Thu·Sep 9, 2021Thursday·September 9, 2021

1. 01*

   Scale Invariant FIMP Miracle

   Basabendu Barman🇨🇴 · Anish Ghoshal🇵🇱

   We study the freeze-in production of vector dark matter (DM) in a classically scale invariant theory, where the Standard Model (SM) is augmented with an abelian $U(1{)}_X$ gauge symmetry that is spontaneously broken due to the non-zero vacuum expectation value (VEV) of a scalar charged under the $U(1{)}_X$. Generating the SM Higgs mass at 1-loop level, it leaves only two parameters in the dark sector, namely, the DM mass $m_X$ and the gauge coupling $g_X$ as independent, and supplement with a naturally light dark scalar particle. We show, for $g_X\sim \mathcal{O}\left(10^{-5}\right)$, it is possible to produce the DM X out-of-equilibrium in the early Universe, satisfying the observed relic abundance for $m_X\sim \mathcal{O}\left(\text{TeV}\right)$, which in turn also determines the scalar mixing angle $\sin \theta \sim \mathcal{O}\left(10^{-5}\right)$. The presence of such naturally light scalar mediator with tiny mixing with the SM, opens up the possibility for the model to be explored in direct search experiment, which otherwise is insensitive to standard freeze-in scenarios. Moreover we show that even with such feeble couplings, necessary for the DM freeze-in, the scenario is testable in several light dark sector searches (e.g., in DUNE and in FASER-II), satisfying constraints from the observed relic abundance as well as big bang nucleosynthesis (BBN). Particularly, we find, regions of the parameter space with $m_X$ $\gtrsim 1.8$ TeV are insensitive to direct detection probes but still can become accessible in lifetime frontier searches, courtesy to the underlying scale invariance of the theory.

   hep-phhep-exJCAP(2022)·39 citations
2. 02*

   Self-interacting neutrinos as a solution to the Hubble tension?

   Anirban Das

   Self-interaction among the neutrinos in the early Universe has been proposed as a solution to the Hubble tension, a discrepancy between the measured values of the Hubble constant from CMB and low-redshift data. However, flavor-universal neutrino self-interaction is highly constrained by Big Bang Nucleosynthesis and other laboratory experiments such as, tau and K-meson decay, double-neutrino beta decay etc. We study the cosmology when only one or two neutrino states are self-interacting. Such flavor-specific interactions are less constrained by the laboratory experiments. Lastly, we address the feasibility of resolving the Hubble tension within the framework of such flavor-specific neutrino self-interaction.

   hep-phastro-ph.COPoS(2022)·10 citations
3. 03*

   Cosmology of the Twin Higgs without explicit ${\mathbb{Z}}_2$ breaking

   Hugues Beauchesne🇹🇼 · Yevgeny Kats🇮🇱

   The cosmology of the Twin Higgs requires the breaking of the ${\mathbb{Z}}_2$ symmetry, but it is still an open question whether this breaking needs to be explicit. In this paper, we study how the Mirror Twin Higgs could be modified to be compatible with current cosmological constraints without explicit ${\mathbb{Z}}_2$ breaking. We first present a simple toy model that can realize baryogenesis without explicit ${\mathbb{Z}}_2$ breaking or reaching temperatures that would lead to domain walls. The model can also either solve the $N_{\text{eff}}$ problem and bring the abundance of mirror atoms to an allowed level or provide the correct dark matter abundance. We then present another simple model that leads to mirror neutron dark matter and thus acceptable dark matter self-interactions. We also include in appendix a series of results on energy exchange between different sectors that might prove useful for other cosmological problems.

   hep-phJHEP(2021)·18 citations
4. 04*

   Development of transverse flow at small and large opacities in conformal kinetic theory

   Victor E. Ambrus🇷🇴 · S. Schlichting🇩🇪 · C. Werthmann🇩🇪

   We employ an effective kinetic description, based on the Boltzmann equation in the relaxation time approximation, to study the space-time dynamics and development of transverse flow of small and large collision systems. By combining analytical insights in the small opacity limit with numerical simulations at larger opacities, we are able to describe the development of transverse flow from very small to very large opacities. Suprisingly, we find that deviations between kinetic theory and hydrodynamics persist even in the limit of very large opacities, which can be attributed to the presence of the early pre-equilibrium phase.

