Fri·Feb 12, 2021Friday·February 12, 2021

1. 01*

   Comment on "$\sigma$-meson: Four-quark versus two-quark components and decay width in a Bethe-Salpeter approach"

   B. Blankleider🇦🇺 · A. N. Kvinikhidze🇬🇪

   In a recent paper by N. Santowsky et al. [Phys. Rev. D 102, 056014 (2020)], covariant coupled equations were derived to describe a tetraquark in terms of a mix of four-quark states $2q2\bar{q}$ and two-quark states $q\bar{q}$. These equations were expressed in terms of vertices describing the disintegration of a tetraquark into identical two-meson states, into a diquark-antidiquark pair, and into a quark-antiquark pair. We show that these equations are inconsistent as they imply a $q\bar{q}$ Bethe-Salpeter kernel that is $q\bar{q}$-reducible.

   hep-phnucl-th2 citations
2. 02*

   Spectrum of the doubly charmed molecular pentaquarks in chiral effective field theory

   Kan Chen🇨🇳 · Bo Wang🇨🇳 · Shi-Lin Zhu🇨🇳

   We perform a systematic study on the interactions of the ${\Sigma }_c^{(\ast )}{D}^{(\ast )}$ systems within the framework of chiral effective field theory. We introduce the contact term, one-pion-exchange and two-pion-exchange contributions to describe the short-, long-, and intermediate-range interactions. The low energy constants of the ${\Sigma }_c^{(\ast )}{D}^{(\ast )}$ systems are estimated from the $N\bar{N}$ scattering data by introducing a quark level Lagrangian. With three solutions of LECs, all the ${\Sigma }_c^{(\ast )}{D}^{(\ast )}$ systems with isospin $I=1/2$ can form bound states, in which different inputs of LECs may lead to distinguishable mass spectra. In addition, we also investigate the interactions of the charmed-bottom ${\Sigma }_c^{(\ast )}{\bar{B}}^{(\ast )}$, ${\Sigma }_b^{(\ast )}{D}^{(\ast )}$, and ${\Sigma }_b^{(\ast )}{\bar{B}}^{(\ast )}$ systems. Among the obtained bound states, the bindings become deeper when the reduced masses of the corresponding systems are heavier.

   hep-phhep-exhep-latnucl-thPRD(2021)·31 citations
3. 03*

   CP Asymmetries and Higher-Order Unitarity Relations

   Tomáš Blažek🇸🇰 · Peter Maták🇸🇰

   The main focus of this paper is to introduce a new method to control perturbative calculations of CP asymmetric reaction rates in the Boltzmann equation. CP asymmetries in particle reactions are traditionally calculated in terms of complex couplings, Feynman integrals, and Cutkosky rules. We use an expansion of the $S$-matrix unitarity condition instead, obtaining a general expression for the asymmetries without reference to the imaginary part of the loops. Asymmetry cancelations implied by CPT and unitarity are manifested in a diagrammatic way and easy to track at any order of perturbation theory. We demonstrate the power of this general framework within the right-handed neutrino and top-quark scattering asymmetries in seesaw type-I leptogenesis.

   hep-phPRD(2021)·16 citations
4. 04*

   What can we learn about light-meson interactions at electron-positron colliders?

   Shuang-shi Fang (IHEP and UCAS, Beijing)🇨🇳 · Bastian Kubis (Bonn U., HISKP)🇩🇪 · Andrzej Kupsc (Uppsala U. and NCBJ, Warsaw)🇸🇪

   Precision studies at electron-positron colliders with center-of-mass energies in the charm-tau region and below have strongly contributed to our understanding of light-meson interactions at low energies. We focus on the processes involving two or three light mesons with invariant masses below nucleon-antinucleon threshold. A prominent role is given to the interactions of the nine lightest pseudoscalar mesons (pions, kaons, $\eta$, and ${\eta }^{\prime }$) and the two narrow neutral isoscalar vector mesons $\omega$ and $\varphi$. Experimental methods used to produce the mesons are reviewed as well as theory tools to extract properties of the meson-meson interactions. Examples of recent results from the DA$\Phi$NE, BEPCII, and VEPP-2000 colliders are presented. In the outlook we briefly discuss prospects for further studies at future super-charm-tau factories.

