Tue·Jan 22, 2019Tuesday·January 22, 2019

1. 01*

   Scotogenic Dark Symmetry as a residual subgroup of Standard Model Symmetries

   Salvador Centelles Chuliá🇪🇸 · Ricardo Cepedello🇪🇸 · Eduardo Peinado🇲🇽 · Rahul Srivastava🇪🇸

   We show that the scotogenic dark symmetry can be obtained as a residual subgroup of the global $U(1{)}_{B-L}$ symmetry already present in Standard Model. We propose a general framework where the $U(1{)}_{B-L}$ symmetry is spontaneously broken to an even ${\mathcal{Z}}_{2n}$ subgroup, setting the general conditions for neutrinos to be Majorana and the dark matter stability in terms of the residual ${\mathcal{Z}}_{2n}$. Under this general framework, as examples, we build a class of simple models where, in the scotogenic spirit, the dark matter candidate is the lightest particle running inside the neutrino mass loop. The global $U(1{)}_{B-L}$ symmetry in our framework being anomaly free can also be gauged in a straightforward manner leading to a richer phenomenology.

   hep-phCPC(2020)·35 citations
2. 02*

   Identification of nuclear effects in neutrino and antineutrino interactions on nuclei using generalized final-state correlations

   Xianguo Lu🇬🇧 · Jan T. Sobczyk🇵🇱

   In the study of neutrino and antineutrino interactions in the GeV regime, kinematic imbalances of the final-state particles have sensitivities to different nuclear effects. Previous ideas based on neutrino quasielastic interactions [Phys. Rev. C94, 015503 (2016), Phys. Rev. C95, 065501 (2017)] are now generalized to antineutrino quasielastic interactions, as well as neutrino and antineutrino pion productions. Measurements of these generalized final-state correlations could provide unique and direct constraints on the nuclear response inherently different for neutrinos and antineutrinos, and therefore delineate effects that could mimic charge-parity violation in neutrino oscillations.

   hep-phhep-exPRC(2019)·37 citations
3. 03*

   Limiting fragmentation at LHC energies

   B. Kellers🇩🇪 · G. Wolschin🇩🇪

   We investigate the validity of the limiting-fragmentation hypothesis in relativistic heavy-ion collisions at energies reached at the Large Hadron Collider (LHC). A phenomenological analysis of central AuAu and PbPb collisions based on a three-source relativistic diffusion model (RDM) is used to extrapolate pseudorapidity distributions of produced charged hadrons from RHIC to LHC energies into the fragmentation region. Data in this region are not yet available at LHC energies, but our results are compatible with the limiting-fragmentation conjecture in the full energy range sqrt(s_NN) = 19.6 GeV to 5.02 TeV.

   hep-phPTEP(2019)·7 citations
4. 04*

   Magnetic renormalons in a scalar self interacting $\lambda {\varphi }^4$ theory

   M. Correa🇨🇱 · M. Loewe🇨🇱 · D. Valenzuela🇨🇱 · R. Zamora🇨🇱

   We present an analysis about the influence of an external magnetic field on renormalons in a self interacting theory $\lambda {\varphi }^4$. In the weak magnetic field region, using an appropriate expansion for the Schwinger propagator's, we find new renormalons as poles on the real axis of the Borel plane, whose position do not depend on the magnetic field, but where the residues acquire in fact a magnetic dependence. In the strong magnetic limit, working in the lowest Landau level approximation (LLLA), these new poles are not longer present. We compare the magnetic scenario with previous results in the literature concerning thermal effects on renormalons in this theory.

   hep-phhep-thPRD(2019)·9 citations
5. 05*

   Soft Pions and More

   Stephen L. Adler🇺🇸

   I review the role that soft pion theorems, current algebras, sum rules, and anomalies played in the foundation of the standard model.

   hep-ph1 citation
6. 06*

   Application of the KMR and MRW unintegrated parton distributions to the EMC ratio of ${}^{6}Li$ nucleus in the $k_t$-factorization framework