   hep-phPRD(2022)·51 citations
5. 05*

   Probing Higgs exotic decay at the LHC with machine learning

   Sunghoon Jung🇰🇷 · Zhen Liu🇺🇸 · Lian-Tao Wang🇺🇸 · Ke-Pan Xie🇺🇸

   We study the tagging of Higgs exotic decay signals using different types of deep neural networks (DNNs), focusing on the $W^{\pm }h$ associated production channel followed by Higgs decaying into $n$ $b$-quarks with $n=4$, 6 and 8. All the Higgs decay products are collected into a fat-jet, to which we apply further selection using the DNNs. Three kinds of DNNs are considered, namely convolutional neural network (CNN), recursive neural network (RecNN) and particle flow network (PFN). The PFN can achieve the best performance because its structure allows enfolding more information in addition to the four-momentums of the jet constituents, such as particle ID and tracks parameters. Using the PFN as an example, we verify that it can serve as an efficient tagger even though it is trained on a different event topology with different $b$-multiplicity from the actual signal. The projected sensitivity to the branching ratio of Higgs decaying into $n$ $b$-quarks at the HL-LHC are 10\%, 3\% and 1\%, for $n=4$, 6 and 8, respectively.

   hep-phhep-exPRD(2022)·12 citations
6. 06*

   Novel description of $P_c(4312{)}^{+}$, $P_c(4380{)}^{+}$, and $P_c(4457{)}^{+}$ with double triangle cusps

   Satoshi X. Nakamura🇨🇳

   We propose a novel scenario for the peak structures, usually interpreted as hidden charm pentaquark ($P_c$) contributions, in the LHCb's ${\Lambda }_b^0\to J/\psi p{K}^{-}$ data. The key idea is to utilize leading or lower-order singularities from double triangle mechanisms. The singularities cause anomalous threshold cusps, which are significantly more singular than the ordinary ones, at the ${\Sigma }_c^{(\ast )}{\bar{D}}^{(\ast )}$ threshold. We demonstrate that the double triangle amplitudes interfere with other common mechanisms to create peak structure that fit well the $P_c(4312{)}^{+}$, $P_c(4380{)}^{+}$, and $P_c(4457{)}^{+}$ peaks in the data. This picture is completely different from commonly used ones such as hadron molecules and compact pentaquarks. Meanwhile, $P_c(4440{)}^{+}$ is included in the proposed model as a resonance with width and strength significantly smaller than previously estimated. The proposed model can (partly) explain the current data for other processes where $P_c^{+}$ signals are expected such as: no $P_c^{+}$ signals in the GlueX $J/\psi$ photoproduction data; a possible signal only from $P_c(4440{)}^{+}$ in the LHCb's ${\Lambda }_b^0\to J/\psi p{\pi }^{-}$ data.

   hep-phhep-exnucl-thPoS(2021)·3 citations
7. 07*

   Coupled-channel effects of the ${\Sigma }_c^{(\ast )}{\bar{D}}^{(\ast )}$-${\Lambda }_c(2595)\bar{D}$ system and molecular nature of the $P_c$ pentaquark states from one-boson exchange model

   Nijiati Yalikun🇨🇳 · Yong-Hui Lin🇩🇪 · Feng-Kun Guo🇨🇳 · Yuki Kamiya🇨🇳 · Bing-Song Zou🇨🇳