   hep-phhep-exPPNP(2021)·34 citations
5. 05*

   Two Component Doublet-Triplet Scalar Dark Matter stabilising the Electroweak vacuum

   Nabarun Chakrabarty🇮🇳 · Rishav Roshan🇮🇳 · Arunansu Sil🇮🇳

   A two-component scalar DM scenario comprising an additional scalar doublet and a $Y$ = 0 scalar triplet is proposed. Key features of the ensuing dark matter phenomenology are highlighted with emphasis on inter-conversion between the two dark matter components. For suitable choices of the model parameters, we show that such inter-conversion can explain the observed relic abundance when the doublet dark matter component has mass in the \emph{desert} region while the triplet component has sub-TeV mass. This finding is important in the context of such mass regions known to predict under-abundant relic for the standalone cases of the scalar doublet and triplet. In addition, we also show that the present scenario can stabilise the electroweak vacuum up to the Planck scale in the parameter space responsible for the requisite dark matter observables.

   hep-phPRD(2022)·26 citations
6. 06*

   Discovering the Origin of Yukawa Couplings at the LHC with a Singlet Higgs and Vector-like Quarks

   Simon J.D. King🇬🇧 · Stephen F. King🇬🇧 · Stefano Moretti🇬🇧 · Samuel J. Rowley🇬🇧

   Although the 125 GeV Higgs boson discovered at the LHC is often heralded as the origin of mass, it may not in fact be the origin of Yukawa couplings. In alternative models, Yukawa couplings may instead arise from a seesaw type mechanism involving the mixing of Standard Model (SM) chiral fermions with new vector-like fermions, controlled by the vacuum expectation value (VEV) of a new complex Higgs singlet field $⟨\Phi ⟩$. For example, the largest third family $(t,b)$ quark Yukawa couplings may be forbidden by a $U(1{)}^{\prime }$ gauge or global symmetry, broken by $⟨\Phi ⟩$, and generated effectively via mixing with a vector-like fourth family quark doublet $(T,B)$. Such theories predict a new physical Higgs singlet $\varphi$, which we refer to as the Yukon, resulting from $⟨\Phi ⟩$, in the same way that the Higgs boson $h^0$ results from $⟨H⟩$. In a simplified model we discuss the prospects for discovering the Yukon $\varphi$ in gluon-gluon fusion production, with $(t,b)$ and $(T,B)$ quarks in the loops, and decaying in the channels $\varphi \to \gamma \gamma ,Z\gamma$ and $\varphi \to tT\to tt{h}^0,ttZ$. The potential for discovery of the Yukon $\varphi$ is studied at present or future hadron colliders such as the LHC (Run 3), HL-LHC, HE-LHC and/or FCC. For example, we find that a 300-350 GeV Yukon $\varphi$ could be accessed at LHC Run 3 in the di-photon channel in the global model, providing a smoking gun signature of the origin of Yukawa couplings. The $tt{h}^0,ttZ$ channels are more involved and warrant a more sophisticated analysis.

   hep-phJHEP(2021)·11 citations
7. 07*

   Baryon axial vector current in large-$N_c$ chiral perturbation theory: Complete analysis for $N_c=3$

   Ruben Flores-Mendieta🇲🇽 · Carlos Isaac Garcia🇲🇽 · Johann Hernandez🇲🇽

   The baryon axial vector current is computed in heavy baryon chiral perturbation theory in the large-$N_c$ limit, where $N_c$ is the number of color charges. One-loop nonanalytic corrections of order $m_q\ln m_q$ are comprised in the analysis, with contributions of both intermediate octet and decuplet baryon states, to all orders in the $1/N_c$ expansion of the axial vector current relevant for $N_c=3$. Theoretical expressions are obtained in the limit of vanishing decuplet-octet mass difference only, which allows one to carry out a full comparison with conventional heavy baryon chiral perturbation theory results for three flavors of light quarks and at the physical value $N_c=3$. Both approaches perfectly agree to all orders considered. Furthermore, a numerical analysis via a least-squares fit is performed in order to extract the values of the free parameters of the theory, using the experimental data available. The predictions of formalism are remarkable.

