Tue·Jan 7, 2020Tuesday·January 7, 2020

1. 01*

   Spacetime development of in-medium hadronization: Scenario for leading hadrons

   B. Guiot🇨🇱 · B. Z. Kopeliovich🇨🇱

   We present a perturbative QCD based model for vacuum and in-medium hadronization. The effects of induced energy loss and nuclear absorption have been included. The main objective is the determination of the relative contribution of these mechanisms to the multiplicity ratio observable, measured in semi-inclusive deep-inelastic scattering off deuterium and nuclear targets. This is directly related to the determination of the production length, $Lp$, necessary for a quark to turn into a prehadron. We compare our results with HERMES data for multiplicity ratio and $p_t$-broadening, and show that the description of the whole data set, keeping the model parameters fixed, puts strong constrains on $Lp$. Contrary to induced-energy-loss based models, we find an important contribution from nuclear absorption at HERMES energies. Finally, we discuss some consequences of our study for the LHC physics, and we present the model predictions for the future EIC experiment.

   hep-phhep-exPRC(2020)·10 citations
2. 02*

   Decay of Cosmic Global String Loops

   Ayush Saurabh🇺🇸 · Tanmay Vachaspati🇺🇸 · Levon Pogosian🇨🇦

   We numerically study the decay of cosmic global string loops due to radiation of Goldstone bosons and massive scalar ($\chi$) particles. The length of loops we study range from 200-1000 times the width of the string core. We find that the lifetime of a loop is $\approx 1.4L$. The energy spectrum of Goldstone boson radiation has a $k^{-1}$ fall off, where $k$ is the wavenumber, and a sharp peak at $k\approx m_{\chi }/2$, where $m_{\chi }$ is the mass of $\chi$. The latter is a new feature and implies a peak at high energies (MeV-GeV) in the cosmological distribution of QCD axions.

   hep-phastro-ph.COhep-thPRD(2020)·53 citations
3. 03*

   Hidden-charm and bottom tetra- and pentaquarks with strangeness in the hadro-quarkonium and compact tetraquark models

   J. Ferretti🇺🇸 · E. Santopinto🇮🇹

   In two recent papers, we used the hadro-quarkonium model to study the properties of hidden-charm and bottom tetraquarks and pentaquarks. Here, we extend the previous results and calculate the masses of heavy-quarkonium-kaon/hyperon systems. We also compute the spectrum of hidden-charm and bottom tetraquarks with strangeness in the compact tetraquark (diquark-antidiquark) model. If heavy-light exotic systems with non-null strangeness content were to be observed experimentally, it might be possible to distinguish among the large variety of available theoretical pictures for tetra- and pentaquark states and, possibly, rule out those which are not compatible with the data.

   hep-phJHEP(2020)·89 citations
4. 04*

   Gravitational wave and electroweak baryogenesis with two Higgs doublet models

   Ruiyu Zhou🇨🇳 · Ligong Bian🇨🇳

   We study stochastic gravitational wave production and baryon number generation at electroweak phase transition with the two Higgs doublet models. The produced stochastic gravitational wave during the strongly first-order phase transition can be probed by future space-based interferometers. The {\it nonlocal} electroweak baryogengesis cannot address the observed Baryon asymmetry of the Universe successfully in the strongly first-order phase transition parameter spaces due to the CP violation phase is severely bounded by the electron electric dipole moment measurement ACMEII.

   hep-phastro-ph.COPLB(2022)·47 citations
5. 05*

   Possible Formation of a Perfect Fluid in $pp$, $p$-Pb, Xe-Xe and Pb-Pb Collisions at the Large Hadron Collider Energies: A Color String Percolation Approach

   Dushmanta Sahu🇮🇳 · Sushanta Tripathy🇮🇳 · Raghunath Sahoo🇮🇳 · Swatantra Kumar Tiwari🇮🇳