   M. Modarres🇮🇷 · H. Hadian🇮🇷

   In the present work, it is intended to calculate the unintegrated parton distribution functions (UPDFs) of the ${}^{6}Li$ nucleus, which depend not only on the longitudinal momentum fraction $x$ (the Bjorken variable) and the factorization scale $\mu$ of partons, but also on their transverse momentum ($k_t$). Therefore, the KMR and MRW procedures are applied to generate the $k_t$-dependent parton distributions from the familiar integrated parton densities (PDFs), which were determined in our recent related work, using the constituent quark exchange model (CQEM) for the ${}^{6}Li$ nucleus. Then, the resulting UPDFs of ${}^{6}Li$ are compared with the UPDFs of free proton from our previous work. Afterwards, from the $k_t$-factorization formalism, the structure function (SF) of ${}^{6}Li$ nucleus is computed to extract its European Muon Collaboration (EMC) ratio. The results are compered with those generated from the ${}^{6}Li$ nucleus PDFs and the available NMC experimental data. It is observed that, especially in the small $x$ region, where the $k_t$ dependence of partons are important in the calculations of the hadron structure functions, the present EMC ratios are extremely improved compared with those of our previous work, and show an excellent agreement with the NMC experimental data.

   hep-phPRD(2018)·14 citations
7. 07*

   Non-minimal Higgs-gravity coupling and naturalness at the LHC and beyond

   Lei Wu🇨🇳 · Huaying Zhang🇨🇳 · Bin Zhu🇨🇳

   The non-minimal Higgs-gravity coupling, $\xi H^{†}HR$, can play an interesting role in particle physics. We utilize the available LHC Run-2 data to obtain the bound on the coupling $\xi$ and discuss the prospects of constraining it at CEPC, FCC-ee and ILC. Also, we investigate its implication on the naturalness.

   hep-phhep-exJCAP(2019)·6 citations
8. 08*

   Les Houches Lectures on Renormalization Theory and Effective Field Theories

   Matthias Neubert (Johannes Gutenberg University Mainz)🇩🇪

   These lectures review the formalism of renormalization in quantum field theories with special regard to effective quantum field theories. While renormalization theory is part of every advanced course on quantum field theory, for effective theories some more advanced topics become particularly important. This includes the renormalization of composite operators, operator mixing under scale evolution, and the resummation of large logarithms of scale ratios. This course thus sets the basis for many of the more specialized lecture courses delivered at the 2017 Les Houches Summer School.

   hep-phLes Houches Lect.Notes(2020)·46 citations
9. 09*

   On the Higgs mechanism in $U(1)\times U(2)\times U(3)$ gauge group as a base for noncommutative standard model

   M.M. Ettefaghi🇮🇷

   Noncommutative (NC) space-time leads to some strong constraints on the possible choices of gauge groups and allowed representations of matter and gauge fields. The standard model based on $U(3)\times U(2)\times U(1)$ can be transcribed to NC space-time consistently with these constraints \cite{nNCSM}. In fact, through two new symmetry reduction mechanisms, this gauge group is reduced to the usual standard model one. In this paper, we show that, on the contrary to the usual standard model, the Goldestone boson equivalence theorem is violated due to the incompatibility of the new symmetry reduction mechanisms with the electroweak Higgs mechanism.

   hep-phhep-th1 citation
10. 10*

    Anomalous features of particle production in high-multiplicity events of pp collisions at the LHC energies

    Samrangy Sadhu🇮🇳 · Premomoy Ghosh🇮🇳

    Prevalent models of multi-particle production in relativistic pp collisions at pre-LHC energies, fail to provide convincing explanations to certain significant features of the final-state charged particles in high-multiplicity pp events at the LHC. This article presents a study, contrasting those features, usually interpreted as collective behaviour of particle production in relativistic heavy-ion collisions, in the framework of hydrodynamic EPOS3 model, emphasizing quantitative comparison between the data and the model-based simulation in the same kinematic ranges, for better cognizance of the data. The work reveals quantitative mismatch between the data and the model.