   hep-phPRD(2021)·10 citations
8. 08*

   Electroproduction of heavy quarkonia: significance of dipole orientation

   B. Z. Kopeliovich🇨🇱 · M. Krelina🇨🇿 · J. Nemchik🇨🇿

   The differential cross section $d\sigma /d{q}^2$ of diffractive electroproduction of heavy quarkonia on protons is a sensitive study tool for the interaction dynamics within the dipole representation. Knowledge of the transverse momentum transfer $\vec{q}$ provides a unique opportunity to identify the reaction plane, due to a strong correlation between the directions of $\vec{q}$ and impact parameter $\vec{b}$. On top of that, the elastic dipole-proton amplitude is subject to a strong correlation between $\vec{b}$ and dipole orientation $\vec{r}$. Most of models for $b$-dependent dipole cross section either completely miss this information, or make unjustified assumptions. We perform calculations basing on a realistic model for $\vec{r}$-$\vec{b}$ correlation, which significantly affect the $q$-dependence of the cross section, in particular the ratio of ${\psi }^{\prime }(2S)$ to $J/\psi$ yields. We rely on realistic potential models for the heavy quarkonium wave function, and the Lorentz-boosted Schrödinger equation. Good agreement with data on $q$-dependent diffractive electroproduction of heavy quarkonia is achieved.

   hep-phPRD(2021)·16 citations
9. 09*

   New insights into nuclear physics and weak mixing angle using electroweak probes

   M. Cadeddu🇮🇹 · N. Cargioli🇮🇹 · F. Dordei🇮🇹 · C. Giunti🇮🇹 · Y.F. Li🇨🇳 · E. Picciau🇮🇹 · C.A. Ternes🇮🇹 · Y.Y. Zhang🇨🇳

   Using the new results on coherent elastic neutrino-nucleus scattering data in cesium-iodide provided by the COHERENT experiment, we determine a new measurement of the average neutron rms radius of ${}^{133}\text{Cs}$ and ${}^{127}\text{I}$. In combination with the atomic parity violation (APV) experimental result, we derive the most precise measurement of the neutron rms radii of ${}^{133}\text{Cs}$ and ${}^{127}\text{I}$, disentangling for the first time the contributions of the two nuclei. By exploiting these measurements we determine the corresponding neutron skin values for ${}^{133}\text{Cs}$ and ${}^{127}\text{I}$. These results suggest a preference for models which predict large neutron skin values, as corroborated by the only other electroweak measurements of the neutron skin of ${}^{208}\text{Pb}$ performed by PREX experiments. Moreover, for the first time, we obtain a data-driven APV+COHERENT measurement of the low-energy weak mixing angle with a percent uncertainty, independent of the value of the average neutron rms radius of ${}^{133}\text{Cs}$ and ${}^{127}\text{I}$, that is allowed to vary freely in the fit. The value of the low-energy weak mixing angle that we found is slightly larger than the standard model prediction.

   hep-phnucl-thPRC(2021)·49 citations
10. 10*

    First analysis of world polarized DIS data with small-$x$ helicity evolution

    Daniel Adamiak🇺🇸 · Yuri V. Kovchegov🇺🇸 · W. Melnitchouk🇺🇸 · Daniel Pitonyak🇺🇸 · Nobuo Sato🇺🇸 · Matthew D. Sievert🇺🇸

    We present a Monte Carlo based analysis of the combined world data on polarized lepton-nucleon deep-inelastic scattering at small Bjorken $x$ within the polarized quark dipole formalism. We show for the first time that double-spin asymmetries at $x<0.1$ can be successfully described using only small-$x$ evolution derived from first-principles QCD, allowing predictions to be made for the $g_1$ structure function at much smaller $x$. Anticipating future data from the Electron-Ion Collider, we assess the impact of electromagnetic and parity-violating polarization asymmetries on $g_1$ and demonstrate an extraction of the individual flavor helicity PDFs at small $x$.

    hep-phhep-exnucl-exnucl-thPRD(2021)·61 citations
11. 11*

    Charged Lepton Flavor Violation at the EIC

    Vincenzo Cirigliano🇺🇸 · Kaori Fuyuto🇺🇸 · Christopher Lee🇺🇸 · Emanuele Mereghetti🇺🇸 · Bin Yan🇺🇸

