Tue·May 28, 2019Tuesday·May 28, 2019

1. 01*

   Quantum Kinetic Theory of Spin Polarization of Massive Quarks in Perturbative QCD: Leading Log

   Shiyong Li🇺🇸 · Ho-Ung Yee🇺🇸

   We present the quantum kinetic equation for spin polarization of massive quarks in leading log order of perturbative QCD, which describes time evolution of the spin density matrix in momentum space of a massive quark interacting with a background QCD plasma. We find that the time evolution operator of the spin density matrix, or the quantum kinetic collision terms, are universally of order ${\alpha }_s^2\log (1/{\alpha }_s)$ in terms of the QCD coupling constant ${\alpha }_s=g^2/(4\pi )$. Our quantum kinetic equation is valid for an arbitrary quark mass $m\gg m_D\sim gT$, where $m_D$ is the Debye mass, and can be used to study relaxation dynamics of spin polarization of massive quarks in perturbative QCD regime.

   hep-phhep-thnucl-thPRD(2019)·88 citations
2. 02*

   Leptogenesis from spontaneous symmetry breaking during inflation

   Yi-Peng Wu🇯🇵 · Louis Yang🇯🇵 · Alexander Kusenko🇺🇸

   Symmetry breaking in the Higgs field via a non-minimal coupling to gravity or higher-dimensional interactions with the inflaton can lead to condensation at a large vacuum expectation value (VEV) during inflation. After inflation is over, the Higgs field must relax to the minimum of its effective potential, creating an era in which the CPT is effectively broken by the time-depended VEV. We show that the matter-antimatter asymmetry can be generated during this relaxation epoch.

   hep-phJHEP(2019)·20 citations
3. 03*

   Dark matter in the Randall-Sundrum model with non-universal coupling

   Ashok Goyal🇮🇳 · Rashidul Islam🇮🇳 · Mukesh Kumar🇿🇦

   We consider simplified dark matter models (DM) interacting gravitationally with the standard model (SM) particles in a Randall-Sundrum (RS) framework. In this framework, the DM particles interact through the exchange of spin-2 Kaluza-Klein (KK) gravitons in the $s$-channel with the SM particles. The parameter space of the RS model with universal couplings to SM particles is known to be strongly constrained from the LHC data. We are thus led to consider models with non-universal couplings. The first model we consider in this study is a top-philic graviton model in which only the right-handed top quarks are taken to interact strongly with the gravitons. In the second, the lepto-philic model, we assume that only the right-handed charged leptons interact strongly with the gravitons. We extend the study to include not only the scalar, vector and spin-1/2 fermions but also spin-3/2 fermionic dark matter. We find that there is a large parameter space in these benchmark models where it is possible to achieve the observed relic density consistent with the direct and indirect searches and yet not to be constrained from the LHC data.

   hep-phJHEP(2019)·16 citations
4. 04*

   Impact of Non-perturbative QCD on CP Violation in Many-Body Final States of Flavor Transitions

   I. I. Bigi🇺🇸

   The title of my talk pointed out central statements: the impact of non-perturbative QCD on {\bf CP} asymmetries in many-body FS in charm \& beauty hadrons. For practical reasons one measures first {\bf CP} violation in two-body final states of heavy flavor hadrons. However, those are small parts of charm hadrons and tiny ones for beauty hadrons; therefore one has to probe {\bf CP} asymmetries in three- \& four-body final states. Thus the transitions to the many-body FS basically give information about the underlying dynamics. The impact of non-perturbative QCD on {\bf CP} asymmetries in many-body FS shows that -- in principle; it is a true challenge even in a semi-quantitative way. One needs correlations with other transitions. That is my strategy; however, I have to discuss the tactics on the same level like using consistent parameterization of the CKM matrix. Our community has entered a novel era: direct {\bf CP} violation has been found in $D^0\to h^{+}{h}^{-}$ decays \cite{CHARM}. Finally I give short comments about the possible impact of New Dynamics on direct {\bf CP} violation in $K_L\to 2\pi$ and probe {\bf CP} asymmetry in $J/\psi \to \bar{\Lambda }\Lambda$ transitions.

   hep-phProceedings of FPCP2019·0 citations
5. 05*

   The 2-Neutrino Exchange Potential with Mixing: A Probe of Neutrino Physics and CP Violation

   D. E. Krause🇺🇸 · Q. Le Thien🇺🇸

   The 2-neutrino exchange potential is a Standard Model weak potential arising from the exchange of virtual neutrino-antineutrino pairs which must include all neutrino properties, including the number of flavors, their masses, fermionic nature (Dirac or Majorana), and CP violation. We describe a new approach for calculating the spin-independent 2-neutrino exchange potential, including the mixing of three neutrino mass states and CP violation.