    hep-phhep-exhep-thPRD(2019)·6 citations
11. 11*

    SMOM - $\overline{MS}$ Matching for $B_K$ at Two-loop Order

    Sebastian Jäger · Sandra Kvedaraitė🇬🇧

    The Kaon bag parameter, $B_K$, is a key non-perturbative ingredient in the search for new physics through CP-violation. It parameterizes the QCD hadronic matrix element of the effective weak $\Delta S=2$ four-quark operator which can only be computed non-perturbatively on the lattice. The perturbative matching of $B_K$ between the lattice renormalization schemes and $\overline{\text{mbox}MS}$ scheme has been done before at one-loop order. In this proceedings we describe an ongoing calculation of the conversion factors for $B_K$ between the four non-exceptional RI-SMOM schemes and the $\overline{\text{mbox}MS}$ scheme at two-loop order in perturbation theory.

    hep-phhep-latPoS(2018)·2 citations
12. 12*

    Littlest mu-tau seesaw

    Stephen F. King🇬🇧 · Ye-Ling Zhou🇬🇧

    We propose a $\mu -\tau$ reflection symmetric Littlest Seesaw ($\mu \tau$-LSS) model. In this model the two mass parameters of the LSS model are fixed to be in a special ratio by symmetry, so that the resulting neutrino mass matrix in the flavour basis (after the seesaw mechanism has been applied) satisfies $\mu -\tau$ reflection symmetry and has only one free adjustable parameter, namely an overall free mass scale. However the physical low energy predictions of the neutrino masses and lepton mixing angles and CP phases are subject to renormalisation group (RG) corrections, which introduces further parameters. Although the high energy model is rather complicated, involving $(S_4\times U(1){)}^2$ and supersymmetry, with many flavons and driving fields, the low energy neutrino mass matrix has ultimate simplicity.

    hep-phJHEP(2019)·22 citations
13. 13*

    Study of dark matter in the extended BLMSSM

    Jing-Jing Feng🇨🇳 · Shu-Min Zhao🇨🇳 · Xing-Xing Dong🇨🇳 · Zhong-Jun Yang🇨🇳 · Hai-Bin Zhang🇨🇳 · Fang Wang🇨🇳 · Tai-Fu Feng🇨🇳

    There are strong evidences for existence of dark matter in some experiments at present. However, the question is that we do not have a reasonable explanation for dark matter in the framework of the Standard Model(SM) of particle physics. It is necessary to extend the SM in order to explain the dark matter. According to the current possible existence conditions of dark matter, we choose ${\chi }_L^0$ and $\tilde{Y}$ as candidates for dark matter in the EBLMSSM. We study the dominant annihilation processes in detail, including ${\bar{\chi }}_L^0{\chi }_L^0(\overline{\stackrel{~}{Y}}\tilde{Y})\to {\bar{l}}^I{l}^I$ and ${\bar{\chi }}_L^0{\chi }_L^0(\overline{\stackrel{~}{Y}}\tilde{Y})\to {\bar{\nu }}^I{\nu }^I$. And we calculate their annihilation cross section $\sigma$ and relic density ${\Omega }_D{h}^2$. Then we analyze the limitations of dark matter relic density on the parameters of the EBLMSSM.

    hep-phPRD(2019)·0 citations
14. 14*

    Difficulties in the description of Drell-Yan processes at moderate invariant mass and high transverse momentum

    Alessandro Bacchetta🇮🇹 · Giuseppe Bozzi🇮🇹 · Martin Lambertsen🇩🇪 · Fulvio Piacenza🇮🇹 · Julius Steiglechner🇩🇪 · Werner Vogelsang🇩🇪

    We study the Drell-Yan cross section differential with respect to the transverse momentum of the produced lepton pair. We consider data with moderate invariant mass Q of the lepton pair, between 4.5 GeV and 13.5 GeV, and similar (although slightly smaller) values of the transverse momentum q_T. We approach the problem by deriving predictions based on standard collinear factorization, which are expected to be valid toward the high-q_T end of the spectrum and to which any description of the spectrum at lower q_T using transverse-momentum dependent parton distributions ultimately needs to be matched. We find that the collinear framework predicts cross sections that in most cases are significantly below available data at high q_T. We discuss additional perturbative and possible non-perturbative effects that increase the predicted cross section, but not by a sufficient amount.