    We present a comprehensive analysis of the potential sensitivity of the Electron-Ion Collider (EIC) to charged lepton flavor violation (CLFV) in the channel $ep\to \tau X$, within the model-independent framework of the Standard Model Effective Field Theory (SMEFT). We compute the relevant cross sections to leading order in QCD and electroweak corrections and perform simulations of signal and SM background events in various $\tau$ decay channels, suggesting simple cuts to enhance the associated estimated efficiencies. To assess the discovery potential of the EIC in $\tau$-$e$ transitions, we study the sensitivity of other probes of this physics across a broad range of energy scales, from $pp\to e\tau X$ at the Large Hadron Collider to decays of $B$ mesons and $\tau$ leptons, such as $\tau \to e\gamma$, $\tau \to e{\ell }^{+}{\ell }^{-}$, and crucially the hadronic modes $\tau \to eY$ with $Y\in \{\pi ,K,\pi \pi ,K\pi ,...\}$. We find that electroweak dipole and four-fermion semi-leptonic operators involving light quarks are already strongly constrained by $\tau$ decays, while operators involving the $c$ and $b$ quarks present more promising discovery potential for the EIC. An analysis of three models of leptoquarks confirms the expectations based on the SMEFT results. We also identify future directions needed to maximize the reach of the EIC in CLFV searches: these include an optimization of the $\tau$ tagger in hadronic channels, an exploration of background suppression through tagging $b$ and $c$ jets in the final state, and a global fit by turning on all SMEFT couplings, which will likely reveal new discovery windows for the EIC.

    hep-phhep-exnucl-exnucl-thJHEP(2021)·90 citations
12. 12*

    Axion/Hidden-Photon Dark Matter Conversion into Condensed Matter Axion

    So Chigusa🇺🇸 · Takeo Moroi🇯🇵 · Kazunori Nakayama🇯🇵

    The QCD axion or axion-like particles are candidates of dark matter of the universe. On the other hand, axion-like excitations exist in certain condensed matter systems, which implies that there can be interactions of dark matter particles with condensed matter axions. We discuss the relationship between the condensed matter axion and a collective spin-wave excitation in an anti-ferromagnetic insulator at the quantum level. The conversion rate of the light dark matter, such as the elementary particle axion or hidden photon, into the condensed matter axion is estimated for the discovery of the dark matter signals.

    hep-phcond-mat.mes-hallJHEP(2021)·26 citations
13. 13*

    Anomaly-free Abelian gauge symmetries with Dirac scotogenic models

    Nicolás Bernal🇨🇴 · Julián Calle🇨🇴 · Diego Restrepo🇨🇴

    We perform a systematic analysis of standard model extensions with an additional anomaly-free gauge $U(1)$ symmetry, to generate Dirac neutrino masses at one loop. Under such symmetry, standard model fields could either transform or be invariant, corresponding to an active $U(1{)}_X$ or a dark $U(1{)}_D$ symmetry, respectively. Having an anomaly-free symmetry imposes nontrivial conditions to the number and charges of the unavoidable new states. We perform an intensive scan, looking for non-anomalous solutions for given number of extra chiral fermions. In particular, we concentrate on solutions giving rise to scotogenic neutrino masses via the effective Dirac mass operator. We study the cases where the Dirac mass operator with dimension 5 or 6, is mediated by Dirac or Majorana states, and corresponds to an active $U(1{)}_X$ or a dark $U(1{)}_D$ symmetry. Finally, we comment on the solutions featuring no massless chiral fermions.

    hep-phPRD(2021)·20 citations
14. 14*

    H Marks the Spot: Searching for Exotic Production of Higgs + X to Map Out New Physics

    Seth Koren🇺🇸 · Umut Öktem🇺🇸

    We propose leveraging our proficiency for detecting Higgs resonances by using the Higgs as a tagging object for new heavy physics. In particular, we argue that searches for exotic Higgs production from decays of color-singlet fields with electroweak charges could beat current searches at the LHC which look for their decays to vectors. As an example, we study the production and decay of vector-like leptons which admit Yukawa couplings with SM leptons. We find that bounds from Run 2 searches are consistent with anywhere from hundreds to many thousands of Higgses having been produced in their decays over the same period, depending on the representation. Dedicated searches for these signatures may thus be able to significantly improve our reach at the electroweak energy frontier.