   hep-ph0 citations
6. 06*

   Scalar neutrino dark matter in $U(1{)}_X$SSM

   Shu-Min Zhao🇨🇳 · Tai-Fu Feng🇨🇳 · Ming-Jie Zhang🇨🇳 · Jin-Lei Yang🇨🇳 · Hai-Bin Zhang🇨🇳 · Guo-Zhu Ning🇨🇳

   $U(1{)}_X$SSM is the extension of the minimal supersymmetric standard model(MSSM) and its local gauge group is $SU(3{)}_C\times SU(2{)}_L\times U(1{)}_Y\times U(1{)}_X$. To obtain this model, three singlet new Higgs superfields and right-handed neutrinos are added to MSSM. In the framework of $U(1{)}_X$SSM, we study the Higgs mass and take the lightest CP-even sneutrino as a cold dark matter candidate. For the lightest CP-even sneutrino, the relic density and the cross section for dark matter scattering off nucleon are both researched. In suitable parameter space of the model, the numerical results satisfy the constraints of the relic density and the cross section with the nucleon.

   hep-phJHEP(2020)·28 citations
7. 07*

   $(g-2{)}_{\mu }$ Versus Flavor Changing Neutral Current Induced by the Light $(B-L{)}_{\mu \tau }$ Boson

   Zhaofeng Kang🇨🇳 · Yoshihiro Shigekami🇨🇳

   We propose the local $(B-L{)}_{\mu \tau }$ model, which minimally retains the local $B-L$ extension for the sake of neutrino phenomenologies, and at the same time presents an invisible gauge boson $Z^{\prime }$ with mass $\sim \mathcal{O}(10)$ MeV to account for the discrepancy of the muon anomalous magnetic moment. However such a scenario is challenged by flavor physics. To accommodate the correct pattern of Cabibbo-Kobayashi-Maskawa matrix, we have to introduce either a $SU(2{)}_L$ doublet flavon or vector-like quarks plus a singlet flavon. In either case $Z^{\prime }$ induces flavor changing neutral current (FCNC) in the quark sector at tree-level. We find that the former scheme cannot naturally suppress the FCNC from the down-type quark sector and thus requires a large fine-tuning to avoid the stringent $K\to \pi \nu \bar{\nu }$ bound. Whereas the latter scheme, in which FCNC merely arises in the up-type quark sector, is still free of strong constraint. In particular, it opens a new window to test our scenario by searching for flavor-changing top quark decay mode $t\to u/c+$(invisible), and the typical branching ratio $\sim \mathcal{O}(10^{-4})$.

   hep-phJHEP(2019)·18 citations
8. 08*

   Asymptotically safe extensions of the Standard Model with flavour phenomenology

   Gudrun Hiller🇩🇪 · Clara Hormigos-Feliu🇩🇪 · Daniel F. Litim🇬🇧 · Tom Steudtner🇬🇧

   We investigate asymptotically safe extensions of the Standard Model with new matter fields arising in the TeV energy range. The new sector contains singlet scalars and vector-like fermions in representations which permit Yukawa interactions with the Standard Model leptons. Phenomenological implications are explored including charged lepton flavour violation, Drell-Yan processes and lepton anomalous magnetic moments. For the latter, we find that BSM contributions can be sizeable enough to explain the present experimental discrepancies of the electron and muon anomalous magnetic moments with the Standard Model.

   hep-phhep-th16 citations
9. 09*

   Hilbert Series and Plethystics: Paving the path towards 2HDM- and MLRSM-EFT

   Anisha🇮🇳 · Supratim Das Bakshi🇮🇳 · Joydeep Chakrabortty🇮🇳 · Suraj Prakash🇮🇳

   Effective Field Theory technique is one of the most elegant ways to capture the impact of high scale theory, if any, at some low energy by incorporating higher mass dimensional ($\ge 5$) effective operators (${\mathcal{O}}_i$). The low energy EFT is described in terms of only light degrees of freedom which can appear on-shell. An essential task while developing the EFT framework is to compute these ${\mathcal{O}}_i$'s. Hilbert Series is a novel and mathematically robust method to construct the complete set of gauge invariant independent, effective operators. The HS requires the knowledge of the transformation properties of the light DOF and the covariant derivatives under the internal gauge symmetries and conformal groups. The Hilbert Series method, by its virtue, automatically takes care of the redundancies in the operator set due to the Equations of Motion of fields and Integration by Parts with impeccable accuracy. In this paper, we have adopted this methodology to construct the complete set of independent operators up to dimension-6 in the ``Warsaw"-like basis for two different Beyond Standard Model scenarios -- 2HDM and MLRSM. For both these cases, we have calculated the corrections to the scalar, gauge boson and fermion mass spectra due to the dimension-6 operators. The additional contributions to all the Feynman vertices are computed and their impact on different observables, namely Weak mixing angle, Fermi constant, $\rho$ and oblique parameters. We have further discussed how the magnetic moments of charged leptons and production and decay of the massive BSM particles, e.g., charged scalar and different rare processes are affected in the presence of effective operators. We have also constructed the effective scalar four-point interactions and commented on the possible reinvestigation of the theoretical constraints, e.g., unitarity and vacuum stability within these frameworks.