   The effects of the ${\Sigma }_c{\bar{D}}^{\ast }$-${\Lambda }_c(2595)\bar{D}$ coupled-channel dynamics and various one-boson-exchange (OBE) forces for the LHCb pentaquark states, $P_c(4440)$ and $P_c(4457)$, are reinvestigated. Both the pion and $\rho$-meson exchanges are considered for the ${\Sigma }_c{\bar{D}}^{\ast }$-${\Lambda }_c(2595)\bar{D}$ coupled-channel dynamics. It is found that the role of the ${\Lambda }_c(2595)\bar{D}$ channel in the descriptions of the $P_c(4440)$ and $P_c(4457)$ states is not significant with the OBE parameters constrained by other experimental sources. The naive OBE models with the short-distance $\delta (\vec{r})$ term of the one-pion exchange (OPE) keep failing to reproduce the $P_c(4440)$ and $P_c(4457)$ states simultaneously. The OPE potential with the full $\delta (\vec{r})$ term results in a too large mass splitting for the $J^P=1/2^{-}$ and $3/2^{-}$ ${\Sigma }_c{\bar{D}}^{\ast }$ bound states with total isospin $I=1/2$. The OBE model with only the OPE $\delta (\vec{r})$ term dropped may fit the splitting much better but somewhat underestimates the splitting. Since the $\delta (\vec{r})$ potential is from short-distance physics, which also contains contributions from the exchange of mesons heavier than those considered explicitly, we vary the strength of the $\delta (\vec{r})$ potential and find that the masses of the $P_c(4312)$, $P_c(4440)$, and $P_c(4457)$ can be reproduced simultaneously with the $\delta (\vec{r})$ term in the OBE model reduced by about 80\%. While two different spin assignments are possible to produce their masses, in the preferred description, the spin parities of the $P_c(4440)$ and $P_c(4457)$ are $3/2^{-}$ and $1/2^{-}$, respectively.

   hep-phPRD(2021)·64 citations
8. 08*

   Asymmetric longitudinal flow decorrelations in proton-nucleus collisions

   Xiang-Yu Wu🇨🇳 · Guang-You Qin🇨🇳

   We perform the first study on asymmetric longitudinal decorrelations of elliptic, triangular and quadrangular flows in proton-nucleus collisions at the LHC and RHIC energies. To measure the longitudinal flow decorrelations for asymmetric collision systems, we propose a new set of rapidity-asymmetric flow decorrelation functions. Our event-by-event hydrodynamic calculations show that the flow decorrelations in proton-going direction are larger than those in nucleus-going direction. We also find that proton-nucleus collisions at RHIC have larger longitudinal flow decorrelation effects than those at the LHC. Our study opens a new window to probe the longitudinal properties and the origin of flows in relativistic nuclear collisions.

   hep-phnucl-exnucl-th13 citations
9. 09*

   All-order renormalization of electric charge in the Standard Model and beyond

   Stefan Dittmaier🇩🇪

   Electric charge, as defined in the Thomson limit of the electron--photon interaction vertex, is renormalized to all orders both in the Standard Model and in any spontaneously broken gauge theory with gauge group GxU(1) with a group factor U(1) that mixes with electromagnetic gauge symmetry. In the framework of the background-field method the charge renormalization constant $Z_e$ is directly obtained from the photon wave-function renormalization constant, similar to the situation in QED, which proves charge universality as a byproduct. Exploiting charge universality in arbitrary $R_{\xi }$ gauge by formulating the charge renormalization condition for a ``fake fermion'' that couples only via an infinitesimal electric charge, $Z_e$ can be expressed in terms of renormalization constants that are obtained solely from gauge-boson self-energies.

   hep-ph1 citation
10. 10*

    Is light thermal scalar dark matter possible?

    Tomoya Hara🇯🇵 · Shinya Kanemura🇯🇵 · Taisuke Katayose🇯🇵

    We study a light thermal scalar dark matter (DM) model with a light scalar mediator mixed with the standard model Higgs boson, including both the theoretical bounds and the current experimental constraints. The thermal scalar DM with the mass below a few GeV is usually strongly constrained by the observation of CMB and/or indirect detection experiments because the leading annihilation mode is S-wave. However, we find that two parameter regions still remain, which are the resonant annihilation region and the forbidden annihilation region. For the both cases, higher partial waves dominantly contribute to the annihilation at the freeze-out era, and the constraint from the cosmological observation is weaker. We consider typical cases of these regions quantitatively, mainly focusing on the mixing angle and the mass of the new particles. Finally, we also discuss the testability of this model at future experiments.

    hep-phPRD(2022)·15 citations
11. 11*

    NLO QCD corrections to Higgs boson production in association with gauge bosons in proton-proton collisions at sqrt(s) = 14 TeV

