. 24*

    Transverse-momentum-dependent parton distributions up to N${}^3$LL from Drell-Yan data

    Alessandro Bacchetta🇮🇹 · Valerio Bertone🇮🇹 · Chiara Bissolotti🇮🇹 · Giuseppe Bozzi🇮🇹 · Filippo Delcarro🇺🇸 · Fulvio Piacenza🇮🇹 · Marco Radici🇮🇹

    We present an extraction of unpolarised Transverse-Momentum-Dependent Parton Distribution Functions based on Drell-Yan production data from different experiments, including those at the LHC, and spanning a wide kinematic range. We deal with experimental uncertainties by properly taking into account correlations. We include resummation of logarithms of the transverse momentum of the vector boson up to N${}^3$LL order, and we include non-perturbative contributions. These ingredients allow us to obtain a remarkable agreement with the data.

    hep-phJHEP(2020)·215 citations
25. 25*

    Spectral, statistical and vertex functions in scalar quantum field theory far from equilibrium

    Linda Shen🇩🇪 · Jürgen Berges🇩🇪

    We compute the far-from-equilibrium dynamics of relativistic scalar quantum fields in 3+1 space-time dimensions starting from over-occupied initial conditions. We determine universal scaling exponents and functions for two-point correlators and the four-vertex in a self-similar regime in time and space or momenta. The scaling form of the momentum-dependent four-vertex exhibits a dramatic fall-off towards low momenta. Comparing spectral functions (commutators) and statistical correlations (anti-commutators) of field operators allows us to detect strong violations of the fluctuation-dissipation relation in this non-perturbative infrared regime. Based on a self-consistent expansion in the number of field components to next-to-leading order, a wide range of interaction strengths is analyzed and compared to weak-coupling estimates in effective kinetic theory and classical-statistical field theory.

    hep-phcond-mat.quant-gasPRD(2020)·18 citations
26. 26*

    Modular symmetry origin of texture zeros and quark lepton unification

    Jun-Nan Lu🇨🇳 · Xiang-Gan Liu🇨🇳 · Gui-Jun Ding🇨🇳

    The even weight modular forms of level $N$ can be arranged into the common irreducible representations of the inhomogeneous finite modular group ${\Gamma }_N$ and the homogeneous finite modular group ${\Gamma }_N^{\prime }$ which is the double covering of ${\Gamma }_N$, and the odd weight modular forms of level $N$ transform in the new representations of ${\Gamma }_N^{\prime }$. We find that the above structure of modular forms can naturally generate texture zeros of the fermion mass matrices if we properly assign the representations and weights of the matter fields under the modular group. We perform a comprehensive analysis for the ${\Gamma }_3^{\prime }\cong T^{\prime }$ modular symmetry. The three generations of left-handed quarks are assumed to transform as a doublet and a singlet of $T^{\prime }$, we find six possible texture zeros structures of quark mass matrix up to row and column permutations. We present five benchmark quark models which can produce very good fit to the experimental data. These quark models are further extended to include lepton sector, the resulting models can give a unified description of both quark and lepton masses and flavor mixing simultaneously although they contain less number of free parameters than the observables.

    hep-phPRD(2020)·105 citations
27. 27*

    Peccei-Quinn Phase Transition at LIGO

    Benedict von Harling🇪🇸 · Alex Pomarol🇪🇸 · Oriol Pujolas🇪🇸 · Fabrizio Rompineve🇺🇸

    The LIGO observatories can potentially detect stochastic gravitational waves arising from phase transitions which happened in the early universe at temperatures around $T\sim 10^8$ GeV. This provides an extraordinary opportunity for discovering the phase transition associated with the breaking of the Peccei-Quinn symmetry, required in QCD axion models. Here we consider the simplest Peccei-Quinn models and study under which conditions a strong first-order phase transition can occur, analyzing its associated gravitational wave signal. To be detectable at LIGO, we show that some supercooling is needed, which can arise either in Coleman-Weinberg-type symmetry breaking or in strongly-coupled models. We also investigate phase transitions that interestingly proceed by first breaking the electroweak symmetry at large scales before tunneling to the Peccei-Quinn breaking vacuum. In this case, the associated gravitational wave signal is more likely to be probed at the proposed Einstein Telescope.