   hep-phhep-thJHEP(2019)·43 citations
10. 10*

    SKA-Phase 1 sensitivity for synchrotron radio emission from multi-TeV Dark Matter candidates

    J. A. R. Cembranos (UCM-IPARCOS)🇪🇸 · A. de la Cruz-Dombriz (UCT)🇿🇦 · V. Gammaldi (IFT-UAM, INFN, SISSA)🇪🇸 · M. Mendez-Isla (UCT)🇿🇦

    In the era of radio astronomy, the high sensitivity of the Square Kilometre Array (SKA) could play a decisive role in the detection of new radio sources. In this work, we study the SKA sensitivity to the synchrotron radio emission expected by the annihilation of TeV DM candidate in the Draco dwarf spheroidal galaxy. On the one hand, we consider model-independent DM candidates: we find out that with 1000 hours of data-taking, SKA1-MID will be able to exclude up to 10 TeV thermal DM candidates that annihilate in $W^{+}{W}^{-}$ and $b\bar{b}$ channels. We also study as these constraints improve by including a density enhancement due to a DM-spike associated with an intermediate-mass black hole in Draco. On the other hand, we consider extra-dimensional brane-world DM candidates, dubbed branons. In this specific scenario, SKA allows us to set constraints on the branon parameter space ($f$,$M$), where $f$ is related to the coupling of the branon to the Standard Model particles and $M$ is the mass of the branon itself. In particular, we consider two different branon DM candidates. We find out that SKA will be able to set more stringent constraints on the branon DM candidate required in order to fit the AMS-02 data, yet the sensitivity of the instrument should be improved in order to study the branon candidate for the Galactic Centre. Nonetheless, we show that SKA represents - among other detectors - the most promising instrument for multi-wavelength detection of synchrotron radio emission by annihilating multi-TeV DM.

    hep-phastro-ph.COPhys.Dark Univ.(2020)·27 citations
11. 11*

    $D$ mesons as a probe of Casimir effect for chiral symmetry breaking

    Tsutomu Ishikawa🇯🇵 · Katsumasa Nakayama🇯🇵 · Daiki Suenaga🇨🇳 · Kei Suzuki🇯🇵

    We propose $D$ mesons as probes to investigate finite-volume effects for chiral symmetry breaking at zero and finite temperature. By using the $2+1$-flavor linear-sigma model with constituent light quarks, we analyze the Casimir effects for the $\sigma$ mean fields: The chiral symmetry is rapidly restored by the antiperiodic boundary for light quarks, and the chiral symmetry breaking is catalyzed by the periodic boundary. We also show the phase diagram of the $\sigma$ mean fields on the volume and temperature plane. For $D$ mesons, we employ an effective model based on the chiral-partner structure, where the volume dependence of $D$ mesons is induced by the $\sigma$ mean fields. We find that $D_s$ mesons are less sensitive to finite volume than $D$ mesons, which is caused by the insensitivity of ${\sigma }_s$ mean fields. An anomalous mass shift of $D$ mesons at high temperature with the periodic boundary will be useful in examinations with lattice QCD simulations. The dependence on the number of compactified spatial dimensions is also studied.

    hep-phhep-latPRD(2019)·8 citations
12. 12*

    Triggering the QCD phase transition through the Unruh effect: chiral symmetry restoration for uniformly accelerated observers

    Adrián Casado-Turrión🇪🇸 · Antonio Dobado🇪🇸

    In this work we study the chiral phase transition as observed by an accelerating observer taking into account the Unruh effect. We use Chiral Perturbation Theory at leading order and the large $N$ limit ($N$ being the number of pions) as an effective description of low-energy QCD, and the Thermalization Theorem to compute the relevant partition function for the accelerating observer. As a result, we obtain that chiral symmetry is restored for uniformly accelerated observers with acceleration $a$ larger than the critical value $a_c=4\pi f_{\pi }$, with $f_{\pi }$ being the pion decay constant.

    hep-phgr-qcPRD(2019)·13 citations
13. 13*

    Multiplicity Dependence in the Non-Extensive Hadronization Model Calculated by the HIJING++ Framework

    Gábor Bíró🇭🇺 · Gergely Gábor Barnaföldi🇭🇺 · Gábor Papp🇭🇺 · Tamás Sándor Biró🇭🇺

    The non-extensive statistical description of the identified final state particles measured in high energy collisions is well-known by its wide range of applicability. However, there are many open questions that need to be answered, including but not limited to, the question of the observed mass scaling of massive hadrons or the size and multiplicity dependence of the model parameters. This latter is especially relevant, since currently the amount of available experimental data with high multiplicity at small systems is very limited. This contribution has two main goals: On the one hand we provide a status report of the ongoing tuning of the soon-to-be-released HIJING++ Monte Carlo event generator. On the other hand, the role of multiplicity dependence of the parameters in the non-extensive hadronization model is investigated with HIJING++ calculations. We present cross-check comparisons of HIJING++ with existing experimental data to verify its validity in our range of interest as well as calculations at high-multiplicity regions where we have insufficient experimental data.