    hep-phhep-exPRD(2021)·3 citations
15. 15*

    Gravitational Production of Dark Matter during Reheating

    Yann Mambrini🇫🇷 · Keith A. Olive🇺🇸

    We consider the direct $s$-channel gravitational production of dark matter during the reheating process. Independent of the identity of the dark matter candidate or its non-gravitational interactions, the gravitational process is always present and provides a minimal production mechanism. During reheating, a thermal bath is quickly generated with a maximum temperature $T_{\max }$, and the temperature decreases as the inflaton continues to decay until the energy densities of radiation and inflaton oscillations are equal, at $T_{\mathrm{RH}}$. During these oscillations, $s$-channel gravitational production of dark matter occurs. We show that the abundance of dark matter (fermionic or scalar) depends primarily on the combination $T_{\max }^4/T_{\mathrm{RH}}{M}_P^3$. We find that a sufficient density of dark matter can be produced over a wide range of dark matter masses: from a GeV to a ZeV.

    hep-phastro-ph.COhep-thPRD(2021)·149 citations
16. 16*

    Early-Universe-Physics Insensitive and Uncalibrated Cosmic Standards: Constraints on ${\Omega }_{\mathrm{m}}$ and Implications for the Hubble Tension

    Weikang Lin🇨🇳 · Xingang Chen🇺🇸 · Katherine J. Mack🇺🇸

    To further shed light on whether pre-recombination models can resolve the Hubble tension, we explore constraints on the cosmic background evolution that are insensitive to early-universe physics. The analysis of the cosmic microwave background (CMB) anisotropy has been thought to highly rely on early-universe physics. However, we show that the fact that the sound horizon at recombination being close to that at the end of the drag epoch is insensitive to early-universe physics. This allows us to link the absolute sizes of the two horizons and treat them as free parameters. Jointly, the CMB peak angular size, Baryon Acoustic Oscillations (BAO), and Type Ia supernovae can be used as "early-universe-physics insensitive and uncalibrated cosmic standards", which measure the cosmic history from recombination to today. They can set strong and robust constraints on the post-recombination cosmic background, especially the matter density parameter with ${\Omega }_{\mathrm{m}}=0.302\pm 0.008$ ($68\%$ C.L.) assuming a flat $\Lambda$CDM after recombination. When we combine these with other non-local observations, we obtain several constraints on $H_0$ with significantly reduced sensitivity to early-universe physics. These are all more consistent with the Planck 2018 result than the local measurement results such as those based on Cepheids. This suggests a tension between the post-recombination, but non-local, observations and the local measurements which cannot be resolved by modifying pre-recombination early universe physics.

    ↳ astro-ph.COhep-phhep-thApJ(2021)·88 citations
17. 17*

    Neutron Stars in Palatini $R+\alpha R^2$ and $R+\alpha R^2+\beta Q$ Theories

    Georg Herzog🇮🇹 · Hèlios Sanchis-Alepuz🇦🇹

    We study solutions of the stellar structure equations for spherically symmetric objects in Palatini $f(R)=R+\alpha R^2$ and $f(R,Q)=R+\alpha R^2+\beta Q$ in the mass-radius region associated to neutron stars. We illustrate the potential impact of the $R^2$ and $Q$ terms by studying a range of viable values of $\alpha$ and $\beta$. Similarly, we use different equations of state (SLy, FPS, HS(DD2) and HS(TMA)) as a simple way to account for the equation of state uncertainty. Our results show that for certain combinations of the $\alpha$ and $\beta$ parameters and equation of state, the effect of modifications of general relativity on the properties of stars is sizeable. Therefore, with increasing accuracy in the determination of the equation of state for neutron stars, astrophysical observations may serve as discriminators of modifications of General Relativity.

    ↳ gr-qchep-phEPJC(2021)·6 citations
18. 18*

    Effective field theory for dilute Fermi systems at fourth order

    C. Wellenhofer🇩🇪 · C. Drischler🇺🇸 · A. Schwenk🇩🇪

    We discuss high-order calculations in perturbative effective field theory for fermions at low energy scales. The Fermi-momentum or $k_{\mathrm{F}}{a}_s$ expansion for the ground-state energy of the dilute Fermi gas is calculated to fourth order, both in cutoff regularization and in dimensional regularization. For the case of spin one-half fermions we find from a Bayesian analysis that the expansion is well-converged at this order for $|k_{\mathrm{F}}{a}_s|\lesssim 0.5$. Further, we show that Padé-Borel resummations can improve the convergence for $|k_{\mathrm{F}}{a}_s|\lesssim 1$. Our results provide important constraints for nonperturbative calculations of ultracold atoms and dilute neutron matter.