    hep-phastro-ph.COJHEP(2020)·128 citations
28. 28*

    The MICROSCOPE Space Mission and Lorentz Violation

    Geoffrey Mo🇺🇸 · Hélène Pihan-Le Bars🇫🇷 · Quentin G. Bailey🇺🇸 · Christine Guerlin🇫🇷 · Jay D. Tasson🇺🇸 · Peter Wolf🇫🇷

    In this contribution to the CPT'19 proceedings, we summarize efforts that use data from the MICROSCOPE space mission to search for Lorentz violation in the Standard-Model Extension.

    hep-phgr-qc1 citation
29. 29*

    Transformation of the spinless Salpeter equation

    Mikhail N. Sergeenko🇧🇾

    Spinless Salpeter equation for two bound particles is analyzed. We use the fact that in relativistic kinematics the spatial two particle relative momentum is relativistic invariant. Free particle hypothesis for the bound state is developed: comstituents move as free particles inside of the system. The Shrödinger-type wave equation is derived. Three equivalent forms of the eigenvalue equation are given. Relative motion of quarks in eigen states is described by the asymptotic solution in the form of the standing wave of $\cos (kx+a)$ for each spatial degree of freedom. To test the model the spin center-of-gravity energy levels for the hydrogen atom are calculated and compared with the NIST data. Complex eigenmasses for the $H$ atom are obtained.

    hep-phquant-ph0 citations
30. 30*

    Conformal $\alpha$-attractor Inflation with Weyl Gauge Field

    Yong Tang🇨🇳 · Yue-Liang Wu🇨🇳

    Conformal scaling invariance should play an important role for understanding the origin and evolution of universe. During inflation period, it appears to be an approximate symmetry, but how it is broken remains uncertain. The appealing $\alpha$-attractor inflation implements the spontaneous breaking of conformal symmetry and a mysterious SO(1,1) global symmetry. To better understand the SO(1,1) symmetry, here we present a systematic treatment of the inflation models with local conformal symmetry in a more general formalism. We find SO(2) is the other possible symmetry in the presence of Weyl gauge field. We also obtain all the analytic solutions that relate the inflation fields between Jordan frame and Einstein frame. We illustrate a class of inflation models with the approximate SO(2) symmetry and trigonometric potential, and find that it can fit the current observations and will be probed by future CMB experiments.

    hep-phastro-ph.COgr-qchep-thJCAP(2020)·15 citations
31. 31*

    On the transverse size of hadrons at asymptotically high energies

    M.L. Nekrasov🇷🇺

    We show that Gribov diffusion of the partons in the impact parameter plane, which leads to the square-root-of-logarithmic growth of the transverse size of the hadrons, can occur only simultaneously with a similar diffusion in the transverse-momentum space. At the same time, a restriction of the partons in the transverse momenta entails an increase in their propagation in the impact parameter plane. Ultimately this leads to a logarithmic growth of the transverse size of hadrons at asymptotically high energies.

    hep-phhep-thMod.Phys.Lett.A(2020)·9 citations
32. 32*

    Model-independent bounds on new physics effects in non-leptonic tree-level decays of B-mesons

    Alexander Lenz🇬🇧 · Gilberto Tetlalmatzi-Xolocotzi🇳🇱

    We present a considerably improved analysis of model-independent bounds on new physics effects in non-leptonic tree-level decays of B-mesons. Our main finding is that contributions of about $\pm 0.1$ to the Wilson coefficient of the colour-singlet operator $Q_2$ of the effective weak Hamiltonian and contributions in the range of $\pm 0.5$ (both for real and imaginary part) to $Q_1$ can currently not be excluded at the $90\%$ C.L.. Effects of such a size can modify the direct experimental extraction of the CKM angle $\gamma$ by up to $10^{\circ }$ and they could lead to an enhancement of the decay rate difference $\Delta {\Gamma }_d$ of up to a factor of 5 over its SM value - a size that could explain the D0 dimuon asymmetry. Future more precise measurements of the semi-leptonic asymmetries $a_{sl}^q$ and the lifetime ratio $\tau (B_s)/\tau (B_d)$ will allow to shrink the bounds on tree-level new physics effects considerably. Due to significant improvements in the precision of the non-perturbative input we update all SM predictions for the mixing obervables in the course of this analysis, obtaining: $\Delta M_s=(18.77\pm 0.86)\text{mbox}{ps}^{-1}$, $\Delta M_d=(0.543\pm 0.029)\text{mbox}{ps}^{-1}$, $\Delta {\Gamma }_s=(9.1\pm 1.3)\cdot 10^{-2}\text{mbox}{ps}^{-1}$, $\Delta {\Gamma }_d=(2.6\pm 0.4)\cdot 10^{-3}\text{mbox}{ps}^{-1}$, $a_{sl}^s=(2.06\pm 0.18)\cdot 10^{-5}$ and $a_{sl}^d=(-4.73\pm 0.42)\cdot 10^{-4}$.