   Isothermal compressibility (${\kappa }_{\mathrm{T}}$) is an important thermodynamic observable which gives information about the deviation of a system from perfect fluid behavior. In this work, for the first time we have estimated the isothermal compressibility of QCD matter formed in high energy hadronic and nuclear collisions using color string percolation model (CSPM), where we investigate the change in ${\kappa }_{\mathrm{T}}$ as a function of final state charged particle multiplicity and initial percolation temperature across various collision species. The estimated initial percolation temperature for different collision systems at different collision energies helps us to have a better understanding of the system at the initial phase of evolution. The comparison of the CSPM results for isothermal compressibility with that for the well known fluids, indicates that the matter formed in heavy-ion collisions might be the {\it closest perfect fluid} found in nature. This estimation complements the well-known observation of minimum shear viscosity to entropy density ratio for a possible QGP medium created in heavy-ion collision experiments. A threshold of pseudorapidity density of charged particles, $⟨d{N}_{\mathrm{ch}}/d\eta ⟩\ge 20$ in the final state event multiplicity is observed, after which one may look for a possible QGP formation at the LHC energies.

   hep-phhep-exnucl-exnucl-thEPJA(2022)·17 citations
6. 06*

   Taming of preasymptotic small x evolution within resummation framework

   Michal Deak🇺🇸 · Leonid Frankfurt🇮🇱 · Mark Strikman🇺🇸 · Anna Stasto🇺🇸

   It is well understood that the leading logarithmic approximation for the amplitudes of high energy processes is insufficient and that the next-to-leading logarithmic effects are very large and lead to instability of the solution. The resummation at low $x$, which includes kinematical constraints and other corrections leads to stable result. Using previously established resummation procedure we study in detail the preasymptotic effects which occur in the solution to the resummed BFKL equation when the energy is not very large. We find that in addition to the well known reduction of the intercept, which governs the energy dependence of the gluon Green's function, resummation leads to the delay of the onset of its small $x$ growth. Moreover the gluon Green's function develops a dip or a plateau in wide range of rapidities, which increases for large scales. The preasymptotic region in the gluon Green's function extends to about $8$ units in rapidity for the transverse scales of the order of $30-100\mathrm{GeV}$. To visualize the expected behavior of physical processes with two equal hard scales we calculate the cross section of the process ${\gamma }^{\ast }+{\gamma }^{\ast }\to X$ to be probed at future very high-energy electron-positron colliders. We find that at ${\gamma }^{\ast }{\gamma }^{\ast }$ energies below $100\mathrm{GeV}$ the BFKL Pomeron leads to smaller value of the cross section than the Born approximation, and only starts to dominate at energies about $100\mathrm{GeV}$. This pattern is significantly different from the one which we find using LL approximation. We also analyze the transverse momentum contributions to the cross section for different virtualities of the photons and find that the dominant contributions to the integral over the transverse momenta comes from lower values than the the external scales in the process under consideration.

   hep-phEPJC(2020)·3 citations
7. 07*

   Basis-independent treatment of the complex 2HDM

   Rafael Boto🇵🇹 · Tiago V. Fernandes🇵🇹 · Howard E. Haber🇺🇸 · Jorge C. Romao🇵🇹 · Joao P. Silva🇵🇹

   The complex 2HDM (C2HDM) is the most general CP-violating two Higgs doublet model that possesses a softly-broken ${\mathbb{Z}}_2$ symmetry. However, the physical consequences of the model cannot depend on the basis of scalar fields used to define it. Thus, to get a better sense of the significance of the C2HDM parameters, we have analyzed this model by employing a basis-independent formalism. This formalism involves transforming to the Higgs basis (which is defined up to an arbitrary complex phase) and identifying quantities that are invariant with respect to this phase degree of freedom. Using this method, we have obtained the constraints that enforce the softly-broken ${\mathbb{Z}}_2$ symmetry. One can then relate the C2HDM parameters to basis-independent quantities up to a two-fold ambiguity. We then show how this remaining ambiguity is resolved. We also examine the possibility of spontaneous CP violation when the scalar potential of the C2HDM is explicitly CP-conserving. Basis-independent constraints are presented that govern the presence of spontaneous CP violation.