    ↳ cond-mat.quant-gashep-phnucl-thPRC(2021)·12 citations
19. 19*

    Dependence on beam energy and nuclear equation of state dependence of anisotropic flow and particle production in low-energy heavy-ion collisions

    Sumit Kumar Kundu🇮🇳 · Yoshini Bailung🇮🇳 · Sudhir Pandurang Rode🇮🇳 · Partha Pratim Bhaduri🇮🇳 · Ankhi Roy🇮🇳

    We analyse various flow coefficients of anisotropic momentum distribution of final state particles in mid-central ($b$ $=$ 5--9 $fm$) Au + Au collisions in the beam energy range ${\mathrm{E}}_{\mathrm{Lab}}$ $=$ $1A-158A$ GeV. Different variants of the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model, namely the pure transport (cascade) mode and the hybrid mode, are employed for this investigation. In the hybrid UrQMD model, the ideal hydrodynamical evolution is integrated with the pure transport calculation for description of the evolution of the fireball. We opt for the different available equations of state (EoS) replicating the hadronic as well as partonic degrees of freedom together with possible phase transitions, viz. hadron gas, chiral + deconfinement EoS and bag model EoS, to investigate their effect on the properties of the final state particles. We also attempt to gain insights about the dynamics of the medium by studying different features of particle production such as particle ratios and net-proton rapidity distribution. The results and conclusions drawn here would be useful to understand the response of various observables to the underlying physics of the model as well as to make comparisons with the upcoming measurements of the future experiments at Facility for Antiproton and Ion Research (FAIR) and Nuclotron-based Ion Collider fAcility (NICA).

    ↳ nucl-thhep-phPRC(2021)·5 citations
20. 20*

    A rapid transition of $G_{\mathrm{eff}}$ at $z_t\simeq 0.01$ as a solution of the Hubble and growth tensions

    Valerio Marra🇧🇷 · Leandros Perivolaropoulos🇬🇷

    The mismatch in the value of the Hubble constant from low- and high-redshift observations may be recast as a discrepancy between the low- and high-redshift determinations of the luminosity of Type Ia supernovae, the latter featuring an absolute magnitude which is $\approx 0.2$~mag lower. Here, we propose that a rapid transition in the value of the relative effective gravitational constant ${\mu }_G\equiv \frac{G_{\mathrm{eff}}}{G_N}$ at $z_t\simeq 0.01$ could explain the lower luminosity (higher magnitude) of local supernovae, thus solving the $H_0$ crisis. A model that features ${\mu }_G=1$ for $z\lesssim 0.01$ but ${\mu }_G\simeq 0.9$ for $z\gtrsim 0.01$ is trivially consistent with local gravitational constraints but would raise the Chandrasekhar mass and so decrease the absolute magnitude of Type Ia supernovae at $z\gtrsim 0.01$ by the required value of $\approx 0.2$~mag. Such a rapid transition of the effective gravitational constant would not only resolve the Hubble tension but it would also help resolve the growth tension as it would reduce the growth of density perturbations without affecting the Planck/$\Lambda$CDM background expansion.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2021)·146 citations
21. 21*

    Pion form factor and charge radius from Lattice QCD at physical point

    Xiang Gao🇺🇸 · Nikhil Karthik🇺🇸 · Swagato Mukherjee🇺🇸 · Peter Petreczky🇺🇸 · Sergey Syritsyn🇺🇸 · Yong Zhao🇺🇸

    We present our results on the electromagnetic form factor of pion over a wide range of $Q^2$ using lattice QCD simulations with Wilson-clover valence quarks and HISQ sea quarks. We study the form factor at the physical point with a lattice spacing $a=0.076$ fm. To study the lattice spacing and quark mass effects, we also present results for 300 MeV pion at two different lattice spacings $a=0.04$ and 0.06 fm. The lattice calculations at the physical quark mass appear to agree with the experimental results. Through fits to the form factor, we estimate the charge radius of pion for physical pion mass to be $⟨r_{\pi }^2⟩=0.42(2){\mathrm{fm}}^2$.