    hep-phUniverse(2019)·3 citations
14. 14*

    Quasinormal modes for quarkonium in a plasma with magnetic fields

    Nelson R. F. Braga🇧🇷 · Luiz F. Ferreira🇧🇷

    Heavy vector mesons detected after a heavy ion collision are important sources of information about the quark gluon plasma. The fraction of such particles that survive the plasma phase and reach the detectors is related to the dissociation degree inside the thermal medium. A consistent picture for the thermal behavior of charmonium and bottomonium quasi-states in a thermal medium was obtained recently using a holographic bottom up model. This model captures the heavy flavour spectroscopy of masses and decay constants in the vacuum (zero temperature) and is consistently extended to finite temperature. The spectral functions that emerge provide a description of the dissociation process in terms of the broadening of the quasi-state peaks with temperature. The holographic approach makes it possible to determine also the quasinormal modes. They are gravity solutions representing the quasi-particle states in the thermal medium, with complex frequencies related to the thermal mass and width. The quasinormal modes for charmonium and bottomonium have been studied very recently and a consistent description of the dissociation process was found. An additional factor can affect the dissociation process: strong magnetic fields are expected to be present when the plasma is formed by non-central heavy ion collisions. So, it is important to understand the effect of such fields on the heavy meson dissociation scenario. Here we extend the holographic determination of quasinormal modes for the case when magnetic fields are present. The real and imaginary parts of the mode frequencies are determined for different values of background $eB$ field. The associated dispersion relations for heavy quarks moving inside the plasma are also investigated for both $c\bar{c}$ and $b\bar{b}$.

    hep-phhep-thPLB(2019)·37 citations
15. 15*

    Varying gauge couplings and collider phenomenology

    Ulf Danielsson🇸🇪 · Rikard Enberg🇸🇪 · Gunnar Ingelman🇸🇪 · Tanumoy Mandal🇸🇪

    In this paper we investigate a natural extension of the Standard Model that involves varying coupling constants. This is a general expectation in any fundamental theory such as string theory, and there are good reasons for why new physics could appear at reachable energy scales. We investigate the collider phenomenology of models with varying gauge couplings where the variations are associated with real singlet scalar fields. We introduce three different heavy scalar fields that are responsible for the variations of the three gauge couplings of the Standard Model. This gives rise to many interesting collider signatures that we explore, resulting in exclusion limits based on the most recent LHC data, and predictions of the future discovery potential at the high-luminosity LHC.

    hep-phhep-thPRD(2019)·8 citations
16. 16*

    Probes of the Standard Model effective field theory extended with a right-handed neutrino

    Julien Alcaide🇪🇸 · Shankha Banerjee🇬🇧 · Mikael Chala🇬🇧 · Arsenii Titov🇬🇧

    If neutrinos are Dirac particles and, as suggested by the so far null LHC results, any new physics lies at energies well above the electroweak scale, the Standard Model effective field theory has to be extended with operators involving the right-handed neutrinos. In this paper, we study this effective field theory and set constraints on the different dimension-six interactions. To that aim, we use LHC searches for associated production of light (and tau) leptons with missing energy, monojet searches, as well as pion and tau decays. Our bounds are generally above the TeV for order one couplings. One particular exception is given by operators involving top quarks. These provide new signals in top decays not yet studied at colliders. Thus, we also design an LHC analysis to explore these signatures in the $t\overline{t}$ production. Our results are also valid if the right-handed neutrinos are Majorana and long-lived.

    hep-phhep-exJHEP(2019)·69 citations
17. 17*

    Locating fixed points in the phase plane

    Yanhua Zhang🇨🇳 · Ye-Yin Zhao🇨🇳 · Lizhu Chen🇨🇳 · Xue Pan🇨🇳 · Mingmei Xu🇨🇳 · Zhiming Li🇨🇳 · Yu Zhou🇨🇳 · Yuanfang Wu🇨🇳

    The critical point is a fixed point in finite-size scaling. To quantify the behaviour of such a fixed point, we define, at a given temperature and scaling exponent ratio, the width of scaled observables for different sizes. The minimum of the width reveals the position of fixed point, its corresponding phase transition temperature, and scaling exponent ratio. The value of this ratio tells the nature of fixed point, which can be a critical point, a point of the first order phase transition line, or a point of the crossover region. To demonstrate the effectiveness of this method, we apply it to three typical samples produced by the 3D three-state Potts model. Results show the method to be more precise and effective than conventional methods. Finally, we discuss a possible application at the beam energy scan program of relativistic heavy-Ion collision.