    K.Djamaa🇩🇿 · A. Mohamed-Meziani🇩🇿

    We suggest some predictions for Standard Model Higgs boson production in association with gauge bosons in proton-proton collisions at sqrt(s) = 14 TeV. Our calculation includes the NLO QCD corrections to these processes using MadGraph5_aMC@NLO event generator. We study the impacts of these corrections on the total cross sections and various kinematical distributions.

    hep-phPhys.Part.Nucl.Lett.(2022)·0 citations
12. 12*

    Gluon EMC effects in nuclear matter

    Xuan-Gong Wang🇦🇺 · Wolfgang Bentz🇯🇵 · Ian C. Cloët🇺🇸 · Anthony W. Thomas🇦🇺

    We investigate the gluonic structure of nuclei within a mean-field model of nuclear structure based upon the modification of the structure of a bound nucleon, with the nucleon described by the Nambu--Jona-Lasinio model. This approach has been shown to reproduce the European Muon Collaboration (EMC) effect, involving the ratio of the spin-independent structure functions of a heavier nucleus to that of the deuteron. It also predicts a significant nuclear modification for the spin structure functions, known as the polarized EMC effect. Here we report sizeable nuclear modifications of the gluon distributions (a "gluon EMC effect") for the ratios of both the unpolarized and polarized gluon distributions in nuclear matter to those of a free nucleon.

    hep-phhep-exhep-latnucl-thJ.Phys.G(2022)·11 citations
13. 13*

    Coulomb gluons will generally destroy coherence

    Jeffrey R. Forshaw🇬🇧 · Jack Holguin🇬🇧

    Coherence violation is an interesting and counter-intuitive phenomenon in QCD. We discuss the circumstances under which violation occurs in observables sensitive to soft radiation and arrive at the conclusion that almost all such observables at hadron colliders will violate coherence to some degree. We illustrate our discussion by considering the gaps-between-jets observable, where coherence violation is super-leading, then we generalise to other observables, including precise statements on the logarithmic order of coherence violation.

    hep-phJHEP(2021)·22 citations
14. 14*

    Symmetry breaking patterns for two coupled complex scalar fields at finite temperature and in an external magnetic field

    R. L. S. Farias🇧🇷 · Rudnei O. Ramos🇧🇷 · Dérick S. Rosa🇧🇷

    A model of two coupled complex scalar fields is studied at finite temperature and under an external magnetic field. The results are obtained in the context of the nonperturbative method of the optimized perturbation theory and contrasted with those obtained in perturbation theory and in the one-loop approximation. The emergence of phenomena related to inverse symmetry breaking and symmetry nonrestoration are analyzed.

    hep-phhep-thPRD(2021)·9 citations
15. 15*

    Particle Ratios within a statistically corrected hadron resonance gas model and EPOS event-generator at AGS, SPS, RHIC and LHC Energies

    Mahmoud Hanafy🇪🇬 · Abdel Nasser Tawfik🇪🇬 · Muhammad Maher🇪🇬

    We further investigate the applicability of our previously suggested quantum-mechanically correlated statistical hadron gas model (HRG) to the ideal hadron resonance gas model (IHRG), which is inspired by a Beth-Uhlenbeck corrected form of the equation of state (EoS). We compute the ratios of several particle yields, both equal-mass pairs ($\bar{p}/p$, $K^{-}/K^{+}$, ${\pi }^{-}/{\pi }^{+}$, $\bar{\Lambda }/\Lambda$, $\bar{\Sigma }/\Sigma$, $\bar{\Omega }/\Omega$) and unequal-mass pairs ($p/{\pi }^{+}$, $k^{+}/{\pi }^{+}$, $k^{-}/{\pi }^{-}$, $\Lambda /{\pi }^{-}$, $\bar{p}/{\pi }^{-}$, $\Omega /{\pi }^{-}$) and investigate how these ratios change with the center-of-mass energy. Next, we present a comparative analysis of the outputs of our suggested HRG model and the IHRG model, Cosmic Ray Monte Carlo (CRMC) EPOS $1.99$ simulations, and experimental data from ALICE, SPS, AGS, and RHIC. When compared to the other models taken into consideration, our HRG model typically shows very close agreement with the experimental results. The proton anomaly reported at top RHIC and LHC energies may be addressed by our new HRG model, which notably exhibits a strong alignment with experimental data for $\bar{p}/{\pi }^{-}$ and $p/{\pi }^{+}$ ratios. However, both our HRG model and the IHRG model seem to significantly underestimate some experimental data for ratios involving hadron couples with uneven mass and (multi)strange content, such as $\Lambda /{\pi }^{-}$ and $\Omega /{\pi }^{-}$. This emphasizes the necessity of additional research to determine whether thermal hadron gas models are appropriate and stresses the significance of any necessary adjustments to improve their correctness.