    hep-phJHEP(2020)·127 citations
33. 33*

    Searches for Decays of New Particles in the DUNE Multi-Purpose Near Detector

    Jeffrey M. Berryman🇺🇸 · André de Gouvêa🇺🇸 · Patrick J. Fox🇺🇸 · Boris J. Kayser🇺🇸 · Kevin J. Kelly🇺🇸 · Jennifer L. Raaf🇺🇸

    One proposed component of the upcoming Deep Underground Neutrino Experiment (DUNE) near detector complex is a multi-purpose, magnetized, gaseous argon time projection chamber: the Multi-Purpose Detector (MPD). We explore the new-physics potential of the MPD, focusing on scenarios in which the MPD is significantly more sensitive to new physics than a liquid argon detector, specifically searches for semi-long-lived particles that are produced in/near the beam target and decay in the MPD. The specific physics possibilities studied are searches for dark vector bosons mixing kinetically with the Standard Model hypercharge group, leptophilic vector bosons, dark scalars mixing with the Standard Model Higgs boson, and heavy neutral leptons that mix with the Standard Model neutrinos. We demonstrate that the MPD can extend existing bounds in most of these scenarios. We illustrate how the ability of the MPD to measure the momentum and charge of the final state particles leads to these bounds.

    hep-phhep-exJHEP(2020)·148 citations
34. 34*

    Gauge coupling beta functions to four-loop order in the Standard Model

    Joshua Davies🇩🇪 · Florian Herren🇩🇪 · Colin Poole🇩🇰 · Matthias Steinhauser🇩🇪 · Anders Eller Thomsen🇩🇰

    We compute the beta functions of the three Standard Model gauge couplings to four-loop order in the modified minimal subtraction scheme. At this order a proper definition of ${\gamma }_5$ in $D=4-2ϵ$ space-time dimensions is required; however, in our calculation we determine the ${\gamma }_5$-dependent terms by exploiting relations with beta function coefficients at lower loop orders.

    hep-phPRL(2020)·41 citations
35. 35*

    Towards the ultimate differential SMEFT analysis

    Shankha Banerjee🇬🇧 · Rick S. Gupta🇬🇧 · Joey Y. Reiness🇬🇧 · Satyajit Seth🇬🇧 · Michael Spannowsky🇬🇧

    We obtain SMEFT bounds using an approach that utilises the complete multi-dimensional differential information of a process. This approach is based on the fact that at a given EFT order, the full angular distribution in the most important electroweak processes can be expressed as a sum of a fixed number of basis functions. The coefficients of these basis functions - the so-called angular moments - and their energy dependance, thus form an ideal set of experimental observables that encapsulates the complete multi-dimensional differential information of the process. This approach is generic and the observables constructed allow to avoid blind directions in the SMEFT parameter space. While this method is applicable to many of the important electroweak processes, as a first example we study the $pp\to V(\ell \ell )h(bb)$ process ($V\equiv Z/W^{\pm },\ell \ell \equiv {\ell }^{+}{\ell }^{-}/{\ell }^{\pm }\nu$), including QCD NLO effects, differentially. We show that using the full differential data in this way plays a crucial role in simultaneously and maximally constraining the different vertex structures of the Higgs coupling to gauge bosons. In particular, our method yields bounds on the $h{V}_{\mu \nu }{V}^{\mu \nu }$, $h{V}_{\mu \nu }{\tilde{V}}^{\mu \nu }$ and $hVff$ ($ff\equiv f\bar{f}/f{\bar{f}}^{\prime }$) couplings, stronger than projected bounds reported in any other process. This matrix-element-based method can provide a transparent alternative to complement machine learning techniques that also aim to disentangle correlations in the SMEFT parameter space.