    hep-phhep-exPRD(2019)·52 citations
15. 15*

    Analysis of strong decays of the $Z_c(4600)$ with the QCD sum rules

    Zhi-Gang Wang🇨🇳

    In this article, we tentatively assign the $Z_c(4600)$ to be the $[dc{]}_P[\bar{u}\bar{c}{]}_A-[dc{]}_A[\bar{u}\bar{c}{]}_P$ type vector tetraquark state and study its two-body strong decays with the QCD sum rules based on solid quark-hadron duality, the predictions for the partial decay widths $\Gamma (Z_c^{-}\to J/\psi {\pi }^{-})=41.4_{-14.9}^{+20.5}\mathrm{MeV}$, $\Gamma (Z_c^{-}\to {\eta }_c{\rho }^{-})=41.6_{-22.2}^{+32.7}\mathrm{MeV}$, $\Gamma (Z_c^{-}\to J/\psi a_0^{-}(980))=10.2_{-6.7}^{+11.3}\mathrm{MeV}$, $\Gamma (Z_c^{-}\to {\chi }_{c0}{\rho }^{-})=3.5_{-3.0}^{+6.7}\mathrm{MeV}$, $\Gamma (Z_c^{-}\to D^{\ast 0}{D}^{\ast -})=39.5_{-19.3}^{+29.6}\mathrm{MeV}$, $\Gamma (Z_c^{-}\to D^0{D}^{-})=6.6_{-3.0}^{+4.6}\mathrm{MeV}$ and $\Gamma (Z_c^{-}\to D^{\ast 0}{D}^{-})=1.0_{-0.6}^{+1.0}\mathrm{MeV}$ can be confronted to the experimental data in the future to diagnose the nature of the $Z_c(4600)$.

    hep-phInt.J.Mod.Phys.A(2019)·19 citations
16. 16*

    BBN constraints on the annihilation of MeV-scale dark matter

    Paul Frederik Depta🇩🇪 · Marco Hufnagel🇩🇪 · Kai Schmidt-Hoberg🇩🇪 · Sebastian Wild🇩🇪

    Thermal dark matter at the MeV scale faces stringent bounds from a variety of cosmological probes. Here we perform a detailed evaluation of BBN bounds on the annihilation cross section of dark matter with a mass $1\text{MeV}\lesssim m_{\chi }\lesssim 1\text{GeV}$. For $p-wave suppressed annihilations, constraints from BBN turn out to be significantly stronger than the ones from CMB observations, and are competitive with the strongest bounds from other indirect searches. We furthermore update the lower bound from BBN on the mass of thermal dark matter using improved determinations of primordial abundances. While being of similar strength as the corresponding bound from CMB, it is significantly more robust to changes in the particle physics model.

    hep-phastro-ph.COJCAP(2019)·132 citations
17. 17*

    Settling the $Z_c(4600)$ in the charged charmonium-like family

    Hua-Xing Chen🇨🇳 · Wei Chen🇨🇳

    Very recently LHCb reported the evidence of a new charged charmonium-like structure in the $J/\psi {\pi }^{-}$ invariant mass spectrum near 4600 MeV. In this work we investigate this structure together with three other charged charmonium-like states, the $Z_c(3900)$, $Z_c(4020)$, and $Z_c(4430)$. Our results suggest that the two higher states can be established as the first radial excitations of the two lower ones, all of which have the quantum numbers $J^{PC}=1^{+-}$. We propose to search for more relationship among exotic hadrons in order to better understand them.

    hep-phhep-exhep-latPRD(2019)·27 citations
18. 18*

    What can be learned from the transition form factor ${\gamma }^{\ast }{\gamma }^{\ast }\to {\eta }^{\prime }$: feasibility study

    Yao Ji🇩🇪 · Alexey Vladimirov🇩🇪

    We present an analysis of the recent measurement of ${\eta }^{\prime }$-meson production by two virtual photons made by BaBar collaboration. It is the first measurement of a transition form factor which is entirely within the kinematic regime of the collinear factorization approach and thus provides a clean test of QCD factorization theorem for distribution amplitudes (DAs). We demonstrate that the data is in agreement with the perturbative QCD. Also, we show that it is sensitive to power corrections to the factorization theorem and to the decay constants. We discuss features of the meson production cross-section and point out the kinematic regions that are sensitive to interesting physics. We also provide an estimation of uncertainties on the extraction of DA parameters.