    hep-ph3 citations
16. 16*

    NLO Multijet Merging for Higgs Production Beyond the VBF Approximation

    Tinghua Chen🇺🇸 · Terrance M. Figy🇺🇸 · Simon Plätzer🇦🇹

    We present results of the simulation of electroweak Higgs boson production at the Large Hadron Collider using both the NLO multijet merging and NLO matching frameworks provided by the general purpose event generator Herwig 7. For the simulation of the hard scattering processes, we use the HJets library for the full calculation and VBFNLO for the approximate calculation to compute the $2\to h+n$ amplitudes at tree-level with $n=2,3,4$ and at one-loop with $n=2,3$.

    hep-phEPJC(2022)·11 citations
17. 17*

    The first exploration of the physical Riemann surfaces of the ratio $G_E^{\Lambda }/G_M^{\Lambda }$

    Alessio Mangoni🇮🇹 · Simone Pacetti🇮🇹 · Egle Tomasi-Gustafsson🇫🇷

    Recently, the BESIII experiment renewed the interest on baryon form factors by measuring the modulus and phase of the ratio $G_E^{\Lambda }/G_M^{\Lambda }$ between the electric and the magnetic $\Lambda$ form factors with unprecedented accuracy. The BESIII measurement together with older, less precise data, can be analyzed by means of a dispersive procedure based on analyticity and a set of first-principle constraints. Such a dispersive procedure shows the unique ability to determine for the first time the complex structure of the ratio knowing its modulus and phase measured by the BESIII collaboration at only one energy point. Different classes of solutions are obtained, and in all cases, the time-like and space-like behaviors show interesting properties: space-like zeros or unexpected large determinations for the phase. More data at different energies would be crucial to enhance the predictive power of the dispersive procedure and to unravel further remarkable features of the $\Lambda$ baryon.

    hep-phPRD(2021)·23 citations
18. 18*

    The anatomy of the multilepton anomalies at the LHC and a candidate for a singlet scalar

    Bruce Mellado🇿🇦

    In this presentation an account of the multi-lepton (electrons and muons) anomalies at the LHC is given. These include the excess production of opposite sign leptons with and without b-quarks, including a corner of the phase-space with a full hadronic jet veto; same sign leptons with and without b-quarks; three leptons with and without b-quarks, including also the presence of a $Z$. Excesses emerge in corners of the phase space where a range of SM processes dominate, indicating that the potential mismodeling of a particular SM process is unlikely to explain them. A procedure is implemented that avoids parameter tuning or scanning the phase-space in order to nullify potential look-else-where effects or selection biases. The internal consistency of these anomalies and their interpretation in the framework of a simplified model are presented. Motivated by the multi-lepton anomalies, a search for narrow resonances with $S\to \gamma \gamma ,Z\gamma$ in association with light jets, $b$-jets or missing transverse energy is performed. The maximum local (global) significance is achieved for $m_S=151.5$\,GeV with 5.1$\sigma$ (4.8$\sigma$).

    hep-phhep-ex1 citation
19. 19*

    Sterile neutrinos existence suggested from LCT covariance

    Raoelina Andriambololona🇲🇬 · Ravo Tokiniaina Ranaivoson🇲🇬 · Hanitriarivo Rakotoson🇲🇬 · Roland Raboanary🇲🇬