    hep-phPRE(2019)·5 citations
18. 18*

    Dark matter seeping through dynamic gauge kinetic mixing

    Avik Banerjee🇮🇳 · Gautam Bhattacharyya🇮🇳 · Debtosh Chowdhury🇫🇷 · Yann Mambrini🇫🇷

    We show for the first time that the loop-driven kinetic mixing between visible and dark Abelian gauge bosons can facilitate dark matter production in the early Universe by creating a 'dynamic' portal, which depends on the energy of the process. The required smallness of the strength of the portal interaction, suited for freeze-in, is justified by a suppression arising from the mass of a heavy vector-like fermion. The strong temperature sensitivity associated with the interaction is responsible for most of the dark matter production during the early stages of reheating.

    hep-phastro-ph.COastro-ph.HEJCAP(2019)·31 citations
19. 19*

    Chiral soliton lattice in QCD-like theories

    Tomáš Brauner🇳🇴 · Georgios Filios🇳🇴 · Helena Kolešová🇳🇴

    Recently, it has been shown that the ground state of quantum chromodynamics (QCD) in sufficiently strong magnetic fields and at moderate baryon number chemical potential carries a crystalline condensate of neutral pions: the chiral soliton lattice (CSL). While the result was obtained in a model-independent manner using effective field theory techniques, its realization from first principles using lattice Monte Carlo simulation is hampered by the infamous sign problem. Here we show that CSL, or a similar inhomogeneous phase, also appears in the phase diagram of a class of vector-like gauge theories that do not suffer from the sign problem even in the presence of a baryon chemical potential and external magnetic field. We also show that the onset of nonuniform order manifests itself already in the adjacent homogeneous Bose-Einstein-condensation phase through a characteristic roton-like minimum in the dispersion relation of the lowest-lying quasiparticle mode. Last but not least, our work gives a class of explicit counterexamples to the long-standing conjecture that positivity of the determinant of the Dirac operator (that is, absence of the sign problem) in a vector-like gauge theory precludes spontaneous breaking of translational invariance, and thus implies the absence of inhomogeneous phases in the phase diagram of the theory.

    hep-phhep-lathep-thJHEP(2019)·33 citations
20. 20*

    Lorentz Violation and Riemann-Finsler Geometry

    Benjamin R. Edwards🇺🇸

    The general charge-conserving effective scalar field theory incorporating violations of Lorentz symmetry is presented. The dispersion relation is used to infer the effects of spin-independent Lorentz violation on point-particle motion. A large class of associated Finsler spaces is derived, and the properties of these spaces is explored.

    hep-phhep-th2 citations
21. 21*

    Primordial Gravitational Waves in Nonstandard Cosmologies

    Nicolás Bernal🇨🇴 · Fazlollah Hajkarim🇩🇪

    Assuming that inflation is followed by a phase where the energy density of the Universe is dominated by a component with a general equation of state, we evaluate the spectrum of primordial gravitational waves induced in the post-inflationary Universe. We show that if the energy density of the Universe is dominated by a component $\varphi$ before Big Bang nucleosynthesis, its equation of state could be constrained by gravitational wave experiments depending on the ratio of energy densities of $\varphi$ and radiation, and also the temperature at the end of the $\varphi$ dominated era. Also, we discuss the impact of scale dependence of tensor modes on the primordial gravitational wave spectrum during the $\varphi$-domination. These models are motivated by beyond Standard Model physics and scenarios for non-thermal production of dark matter in the early Universe. We also constrain the parameter space of the tensor spectral index and the tensor-to-scalar ratio, using the experimental limits from gravitational wave experiments.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2019)·120 citations
22. 22*

    A 3+1 Decomposition of the Minimal Standard-Model Extension Gravitational Sector

    Nils A. Nilsson🇵🇱 · Kellie O'Neal-Ault🇺🇸 · Quentin G. Bailey🇺🇸

    The 3+1 (ADM) formulation of General Relativity is used in, for example, canonical quantum gravity and numerical relativity. Here we present a 3+1 decomposition of the minimal Standard-Model Extension gravity Lagrangian. By choosing the leaves of foliation to lie along a timelike vector field we write the theory in a form which will allow for comparison and matching to other gravity models.