    hep-phhep-exJHEP(2020)·67 citations
36. 36*

    The Boundaries of KKLT

    Lisa Randall🇺🇸

    We consider the conundrum of generating de Sitter space from higher-dimensional geometry, with particular attention to KKLT-type constructions arXiv:hep-th/0301240 and their 5d implications. We show that even in the probe approximation with small $g_s$, a consistent higher-dimensional solution requires a deformation of a modulus field playing the role of a Goldberger-Wise stabilizing field in Randall-Sundrum type geometries that occurs through a shift in a the throat length. We identify the light radion field that sets the length of the throat, whose origin is the dynamical conifold deformation parameter. By analyzing the theory as a 5d model of mismatched branes in AdS5 space with a GW stabilization mechanism, we show how energy (and supersymmetry breaking) is transferred to both the IR and UV regions of the throat to generate a consistent 4d de Sitter sliced geometry. This should help resolve some of the recent apparent paradoxes in explicit higher-dimensional constructions. Moreover, the radion gives insight into the potential for the previously identified ``conifold instability". We argue that this instability would be a destabilization of the potential for the radion in KKLT, which can occur when the perturbation is too large. If indeed $\sqrt{g_s}M$ is too small, the radion would enter on its runaway direction and the conifold deformation would shrink to zero size. It is difficult to satisfy the required bound and a) maintain a hierarchy in the simpler CY manifolds and b) complete the cosmological phase transition into the stabilized throat, We also discuss the implications of this type of setup for supersymmetry breaking, and how multiple throats can introduce hierarchies of supersymmetry breaking masses, even in an anomaly-mediated scenario. In an appendix we consider general compactification constraints.

    ↳ hep-thhep-phFortsch.Phys.(2020)·55 citations
37. 37*

    The Structure of Dissipative Dark Matter Halos

    Ran Huo🇺🇸 · Hai-Bo Yu🇺🇸 · Yi-Ming Zhong🇺🇸

    Dissipative dark matter self-interactions can affect halo evolution and change its structure. We perform a series of controlled N-body simulations to study impacts of the dissipative interactions on halo properties. The interplay between gravitational contraction and collisional dissipation can significantly speed up the onset of gravothermal collapse, resulting in a steep inner density profile. For reasonable choices of model parameters controlling the dissipation, the collapse timescale can be a factor of 10-100 shorter than that predicted in purely elastic self-interacting dark matter. The effect is maximized when energy loss per collision is comparable to characteristic kinetic energy of dark matter particles in the halo. Our simulations provide guidance for testing the dissipative nature of dark matter with astrophysical observations.

    ↳ astro-ph.COastro-ph.GAhep-phJCAP(2020)·53 citations
38. 38*

    Right-handed neutrinos and $U{\left(1\right)}_X$ symmetry-breaking

    C. Herbert Clemens🇺🇸 · Stuart Raby🇺🇸

    The authors have proposed a global model for Heterotic $F$-theory duality with Wilson line symmetry-breaking and a $4+1$ split of the $F$-theory spectral divisor. Goals of this note are to treat the existence of right-handed neutrinos in our $F$-theory model, show that the ${\mathbb{Z}}_2$-action in our model breaks the $U{\left(1\right)}_X$-symmetry associated to the $4+1$ split to ${\mathbb{Z}}_2$-matter parity, and to identify Yukawa couplings for the MSSM matter fields.

    ↳ hep-thhep-phJHEP(2020)·6 citations
39. 39*

    Compton scattering from ${}^4$He at the TUNL HI$\gamma$S facility

    X. Li🇺🇸 · M.W. Ahmed🇺🇸 · A. Banu🇺🇸 · C. Bartram🇺🇸 · B. Crowe🇺🇸 · E.J. Downie🇺🇸 · M. Emamian🇺🇸 · G. Feldman🇺🇸 · H. Gao🇺🇸 · D. Godagama🇺🇸 · H.W. Grießhammer🇺🇸 · C.R. Howell🇺🇸 and 17 other authors

    Differential cross sections for elastic Compton scattering from ${}^4$He have been measured with high statistical precision at the High Intensity $\gamma$-ray Source at laboratory scattering angles of $55^{\circ }$, $90^{\circ }$, and $125^{\circ }$ using a quasi-monoenergetic photon beam with a weighted mean energy value of $81.3$ MeV. The results are compared to previous measurements and similar fore-aft asymmetry in the angular distribution of the differential cross sections is observed. This experimental work is expected to strongly motivate the development of effective-field-theory calculations of Compton scattering from ${}^4$He to fully interpret the data.