   hep-phPRD(2020)·42 citations
8. 08*

   Stable scalar tetraquark $T_{bb;\bar{u}\bar{d}}^{-}$

   S. S. Agaev🇦🇿 · K. Azizi🇮🇷 · B. Barsbay🇹🇷 · H. Sundu🇹🇷

   The mass and coupling of the scalar tetraquark $T_{bb;\overline{u}\overline{d}}^{-}$ (hereafter $T_{b:\overline{d}}^{-}$) are calculated in the context of the QCD two-point sum rule method. In computations we take into account effects of various quark, gluon and mixed condensates up to dimension ten. The result obtained for the mass of this state $m=(10135\pm 240)\mathrm{MeV}$ demonstrates that it is stable against the strong and electromagnetic decays. We also explore the dominant semileptonic $T_{b:\overline{d}}^{-}\to {\tilde{Z}}_{bc;\bar{u}\bar{d}}^{0}l{\overline{\nu }}_l$ and nonleptonic decays $T_{b:\overline{d}}^{-}\to {\tilde{Z}}_{bc;\bar{u}\bar{d}}^{0}M$, where ${\tilde{Z}}_{bc;\bar{u}\bar{d}}^0$ is the scalar tetraquark composed of color-sextet diquark and antidiquark, and $M$ is one of the final-state pseudoscalar mesons ${\pi }^{-},K^{-},D^{-}$ and $D_s^{-}$ , respectively. The partial widths of these processes are calculated in terms of the weak form factors $G_{1(2)}(q^2)$, which are determined from the QCD three-point sum rules. Predictions for the mass, full width ${\Gamma }_{\mathrm{full}}=(10.88\pm 1.88)\times 10^{-10}\mathrm{MeV}$, and mean lifetime $\tau =0.61_{-0.09}^{+0.13}\mathrm{ps}$ of the $T_{b:\overline{d}}^{-}$ obtained in the present work can be used in theoretical and experimental studies of this exotic state.

   hep-phhep-exhep-latEPJA(2020)·24 citations
9. 09*

   The Geometric Standard Model Effective Field Theory

   Andreas Helset🇩🇰 · Adam Martin🇺🇸 · Michael Trott🇩🇰

   We develop the geometric formulation of the Standard Model Effective Field Theory (SMEFT). Using this approach we derive all-orders results in the $\sqrt{2⟨H^{†}H⟩}/\Lambda$ expansion relevant for studies of electroweak precision and Higgs data.

   hep-phJHEP(2020)·119 citations
10. 10*

    Light Dark Sectors through the Fermion Portal

    Luc Darmé🇮🇹 · Sebastian A. R. Ellis🇺🇸 · Tevong You🇨🇭

    Pairs of Standard Model fermions form dimension-3 singlet operators that can couple to new dark sector states. This "fermion portal" is to be contrasted with the lower-dimensional Higgs, vector and neutrino singlet portals. We characterise its distinct phenomenology and place effective field theory bounds on this framework, focusing on the case of fermion portals to a pair of light dark sector fermions. We obtain current and projected limits on the dimension-6 effective operator scale from a variety of meson decay experiments, missing energy and long-lived particle searches at colliders, as well as astrophysical and cosmological bounds. The DarkEFT public code is made available for recasting these limits, which we illustrate with various examples including an integrated-out heavy dark photon.