    ↳ gr-qchep-phCPT and Lorentz Symmetry, pp. 198-200 (20…·5 citations
23. 23*

    Rescattering effects in antiproton-induced exclusive $J/\psi$ and ${\psi }^{\prime }$ production on the deuteron

    A.B. Larionov🇩🇪 · A. Gillitzer🇩🇪 · M. Strikman🇺🇸

    On the basis of the generalized eikonal approximation we study the exclusive reactions $\bar{p}d\to J/\psi n$ and $\bar{p}d\to {\psi }^{\prime }n$ in vicinity of the thresholds for charmonium production on a free proton target. It is shown that the rescattering of the incoming antiproton and outgoing charmonium on the spectator neutron leads to a depletion of the charmonium production at low- and to an enhancement at high transverse momenta. This is in qualitative agreement with previous studies of hard proton knockout in proton-deuteron collisions. We analyze different physical sources of uncertainty which may influence the extraction of the total charmonium-neutron cross section. The color transparency effect for the incoming $\bar{p}$ largely compensates the influence of charmonium rescattering both at low and high transverse momenta. Different choices of the deuteron wave function lead to significant uncertainties at high transverse momenta. As an outcome of the calculations of charmonium production, we also provide predictions on the production of open charm hadrons due to the dissociation of the charmonium on the neutron. It is shown that the open charm production cross section is proportional to the total charmonium-nucleon cross section and quite stable with respect to the variation of other parameters of the model. We thus suggest that open charm channels are most suited for future studies of charmonium-nucleon interactions at PANDA with a deuteron target.

    ↳ nucl-thhep-exhep-phnucl-exEPJA(2019)·3 citations
24. 24*

    Some remarks on the spectral functions of the Abelian Higgs Model

    D. Dudal🇧🇪 · D. M. van Egmond🇧🇷 · M. S. Guimaraes🇧🇷 · O. Holanda🇧🇷 · B. W. Mintz🇧🇷 · L. F. Palhares🇧🇷 · G. Peruzzo🇧🇷 · S. P. Sorella🇧🇷

    We consider the unitary Abelian Higgs model and investigate its spectral functions at one-loop order. This analysis allows to disentangle what is physical and what is not at the level of the elementary particle propagators, in conjunction with the Nielsen identities. We highlight the role of the tadpole graphs and the gauge choices to get sensible results. We also introduce an Abelian Curci-Ferrari action coupled to a scalar field to model a massive photon which, like the non-Abelian Curci-Ferarri model, is left invariant by a modified non-nilpotent BRST symmetry. We clearly illustrate its non-unitary nature directly from the spectral function viewpoint. This provides a functional analogue of the Ojima observation in the canonical formalism: there are ghost states with nonzero norm in the BRST-invariant states of the Curci-Ferrari model.

    ↳ hep-thhep-phPRD(2019)·24 citations
25. 25*

    Heavy flavor dissociation in the framework of multi-body Dirac equations

    Shuzhe Shi🇨🇦 · Jiaxing Zhao🇨🇳 · Pengfei Zhuang🇨🇳

    We study heavy flavor properties at finite temperature in the framework of a relativistic potential model. With an improved method to solve the three-body Dirac equation, we determine a universal set of model parameters for both mesons and baryons by fitting heavy flavor masses in vacuum. Taking heavy quark potential from lattice QCD simulations in hot medium, we systematically calculate heavy flavor binding energies and averaged sizes as functions of temperature. The meson and baryons are separately sequentially dissociated in the quark-gluon plasma, and the mesons can survive at higher temperature due to the stronger potential between quark-antiquark pairs than that between quark-quark pairs.

    ↳ nucl-thhep-phCPC(2020)·23 citations
26. 26*

    Exponentially suppressed cosmological constant with enhanced gauge symmetry in heterotic interpolating models

    H. Itoyama🇯🇵 · Sota Nakajima🇯🇵

    A few nine-dimensional interpolating models with two parameters are constructed and the massless spectra are studied by considering compactification of heterotic strings on a twisted circle with Wilson line. It is found that there are some conditions between radius R and Wilson line A under which the gauge symmetry is enhanced. In particular, when the gauge symmetry is enhanced to SO(18) \times SO(14), the cosmological constant is exponentially suppressed. We also construct a non-supersymmetric string model which is tachyon-free in all regions of moduli space and whose gauge symmetry involves E_8.

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

    Hyperbolic field space and swampland conjecture for DBI scalar

    Shuntaro Mizuno🇯🇵 · Shinji Mukohyama🇯🇵 · Shi Pi🇯🇵 · Yun-Long Zhang🇯🇵

    We study a model of two scalar fields with a hyperbolic field space and show that it reduces to a single-field Dirac-Born-Infeld (DBI) model in the limit where the field space becomes infinitely curved. We apply the de Sitter swampland conjecture to the two-field model and take the same limit. It is shown that in the limit, all quantities appearing in the swampland conjecture remain well-defined within the single-field DBI model. Based on a consistency argument, we then speculate that the condition derived in this way can be considered as the de Sitter swampland conjecture for a DBI scalar field by its own. The condition differs from those proposed in the literature and only the one in the present paper passes the consistency argument. As a byproduct, we also point out that one of the inequalities in the swampland conjecture for a multi-field model with linear kinetic terms should involve the lowest mass squared for scalar perturbations and that this quantity can be significantly different from the lowest eigenvalue of the Hessian of the potential in the local orthonormal frame if the field space is highly curved. Finally, we propose an extension of the de Sitter swampland conjecture to a more general scalar field with the Lagrangian of the form $P(X,\phi )$, where $X=-(\partial \phi {)}^2/2$.

