Thu·Dec 30, 2021Thursday·December 30, 2021

1. 01*

   Planar three-loop master integrals for $2\to 2$ processes with one external massive particle

   Dhimiter D. Canko🇬🇷 · Nikolaos Syrrakos🇬🇷

   We present analytic results for the two tennis-court integral families relevant to $2\to 2$ scattering processes involving one massive external particle and massless propagators in terms of Goncharov polylogarithms of up to transcendental weight six. We also present analytic results for physical kinematics for the ladder-box family and the two tennis-court families in terms of real-valued polylogarithmic functions, making our solutions well-suited for phenomenological applications.

   hep-phJHEP(2022)·35 citations
2. 02*

   Restricting the parameter space of Type-II Two Higgs Doublet Models with CP violation

   Mariana Frank🇨🇦 · Eric Gyabeng Fuakye🇨🇦 · Manuel Toharia🇨🇦

   We explore the parameter space of the type-II two-Higgs-doublet model with softly broken Z2 symmetry, allowing for CP violation in the scalar potential. Imposing theory-motivated and experimentally-driven constraints, we show that as the CP-violating phases are increased, only small regions of parameter space survive, including regions slightly away from the alignment limit. Electroweak oblique parameters and electric dipole moments emerge as most restrictive constraints. We show that imposing these constraints (as well as theoretical bounds such as perturbativity) the masses of the charged and heavy neutral Higgs, unlike in the CP conserving case, are bound from above and below. In particular, the heavy neutral Higgs masses are almost degenerate. In this parameter space region we highlight the relevant decay signals of the heavy neutral Higgs, involving both Zh and WW=ZZ, indicative of CP violation in the model.

   hep-phPRD(2022)·9 citations
3. 03*

   Large-x power laws of parton distributions remain inconclusive

   Aurore Courtoy🇲🇽 · Pavel M. Nadolsky🇺🇸

   Focusing on hadron scattering at large partonic momentum fractions $x$, we compare nonperturbative QCD predictions for the asymptotic behavior of DIS structure functions and parton distribution functions (PDFs) to the $x$ and $Q$ dependence of phenomenological PDFs. In the CT18 NNLO global QCD analysis, higher-order radiative contributions and functional mimicry of PDF parametrizations result in about one unit of uncertainty in the effective powers of $(1-x)$ falloff of nucleon PDFs. Similar uncertainties are present in the case of the pion PDF, an object of growing interest in phenomenology.

   hep-phRev.Mex.Fis.Suppl.(2022)·1 citation
4. 04*

   Implication of two-baryon azimuthal correlations in $pp$ collisions at LHC energies on the QGP

   Liuyao Zhang (1)🇨🇳 · Jinhui Chen (1)🇨🇳 · Wei Li (2)🇺🇸 · Zi-Wei Lin (3) ((1) Key Laboratory of Nuclear Physics and Ion-beam Application (MOE), Institute of Modern Physics, Fudan University, Shanghai, China, (2) T.W. Bonner Nuclear Laboratory, Rice University, Houston, Texas, USA, (3) Department of Physics, East Carolina University, Greenville, North Carolina, USA)🇺🇸

   The near-side depression in two-proton or two-antiproton azimuthal correlations in $pp$ collisions at $\sqrt{s}=$7 TeV has been observed experimentally and then qualitatively reproduced in our earlier studies with a multi-phase transport model. In this study, we further investigate the origin of the depression feature in two-baryon correlations in small collision systems. We find that the initial parton-level spatial correlation, a finite expansion in the parton stage, and quark coalescence are important ingredients leading to the near-side depression. In particular, we find that a finite expansion of the parton system leads to a finite space-momentum correlation at hadronization, which then converts the near-side depression in the coordinate space to that in the momentum space. These results suggest that a partonic matter with a finite lifetime is formed in the pp collisions. Further studies are needed to determine whether the partonic matter is near local equilibrium and can thus be called a QGP or far away from local equilibrium.

   hep-phPLB(2022)·10 citations
5. 05*

   Quantum kinetic theory for spin transport of quarks with background chromo-electromagnetic fields

   Di-Lun Yang🇹🇼

   We derive the quantum kinetic equations for massive and massless quarks coupled with the background chromo-electromagnetic fields from the Wigner-function approach with the $\hslash$ expansion and effective power-counting scheme. For each case, one obtains coupled color-singlet and color-octet kinetic equations, which also involve the scalar and axial-vector components for the charge and spin transport. These kinetic equations delineate entangled evolution of the corresponding distribution functions decomposed in color space. At weak coupling, we derive the close form of the color-singlet kinetic equations for spin transport, which incorporates the diffusion term and the source term that triggers dynamical spin polarization led by correlation functions of color fields. Also, the non-dynamical source term is found in the axial Wigner function. The induced spin polarization and axial charge currents by these source terms are discussed under physical assumptions for color-field correlators in near-equilibrium quark gluon plasmas. In the constant-field limit, we further obtain non-vanishing axial Ward identities, from which we extract the pseudo-scalar condensate for massive quarks at finite temperature.

   hep-phhep-thnucl-thJHEP(2022)·31 citations
6. 06*

   Direct CP violation in charmed meson decays within the standard model

   Hai-Yang Cheng🇹🇼 · Cheng-Wei Chiang🇹🇼

   Direct CP violation in two-body $D\to PP$ and $D\to VP$ decays is studied within the framework of the topological amplitude approach for tree amplitudes and the QCD factorization approach for penguin amplitudes. It is the interference between tree and long-distance penguin and penguin-exchange amplitudes that pushes CP asymmetry difference between $D^0\to K^{+}{K}^{-}$ and ${\pi }^{+}{\pi }^{-}$ modes up to the per mille level. Using the same mechanism, we find that CP asymmetry can also occur at the $10^{-3}$ level in many of the $D\to VP$ channels or otherwise be negligibly small. There are six golden modes which have sufficiently large branching fractions and direct CP violation at the per mille level. In particular, the direct CP asymmetry difference between $D^0\to K^{+}{K}^{\ast -}$ and ${\pi }^{+}{\rho }^{-}$ is predicted to be $(-1.61\pm 0.33)\times 10^{-3}$, very similar to the counterpart in the $PP$ sector. The LHCb's observation of CP asymmetry difference can be explained within the standard model without the need of new physics. The key lies in the long-distance penguin topology (penguin and penguin-exchange) arising from final-state rescattering.