    hep-phhep-exJHEP(2020)·49 citations
11. 11*

    Precision unification and Higgsino dark matter in GUT scale supersymmetry

    V. Suryanarayana Mummidi🇮🇳 · Ketan M. Patel🇮🇳

    Even if the concerns related to the naturalness of the electroweak scale are repressed, the Higgs mass and stability of the electroweak vacuum do not allow arbitrarily large supersymmetry breaking scale, $M_S$, in the minimal models with split or high-scale supersymmetry. We show that $M_S$ can be raised to the GUT scale if the theory below $M_S$ contains a Higgs doublet, a pair of TeV scale Higgsino and widely separated gauginos in addition to the Standard Model particles. The presence of wino and gluino below $\mathcal{O}(100)$ TeV leads to precision unification of the gauge couplings consistent with the current limits on the proton lifetime. Wino, at this scale, renders the Higgsino as pseudo-Dirac dark matter which in turn evades the existing constraints from the direct detection experiments. Bino mass scale is required to be $\gtrsim 10^{10}$ GeV to get the observed Higgs mass respecting the current limit on the charged Higgs mass. The framework predicts, $1\lesssim \tan \beta \lesssim 2.2$ and $\tau [p\to e^{+}{\pi }^0]<7\times 10^{35}$ years, almost independent of values of the other parameters. The electroweak vacuum is found to be stable or metastable. The underlying framework provides an example of a viable sub-GUT scale theory of supersymmetric grand unified theory in which supersymmetry and unified gauge symmetry are broken at a common scale.

    hep-phPRD(2020)·6 citations
12. 12*

    Role of the Soffer bound in determination of transversity and the tensor charge

    Umberto D'Alesio🇮🇹 · Carlo Flore🇮🇹 · Alexei Prokudin🇺🇸

    The transversity and the tensor charge of the nucleon, currently under active investigation experimentally and theoretically, are fundamental quantities in hadron physics as well as for our comprehension of the nucleon structure. Some tension between the values of the tensor charge, as computed on the basis of phenomenological extractions and lattice QCD calculations, has been observed. In this letter, by means of an explicit example, we study the role of assumptions, usually adopted in phenomenological parametrizations, and we show that, by relaxing some of them, such a tension could be eased.

    hep-phhep-exhep-latPLB(2020)·57 citations
13. 13*

    Ab initio calculations of reactor antineutrino fluxes with exact lepton wave functions

    Dong-Liang Fang🇨🇳 · Yu-Feng Li🇨🇳 · Di Zhang🇨🇳

    New \textit{ab initio} calculations of the isotopic reactor antineutrino fluxes are provided with exact numerical calculations of the lepton wave functions, assuming all the decay branches are allowed GT transitions. We illustrate that the analytical Fermi function and finite size effect each could have the largest spectral deviation of $\mathcal{O}(10\%)$, whereas the effect of their combination could result in spectral deviations at the level of 5%-10%. Meanwhile, we also find that several forms of the extended charge distributions have negligible effects on the spectral variation. Using the state-of-the-art nuclear databases, compared to usual \textit{ab initio} calculations using the analytical single beta decay spectrum, our new calculation shows sizable but opposite spectral deviations at the level of 2%-4% for the cumulative antineutrino and electron energy spectra which may partially contribute to the observed spectral excess in the high energy antineutrino range. Finally we observe that the {bias} of analytical beta decay spectrum approximation is rather universal for all the four fissionable isotopes.

    hep-phhep-exnucl-thPLB(2021)·7 citations
14. 14*

    Holographic Wigner distributions for the pion

    Mohammad Ahmady🇨🇦 · Chandan Mondal🇨🇳 · Ruben Sandapen🇨🇦 · James P. Vary🇺🇸 · Xingbo Zhao🇨🇳

    We study the Wigner distributions of the pion using a holographic light-front pion wavefunction with dynamical spin effects to reveal its multidimensional structure.

    hep-phHADRON 2019, 638-642·4 citations
15. 15*

    Emergent Gauge Symmetries and Particle Physics

    Steven D. Bass🇵🇱

    Hadron properties and interactions are emergent from QCD. Atomic and condensed matter physics are emergent from QED. Could the local gauge symmetries of particle physics also be emergent? We give an introduction to this question and recent ideas connecting it to the (meta)stability of the Standard Model Higgs vacuum. With an emergent Standard Model the gauge symmetries would "dissolve" in the ultraviolet. This scenario differs from unification models which exhibit maximum symmetry in the extreme ultraviolet. With emergence, new global symmetry violations would appear in higher dimensional operators.