    hep-phhep-exEPJC(2019)·4 citations
19. 19*

    Strong coupling constant and heavy quark masses in 2+1 flavor QCD

    P. Petreczky🇺🇸 · J. H. Weber🇺🇸

    We present a determination of the strong coupling constant and heavy quark masses in (2+1)-flavor QCD using lattice calculations of the moments of the pseudo-scalar quarkonium correlators at several values of the heavy valence quark mass with Highly Improved Staggered Quark (HISQ) action. We determine the strong coupling constant in the $\overline{MS}$ scheme at four low-energy scales corresponding to $m_c$, $1.5m_c$, $2m_c$, and $3m_c$, with $m_c$ being the charm quark mass. The novel feature of our analysis that up to eleven lattice spacings are used in the continuum extrapolations, with the smallest lattice spacing being $0.025$ fm. We obtain ${\Lambda }_{\overline{MS}}^{n_f=3}=298\pm 16$ MeV, which is equivalent to ${\alpha }_s(\mu =M_Z,n_f=5)=0.1159(12)$. For the charm and bottom quark masses in the $\overline{MS}$ scheme, we obtain: $m_c(\mu =m_c,n_f=4)=1.265(10)$ GeV and $m_b(\mu =m_b,n_f=5)=4.188(37)$ GeV.

    ↳ hep-lathep-phPRD(2019)·62 citations
20. 20*

    Heavy-Flavor Theory at "Hard and Electromagnetic Probes 2018"

    Ralf Rapp🇺🇸

    An overview is given of the theoretical developments on heavy quarks and quarkonia in heavy-ion collisions as reported at the "Hard and EM Probes 2018" conference. Specifically, we address progress in the understanding of heavy-flavor diffusion and its hadronization, quarkonium transport and the extraction of quarkonium melting temperatures, energy loss of heavy quarks at high momentum, and their rescattering in small colliding systems.

    ↳ nucl-thhep-phnucl-exPoS(2019)·3 citations
21. 21*

    Cylindrical Systems in General Relativity

    K. Bronnikov🇷🇺 · N. O. Santos🇫🇷 · Anzhong Wang🇺🇸

    With the arrival of the era of gravitational wave astronomy, the strong gravitational field regime will be explored soon in various aspects. In this article, we provide a general review over cylindrical systems in Einstein's theory of general relativity. In particular, we first review the general properties, both local and global, of several important solutions of Einstein's field equations, including the Levi-Civita and Lewis solutions and their extensions to include the cosmological constant and matter fields, and pay particular attention to properties that represent the generic features of the theory, such as the formation of the observed extragalactic jets and gravitational Faraday rotation. We also review studies of cylindrical wormholes, gravitational collapse and Hoop conjecture, and polarizations of gravitational waves. In addition, by rigorously defining cylindrically symmetric spacetimes, we clarify various (incorrect) claims existing in the literature, regarding to the generality of such spacetimes.

    ↳ gr-qcastro-ph.COhep-phhep-thClass.Quant.Grav.(2020)·74 citations
22. 22*

    Exploring non-Abelian gauge theory with energy-momentum tensor; stress, thermodynamics and correlations

    Masakiyo Kitazawa🇯🇵

    We perform various lattice numerical analyses with the energy-momentum tensor (EMT) defined through the gradient flow. We explore the spatial distribution of the stress tensor in static quark-anti-quark systems and thermodynamic quantities at nonzero temperature, as well as the correlation functions of EMT. The stress tensor distribution is also studied in the Abelian-Higgs model, which is compared with the lattice result.

    ↳ hep-lathep-phPoS(2019)·4 citations
23. 23*

    Fate of spin polarization in a relativistic fluid: An entropy-current analysis

    Koichi Hattori🇯🇵 · Masaru Hongo🇯🇵 · Xu-Guang Huang🇨🇳 · Mamoru Matsuo🇨🇳 · Hidetoshi Taya🇨🇳

    We derive relativistic hydrodynamic equations with a dynamical spin degree of freedom on the basis of an entropy-current analysis. The first and second laws of local thermodynamics constrain possible structures of the constitutive relations including a spin current and the antisymmetric part of the (canonical) energy-momentum tensor. Solving the obtained hydrodynamic equations within the linear-mode analysis, we find spin-diffusion modes, indicating that spin density is damped out after a characteristic time scale controlled by transport coefficients introduced in the antisymmetric part of the energy-momentum tensor in the entropy-current analysis. This is a consequence of mutual convertibility between spin and orbital angular momentum.