   hep-phhep-exPoS(2023)·2 citations
7. 07*

   Validity of equivalent photon spectra and the photoproduction processes in p-p collisions

   Zhi-Lei Ma🇨🇳 · Zhun Lu🇨🇳 · Li Zhang🇨🇳

   Through a consistent analysis of the terms neglected in going from the accurate expression to the one of Weizsäcker-Williams approximation (WWA), the validity of equivalent photon spectra is studied, and a modified photon flux of proton is also derived. We take the photoproductions of photons and dileptons as examples, to provide the comparison between the exact results and the ones based on various photon fluxes. We present the results for the distributions in $Q^2$ (virtuality of photons), $y$ and $p_T$, the total cross sections are also estimated. The numerical results show that the modified equivalent photon spectrum reproduces the exact result within less than one percent. And the corrections of photoproduction processes to the dileptons and photons productions are about $20\%$.

   hep-phNPB(2022)·6 citations
8. 08*

   A general formula by $LD{L}^T$ decomposition for the type-I seesaw mechanism

   Masaki J. S. Yang🇯🇵

   By performing an approximate spectral decomposition to the inverse mass matrix of the right-handed neutrinos $M^{-1}$, we obtain a basis-independent formula for the type-I seesaw mechanism. Mathematically, it is based on the generalized Cholesky (or $LD{L}^T$) decomposition of the symmetric matrix $M^{-1}=LD{L}^T$, with a diagonal matrix $D$ and a lower unitriangular matrix $L$. Since the diagonalization of $L$ can be inverted without solving cubic equations, the formula will be useful to investigate general properties of the mechanism, such as flavor symmetries, generalized $CP$ symmetries, and fine-tunings.

   hep-phPTEP(2022)·3 citations
9. 09*

   Renormalon subtraction using Fourier transform: Analyses of simplified models

   Yuuki Hayashi🇯🇵

   For precise QCD prediction of observables, the ambiguity due to renormalons in perturbative calculations should be appropriately separated from Wilson coefficients in the framework of the operator-product-expansion. Recently, a new method has been developed which utilizes the properties of Fourier transform to separate multiple renormalons simultaneously from the Wilson coefficients. To understand how this method works analytically, we perform a renormalon separation from various toy models with the one-loop beta function. We confirm that each of the results is consistent with the theoretical expectations. In addition, we present a new formula for the resummation of UV renormalons and study its validity using one of the toy models.

   hep-phJHEP(2022)·2 citations
10. 10*

    Multi-Emission Kernels for Parton Branching Algorithms

    Maximilian Löschner🇩🇪 · Simon Plätzer🇦🇹 · Emma Simpson Dore🇩🇪

    We introduce a general framework to construct multi-emission kernels for parton branching algorithms at the amplitude level and across different soft and collinear limits. We highlight the connection of kinematic parameterizations and recoil schemes to the underlying power counting, and discuss in detail how soft radiation can be partitioned in between different collinear configurations beyond the single-emission picture underpinning the traditional dipole and angular ordering approaches. Our work is a vital cornerstone to build parton branching algorithms which include multiply-unresolved emissions in a fully differential way, and our construction can also be used to obtain splitting functions for probabilistic algorithms or other cross-section level objects such as subtraction terms.

    hep-ph13 citations
11. 11*

    Tracking Down the Route to the SM with Inflation and Gravitational Waves

    Eung Jin Chun🇰🇷 · Liliana Velasco-Sevilla🇰🇷

    We explore supersymmetric SO(10) models predicting observable proton decay and various topological defects which produce different shapes and strengths of gravitational wave backgrounds depending on the scales of intermediate symmetry breaking and inflation as well. We compare these to their non-supersymmetric counterparts. By identifying the scales at which gravitational wave signals appear, we would be able to track down a particular breaking chain and discern if it has a supersymmetric origin or not. It would also be useful to observe gravitational waves from more than one source among all possible topological defects and first order phase transitions for a realistic breaking chain. For these purposes, we work out specific examples in which the grand unification and relevant intermediate scales are calculable explicitly. It turns out that examples with gravitational waves from different sources are quite difficult to obtain, and the predicted gravitational wave profiles from domain walls and first order phase transitions obtained in some examples will require detectors in the kHz to MHz region.

    hep-phPRD(2022)·9 citations
12. 12*

    Identification of the low energy excess in dark matter searches with crystal defects

    Matti Heikinheimo🇫🇮 · Sebastian Sassi🇫🇮 · Kai Nordlund🇫🇮 · Kimmo Tuominen🇫🇮 · Nader Mirabolfathi🇺🇸

    An excess of events of unknown origin at low energies below 1 keV has been observed in multiple low-threshold dark matter detectors. Depending on the target material, nuclear recoil events at these energies may cause lattice defects, in which case a part of the true recoil energy is stored in the defect and not observed in the phonon detector. If the threshold for defect creation is sharp, this effect leads to a prominent feature in the observed recoil spectrum. Electronic recoils at low energies do not create defects and therefore the feature in the observed spectrum is not expected in that case. We propose to use the sharp defect creation threshold of diamond to test if the low energy events are due to nuclear recoils. Based on simulated data we expect the nuclear recoil bump in the observed spectrum to be visible in diamond with just ~0.1 gram days of exposure.

    hep-phPRD(2022)·19 citations
13. 13*

    Bottom quark and tau lepton masses in a toy $\mathrm{SU}(6)$

    Ning Chen🇨🇳 · Ying-nan Mao🇨🇳 · Zhaolong Teng🇨🇳

    We study a toy $\mathrm{SU}(6)$ model with the symmetry breaking pattern of the extended $331$ symmetry of $\mathrm{SU}(3{)}_c\otimes \mathrm{SU}(3{)}_W\otimes \mathrm{U}(1{)}_X$. A "fermion-Higgs mismatching" symmetry breaking pattern is proposed for more realistic model building. Within such symmetry breaking pattern, only one Higgs doublet develops vacuum expectation value for the spontaneous electroweak symmetry breaking, and gives tree-level top quark mass. A natural VEV splittings in the $331$ breaking Higgs fields gives tree-level masses to both bottom quark and tau lepton. The $125\mathrm{GeV}$ SM-like Higgs boson discovered at the LHC can have Yukawa couplings to bottom quark and tau lepton as in the SM prediction, and this suggests the $331$ symmetry breaking scale to be $\sim \mathcal{O}(10)\mathrm{TeV}$.