    Sterile neutrinos are known to be hypothetical neutrinos which do not interact via the fundamental interactions described within the Standard Model of Particles Physics i.e. electroweak and strong interactions. They are expected to be important for the understanding of the physics beyond the current Standard Model. In the present work, it is shown that the existence of these particles can be suggested from covariance principle using a covariance group formed by Linear Canonical Transformations (LCTs) associated to a pentadimensional pseudo-Euclidian space. It is established that a spin representation of the LCT group gives a particle classification, applicable to the three families of leptons and quarks, which leads to the prediction of the existence of three sterile neutrinos and their antiparticles

    hep-phJ.Phys.Comm.(2021)·5 citations
20. 20*

    Heavy neutral leptons below the kaon mass at hodoscopic detectors

    Carlos A. Argüelles🇺🇸 · Nicolò Foppiani🇺🇸 · Matheus Hostert🇺🇸

    Heavy neutral leptons ($N$) below the kaon mass are severely constrained by cosmology and lab-based searches for their decays in flight. If $N$ interacts via an additional force, $N\to \nu e^{+}{e}^{-}$ decays are enhanced and cosmological limits can be avoided. We show that the T2K and MicroBooNE neutrino experiments provide the best limits on the mixing of $N$ with muon-neutrinos, outperforming past-generation experiments, previously thought to dominate. We constrain models with electromagnetically-decaying and long-lived $N$, such as in a transition-magnetic-moment portal and in a leptophilic axion-like particle portal, invoked to explain the MiniBooNE excess. By considering these models as representative examples, our results show that explanations of the MiniBooNE excess that involve $e^{+}{e}^{-}$ pairs from long-lived particles are in tension with T2K, PS191, and MicroBooNE data. Similarly, these searches also constrain MiniBooNE explanations based on single photons due to the associated $e^{+}{e}^{-}$ decay mode via a virtual photon.

    hep-phhep-exPRD(2022)·69 citations
21. 21*

    LFU violations in leptonic $\tau$ decays and B-physics anomalies

    Lukas Allwicher🇨🇭 · Gino Isidori🇨🇭 · Nudzeim Selimovic🇨🇭

    We present a complete analysis of Lepton Flavor Universality (LFU) violations in leptonic $\tau$ decays in motivated models addressing the $B$-physics anomalies, based on the $SU(4)\times SU(3)\times SU(2)\times U(1)$ gauge group. We show that the inclusion of vector-like fermions, required by $B$-physics data, leads to sizable modifications of the leading-log results derived within an Effective Field Theory approach. In the motivated parameter-space region relevant to the $B$-physics anomalies, the models predict a few per-mil decrease of the effective $W$-boson coupling to $\tau$, within the reach of future experiments.

    hep-phPLB(2022)·18 citations
22. 22*

    Simplified derivation of the Kompaneets equation

    Peter W. Milonni🇺🇸

    An isotropic electromagnetic field in a plasma of thermalized electrons undergoes changes in energy as a result of Compton scattering and an Einstein-Hopf drag force on the electrons, eventually approaching a Bose-Einstein photon distribution at the electron temperature. The rate of change of feld energy due to the combined effects of Compton scattering and the drag force is shown to be described by the Kompaneets equation for photon diffusion in frequency space. A similarity is noted between this approach and Einstein's derivation of the Planck spectrum based on the recoil of atoms as they absorb and emit radiation.

    hep-phphysics.plasm-phPhys.Plasmas(2021)·0 citations
23. 23*

    New constraints on light Axion-Like Particles using Chandra Transmission Grating Spectroscopy of the powerful cluster-hosted quasar H1821+643

    Júlia Sisk Reynés🇬🇧 · James H. Matthews🇬🇧 · Christopher S. Reynolds🇬🇧 · Helen R. Russell🇬🇧 · Robyn N. Smith🇺🇸 · M. C. David Marsh🇸🇪