    ↳ hep-lathep-exhep-phnucl-thPRD(2021)·60 citations
22. 22*

    Eigenvalue spectra of QCD and the fate of $U_A(1)$ breaking towards the chiral limit

    Olaf Kaczmarek🇩🇪 · Lukas Mazur🇩🇪 · Sayantan Sharma🇮🇳

    The finite temperature phase diagram of QCD with two massless quark flavors is not yet understood because of the subtle effects of anomalous $U_A(1)$ symmetry. In this work we address this issue by studying the fate of the anomalous $U_A(1)$ symmetry in $2+1$ flavor QCD just above the chiral crossover transition temperature $T_c$, lowering the light quark mass towards the chiral limit along line of constant physical strange quark mass. We use the gauge configurations generated using the Highly Improved Staggered Quark (HISQ) discretization on lattice volumes $32^3\times 8$ and $56^3\times 8$ to study the renormalized eigenvalue spectrum of QCD with valence overlap Dirac operator. We have implemented new numerical techniques that have allowed us to measure about $100$-$200$ eigenvalues of the gauge ensembles with light quark masses $\gtrsim 0.6$ MeV. From a detailed analysis of the dependence of the renormalized eigenvalue spectrum and $U_A(1)$ breaking observables on the light quark mass, our study suggests $U_A(1)$ is broken at $T\gtrsim T_c$ even when the chiral limit is approached.

    ↳ hep-lathep-phPRD(2021)·61 citations
23. 23*

    Integrable Models and Supersymmetry Breaking

    P. Pelliconi🇮🇹 · A. Sagnotti🇮🇹

    We elaborate on integrable dynamical systems from scalar-gravity Lagrangians that include the leading dilaton tadpole potentials of broken supersymmetry. In the static Dudas-Mourad compactifications from ten to nine dimensions, which rest on these leading potentials, the string coupling and the space-time curvature become unbounded in some regions of the internal space. On the other hand, the string coupling remains bounded in several corresponding solutions of these integrable models. One can thus identify corrected potential shapes that could grant these features generically when supersymmetry is absent or non-linearly realized. On the other hand, large scalar curvatures remain present in all our examples. However, as in other contexts, the combined effects of the higher-derivative corrections of String Theory could tame them.

    ↳ hep-thgr-qchep-phmath-ph+1NPB(2021)·8 citations
24. 24*

    The Cosmological Evolution of Self-interacting Dark Matter

    Daniel Egana-Ugrinovic🇨🇦 · Rouven Essig🇺🇸 · Daniel Gift🇺🇸 · Marilena LoVerde🇺🇸

    We study the evolution of cosmological perturbations in dark-matter models with elastic and velocity-independent self interactions. Such interactions are imprinted in the matter-power spectrum as dark acoustic oscillations, which can be experimentally explored to determine the strength of the self scatterings. Models with self interactions have similarities to warm dark matter, as they lead to suppression of power on small scales when the dark-matter velocity dispersion is sizable. Nonetheless, both the physical origin and the extent of the suppression differ for self-interacting dark matter from conventional warm dark matter, with a dark sound horizon controlling the reduction of power in the former case, and a free-streaming length in the latter. We thoroughly analyze these differences by performing computations of the linear power spectrum using a newly developed Boltzmann code. We find that while current Lyman-$\alpha$ data disfavor conventional warm dark matter with a mass less than 5.3 keV, when self interactions are included at their maximal value consistent with bounds from the Bullet Cluster, the limits are relaxed to 4.4 keV. Finally, we make use of our analysis to set novel bounds on light scalar singlet dark matter.

    ↳ astro-ph.COhep-phJCAP(2021)·41 citations
25. 25*

    Hawking-Radiation Recoil of Microscopic Black Holes

    Samuel Kováčik🇸🇰

    Hawking radiation would make microscopic black holes evaporate rapidly, which excludes them from many astrophysical considerations. However, it has been argued that the quantum nature of space would alter this behaviour: the temperature of a Planck-size black hole vanishes, and what is left behind is a Planck-mass remnant with the cross-section of $\approx 10^{-70}\text{mbox}{m}^2$, which makes a direct observation nearly impossible. Such black hole remnants have been identified as possible dark matter candidates. Here, we argue that the final stage of evaporation has a recoil effect that gives them a velocity up to $\approx 10^{-1}c$. This would lead to a disagreement with the cold dark matter cosmological model unless the primordial black hole formation ceased shortly after the inflation era.

    ↳ gr-qcastro-ph.COhep-phPhys.Dark Univ.(2021)·18 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.