    ↳ hep-thastro-ph.COgr-qchep-phJCAP(2019)·45 citations
28. 28*

    Search of QCD phase transition points in the canonical approach of the NJL model

    Masayuki Wakayama🇯🇵 · Atsushi Hosaka🇯🇵

    We study the Lee-Yang zeros in the canonical approach to search phase transition points at finite temperature and density in the Nambu-Jona-Lasinio (NJL) model as an effective model of QCD. The canonical approach is a promising method to avoid the sign problem in lattice QCD at finite density. We find that a set of Lee-Yang zeros computed with finite degrees of freedom can be extrapolated to those with infinite degrees of freedom, providing the correct phase transition point. We propose the present method as a useful method for actual lattice simulations for QCD.

    ↳ hep-lathep-phPLB(2019)·8 citations
29. 29*

    On the impact of Majorana masses in gravity-matter systems

    Gustavo P. de Brito🇧🇷 · Yuta Hamada🇬🇷 · Antonio D. Pereira🇧🇷 · Masatoshi Yamada🇩🇪

    We investigate the Higgs-Yukawa system with Majorana masses of a fermion within asymptotically safe quantum gravity. Using the functional renormalization group method we derive the beta functions of the Majorana masses and the Yukawa coupling constant and discuss the possibility of a non-trivial fixed point for the Yukawa coupling constant. In the gravitational sector we take into account higher derivative terms such as $R^2$ and $R_{\mu \nu }{R}^{\mu \nu }$ in addition to the Einstein-Hilbert term for our truncation. For a certain value of the gravitational coupling constants and the Majorana masses, the Yukawa coupling constant has a non-trivial fixed point value and becomes an irrelevant parameter being thus a prediction of the theory. We also discuss consequences due to the Majorana mass terms to the running of the quartic coupling constant in the scalar sector.

    ↳ hep-thgr-qchep-phJHEP(2019)·58 citations
30. 30*

    Gravitational wave standard sirens and cosmological parameter measurement

    Xin Zhang🇨🇳

    Gravitational wave standard sirens can be used to arbitrate the $H_0$ tension within the following several years. In the future, the observation of gravitational wave standard sirens would be developed into a powerful new cosmological probe because they can play an important role in breaking parameter degeneracies formed by other observations. Therefore, gravitational wave standard sirens are of great importance for the future accurate measurement of cosmological parameters.

    ↳ astro-ph.COgr-qchep-phSCPMA(2019)·77 citations
31. 31*

    Gravitational Wave Signatures of Highly Magnetized Neutron Stars

    Cesar V. Flores🇧🇷 · Luiz L. Lopes🇧🇷 · Luis B. Castro🇧🇷 · Débora P. Menezes🇧🇷

    Motivated by the recent gravitational wave detection by the LIGO-VIRGO observatories, we study the Love number and dimensionless tidal polarizability of highly magnetized stars. We also investigate the fundamental quasi-normal mode of neutron stars subject to high magnetic fields. To perform our calculations we use the chaotic field approximation and consider both nucleonic and hyperonic stars. As far as the fundamental mode is concerned, we conclude that the role played by the constitution of the stars is far more relevant than the intensity of the magnetic field and if massive stars are considered, the ones constituted by nucleons only present frequencies somewhat lower than the ones with hyperonic cores, a feature that can be used to point out the real internal structure of neutron stars. Moreover, our studies clearly indicate that strong magnetic fields play a crucial role in the deformability of low mass neutron stars, with possible consequences on the interpretation of the detected gravitational waves signatures.

    ↳ nucl-thastro-ph.HEhep-phEPJC(2020)·27 citations
32. 32*

    Unitarity of the infinite-volume three-particle scattering amplitude arising from a finite-volume formalism

    Raúl A. Briceño🇺🇸 · Maxwell T. Hansen🇨🇭 · Stephen R. Sharpe🇺🇸 · Adam P. Szczepaniak🇺🇸

    In a previous publication, two of us derived a relation between the scattering amplitude of three identical bosons, ${\mathcal{M}}_3$, and a real function referred to as the {divergence-free} K matrix and denoted ${\mathcal{K}}_{\text{df},3}$. The result arose in the context of a relation between finite-volume energies and ${\mathcal{K}}_{\text{df},3}$, derived to all orders in the perturbative expansion of a generic low-energy effective field theory. In this work we set aside the role of the finite volume and focus on the infinite-volume relation between ${\mathcal{K}}_{\text{df},3}$ and ${\mathcal{M}}_3$. We show that, for any real choice of ${\mathcal{K}}_{\text{df},3}$, ${\mathcal{M}}_3$ satisfies the three-particle unitarity constraint to all orders. Given that ${\mathcal{K}}_{\text{df},3}$ is also free of a class of kinematic divergences, the function may provide a useful tool for parametrizing three-body scattering data. Applications include the phenomenological analysis of experimental data (where the connection to the finite volume is irrelevant) as well as calculations in lattice quantum chromodynamics (where the volume plays a key role).