    hep-phEPJC(2023)·8 citations
14. 14*

    Pseudo-Dirac Sterile Neutrino Dark Matter

    Wei Chao · Siyu Jiang · Zhu-Yao Wang · Yu-Feng Zhou

    Sterile neutrino is a promising dark matter (DM) candidate. However the parameter space of this scenario has almost been ruled out by the X-ray observation results whenever the sterile neutrino is solely produced by the Dodelson-Widrow (DW) mechanism in the early Universe. In this letter we propose an extension to the minimal sterile neutrino DM model by introducing the pseudo-Dirac sterile neutrino, which implies the existence of two nearly degenerate Majorana states ${\hat{N}}_{1,2}^{}$, and a permutation symmetry. The heavy state ${\hat{N}}_1$ is produced via the DW mechanism, and the light state ${\hat{N}}_2$, which serves as the DM, is produced from the decay of ${\hat{N}}_1$ in the early Universe. The X-ray constraint is avoided by the permutation symmetry, which forbidden the two-body decay of the DM into active neutrinos and photon. A promising signal of this scenario is the effective number of neutrino species, which will be precisely measured in future experiments, such as CMB stage IV. We further study the impact of this model on the cosmological parameters. The Markov Chain Monte Carlo analysis for the Planck + BAO+R19 data gives $H_0=69.2_{-0.59}^{+0.58}$, which may relieve the Hubble tension.

    hep-phastro-ph.COEPJC(2025)·4 citations
15. 15*

    Kaon and Nucleon States with Hidden Charm

    Brenda B. Malabarba🇧🇷 · A. Martínez Torres🇧🇷 · K.P. Khemchandani🇧🇷 · Xiu-Lei Ren🇩🇪 · Li-Sheng Geng🇨🇳

    In this talk we discuss the formation of exotic hadrons with hidden charm arising from three-body interactions. To be more specific, in the strangeness sector, we predict the existence of a mesonic state, $K^{\ast }(4307)$, which is dynamically generated from the three-body interactions of the $KD{\bar{D}}^{\ast }$ system, has mass around $4307$ MeV and quantum numbers $I(J^P)=1/2(1^{-})$. In the baryonic sector, we predict the existence of $N^{\ast }$ states, which are generated from the three-body interactions of the $ND{\bar{D}}^{\ast }$ system, with masses around $4400\sim 4600$ MeV, widths of $2\sim 20$ MeV and positive parity.

    hep-phnucl-thRev.Mex.Fis.Suppl.(2022)·0 citations
16. 16*

    Nucleons as modified Ising models

    Shu-Man Hu🇨🇳 · Yin-Sen Luan🇨🇳 · Ji Xu🇨🇳

    In this paper, we propose a map which connects nucleons bound in nuclei and Ising spins in Ising model. This proposal is based on the fact that the description of states of nucleons and Ising spins could share the same type of observables. We present a nuclear model as a correspondence to an explicit modified Ising model and qualitatively confirm the correctness of this map by simulation on a two-dimensional square lattice. This map would help us understand the profound connections between different physical systems.

    hep-phCPC(2023)·2 citations
17. 17*

    A smuon in the NMSSM confronted with the muon g-2 and SUSY searches

    Kun Wang🇨🇳 · Jingya Zhu🇨🇳

    Motivated by the recent supersymmetry (SUSY) search results which prefer most SUSY particles heavy, and muon g-2 anomaly which prefers colorless SUSY particles light, we explore the status of a light smuon (the SUSY partner of left-handed muon lepton) in the Next-to-Minimal Supersymmetric Standard Model (NMSSM). Assuming colored SUSY particles be heavy, and considering numerous experimental constraints including muon g-2, SUSY searches, and dark matter, we scan the parameter space in the NMSSM with Z3-symmetry, checking the status of colorless SUSY particles and their possible mass order, and paying special attention to the smuon. After calculation and discussions, we draw the following conclusions: (i) The dominated SUSY contributions to muon g-2 come from the chargino-sneutrino loops, but the muon g-2 anomaly can also constrain the mass of smuon seriously because of the mass-degenerate relation between smuon and muon sneutrino. To interpret the muon g-2 anomaly at $1\sigma$ ($2\sigma$) level, the smuon need to be lighter than 1 TeV (1.8 TeV). (ii) When ${\tilde{\chi }}_1^0$ is wino- or higgsino-dominated, the smuon can escape from the direct searches with low mass, e.g., 300 GeV. (iii) When smuon and ${\tilde{\chi }}_1^0$ are mass-degenerate, the smuon can be as light as 200 GeV, while the ${\tilde{\chi }}_1^0$ is usually bino-dominated, or some singlino-dominated, and its relic density can most likely reach the observed value, and the dominated annihilating mechanism is slepton annihilations. In addition, we also list several benchmark points for further studies.

    hep-phhep-exCPC(2023)·21 citations
18. 18*

    S-wave pion-pion scattering lengths from nucleon-meson fluctuations

    Jürgen Eser🇫🇷 · Jean-Paul Blaizot🇫🇷

    We present calculations of the $S$-wave isospin-zero and isospin-two pion-pion scattering lengths within a nucleon-meson model with parity doubling. Both scattering lengths are computed in various approximations, ranging from a mean-field (MF) calculation towards the inclusion of loop corrections by means of the functional renormalization group (FRG). The bosonic part of the investigated nucleon-meson model is formulated in terms of stereographic projections as a "natural" set of coordinates on the respective vacuum manifold. We thereby elucidate subtleties concerning the truncation of the effective action w.r.t. higher-derivative pion interactions and the "successful" computation of the scattering lengths. As the main result, we find simultaneous agreement for the isospin-zero and isospin-two scattering lengths with experimental data within the ${\mathrm{LPA}}^{\prime }$-truncation of the FRG, together with chiral symmetry breaking (roughly) occurring at the characteristic scale of $4\pi f_{\pi }$. The isoscalar $\sigma$-mass is dynamically generated by the FRG integration of momentum modes, and is a prediction of the model. It ends being of the order of $500\mathrm{MeV}$, i.e., much lower than the value ($>1\mathrm{GeV}$) found in MF or one-loop treatment of this or related models. Finally, the convergence of the corresponding low-energy expansion of the quantum effective action in terms of pion momenta is discussed.

    hep-phnucl-thPRD(2022)·8 citations
19. 19*

    Correlated signals of first-order phase transitions and primordial black hole evaporation