    hep-phPPNP(2020)·14 citations
16. 16*

    Vacuum energy with mass generation and Higgs bosons

    Steven D. Bass🇵🇱 · Janina Krzysiak🇵🇱

    We discuss the Higgs mass and cosmological constant hierarchy puzzles with emphasis on the interplay of Poincare invariance, mass generation and renormalization group invariance. A plausible explanation involves an emergent Standard Model with the cosmological constant scale suppressed by power of the large scale of emergence. In this scenario the cosmological constant scale and neutrino masses should be of similar size.

    hep-phastro-ph.COgr-qcPLB(2020)·18 citations
17. 17*

    Entanglement, partial set of measurements, and diagonality of the density matrix in the parton model

    Haowu Duan🇺🇸 · Candost Akkaya🇺🇸 · Alex Kovner🇺🇸 · Vladimir V. Skokov🇺🇸

    We define the "entropy of ignorance" which quantifies the entropy associated with ability to perform only a partial set of measurement on a quantum system. For a parton model the entropy of ignorance is equal to a Boltzmann entropy of a classical system of partons. We analyze a calculable model used for describing low x gluons in Color Glass Condensate approach, which has similarities with the parton model of QCD. In this model we calculate the entropy of ignorance in the particle number basis as well as the entanglement entropy of the observable degrees of freedom. We find that the two are similar at high momenta, but differ by a factor of order unity at low momenta. This holds for the Renyi as well as von Neumann entropies. We conclude that the entanglement does not seem to play an important role in the context of the parton model.

    hep-phPRD(2020)·45 citations
18. 18*

    Eclectic Flavor Groups

    Hans Peter Nilles🇩🇪 · Saul Ramos-Sanchez🇲🇽 · Patrick K.S. Vaudrevange🇩🇪

    The simultaneous study of top-down and bottom-up approaches to modular flavor symmetry leads necessarily to the concept of eclectic flavor groups. These are nontrivial products of modular and traditional flavor symmetries that exhibit the phenomenon of local flavor enhancement in moduli space. We develop methods to determine the eclectic flavor groups that can be consistently associated with a given traditional flavor symmetry. Applying these methods to a large family of prominent traditional flavor symmetries, we try to identify potential candidates for realistic eclectic flavor groups and show that they are relatively rare. Model building with finite modular flavor symmetries thus appears to be much more restrictive than previously thought.

    hep-phhep-thJHEP(2020)·108 citations
19. 19*

    Dark Matter and Torsion

    G. Grensing🇩🇪

    Superheavy right-handed Majorana neutrinos are proposed as a promising candidate for dark matter, with dynamical axial torsion as the mediating agent.

    hep-phhep-thGen.Rel.Grav.(2021)·2 citations
20. 20*

    Strong decays of the newly observed narrow ${\Omega }_b$ structures

    Wei Liang🇨🇳 · Qi-Fang Lü🇨🇳

    Motivated by the newly observed narrow structures ${\Omega }_b(6316{)}^{-}$, ${\Omega }_b(6330{)}^{-}$, ${\Omega }_b(6340{)}^{-}$, and ${\Omega }_b(6350{)}^{-}$ in the ${\Xi }_b^0{K}^{-}$ mass spectrum, we investigate the strong decays of the low-lying ${\Omega }_b$ states within the ${}^3{P}_0$ model systematically. According to their masses and decay widths, the observed ${\Omega }_b(6316{)}^{-}$, ${\Omega }_b(6330{)}^{-}$, ${\Omega }_b(6340{)}^{-}$, and ${\Omega }_b(6350{)}^{-}$ resonances can be reasonably assigned as the $\lambda -$mode ${\Omega }_b(1P)$ states with $J^P=1/2^{-},3/2^{-},3/2^{-}$, and $5/2^{-}$. Meanwhile, the remaining $P-$wave state with $J^P=1/2^{-}$ should have a rather broad width, which can hardly be observed by experiments. For the ${\Omega }_b(2S)$ and ${\Omega }_b(1D)$ states, our predictions show that these states have relatively narrow total widths and mainly decay into the ${\Xi }_b\bar{K}$, ${\Xi }_b^{\prime }\bar{K}$ and ${\Xi }_b^{\prime \ast }\bar{K}$ final states. These abundant theoretical predictions may be valuable for searching more excited ${\Omega }_b$ states in future experiments.