    ↳ hep-thcond-mat.mes-hallcond-mat.stat-mechhep-ph+1PLB(2019)·230 citations
24. 24*

    Scalar Field Theory Description of the Running Vacuum Model: the Vacuumon

    Spyros Basilakos🇬🇷 · Nick E. Mavromatos🇬🇧 · Joan Sola🇪🇸

    We investigate the running vacuum model (RVM) in the framework of scalar field theory.This dynamical vacuum model provides an elegant global explanation of the cosmic history, namely the universe starts from a non-singular initial de Sitter vacuum stage, it passes smoothly from an early inflationary era to a radiation epoch ("graceful exit") and finally it enters the dark matter and dark energy (DE) dominated epochs, where it can explain the large entropy problem and predicts a mild dynamical evolution of the DE. Within this phenomenologically appealing context, we formulate an effective {\it classical} scalar field description of the RVM through a field $\varphi$, called the {\it vacuumon}, which turns out to be very helpful for an understanding and practical implementation of the physical mechanisms of the running vacuum during both the early universe and the late time cosmic acceleration. In the early universe the potential for the vacuumon may be mapped to a potential that behaves similarly to that of the scalaron field of Starobinsky-type inflation at the {\it classical} level, whilst in the late universe it provides an effective scalar field description of DE. The two representations, however, are not physically equivalent since the mechanisms of inflation are entirely different. Moreover, unlike the scalaron, vacuumon is treated as a classical background field, and not a fully fledged quantum field, hence cosmological perturbations will be different between the two pictures of inflation.

    ↳ gr-qchep-phhep-thJCAP(2019)·18 citations
25. 25*

    Evading Derrick's theorem in curved space: Static metastable spherical domain wall

    G. Alestas🇬🇷 · L. Perivolaropoulos🇬🇷

    A recent analysis by one of the authors\cite{Perivolaropoulos:2018cgr} has pointed out that Derrick's theorem can be evaded in curved space. Here we extend that analysis by demonstrating the existence of a static metastable solution in a wide class of metrics that include a Schwarzschild-Rindler-AntideSitter spacetime (Grumiller metric) defined as $d{s}^2=f(r)d{t}^2-f(r{)}^{-1}d{r}^2-r^2(d{\theta }^2+{\sin }^2\theta d{\varphi }^2)$ with $f(r)=1-\frac{2Gm}{r}+2br-\frac{\Lambda }{3}{r}^2$ ($\Lambda <0b<0$). This metric emerges generically as a spherically symmetric vacuum solution in a class of scalar-tensor theories\cite{Grumiller:2010bz} as well as in Weyl conformal gravity\cite{Mannheim:1988dj}. It also emerges in General Relativity (GR) in the presence of a cosmological constant and a proper spherically symmetric perfect fluid. We demonstrate that this metric supports a static spherically symmetric metastable soliton scalar field solution that corresponds to a spherical domain wall. We derive the static solution numerically and identify a range of parameters $m,b,\Lambda$ of the metric for which the spherical wall is metastable. Our result is supported by both a minimization of the scalar field energy functional with proper boundary conditions and by a numerical simulation of the scalar field evolution. The metastable solution is very well approximated as $\varphi (r)=Tanh\left[q(r-r_0)\right]$ where $r_0$ is the radius of the metastable wall that depends on the parameters of the metric and $q$ determines the width of the wall. We also find the gravitational effects of the thin spherical wall solution and its backreaction on the background metric that allows its formation. We show that this backreaction does not hinder the metastability of the solution even though it can change the range of parameters that correspond to metastability.

    ↳ gr-qcastro-ph.COhep-phhep-th+1PRD(2019)·22 citations
26. 26*

    Four loop scalar ${\varphi }^4$ theory using the functional renormalization group

    M.E. Carrington🇨🇦 · C.D. Phillips🇨🇦

    We consider a symmetric scalar theory with quartic coupling in 4-dimensions. We show that the 4 loop 2PI calculation can be done using a renormalization group method. The calculation involves one bare coupling constant which is introduced at the level of the Lagrangian and is therefore conceptually simpler than a standard 2PI calculation, which requires multiple counterterms. We explain how our method can be used to do the corresponding calculation at the 4PI level, which cannot be done using any known method by introducing counterterms.