    Danny Marfatia🇺🇸 · Po-Yan Tseng🇹🇼

    Fermi balls produced in a cosmological first-order phase transition may collapse to primordial black holes (PBHs) if the fermion dark matter particles that comprise them interact via a sufficiently strong Yukawa force. We show that phase transitions described by a quartic thermal effective potential with vacuum energy, $0.1\lesssim B^{1/4}/\mathrm{MeV}\lesssim 10^3$, generate PBHs of mass, $10^{-20}\lesssim M_{\mathrm{PBH}}/M_{\odot }\lesssim 10^{-16}$, and gravitational waves from the phase transition (at THEIA/$\mu$Ares) can be correlated with an isotropic extragalactic X-ray/$\gamma$-ray background from PBH evaporation (at AMEGO-X/e-ASTROGAM).

    hep-phastro-ph.COhep-exJHEP(2022)·42 citations
20. 20*

    Topological tensor invariants and the current algebra approach: Analysis of 196 nonleptonic two-body decays of single and double charm baryons -- a review

    Stefan Groote🇪🇪 · Jürgen G. Körner🇩🇪

    We shed new light on the standard current algebra approach to the nonleptonic two-body decays of single and double heavy charm baryons. By making use of the completeness relation for the flavor wave functions of the ground state baryon {\bf 20'} representation we are able to rewrite the results of the current algebra approach in terms of the seven topological tensor invariants describing the decays. The representation of the current algebra results in terms of topological tensor invariants depends only on the initial and final state of the process. The summation over intermediate states inherent to the current algebra result is automatically taken care of in the tensor representation. In this way one arrives at a new, quick and very compact assessment of the results of the current algebra/pole model calculation. For example, one can quickly identify the decays in which the p.v.\ $S$-wave amplitude is predicted to vanish implying zero polarization asymmetries in these decays. We provide tables of the values of the seven topological tensor invariants for all Cabibbo favored and singly and doubly Cabibbo suppressed nonleptonic single and double charm baryon decays. In total we treat 196 charm baryon decays. We also discuss the charm preserving $\Delta C=0$ decays of single charm baryons and the usual hyperon decays.

    hep-phhep-exnucl-thEPJC(2022)·27 citations
21. 21*

    A composite Froggatt-Nielsen model of flavor

    Leandro Da Rold (Centro Atómico Bariloche, Instituto Balseiro and CONICET)🇦🇷 · Federico Lamagna (Centro Atómico Bariloche, Instituto Balseiro and CONICET)🇦🇷

    A natural composite Higgs demands the presence of light resonances at the TeV scale, that in general are in conflict with bounds from flavor and CP violation. We propose a composite model with a Froggatt-Nielsen mechanism, that offers new possibilities for the origin of flavor. We analyse the interplay of partial compositeness and the horizontal U(1) symmetry in achieving the quark masses and mixing angles. We study the contributions to $\Delta F=2$ 4-fermion operators, as well as to $\Delta F=1$ and neutron dipole operators. We find scenarios in which the contribution to Left-Right and Right-handed operators involving the first and second generations can be suppressed, in particular for a region of parameter space it is possible to simultaneously suppress the mixed-chirality contribution to $K^0-{\bar{K}}^0$ mixing by one power of the Cabibbo angle, ${\lambda }_C$, and the dipole moments by ${\lambda }_C^2$ compared with anarchic partial compositeness, possibly making the resonances accessible at LHC. 4-fermion operators of $B_s$-meson mixing and Left-handed operators are not suppressed.

    hep-phPRD(2022)·2 citations
22. 22*

    Revisiting mono-$\tau$ tails at the LHC

    Florentin Jaffredo🇫🇷

    We revisit the constraints on semileptonic operators derived from the mono-$\tau$ high-$p_T$ events in $pp$ collisions at LHC. Like in previous studies, we obtain limits on the New Physics couplings from the CMS data much stronger than from the ATLAS data, despite a nearly equal integrated luminosity. We find that a neglected systematics on the $\tau$ lepton reconstruction efficiency can partly explain that difference. We then provide new limits on the New Physics couplings relevant to decays based on $b\to c\tau \bar{\nu }$ by using the recent ATLAS data with 139 ${\mathrm{fb}}^{-1}$. We also show that the inclusion of propagation of the New Physics particle can significantly worsen the bounds obtained by relying on Effective Field Theoretical treatment of New Physics.

    hep-phEPJC(2022)·15 citations
23. 23*

    Gravitational dark matter: free streaming and phase space distribution

    Md Riajul Haque🇮🇳 · Debaprasad Maity🇮🇳

    Gravitational dark matter (DM) is the simplest possible scenario that has recently gained interest in the early universe cosmology. In this scenario, DM is assumed to be produced from the decaying inflaton through the gravitational interaction during reheating. Gravitational production from the radiation bath will be ignored as our analysis shows it to be suppressed for a wide range of reheating temperatures. Ignoring any other internal parameters except the DM mass and spin, a particular inflation model such as $\alpha$-attractor, with a specific scalar spectral index $(n_s)$ has been shown to uniquely fix the dark matter mass. For fermion type dark matter we found the mass $m_f$ should be within $(10^4-10^{13})$ GeV, and for boson type DM, the mass $m_{s/X}$ turned out to be within $(10^{-8}-10^{13})$ GeV. Interestingly, if the inflaton equation of state ${\omega }_{\varphi }\to 1/3$, the DM mass also approaches towards unique value, $m_f\sim 10^{10}$ GeV and $m_{s/X}\sim 10^3(8\times 10^3)$ GeV irrespective of the value of ${\omega }_{\varphi }$. We further analyzed the phase space distribution $(f_Y)$, and free streaming length $({\lambda }_{fs})$ of these gravitationally produced DM. $f_Y$, which is believed to encode important information about DM, is shown to contain a characteristic primary peak at the initial time where the gravitational production is maximum for both fermion/boson. Apart from this fermionic phase-space distribution function contains an additional peak near the inflaton and fermion mass equality ($m_Y=m_{\varphi }$) arising for ${\omega }_{\varphi }>5/9$. Since dark matter is produced during the reheating phase, gravitational instability forming small-scale DM structures during this period will encode those phase space information and be observed at present. Crucial condition ${\lambda }_{fs}<{\lambda }_{re}$ of forming such a small scale DM structure has been analyzed in detail.

    hep-phastro-ph.COgr-qchep-thPRD(2022)·66 citations
24. 24*

    Holographic models of composite Higgs in the Veneziano limit. Part II. Fermionic sector