    hep-phhep-exnucl-thEPJC(2020)·32 citations
21. 21*

    Relativistic Plasma Physics in Supercritical Fields

    P. Zhang🇨🇳 · S. S. Bulanov🇺🇸 · D. Seipt🇺🇸 · A. V. Arefiev🇺🇸 · A. G. R. Thomas🇺🇸

    Since the invention of chirped pulse amplification, which was recognized by a Nobel prize in physics in 2018, there has been a continuing increase in available laser intensity. Combined with advances in our understanding of the kinetics of relativistic plasma, studies of laser-plasma interactions are entering a new regime where the physics of relativistic plasmas is strongly affected by strong-field quantum electrodynamics (QED) processes, including hard photon emission and electron-positron ($e^{+}$-$e^{-}$) pair production. This coupling of quantum emission processes and relativistic collective particle dynamics can result in dramatically new plasma physics phenomena, such as the generation of dense $e^{+}$-$e^{-}$ pair plasma from near vacuum, complete laser energy absorption by QED processes or the stopping of an ultrarelativistic electron beam, which could penetrate a cm of lead, by a hair's breadth of laser light. In addition to being of fundamental interest, it is crucial to study this new regime to understand the next generation of ultra-high intensity laser-matter experiments and their resulting applications, such as high energy ion, electron, positron, and photon sources for fundamental physics studies, medical radiotherapy, and next generation radiography for homeland security and industry.

    ↳ physics.plasm-phhep-phPhys.Plasmas(2020)·110 citations
22. 22*

    The BESIII Physics Programme

    Chang-Zheng Yuan (IHEP & UCAS)🇨🇳 · Stephen Lars Olsen (UCAS)🇨🇳

    The standard model of particle physics is a well-tested theoretical framework, but there are still a number of issues that deserve further experimental and theoretical investigation. For quark physics, such questions include: the nature of quark confinement, the mechanism that connects the quarks and gluons of the standard model theory to the strongly interacting particles; and the weak decays of quarks, which may provide insights into new physics mechanisms responsible for the matter-antimatter asymmetry of the Universe. These issues are addressed by the Beijing Spectrometer III (BESIII) experiment at the Beijing Electron-Positron Collider II (BEPCII) storage ring, which for the past decade has been studying particles produced in electron-positron collisions in the tau-charm energy-threshold region, and has by now accumulated the world's largest datasets that enables searches for nonstandard hadrons, weak decays of the charmed particles, and new physics phenomena beyond the standard model. Here, we review the contributions of BESIII to such studies and discuss future prospects for BESIII and other experiments.

    ↳ hep-exhep-phNature Rev.Phys.(2019)·61 citations
23. 23*

    Proposals for the test of the isospin invariance in the pion-nucleon interaction at low energy

    Evangelos Matsinos · Günther Rasche

    This work elaborates on former remarks of ours regarding two sets of predictions for the observables of the charge-exchange reaction ${\pi }^{-}p\to {\pi }^{0}n$ at low energy (pion laboratory kinetic energy $T\le 100$ MeV). The first prediction is obtained via the triangle identity from the results of fits to low-energy ${\pi }^{\pm }p$ elastic-scattering data, whereas the second is based on the same analysis of the combined low-energy ${\pi }^{+}p$ and charge-exchange databases. Assuming the integrity of the data used in our fits (i.e., the absence of significant systematic effects in the determination of the absolute normalisation of the datasets) and the insignificance of residual effects in the electromagnetic corrections, a significant difference between these two sets of predictions may be interpreted as departure from the isospin invariance in the low-energy $\pi N$ interaction. We examine the sensitivity of the standard low-energy observables to the effect, and identify the kinematical regions which are promising for experimental survey. Accurate experiments under the suggested conditions will differentiate between the predictions, and thus provide an independent test of the isospin invariance in the low-energy $\pi N$ interaction.