    ↳ hep-thhep-phUniverse(2019)·3 citations
27. 27*

    Causality of the Einstein-Israel-Stewart Theory with Bulk Viscosity

    Fabio S. Bemfica (Rio Grande do Norte U.)🇧🇷 · Marcelo M. Disconzi (Vanderbilt U.)🇺🇸 · Jorge Noronha (Sao Paulo U.)🇧🇷

    We prove that Einstein's equations coupled to equations of Israel-Stewart-type, describing the dynamics of a relativistic fluid with bulk viscosity and nonzero baryon charge (without shear viscosity or baryon diffusion) dynamically coupled to gravity, are causal in the full nonlinear regime. We also show that these equations can be written as a first-order symmetric hyperbolic system, implying local existence and uniqueness of solutions to the equations of motion. We use an arbitrary equation of state and do not make any simplifying symmetry or near-equilibrium assumption, requiring only physically natural conditions on the fields. These results pave the way for the inclusion of bulk viscosity effects in simulations of gravitational-wave signals coming from neutron star mergers.

    ↳ gr-qcastro-ph.HEhep-phmath-ph+2PRL(2019)·124 citations
28. 28*

    Paramagnetic squeezing of a uniformly expanding quark-gluon plasma in and out of equilibrium

    N. Sadooghi🇮🇷 · S.M.A. Tabatabaee🇮🇷

    The plasma of quarks and gluons created in ultrarelativistic heavy-ion collisions turns out to be paramagnetic. In the presence of a background magnetic field, this paramagnetism thus leads to a pressure anisotropy, similar to anisotropies appearing in a viscous fluid. In the present paper, we use this analogy, and develop a framework similar to anisotropic hydrodynamics, to take the pressure anisotropy caused, in particular, by the nonvanishing magnetization of a plasma of quarks and gluons into account. We consider the first two moments of the classical Boltzmann equation in the presence of an electromagnetic source in the relaxation-time approximation, and derive a set of coupled differential equations for the anisotropy parameter ${\xi }_0$ and the effective temperature ${\lambda }_0$ of an ideal fluid with nonvanishing magnetization. We also extend this method to a dissipative fluid with finite magnetization in the presence of a strong and dynamical magnetic field. We present a systematic method leading to the one-particle distribution function of this magnetized dissipative medium in a first-order derivative expansion, and arrive at analytical expressions for the shear and bulk viscosities in terms of the anisotropy parameter $\xi$ and effective temperature $\lambda$. We then solve the corresponding differential equations for $({\xi }_0,{\lambda }_0)$ and $(\xi ,\lambda )$ numerically, and determine, in this way, the proper time and temperature dependence of the energy density, directional pressures, speed of sound, and the magnetic susceptibility of a longitudinally expanding magnetized quark-gluon plasma in and out of equilibrium.

    ↳ nucl-thcond-mat.str-elhep-lathep-phPRD(2019)·8 citations
29. 29*

    Chiral symmetry breaking and the Unruh effect

    Adrian Casado-Turrion🇪🇸 · Antonio Dobado🇪🇸

    The possibility of chiral symmetry restoration by acceleration is considered. The Thermalization Theorem formalism and the large $N$ limit (with $N$ being the number of pions) are employed to solve the lowest-order approximation to QCD at low energies in Rindler spacetime. It is shown that chiral symmetry is restored for accelerations higher than the critical value $a_c=4\pi f_{\pi }$, with $f_{\pi }$ being the pion decay constant. The results are completely analogous to those obtained in the inertial, finite-temperature case, evincing the ontic character of the Unruh effect.