    Axion-Like Particles (ALPs) are predicted by several Beyond the Standard Model theories, in particular, string theory. In the presence of an external magnetic field perpendicular to the direction of propagation, ALPs can couple to photons. Therefore, if an X-ray source is viewed through a magnetised plasma, such as a luminous quasar in a galaxy cluster, we may expect spectral distortions that are well described by photon-ALP oscillations. We present a $571\mathrm{ks}$ combined High and Low Energy Transmission Grating (HETG/LETG) Chandra observation of the powerful radio-quiet quasar H1821+643, hosted by a cool-core cluster at redshift $0.3$. The spectrum is well described by a double power-law continuum and broad$+$narrow iron line emission typical of type-1 Active Galactic Nuclei (AGN), with remaining spectral features $<2.5\%$. Using a cell-based approach to describe the turbulent cluster magnetic field, we compare our spectrum with photon-ALP mixing curves for 500 field realisations assuming that the thermal-to-magnetic pressure ratio remains constant up to the virial radius. At $99.7\%$ credibility and taking $\beta =100$, we exclude all couplings $g_{\mathrm{a}\gamma }>6.3\times 10^{-13}{\mathrm{GeV}}^{-1}$ for most ALP masses $<10^{-12}\mathrm{eV}$. Our results are moderately more sensitive to constraining ALPs than the best previous result from Chandra observations of the Perseus cluster, albeit with a less constrained field model. We reflect on the promising future of ALP studies with bright AGN embedded in rich clusters, especially with the upcoming Athena mission.

    ↳ astro-ph.HEastro-ph.COhep-phMNRAS(2021)·151 citations
24. 24*

    Near-horizon microstructure and superradiant instability of black holes

    Rong-Zhen Guo🇨🇳 · Chen Yuan🇨🇳 · Qing-Guo Huang🇨🇳

    Ultralight bosons, as important candidates of dark matter, can condense around spinning black holes (BHs) to form long-lived ``boson clouds'' due to superradiance instability. The boson-BH system can be observed through gravitational wave detection and may become a new window to find traces of ultralight bosons. In this letter we explore the effects on the superradiant instability of BHs from the near-horizon microstructure. By introducing the reflection parameter near a BH horizon, we derived analytical results on the corrections to both energy levels of bosonic cloud and its characteristic frequencies of superradiance instability. Our results imply that the evolution of a boson-BH system and gravitational waves it emits would be influenced by the near-horizon physics of a BH.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2022)·17 citations
25. 25*

    On channeling of charged particles in a single dielectric capillary

    S.B. Dabagov🇮🇹 · A.V. Dik🇷🇺

    We analytically analyse the motion of a nonrelativistic charged particle in a cylindrical single capillary. The effective potential for interaction of a charged particle with the inner surface of a capillary is derived as a sum of the averaged atomic potential of the capillary wall surface and the induced potential defined by collective surface excitations. We have shown that under certain conditions this potential becomes attractive and may hold a particle in a bound state due to the surface excitations that defines a so-called surface channeling regime of motion. For the first time we have evaluated the induced potential revealing two limits to form either a well or a barrier that are delineated by the ratio of the insulator plasmon frequency to the frequency defined by the particle motion in a capillary.

    ↳ physics.acc-phhep-phphysics.ins-det0 citations
26. 26*

    Effects of chiral symmetry restoration on meson and dilepton production in relativistic heavy-ion collisions

    A.B. Larionov🇷🇺 · L. von Smekal🇩🇪

    We include effects of chiral symmetry and its restoration in the kinetic equations for baryon propagation and explore the consequences for $\eta$, ${\pi }^0$, $\rho$ and dilepton production in heavy-ion collisions at 1-2A GeV. Numerical calculations are performed using the GiBUU microscopic transport model supplemented by the parity-doublet model for the mean fields of the nucleon and the $N^{\ast }(1535)$ resonance. In this chiral model, a strong dropping of the Dirac mass of the $N^{\ast }(1535)$ in the high-density stage of a collision leads to a considerable enhancement in the production of this resonance as compared to the standard (non-linear) Walecka model. As the system expands, the Dirac masses of these abundant soft $N^{\ast }(1535)$ resonances gradually increase and ultimately cross the $N\eta$ decay threshold. As a result, an enhanced low-energy $\eta$ production is observed in the calculations with chiral mean fields. Comparing with TAPS data on $\eta$ and ${\pi }^0$ production we find that the chiral model improves the agreement for the $m_t$-spectra of $\eta$'s at small $m_t$ in heavy colliding systems. A similar enhancement is also observed in the soft $\rho$ production due to chiral symmetry and its partial restoration. The resulting dilepton yields at low and intermediate invariant masses are slightly enhanced due to these chiral effects which further improve the agreement between GiBUU transport simulations and HADES data for C+C at 1A GeV.