    ↳ nucl-exhep-exhep-phnucl-thPRC(2020)·9 citations
40. 40*

    Infrared structure of $\mathcal{N}$ = 4 SYM and leading transcendentality principle in gauge theory

    Taushif Ahmed🇩🇪 · Pulak Banerjee🇨🇭 · Amlan Chakraborty🇮🇳 · Prasanna K. Dhani🇮🇹 · V. Ravindran🇮🇳 · Satyajit Seth🇬🇧

    We present a detailed study on the infrared structure of $\mathcal{N}=4$ SYM and its connection to QCD. Calculation of collinear splitting functions helps to understand the structure and thus one can get infrared safe cross sections. We also demonstrate the factorization property that soft plus virtual part of the cross section satisfies and through factorization, we calculate soft distribution function up to third order in perturbation theory. We show that the soft distribution function is process independent that includes operators as well as external legs. In addition to this we compare our findings against the known results in QCD through principle of maximum transcendentality (PMT). We extend our analysis further for the case of three-point form factors involving stress tensor and find that it violates the PMT while comparing with the corresponding quantity in the standard model, observed for the first time at the level of form factor.

    ↳ hep-thhep-phPoS(2019)·1 citation
41. 41*

    Primordial backgrounds of relic gravitons

    Massimo Giovannini🇨🇭

    The diffuse backgrounds of relic gravitons with frequencies ranging between the aHz band and the GHz region encode the ultimate information on the primeval evolution of the plasma and on the underlying theory of gravity well before the electroweak epoch. While the temperature and polarization anisotropies of the microwave background radiation probe the low-frequency tail of the graviton spectra, during the next score year the pulsar timing arrays and the wide-band interferometers (both terrestrial and hopefully space-borne) will explore a much larger frequency window encompassing the nHz domain and the audio band. The salient theoretical aspects of the relic gravitons are reviewed in a cross-disciplinary perspective touching upon various unsettled questions of particle physics, cosmology and astrophysics.

    ↳ astro-ph.COgr-qchep-phPPNP(2020)·70 citations
42. 42*

    Non-linear statistics of primordial black holes from gaussian curvature perturbations

    Cristiano Germani🇪🇸 · Ravi K. Sheth🇺🇸

    We develop the non-linear statistics of primordial black holes generated by a gaussian spectrum of primordial curvature perturbations. This is done by employing the compaction function as the main statistical variable under the constraints that: a) the over-density has a high peak at a point ${\vec{x}}_0$, b) the compaction function has a maximum at a smoothing scale $R$, and finally, c) the compaction function amplitude at its maximum is higher than the threshold necessary to trigger a gravitational collapse into a black hole of the initial over-density. Our calculation allows for the fact that the patches which are destined to form PBHs may have a variety of profile shapes and sizes. The predicted PBH abundances depend on the power spectrum of primordial fluctuations. For a very peaked power spectrum, our non-linear statistics, the one based on the linear over-density and the one based on the use of curvature perturbations, all predict a narrow distribution of PBH masses and comparable abundance. For broader power spectra the linear over-density statistics over-estimate the abundance of primordial black holes while the curvature-based approach under-estimates it. Additionally, for very large smoothing scales, the abundance is no longer dominated by the contribution of a mean over-density but rather by the whole statistical realisations of it.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2020)·130 citations
43. 43*

    Gluon polarization tensor in a magnetized medium: Analytic approach starting from the sum over Landau levels

    Alejandro Ayala🇲🇽 · Jorge David Castaño-Yepes🇲🇽 · M. Loewe🇨🇱 · Enrique Muñoz🇨🇱

    We present an analytic method to compute the one-loop magnetic correction to the gluon polarization tensor starting from the Landau-level representation of the quark propagator in the presence of an external magnetic field. We show that the general expression contains the vacuum contribution that can be isolated from the zero-field limit for finite gluon momentum. The general tensor structure for the gluon polarization also contains two spurious terms that do not satisfy the transversality properties. However, we also show that the coefficients of this structures vanish and thus do not contribute to the polarization tensor, as expected. In order to check the validity of the expressions we study the strong and weak field limits and show that well established results are reproduced. The findings can be used to study the conditions for gluons to equilibrate with the magnetic field produced during the early stages of a relativistic heavy-ion collision.