    Daniel Elander🇫🇷 · Michele Frigerio🇫🇷 · Marc Knecht🇫🇷 · Jean-Loic Kneur🇫🇷

    We continue our study of strongly-coupled, approximately scale-invariant gauge theories with a large number of flavours, which provide a suitable ultraviolet completion of the composite-Higgs scenario. We identify the requisite operators to realise partial compositeness of the Standard-Model fermions. In order to compute the spectrum of composite fermionic states, we extend the bottom-up holographic models, which we previously introduced to capture the main features of the non-perturbative dynamics in the Veneziano limit, by adding fermion fields in the bulk. We identify regions in parameter space where some fermionic bound states become light, depending in particular on the number of flavours, the operator scaling dimensions, and the bulk Yukawa couplings. We also observe a dense spectrum of states, when multi-scale dynamics is induced by a large backreaction of bulk scalars on the geometry. Adapting the formalism of the holographic Wilsonian renormalisation group, we study the linear coupling between the composite and elementary fermions, as a function of energy scale. We find that, in some circumstances, the associated operators are dangerously irrelevant: the renormalisation-group flow gives rise to a large linear coupling in the infrared, even when it is irrelevant from the point of view of the ultraviolet fixed point. We finally compute the partially composite spectrum, correlate it with the analysis of the flow, and assess the potential phenomenological implications, e.g. for the top-quark partners.

    hep-phhep-lathep-thJHEP(2022)·29 citations
25. 25*

    Composite self-interacting dark matter and Higgs

    Martin Rosenlyst🇬🇧

    We propose a novel mechanism in composite models that provides self-interacting dark matter along with the Higgs itself as composite particles, alleviating the Standard Model naturalness problem and explaining small-scale discrepancies such as the core-cusp and "too big to fail" problems. These dark matter candidates are stable due to global U(1) symmetries of the composite dynamics and their strong self-interactions are created by the novel mechanism based on top-quark partial compositeness. The relic density of the dark matter candidates is particle anti-particle symmetric and due to thermal freeze-out. We implement this mechanism in a four-dimensional gauge theory with a minimal number of fermions charged under a new confining gauge group $G_{\text{HC}}$.

    hep-phhep-thPLB(2022)·6 citations
26. 26*

    Modular flavor symmetry and vector-valued modular forms

    Xiang-Gan Liu🇨🇳 · Gui-Jun Ding🇨🇳

    We revisit the modular flavor symmetry from a more general perspective. The scalar modular forms of principal congruence subgroups are extended to the vector-valued modular forms, then we have more possible finite modular groups including ${\Gamma }_N$ and ${\Gamma }_N^{\prime }$ as the flavor symmetry. The theory of vector-valued modular forms provide a method of differential equation to construct the modular multiplets, and it also reveals the simple structure of the modular invariant mass models. We review the theory of vector-valued modular forms and give general results for the lower dimensional vector-valued modular forms. The general finite modular groups are listed up to order 72. We apply the formalism to construct two new lepton mass models based on the finite modular groups $A_4\times Z_2$ and $GL(2,3)$.

    hep-phhep-thJHEP(2022)·50 citations
27. 27*

    Models of ultra-heavy dark matter visible to macroscopic mechanical sensing arrays

    Carlos Blanco🇺🇸 · Bahaa Elshimy🇺🇸 · Rafael F. Lang🇺🇸 · Robert Orlando🇺🇸

    In recent years, the sensitivity of opto-mechanical force sensors has improved leading to increased interest in using these devices as particle detectors. In this study we consider scenarios where dark matter with mass close to the Planck scale may be probed by a large array of opto-mechanical accelerometers. We motivate a macroscopic mechanical search for ultra-heavy dark matter, exemplified by the efforts of the Windchime collaboration, by providing a survey of the model space that would be visible to such a search. We consider two classes of models, one that invokes a new long-range unscreened force and another that is only gravitationally interacting. We identify significant regions of well-motivated, potentially visible parameter space for versatile models such as Q-balls, composite dark matter, relics of gravitational singularities, and gravitationally produced ultra-heavy particles.

    hep-phhep-exPRD(2022)·16 citations
28. 28*

    Unified Origin of Dark Matter Self-Interactions and Low Scale Leptogenesis

    Debasish Borah (1)🇮🇳 · Arnab Dasgupta (2)🇺🇸 · Satyabrata Mahapatra (3)🇮🇳 · Narendra Sahu (3) ((1) Indian Institute of Technology Guwahati, (2) University of Pittsburgh, (3) Indian Institute of Technology Hyderabad)🇮🇳

    We propose a novel and minimal framework where a light scalar field can give rise to dark matter (DM) self-interactions, while enhancing the CP symmetry required for successful baryon asymmetry of the Universe via leptogenesis route. For demonstration purpose we choose to work in a scotogenic seesaw scenario where the lightest among the right handed neutrinos (RHN), introduced for generating light neutrino masses radiatively, play the role of DM while the heavier two can play non-trivial roles in generating DM relic as well as lepton asymmetry. While dark matter self-interactions mediated by an additional singlet scalar can alleviate the small scale issues of cold dark matter paradigm, the same scalar can give rise to new one-loop decay processes of heavy RHN into standard model leptons providing an enhanced contribution to CP asymmetry, even with sub-TeV scale RHN mass. The thermally under-abundant relic of DM due to large annihilation rates into its light mediator receives a late non-thermal contribution from a heavier RHN. With only five new particles involved in the scotogenic seesaw, each having non-trivial roles in generating DM relic and baryon asymmetry, the model can explain non-zero neutrino mass while being verifiable at different experiments related to DM direct detection, flavour physics and colliders. The mechanism we demonstrated here by using a scotogenic seesaw scenario is also applicable to other models.

    hep-phastro-ph.COPRD(2022)·17 citations
29. 29*

    First Measurement of the ${\Lambda }_c^{+}\to p{\eta }^{\prime }$ decay

    Belle Collaboration: S. X. Li🇨🇳 · J. X. Cui🇨🇳 · C. P. Shen🇨🇳 · I. Adachi🇯🇵 · H. Aihara🇯🇵 · S. Al Said🇸🇦 · D. M. Asner🇺🇸 · H. Atmacan🇺🇸 · T. Aushev🇷🇺 · R. Ayad🇸🇦 · V. Babu🇩🇪 · P. Behera🇮🇳 and 187 other authors