    ↳ nucl-thhep-exhep-phnucl-exPRC(2022)·12 citations
27. 27*

    Spontaneous symmetry breaking via inhomogeneities and the differential surface tension

    Gergely Endrődi🇩🇪 · Tamás György Kovács🇭🇺 · Gergely Markó🇩🇪

    We discuss spontaneously broken quantum field theories with a continuous symmetry group via the constraint effective potential. Employing lattice simulations with constrained values of the order parameter, we demonstrate explicitly that the path integral is dominated by inhomogeneous field configurations and that these are unambiguously related to the flatness of the effective potential in the broken phase. We determine characteristic features of these inhomogeneities, including their topology and the scaling of the associated excess energy with their size. Concerning the latter we introduce the differential surface tension -- the generalization of the concept of a surface tension pertaining to discrete symmetries. Within our approach, spontaneous symmetry breaking is captured merely via the existence of inhomogeneities, i.e. without the inclusion of an explicit breaking parameter and a careful double limiting procedure to define the order parameter. While here we consider the three-dimensional $O(2)$ model, we also elaborate on possible implications of our findings for the chiral limit of QCD.

    ↳ hep-latcond-mat.stat-mechhep-phhep-thPRL(2021)·11 citations
28. 28*

    Anisotropic Spacetimes in Chiral Scalar Field Cosmology

    A. Giacomini🇨🇱 · P.G.L. Leach🇿🇦 · G. Leon🇨🇱 · A. Paliathanasis🇿🇦

    Study the behaviour and the evolution of the cosmological field equations in an homogeneous and anisotropic spacetime with two scalar fields coupled in the kinetic term. Specifically, the kinetic energy for the scalar field Lagrangian is that of the Chiral model and defines a two-dimensional maximally symmetric space with negative curvature. For the background space we assume the locally rotational spacetime which describes the Bianchi I, the Bianchi III and the Kantowski-Sachs anisotropic spaces. We work on the $H$% -normalization and we investigate the stationary points and their stability. For the exponential potential we find a new exact solution which describes an anisotropic inflationary solution. The anisotropic inflation is always unstable, while future attractors are the scaling inflationary solution or the hyperbolic inflation. For scalar field potential different from the exponential, the de Sitter universe exists.

    ↳ gr-qchep-phEur.Phys.J.Plus(2021)·8 citations
29. 29*

    Bosonic Dark Matter in Neutron Stars and its Effect on Gravitational Wave Signal

    Davood Rafiei Karkevandi🇮🇷 · Soroush Shakeri🇮🇷 · Violetta Sagun🇵🇹 · Oleksii Ivanytskyi🇵🇱

    We study an impact of self-interacting bosonic dark matter (DM) on various observable properties of neutron stars (NSs). The analysis is performed for asymmetric DM with masses from few MeV to GeV, the self-coupling constant of order $\mathcal{O}(1)$ and various DM fractions. Allowing a mixture between DM and baryonic matter, the formation of a dense DM core or an extended dark halo have been explored. We find that both distribution regimes crucially depend on the mass and fraction of DM for sub-GeV boson masses in the strong coupling regime. From the combined analysis of the mass-radius relation and the tidal deformability of compact stars including bosonic DM, we set a stringent constraint on DM fraction. We conclude that observations of 2$M_{\odot }$ NSs together with ${\Lambda }_{1.4}\le 580$ constraint, set by LIGO/Virgo Collaboration, favour sub-GeV DM particles with low fractions below $\sim 5\%$.

    ↳ astro-ph.HEhep-phnucl-thPRD(2022)·198 citations
30. 30*

    A universal formula for the density of states in theories with finite-group symmetry

    Daniel Harlow🇺🇸 · Hirosi Ooguri🇺🇸

    In this paper we use Euclidean gravity to derive a simple formula for the density of black hole microstates which transform in each irreducible representation of any finite gauge group. Since each representation appears with nonzero density, this gives a new proof of the completeness hypothesis for finite gauge fields. Inspired by the generality of the argument we further propose that the formula applies at high energy in any quantum field theory with a finite-group global symmetry, and give some evidence for this conjecture.

    ↳ hep-thcond-mat.str-elgr-qchep-phClass.Quant.Grav.(2022)·31 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.