    ↳ hep-thgr-qchep-ph0 citations
30. 30*

    TXS 0506+056, the first cosmic neutrino source, is not a BL Lac

    P. Padovani🇩🇪 · F. Oikonomou🇩🇪 · M. Petropoulou🇺🇸 · P. Giommi🇮🇹 · E. Resconi🇩🇪

    We present evidence that TXS 0506+056, the first plausible non-stellar neutrino source, despite appearances, is not a blazar of the BL Lac type but is instead a masquerading BL Lac, i.e., intrinsically a flat-spectrum radio quasar with hidden broad lines and a standard accretion disk. This re-classification is based on: (1) its radio and O II luminosities; (2) its emission line ratios; (3) its Eddington ratio. We also point out that the synchrotron peak frequency of TXS 0506+056 is more than two orders of magnitude larger than expected by the so-called "blazar sequence", a scenario which has been assumed by some theoretical models predicting neutrino (and cosmic-ray) emission from blazars. Finally, we comment on the theoretical implications this re-classification has on the location of the $\gamma$-ray emitting region and our understanding of neutrino emission in blazars.

    ↳ astro-ph.HEastro-ph.GAhep-exhep-phMNRAS(2019)·199 citations
31. 31*

    Parton energy loss in the reformulated weakly-coupled kinetic approach

    Tianyu Dai🇺🇸 · Steffen A. Bass🇺🇸 · Jean-François Paquet🇺🇸 · Derek Teaney🇺🇸

    Interactions between hard partons and the quark-gluon plasma range from frequent soft interactions to rare hard scatterings. The larger number of soft interactions makes possible an effective stochastic description of parton-plasma interactions in terms of drag and diffusion transport coefficients. In this work, we present a numerical implementation that builds upon this systematic division between soft and hard parton-plasma interactions. We study the dependence of the single parton distribution on the cutoff between soft and hard parton-plasma interactions, both for small and phenomenological values of the strong coupling constant.

    ↳ nucl-thhep-phPoS(2019)·1 citation
32. 32*

    Inverse Compton emission from millisecond pulsars in the Galactic bulge

    Deheng Song🇺🇸 · Oscar Macias🇯🇵 · Shunsaku Horiuchi🇺🇸

    Analyses of Fermi Gamma-Ray Space Telescope data have revealed a source of excess diffuse gamma rays towards the Galactic center that extends up to roughly $\pm$20 degrees in latitude. The leading theory postulates that this GeV excess is the aggregate emission from a large number of faint millisecond pulsars (MSPs). The electrons and positrons ($e^{\pm }$) injected by this population could produce detectable inverse-Compton (IC) emissions by up-scattering ambient photons to gamma-ray energies. In this work, we calculate such IC emissions using GALPROP. A triaxial three-dimensional model of the bulge stars obtained from a fit to infrared data is used as a tracer of the putative MSP population. This model is compared against one in which the MSPs are spatially distributed as a Navarro-Frenk-White squared profile. We show that the resulting spectra for both models are indistinguishable, but that their spatial morphologies have salient recognizable features. The IC component above $\sim$TeV energies carries information on the spatial morphology of the injected $e^{\pm }$. Such differences could potentially be used by future high-energy gamma-ray detectors such as the Cherenkov Telescope Array to provide a viable multiwavelength handle for the MSP origin of the GeV excess.

    ↳ astro-ph.HEastro-ph.GAhep-phPRD(2019)·20 citations
33. 33*

    Physics Beyond Colliders at CERN: Beyond the Standard Model Working Group Report

    J. Beacham🇺🇸 · C. Burrage🇬🇧 · D. Curtin🇨🇦 · A. De Roeck🇨🇭 · J. Evans🇺🇸 · J. L. Feng🇺🇸 · C. Gatto🇮🇹 · S. Gninenko🇷🇺 · A. Hartin🇬🇧 · I. Irastorza🇪🇸 · J. Jaeckel🇩🇪 · K. Jungmann🇳🇱 and 21 other authors

    The Physics Beyond Colliders initiative is an exploratory study aimed at exploiting the full scientific potential of the CERN's accelerator complex and scientific infrastructures through projects complementary to the LHC and other possible future colliders. These projects will target fundamental physics questions in modern particle physics. This document presents the status of the proposals presented in the framework of the Beyond the Standard Model physics working group, and explore their physics reach and the impact that CERN could have in the next 10-20 years on the international landscape.

    ↳ hep-exhep-phphysics.ins-detJ.Phys.G(2020)·779 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.