    We present the first measurement of the branching fraction of the singly Cabibbo-suppressed (SCS) decay ${\Lambda }_c^{+}\to p{\eta }^{\prime }$ with ${\eta }^{\prime }\to \eta {\pi }^{+}{\pi }^{-}$, using a data sample corresponding to an integrated luminosity of 981 $\mathrm{f}{\mathrm{b}}^{-1}$, collected by the Belle detector at the KEKB $e^{+}$$e^{-}$ asymmetric-energy collider. A significant ${\Lambda }_c^{+}$ signal is observed for the first time with a signal significance of 5.4$\sigma$. The relative branching fraction with respect to the normalization mode ${\Lambda }_c^{+}\to p{K}^{-}{\pi }^{+}$ is measured to be \begin{equation*} \frac{{\cal B}(\Lambda_c^+ \to p \eta')}{{\cal B}(\Lambda_c^+ \to p K^-\pi^+)} = (7.54 \pm 1.32 \pm 0.75) \times 10^{-3}, \end{equation*} where the uncertainties are statistical and systematic, respectively. Using the world-average value of $\mathcal{B}({\Lambda }_c^{+}\to p{K}^{-}{\pi }^{+})=(6.28\pm 0.32)\times 10^{-2}$, we obtain \begin{equation*} {\cal B}(\Lambda_c^+ \to p \eta') = (4.73 \pm 0.82 \pm 0.47 \pm 0.24)\times 10^{-4}, \end{equation*} where the uncertainties are statistical, systematic, and from $\mathcal{B}({\Lambda }_c^{+}\to p{K}^{-}{\pi }^{+})$, respectively.

    ↳ hep-exhep-phJHEP(2022)·15 citations
30. 30*

    Lorentz violation in Dirac and Weyl semimetals

    Alan Kostelecky🇺🇸 · Ralf Lehnert🇺🇸 · Navin McGinnis🇨🇦 · Marco Schreck🇧🇷 · Babak Seradjeh🇺🇸

    We propose a correspondence between the description of emergent Lorentz symmetry in condensed-matter systems and the established general effective field theory for Lorentz violation in fundamental theories of spacetime and matter. This correspondence has potential implications in both directions. We illustrate the proposal by investigating its consequences for the spectral and transport properties of Dirac and Weyl semimetals. Particular realizations of this framework give rise to Dirac nodal spectra with nodal lines and rings. We demonstrate a bulk-boundary correspondence between bulk topological invariants and drumhead surface states of these Dirac nodal semimetals. We calculate their transport coefficients in leading-order perturbation theory, thereby characterizing the unconventional electromagnetic response due to small deviations from emergent Lorentz invariance. Some prospective future applications of the correspondence are outlined.

    ↳ cond-mat.mes-hallcond-mat.mtrl-scicond-mat.str-elhep-ph+1PRResearch(2022)·76 citations
31. 31*

    Observation of $J/\psi$ Electromagnetic Dalitz Decays to $X(1835)$, $X(2120)$ and $X(2370)$

    BESIII Collaboration: M. Ablikim · M. N. Achasov · P. Adlarson · M. Albrecht · R. Aliberti · A. Amoroso · M. R. An · Q. An · X. H. Bai · Y. Bai · O. Bakina · R. Baldini Ferroli and 542 other authors

    Using a sample of about 10 billion $J/\psi$ events collected at a center-of-mass energy $\sqrt{s}=3.097$ GeV with the BESIII detector, the electromagnetic Dalitz decays $J/\psi \to e^{+}{e}^{-}{\pi }^{+}{\pi }^{-}{\eta }^{\prime }$, with ${\eta }^{\prime }\to \gamma {\pi }^{+}{\pi }^{-}$ and ${\eta }^{\prime }\to {\pi }^{+}{\pi }^{-}\eta$, have been studied. The decay $J/\psi \to e^{+}{e}^{-}X(1835)$ is observed with a significance of $15\sigma$, and the transition form factor of $J/\psi \to e^{+}{e}^{-}X(1835)$ is presented for the first time. The intermediate states $X(2120)$ and $X(2370)$ are also observed in the ${\pi }^{+}{\pi }^{-}{\eta }^{\prime }$ invariant mass spectrum with significances of $5.3\sigma$ and $7.3\sigma$. The corresponding product branching fractions for $J/\psi \to e^{+}{e}^{-}X$, $X\to {\pi }^{+}{\pi }^{-}{\eta }^{\prime }$ $(X=X(1835),X(2120)$ and $X(2370))$, are reported.

    ↳ hep-exhep-phPRL(2022)·16 citations
32. 32*

    Approximate symmetries, pseudo-Goldstones, and the second law of thermodynamics

    Jay Armas🇳🇱 · Akash Jain🇳🇱 · Ruben Lier🇩🇪

    We propose a general hydrodynamic framework for systems with spontaneously broken approximate symmetries. The second law of thermodynamics naturally results in relaxation in the hydrodynamic equations, and enables us to derive a universal relation between damping and diffusion of pseudo- Goldstones. We discover entirely new physical effects sensitive to explicitly broken symmetries. We focus on systems with approximate U(1) and translation symmetries, with direct applications to pinned superfluids and charge density waves. We also comment on the implications for chiral perturbation theory.

    ↳ hep-thcond-mat.softcond-mat.str-elhep-phPRD(2023)·42 citations
33. 33*

    Evolution of $\Lambda$ polarization in the hadronic phase of heavy-ion collisions

    Yifeng Sun🇮🇹 · Zhen Zhang🇨🇳 · Che Ming Ko🇺🇸 · Wenbin Zhao🇺🇸

    Using the AMPT + MUSIC+UrQMD hybrid model, we study the global and local spin polarizations of $\Lambda$ hyperons as functions of the freeze-out temperature of the spin degree of freedom in the hadronic phase of Au+Au collisions at $\sqrt{s_{NN}}=19.6$ GeV. Including contributions from both the thermal vorticity and thermal shear of the hadronic matter, we find that, with the spin freeze-out temperature dropping from the hadronization temperature of 160 MeV to 110 MeV at the kinetic freeze-out, both the global and local spin polarizations of $\Lambda$ hyperons due to the thermal vorticity decrease by a factor of two, while those due to the thermal shear decrease quickly and become negligibly small at 140 MeV. Our results suggest the importance of understanding the dynamical evolution of the spin degree of freedom in the hadronic stage in relativistic heavy-ion collisions.