    ↳ nucl-thhep-ph0 citations
24. 24*

    Vorticity in low-energy heavy-ion collisions

    Xian-Gai Deng🇨🇳 · Xu-Guang Huang🇨🇳 · Yu-Gang Ma🇨🇳 · Song Zhang🇨🇳

    We study the kinematic and thermal vorticities in low-energy heavy-ion collisions by using the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model. We explore their time evolution and spatial distribution. We find that the initial vorticities have a non-monotonic dependence on the collision energy $\sqrt{s_{\mathrm{NN}}}$: as $\sqrt{s_{\mathrm{NN}}}$ grows the vorticities first increase steeply and then decrease with the turning point around $\sqrt{s_{\mathrm{NN}}}\sim 3-5$ GeV depending on the centrality.

    ↳ nucl-thhep-phnucl-exPRC(2020)·103 citations
25. 25*

    Applying Noether's theorem to matter in the Milky Way: evidence for external perturbations and non-steady-state effects from Gaia Data Release 2

    Susan Gardner🇺🇸 · Austin Hinkel🇺🇸 · Brian Yanny🇺🇸

    We apply Noether's theorem to observations of main-sequence stars from the Gaia Data Release 2 archive to probe the matter distribution function of the Galaxy. That is, we examine the axial symmetry of stars at vertical heights $z$, $0.2\le |z|\le 3$ kpc, to probe the quality of the angular momentum $L_z$ as an integral of motion. The failure of this symmetry test would speak to a Milky Way, in both its visible and dark matter, that is not isolated and/or not in steady state. The left-right symmetry-breaking pattern we have observed, north and south, reveals both effects, with a measured deviation from symmetry of typically 0.5%. We show that a prolate form of the gravitational distortion of the Milky Way by the Large Magellanic Cloud, determined from fits to the Orphan stream by Erkal et al., 2019, is compatible with the size and sign of the axial-symmetry-breaking effects we have discovered in our sample of up to 14.4 million main-sequence stars, speaking to a distortion of an emergent, rather than static, nature.

    ↳ astro-ph.GAhep-phnucl-thApJ(2020)·9 citations
26. 26*

    Approach to thermalization and hydrodynamics

    Yukinao Akamatsu🇯🇵

    I review recent progress in thermalization in heavy-ion collisions, with particular emphasis on hydrodynamic attractor, and also report recent progress in hydrodynamic fluctuations.

    ↳ nucl-thhep-phhep-thnucl-exNPA(2021)·4 citations
27. 27*

    Effects of nonlinearity of $f(R)$ gravity and perfect fluid in Kaluza-Klein models with spherical compactification

    Ezgi Canay🇹🇷 · Maxim Eingorn🇺🇸 · Alexander Zhuk🇹🇷

    We study the effects associated with nonlinearity of $f(R)$ gravity and of the background perfect fluid manifested in the Kaluza-Klein model with spherical compactification. The background space-time is perturbed by a massive gravitating source which is pressureless in the external space but has an arbitrary equation of state (EoS) parameter in the internal space. As characteristics of a nonlinear perfect fluid, the squared speeds of sound are not equal to the background EoS parameters in the external and internal spaces. In this setting, we find exact solutions to the linearized Einstein equations for the perturbed metric coefficients. For nonlinear models with $f^{\prime \prime }(R_0)\ne 0$, we show that these coefficients acquire correction terms in the form of two summed Yukawa potentials and that in the degenerated case, the solutions are reduced to a single Yukawa potential with some "corrupted" prefactor (in front of the exponential function), which, in addition to the standard $1/r$ term, contains a contribution independent of the three-dimensional distance $r$. In the linear $f^{\prime \prime }(R)=0$ model, we generalize the previous studies to the case of an arbitrary nonlinear perfect fluid. We also investigate the particular case of the nonlinear background perfect fluid with zero speed of sound in the external space and demonstrate that a non-trivial solution exists only in the case of $f^{\prime \prime }(R_0)=0$.