    ↳ hep-lathep-phPRD(2019)·80 citations
33. 33*

    Simulations of the 3-Dimensional Velocity Distribution of Halo Weakly Interacting Massive Particles for Directional Dark Matter Detection Experiments

    Chung-Lin Shan🇹🇼

    In this paper, as a preparation of developing data analysis procedures for using 3-dimensional information offered by directional Dark Matter (DM) detection experiments, we study the patterns of the angular distribution of the Monte Carlo-generated 3-D velocity of halo Weakly Interacting Massive Particles (WIMPs) as well as apply the Bayesian fitting technique to reconstruct the radial distribution of the 3-D WIMP velocity. Besides the diurnal modulation of the angular WIMP velocity distribution, the so-called "directionality" of DM signals proposed in literature, we will also demonstrate possible "annual" modulations of both of the angular and the radial distributions of the 3-D WIMP velocity. Our Bayesian reconstruction results of (the annual modulation of) the radial WIMP velocity distribution will also be discussed in detail. For readers' reference, the angular distribution patterns of the 3-D WIMP velocity in the "laboratory (location)-dependent" reference frames of several underground laboratories are given in the Appendix.

    ↳ astro-ph.HEhep-ph11 citations
34. 34*

    Thermalisation of sterile neutrinos in the early Universe in the 3+1 scheme with full mixing matrix

    S. Gariazzo🇪🇸 · P. F. de Salas🇸🇪 · S. Pastor🇪🇸

    In the framework of a 3+1 scheme with an additional inert state, we consider the thermalisation of sterile neutrinos in the early Universe taking into account the full $4\times 4$ mixing matrix. The evolution of the neutrino energy distributions is found solving the momentum-dependent kinetic equations with full diagonal collision terms, as in previous analyses of flavour neutrino decoupling in the standard case. The degree of thermalisation of the sterile state is shown in terms of the effective number of neutrinos, $N_{\mathrm{eff}}$, and its dependence on the three additional mixing angles (${\theta }_{14}$, ${\theta }_{24}$, ${\theta }_{34}$) and on the squared mass difference $\Delta m_{41}^2$ is discussed. Our results are relevant for fixing the contribution of a fourth light neutrino species to the cosmological energy density, whose value is very well constrained by the final Planck analysis. For the preferred region of active-sterile mixing parameters from short-baseline neutrino experiments, we find that the fourth state is fully thermalised ($N_{\mathrm{eff}}\simeq 4$).

    ↳ astro-ph.COhep-phJCAP(2019)·137 citations
35. 35*

    Modelling conditional probabilities with Riemann-Theta Boltzmann Machines

    Stefano Carrazza🇮🇹 · Daniel Krefl🇨🇭 · Andrea Papaluca🇮🇹

    The probability density function for the visible sector of a Riemann-Theta Boltzmann machine can be taken conditional on a subset of the visible units. We derive that the corresponding conditional density function is given by a reparameterization of the Riemann-Theta Boltzmann machine modelling the original probability density function. Therefore the conditional densities can be directly inferred from the Riemann-Theta Boltzmann machine.

    ↳ stat.MLcs.LGhep-phJ.Phys.Conf.Ser.(2020)·0 citations
36. 36*

    The Different Regimes of Axion Gauge Field Inflation

    Valerie Domcke🇩🇪 · Stefan Sandner🇩🇪

    In axion gauge field inflation an axion-like particle driving cosmic inflation is coupled to the Chern-Simons density of an Abelian or non-Abelian gauge group. In the case of a non-Abelian gauge group, this can lead to the formation of a stable, homogeneous and isotropic gauge field background. We study the dynamics of the inflaton and gauge fields in terms of the two effective coupling parameters: the gauge coupling and the axion decay constant. Starting from the Bunch-Davies vacuum in the far past, we find that the non-trivial gauge field background arises only significantly after the cosmic microwave background (CMB) scales have left the horizon. At these scales, the model thus closely resembles Abelian axion inflation, thereby naturally reconciling the tension of non-Abelian axion gauge field inflation with the latest CMB observations. We further consider two exemplary UV-completions of this setup: multiple Peccei-Quinn axions and axion monodromy in string theory. In both cases we find that the majority of the parameter space is excluded by theoretical or observational constraints. The remaining parameter space can be divided into three regimes. (i) For small gauge couplings we recover natural inflation. For large gauge couplings the non-Abelian gauge theory either (ii) mimics the Abelian theory or (iii) non-linear interactions prohibit a linear analysis of the gauge field perturbations.

    ↳ astro-ph.COhep-phJCAP(2019)·11 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.