    ↳ hep-thhep-phPRD(2020)·24 citations
44. 44*

    Antiproton physics

    Jean-Marc Richard🇫🇷

    We review the physics of low-energy antiprotons, and its link with the nuclear forces. This includes: antinucleon scattering on nucleons and nuclei, antiprotonic atoms and antinucleon-nucleon annihilation into mesons.

    ↳ nucl-thhep-phFront.in Phys.(2020)·25 citations
45. 45*

    Two-particle azimuthal correlations as a probe of collective behaviour in deep inelastic $\text{ep}$ scattering at HERA

    ZEUS Collaboration

    Two-particle azimuthal correlations have been measured in neutral current deep $\text{mbox}inelastic$ $\text{ep}$ scattering with virtuality $Q^2>5$ GeV${}^2$ at a centre-of-mass energy $\sqrt{s}=318$ GeV recorded with the ZEUS detector at HERA. The correlations of charged particles have been measured in the range of laboratory pseudorapidity $-1.5<\eta <2.0$ and transverse momentum $0.1<p_{\text{T}}<5.0$ GeV and event multiplicities $N_{\text{ch}}$ up to six times larger than the average $⟨N_{\text{ch}}⟩\approx 5$. The two-particle correlations have been measured in terms of the angular observables $c_n\{2\}=⟨⟨\cos n\Delta \phi ⟩⟩$, where $n$ is between 1 and 4 and $\Delta \phi$ is the relative azimuthal angle between the two particles. Comparisons with available models of deep inelastic scattering, which are tuned to reproduce inclusive particle production, suggest that the measured two-particle correlations are dominated by contributions from multijet production. The correlations observed here do not indicate the kind of collective behaviour recently observed at the highest RHIC and LHC energies in high-multiplicity hadronic collisions.

    ↳ hep-exhep-phnucl-exnucl-thJHEP(2020)·56 citations
46. 46*

    Dirac spectrum and the BEC-BCS crossover in QCD at nonzero isospin asymmetry

    B. B. Brandt🇩🇪 · F. Cuteri🇩🇪 · G. Endrődi🇩🇪 · S. Schmalzbauer🇩🇪

    For large isospin asymmetries, perturbation theory predicts the QCD ground state to be a superfluid phase of $u$ and $\bar{d}$ Cooper pairs. This phase, which is denoted as the BCS phase, is expected to be smoothly connected to the standard phase with Bose-Einstein condensation (BEC) of charged pions at ${\mu }_I\ge m_{\pi }/2$ by an analytic crossover. A first hint for the existence of the BCS phase, which is likely characterised by the presence of both, deconfinement and charged pion condensation, is coming from the lattice observation that the deconfinement crossover smoothly penetrates into the BEC phase. To further scrutinize the existence of the BCS phase, in this proceedings article we investigate the complex spectrum of the massive Dirac operator in 2+1-flavor QCD at nonzero temperature and isospin chemical potential. The spectral density near the origin is related to the BCS gap via a generalization of the Banks-Casher relation to the case of complex Dirac eigenvalues (derived for the zero-temperature, high-density limits of QCD at nonzero isospin chemical potential).

    ↳ hep-lathep-phnucl-thParticles(2020)·23 citations
47. 47*

    Looking for MACHOs in the Spectra of Fast Radio Bursts

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

    We explore a novel search strategy for dark matter in the form of massive compact halo objects (MACHOs) such as primordial black holes or dense mini-halos in the mass range from $10^{-4}$ to 0.1 solar masses. These objects can gravitationally lens the signal of fast radio bursts (FRBs), producing a characteristic interference pattern in the frequency spectrum, similar to the previously studied femtolensing signal in gamma ray burst spectra. Unlike traditional searches using microlensing, FRB lensing will probe the abundance of MACHOs at cosmological distance scales (~Gpc) rather than just their distribution in the neighborhood of the Milky Way. The method is thus particularly relevant for dark mini-halos, which may be inaccessible to microlensing due to their finite spatial extent or tidal disruption in galaxies. We find that the main complication in FRB lensing will be interstellar scintillation in the FRB's host galaxy and in the Milky Way. Scintillation is difficult to quantify because it heavily depends on turbulence in the interstellar medium, which is poorly understood. We show that, nevertheless, for realistic scintillation parameters, FRB lensing can set competitive limits on compact dark matter object, and we back our findings with explicit simulations.