    ↳ nucl-thhep-phPRC(2022)·34 citations
34. 34*

    Damping signatures at JUNO, a medium-baseline reactor neutrino oscillation experiment

    JUNO collaboration: Jun Wang · Jiajun Liao · Wei Wang · Angel Abusleme · Thomas Adam · Shakeel Ahmad · Rizwan Ahmed · Sebastiano Aiello · Muhammad Akram · Fengpeng An · Qi An · Giuseppe Andronico and 594 other authors

    We study damping signatures at the Jiangmen Underground Neutrino Observatory (JUNO), a medium-baseline reactor neutrino oscillation experiment. These damping signatures are motivated by various new physics models, including quantum decoherence, ${\nu }_3$ decay, neutrino absorption, and wave packet decoherence. The phenomenological effects of these models can be characterized by exponential damping factors at the probability level. We assess how well JUNO can constrain these damping parameters and how to disentangle these different damping signatures at JUNO. Compared to current experimental limits, JUNO can significantly improve the limits on ${\tau }_3/m_3$ in the ${\nu }_3$ decay model, the width of the neutrino wave packet ${\sigma }_x$, and the intrinsic relative dispersion of neutrino momentum ${\sigma }_{\mathrm{rel}}$.

    ↳ hep-exhep-phJHEP(2022)·27 citations
35. 35*

    Modified entropy of Kerr-de Sitter black hole in Lorentz symmetry violation theory

    Y. Onika Laxmi🇮🇳 · T. Ibungochouba Singh🇮🇳 · I. Ablu MEitei🇮🇳

    The quantum tunneling radiation of scalar particles near the event horizon of Kerr-de Sitter black hole is investigated in three systems of coordinates namely naive coordinate system, Painleve coordinate system and Eddington coordinate system using Lorentz violation theory in curved space time. The Klein-Gordon equation of scalar particles is transformed into Hamilton-Jacobi equation by using Lorentz violation theory in curved space time. We observe that due to Lorentz violation theory, the expressions of Hawking temperatures, the Bekenstein-Hawking entropies and specific heat capacities near the event horizon of Kerr-de Sitter black hole are modified. The Hawking temperatures, entropies and specific heat capacities increase or decrease depending upon the choices of ether like vectors $u^{\alpha }$

    ↳ gr-qchep-phGen.Rel.Grav.(2022)·21 citations
36. 36*

    Extended relaxation time approximation and relativistic dissipative hydrodynamics

    Dipika Dash🇮🇳 · Samapan Bhadury🇮🇳 · Sunil Jaiswal🇮🇳 · Amaresh Jaiswal🇮🇳

    Development of a new framework for derivation of order-by-order hydrodynamics from Boltzmann equation is necessary as the widely used Anderson-Witting formalism leads to violation of fundamental conservation laws when the relaxation-time depends on particle energy, or in a hydrodynamic frame other than the Landau frame. We generalize an existing framework for consistent derivation of relativistic dissipative hydrodynamics from the Boltzmann equation with a energy-dependent relaxation-time by extending the Anderson-Witting relaxation-time approximation. We argue that the present framework is compatible with conservation laws and derive first-order hydrodynamic equations in landau frame. Further, we show that the transport coefficients, such as shear and bulk viscosity as well as charge and heat diffusion currents, have corrections due to the energy dependence of relaxation time compared to what one obtains from the Anderson-Witting approximation of the collision term. The ratio of these transport coefficients are studied using a parametrized relaxation-time, and several interesting scaling features are reported.

    ↳ nucl-thhep-phhep-thPLB(2022)·38 citations
37. 37*

    The Power of Locality: Primordial Non-Gaussianity at the Map Level

    Daniel Baumann🇳🇱 · Daniel Green🇺🇸

    Primordial non-Gaussianity is a sensitive probe of the inflationary era, with a number of important theoretical targets living an order of magnitude beyond the reach of current CMB constraints. Maps of the large-scale structure of the universe, in principle, have the raw statistical power to reach these targets, but the complications of nonlinear evolution are thought to present serious, if not insurmountable, obstacles to reaching these goals. In this paper, we will argue that the challenge presented by nonlinear structure formation has been overstated. The information encoded in primordial non-Gaussianity resides in nonlocal correlations of the density field at three or more points separated by cosmological distances. In contrast, nonlinear evolution only alters the density field locally and cannot create or destroy these long-range correlations. This locality property of the late-time non-Gaussianity is obscured in Fourier space and in the standard bispectrum searches for primordial non-Gaussianity. We therefore propose to measure non-Gaussianity in the position space maps of the large-scale structure. As a proof of concept, we study the case of equilateral non-Gaussianity, for which the degeneracy with late-time nonlinearities is the most severe. We show that a map-level analysis is capable of breaking this degeneracy and thereby significantly improve the constraining power over previous estimates. Our findings suggest that "simulation-based inference" involving the forward modeling of large-scale structure maps has the potential to dramatically impact the search for primordial non-Gaussianity.

    ↳ astro-ph.COhep-phhep-thJCAP(2022)·46 citations
38. 38*

    Sound velocity effects on the phase transition gravitational wave spectrum in the sound shell model

    Xiao Wang🇨🇳 · Fa Peng Huang🇨🇳 · Yongping Li🇨🇳

    A cosmological first-order phase transition gravitational wave could provide a novel approach to studying the early Universe. In most cases, the acoustic gravitational wave from the sound wave mechanism is dominant. Considering different sound velocities in symmetric and broken phases, we study sound velocity effects on the acoustic phase transition gravitational wave spectra in the sound shell model. We demonstrate that different sound velocities could obviously modify the peak frequency and peak amplitude of the gravitational wave power spectra. Therefore, taking more realistic sound velocities might provide more accurate predictions for various gravitational wave experiments.

    ↳ astro-ph.COhep-phPRD(2022)·27 citations
39. 39*

    Characteristic momentum of Hydro+ and a bound on the speed of sound near the QCD critical point

    Navid Abbasi🇨🇳 · Matthias Kaminski🇺🇸

    Near the critical point in the QCD phase diagram, hydrodynamics breaks down at a momentum where the frequency of the fastest hydrodynamic mode becomes comparable with the decay rate of the slowest non-hydrodynamic mode. Hydro+ was developed as a framework which extends the range of validity of hydrodynamics beyond that momentum value. This was achieved through coupling the hydrodynamic modes to the slowest non-hydrodynamic mode. In this work, analyzing the spectrum of linear perturbations in Hydro+, we find that a slow mode falls out of equilibrium if its momentum is greater than a characteristic momentum value. That characteristic momentum turns out to be set by the branch points of the dispersion relations. These branch points occur at the critical momenta of so-called spectral curves and are related to the radius of convergence of the derivative expansion. The existence of such a characteristic momentum scale suggests that a particular class of slow modes has no remarkable effect on the flow of the plasma. Based on these results and previously derived relations to the stiffness of the equation of state, we find a temperature-dependent upper bound for the speed of sound near the critical point in the QCD phase diagram.