    ↳ gr-qcastro-ph.COhep-phhep-thEPJC(2020)·0 citations
28. 28*

    Stringy excited baryons in holographic QCD

    Yasuhiro Hayashi🇯🇵 · Takahiro Ogino🇯🇵 · Tadakatsu Sakai🇯🇵 · Shigeki Sugimoto🇯🇵

    We analyze excited baryon states using a holographic dual of QCD that is defined on the basis of an intersecting D4/D8-brane system. Studies of baryons in this model have been made by regarding them as a topological soliton of a gauge theory on a five-dimensional curved spacetime. However, this allows one to obtain only a certain class of baryons. We attempt to present a framework such that a whole set of excited baryons can be treated in a systematic way. This is achieved by employing the original idea of Witten, which states that a baryon is described by a system composed of $N_c$ open strings emanating from a baryon vertex. We argue that this system can be formulated by an ADHM-type matrix model of Hashimoto-Iizuka-Yi together with an infinite tower of the open string massive modes. Using this setup, we work out the spectra of excited baryons and compare them with the experimental data. In particular, we derive a formula of the nucleon Regge trajectory assuming that the excited nucleons lying the trajectory are characterized by the excitation of a single open string attached on the baryon vertex.

    ↳ hep-thhep-lathep-phnucl-thPTEP(2020)·6 citations
29. 29*

    Upper Limit on the Dissipation of Gravitational Waves in Gravitationally Bound Systems

    Abraham Loeb (Harvard)🇺🇸

    It is shown that a gravitationally bound system with a one-dimensional velocity dispersion sigma can at most dissipate a fraction ~36(sigma/c)^3 of the gravitational wave energy propagating through it, even if their dynamical time is shorter than the wave period. The limit is saturated for particles with a mean-free-path equal to the size of the system, such as hot protons in galaxy clusters, strongly-interacting dark matter particles in halos, or massive black holes in clusters. For such systems with random motions and no resonances, the dissipated fraction, <10^{-6}, does not degrade the use of gravitational waves as cosmological probes. At high wave frequencies, the dissipated fraction is additionally suppressed by the square of the ratio between the collision frequency and the wave frequency. The electromagnetic counterparts that result from the dissipation are too faint to be detectable at cosmological distances.

    ↳ astro-ph.HEgr-qchep-phApJL(2020)·8 citations
30. 30*

    A search for IceCube events in the direction of ANITA neutrino candidates

    IceCube Collaboration: M. G. Aartsen🇳🇿 · M. Ackermann🇩🇪 · J. Adams🇳🇿 · J. A. Aguilar🇧🇪 · M. Ahlers🇩🇰 · M. Ahrens🇸🇪 · C. Alispach🇨🇭 · K. Andeen🇺🇸 · T. Anderson🇺🇸 · I. Ansseau🇧🇪 · G. Anton🇩🇪 · C. Argüelles🇺🇸 and 348 other authors

    During the first three flights of the Antarctic Impulsive Transient Antenna (ANITA) experiment, the collaboration detected several neutrino candidates. Two of these candidate events were consistent with an ultra-high-energy up-going air shower and compatible with a tau neutrino interpretation. A third neutrino candidate event was detected in a search for Askaryan radiation in the Antarctic ice, although it is also consistent with the background expectation. The inferred emergence angle of the first two events is in tension with IceCube and ANITA limits on isotropic cosmogenic neutrino fluxes. Here, we test the hypothesis that these events are astrophysical in origin, possibly caused by a point source in the reconstructed direction. Given that any ultra-high-energy tau neutrino flux traversing the Earth should be accompanied by a secondary flux in the TeV-PeV range, we search for these secondary counterparts in seven years of IceCube data using three complementary approaches. In the absence of any significant detection, we set upper limits on the neutrino flux from potential point sources. We compare these limits to ANITA's sensitivity in the same direction and show that an astrophysical explanation of these anomalous events under standard model assumptions is severely constrained regardless of source spectrum.

    ↳ astro-ph.HEhep-phApJ(2020)·47 citations

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