    ↳ astro-ph.COastro-ph.HEhep-phMNRAS(2020)·48 citations
48. 48*

    Gravitational-wave versus X-ray tests of strong-field gravity

    Alejandro Cardenas-Avendano🇨🇴 · Sourabh Nampalliwar🇩🇪 · Nicolas Yunes🇺🇸

    Electromagnetic observations of the radiation emitted by an accretion disk around a black hole, as well as gravitational wave observations of coalescing binaries, can be used to probe strong-field gravity. We here compare the constraints that these two types of observations can impose on theory-agnostic, parametric deviations from the Schwarzschild metric. On the gravitational wave side, we begin by computing the leading-order deviation to the Hamiltonian of a binary system in a quasi-circular orbit within the post-Newtonian approximation, given a parametric deformation of the Schwarzschild metrics of each binary component. We then compute the leading-order deviation to the gravitational waves emitted by such a binary in the frequency domain, assuming purely Einsteinian radiation-reaction. We compare this model to the LIGO-Virgo collaboration gravitational wave detections and place constraints on the metric deformation parameters, concluding with an estimate of the constraining power of aLIGO at design sensitivity. On the electromagnetic side, we first simulate observations with current and future X-ray instruments of an X-ray binary with a parametrically-deformed Schwarzschild black hole, and we then estimate constraints on the deformation parameters using these observations.We find that current gravitational wave observations have already placed constraints on the metric deformation parameters than are slightly more stringent than what can be achieved with current X-ray instruments. Moreover, future gravitational wave observations with aLIGO at design sensitivity by 2026 will be even more stringent, becoming stronger than constraints achievable with future ATHENA X-ray observations before it flies in 2034.

    ↳ gr-qchep-phClass.Quant.Grav.(2020)·68 citations
49. 49*

    A new state of dense matter in neutron stars with nucleon structure

    Vikram Soni🇮🇳

    The existence of stars with a large mass of 2 solar masses means that the equation of state is stiff enough to provide high enough pressure at large central densities. Previous work shows that such a stiff equation of state is possible if the ground state has nucleons as its constituents. We find this to be so in a chiral soliton ( skyrmion ) model for a composite nucleon which has bound state quarks. The strong binding of the quarks in this composite nucleon is plausibly the origin of the nucleon-nucleon hard core. In this model we find a new state of superdense matter at high density which is a 'topological'cubic crystal of overlapping composite nucleons that are solitons with relativistic quark bound states. The quarks are frozen in a filled band of a unique state, which not an eigenstate of spin or isospin but an eigenstate of spin plus isospin, $\vec{S}+\vec{I}=0$. In this alternative model we find that all neutron stars have no regular `free'quark matter. Neutron stars whose central density crosses a threshold baryon density of approximately, $n_b\sim 1/f{m}^3$, will become unstable and go through a decompression (sudden) density discontinuity to conventional quark matter. Sequentially, this contraction of the core of the star will soften the equation of state release a large amount of gravitational potential energy which can give rise to a shock wave and matter ejection. Since the merger of two neutron stars gives a compact state whose mass is larger than the allowed maximum mass, this will be followed by a jet and a short gamma ray burst while transiting into a black hole.

    ↳ nucl-thhep-ph1 citation
50. 50*

    Faster-Than-Light Solitons in 1 + 1 Dimensions

    Mohammad Mohammadi🇮🇷 · Nematollah Riazi🇮🇷 · Mohammad Hassan Dhegihani🇮🇷

    The existence of a faster-than-light particle is in direct opposition to Einstein's relativity and the principle of causality. However, we show that the theory of classical relativistic fields is not inherently inconsistent with the existence of the faster-than-light particle-like soliton solutions in $1+1$ dimensions. We introduce two extended KG models ($k$-fields) that lead to a zero-energy and a nonzero-energy stable particle-like solution with faster-than light speeds, respectively.

    ↳ physics.class-phhep-phAnnals Phys.(2022)·1 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.