    ↳ nucl-thhep-phhep-thPRD(2022)·11 citations
40. 40*

    Cobordism and Deformation Class of the Standard Model

    Juven Wang🇺🇸 · Zheyan Wan🇨🇳 · Yi-Zhuang You🇺🇸

    't Hooft anomalies of quantum field theories (QFTs) with an invertible global symmetry G (including spacetime and internal symmetries) in a $d$d spacetime are known to be classified by a $d+1$d cobordism group TP${}_{d+1}$(G), whose group generator is a $d+1$d cobordism invariant written as an invertible topological field theory (iTFT) Z${}_{d+1}$. The deformation class of QFT is recently proposed to be specified by its symmetry G and an iTFT Z${}_{d+1}$. Seemingly different QFTs of the same deformation class can be deformed to each other via quantum phase transitions. In this work, we ask which deformation class controls the 4d ungauged or gauged (SU(3)$\times$SU(2)$\times$U(1))/${\mathbb{Z}}_q$ Standard Model (SM) for $q=1,2,3,6$ with a continuous or discrete $(\mathbf{B}-\mathbf{L})$ symmetry. We show that the answer contains some combination of 5d iTFTs: two $\mathbb{Z}$ classes associated with $(\mathbf{B}-\mathbf{L}{)}^3$ and $(\mathbf{B}-\mathbf{L})$-(gravity)${}^2$ 4d perturbative local anomalies, a mod 16 class Atiyah-Patodi-Singer $\eta$ invariant and a mod 2 class Stiefel-Whitney $w_2{w}_3$ invariant associated with 4d nonperturbative global anomalies, and additional ${\mathbb{Z}}_3\times {\mathbb{Z}}_2$ classes involving higher symmetries whose charged objects are Wilson electric or 't Hooft magnetic line operators. Out of $\mathbb{Z}$ classes of local anomalies and 24576 classes of global anomalies, we pin down a deformation class of SM labeled by $(N_f,n_{{\nu }_R},$ p${}^{\prime },q)$, the family and "right-handed sterile" neutrino numbers, magnetic monopole datum, and mod $q$ relation. Grand Unifications and Ultra Unification that replaces sterile neutrinos with new exotic gapped/gapless sectors (e.g., topological or conformal field theory) or gravitational sectors with topological or cobordism constraints, all reside in an SM deformation class. Neighbor phases/transitions/critical regions near SM exhibit beyond SM phenomena.

    ↳ hep-thcond-mat.str-elhep-lathep-ph+2PRD(2022)·37 citations
41. 41*

    Ionization of Gravitational Atoms

    Daniel Baumann🇳🇱 · Gianfranco Bertone🇳🇱 · John Stout🇺🇸 · Giovanni Maria Tomaselli🇳🇱

    Superradiant instabilities may create clouds of ultralight bosons around rotating black holes, forming so-called "gravitational atoms." It was recently shown that the presence of a binary companion can induce resonant transitions between bound states of these clouds, whose backreaction on the binary's orbit leads to characteristic signatures in the emitted gravitational waves. In this work, we show that the interaction with the companion can also trigger transitions from bound to unbound states of the cloud -- a process that we refer to as "ionization" in analogy with the photoelectric effect in atomic physics. The orbital energy lost in the process overwhelms the losses due to gravitational wave emission and contains sharp features carrying information about the energy spectrum of the cloud. Moreover, we also show that if the companion is a black hole, then the part of the cloud impinging on the event horizon will be absorbed. This "accretion" leads to a significant increase of the companion's mass, which alters the dynamical evolution and ensuing waveform of the binary. We argue that a combined treatment of resonances, ionization, and accretion is crucial to discover and characterize gravitational atoms with upcoming gravitational wave detectors.

    ↳ gr-qchep-phhep-thPRD(2022)·158 citations
42. 42*

    Detection of Prompt Fast-Variable Thermal Component in Multi-Pulse Short Gamma-Ray Burst 170206A

    Peng-Wei Zhao🇨🇳 · Qing-Wen Tang🇨🇳 · Yuan-Chuan Zou🇨🇳 · Kai Wang🇨🇳

    We report the detection of a strong thermal component in the short Gamma-Ray Burst 170206A with three intense pulses in its light curves, throughout which the fluxes of this thermal component exhibit fast temporal variability same as that of the accompanying non-thermal component. The values of the time-resolved low-energy photon index in the non-thermal component are between about -0.79 and -0.16, most of which are harder than -2/3 excepted in the synchrotron emission process. In addition, we found a common evolution between the thermal component and the non-thermal component, $E_{\mathrm{p},\mathrm{CPL}}\propto k{T}_{\mathrm{BB}}^{0.95\pm 0.28}$, and $F_{\mathrm{CPL}}\propto F_{\mathrm{BB}}^{0.67\pm 0.18}$, where $E_{\mathrm{p},\mathrm{CPL}}$ and $F_{\mathrm{CPL}}$ are the peak photon energy and corresponding flux of the non-thermal component, and $k{T}_{\mathrm{BB}}$ and $F_{BB}$ are the temperature and corresponding flux of the thermal component, respectively. Finally, we proposed that the photospheric thermal emission and the Comptonization of thermal photons may be responsible for the observational features of GRB 170206A.

    ↳ astro-ph.HEhep-phApJ(2022)·4 citations
43. 43*

    Steady asymptotic equilibria in conformal relativistic fluids

    Esteban Calzetta🇦🇷

    When one considers a shock wave in the frame where the shock is at rest, on either side one has a steady flow which converges to equilibrium away from the shock. However, hydrodynamics is unable to describe this flow if the asymptotic velocity is higher than the characteristic speed of the theory. We obtain an exact solution for the decay rate to equilibrium for a conformal fluid in kinetic theory under the relaxation time approximation, and compare it to two hydrodynamic schemes, one accounting for the second moments of the distribution function and thus equivalent, in the small deviations from equilibrium limit, to an Israel-Stewart framework, and another accounting for both second and third moments. While still having a finite characteristic speed, the second model is a significant improvement on the first.

    ↳ nucl-thhep-phphysics.flu-dynPRD(2022)·7 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.