Wed·Mar 10, 2021Wednesday·March 10, 2021

1. 01*

   Topological Susceptibility in a Uniform Magnetic Field

   Prabal Adhikari🇺🇸

   We study the topological susceptibility and the fourth cumulant of the QCD vacuum in the presence of a uniform, background magnetic field in two-and-three flavor QCD finding novel, model-independent sum rules relating the shift in the topological susceptibility due to the background field to the shift in the quark condensates, and the shift in the fourth cumulant to the shifts in the quark condensates and susceptibilities

   hep-phhep-lathep-thPLB(2022)·12 citations
2. 02*

   Searching for axion-like particles at future electron-positron colliders

   Hua-Ying Zhang🇨🇳 · Chong-Xing Yue🇨🇳 · Yu-Chen Guo🇨🇳 · Shuo Yang🇨🇳

   We investigate the prospects for discovering axion-like particles (ALPs) via a light-by-light (LBL) scattering at two colliders, the future circular collider (FCC-ee) and circular electron-positron collider (CEPC). The promising sensitivities to the effective ALP-photon coupling $g_{a\gamma \gamma }$ are obtained. Our numerical results show that the FCC-ee and CEPC might be more sensitive to the ALPs with mass 2 GeV $\sim$ 10 GeV than the LHC and CLIC.

   hep-phPRD(2021)·38 citations
3. 03*

   Production of $P_{cs}(4459)$ from ${\Xi }_b$ decay

   Qi Wu🇨🇳 · Dian-Yong Chen🇨🇳 · Ran Ji🇺🇸

   Inspired by the $P_{cs}(4459)$ reported by the LHCb collaboration recently, we investigate the $P_{cs}(4459)$ production from ${\Xi }_b$ decay in a molecular scenario using an effective Lagrangian approach. With different $J^P$ assignments to $P_{cs}(4459)$, the magnitude of branching fractions of ${\Xi }_b\to P_{cs}(4459)K$ is estimated, which is of the order of $10^{-4}$. Together with the decay properties of $P_{cs}(4459)$, the present estimations could be further testified by precise measurements and contribute to a better understanding of the molecular interpretations and the exploration of $J^P$ quantum numbers of $P_{cs}(4459)$.

   hep-phChin.Phys.Lett.(2021)·49 citations
4. 04*

   Baryon production in the quantized fragmentation of helical QCD string

   Šárka Todorova-Nová🇨🇭

   Baryon production is studied within the framework of quantized fragmentation of QCD string. Baryons appear in the model in a fairly intuitive way, with help of causally connected string breakups. A simple helical approximation of QCD flux tube with parameters constrained by mass spectrum of light mesons is sufficient to reproduce masses of light baryons.

   hep-phPRD(2021)·5 citations
5. 05*

   Threshold effects as the origin of $Z_{cs}(4000)$, $Z_{cs}(4220)$ and $X(4700)$ observed in $B^{+}\to J/\psi \varphi K^{+}$

   Ying-Hui Ge🇨🇳 · Xiao-Hai Liu🇨🇳 · Hong-Wei Ke🇨🇳

   We investigate the $B^{+}\to J/\psi \varphi K^{+}$ decay via various rescattering diagrams. Without introducing genuine exotic resonances, it is shown that the $Z_{cs}(4000)$, $Z_{cs}(4220)$ and $X(4700)$ reported by the LHCb collaboration can be simulated by the $J/\psi K^{\ast +}$, ${\psi }^{\prime }{K}^{+}$ and ${\psi }^{\prime }\varphi$ threshold cusps, respectively. These cusps are enhanced by some nearby triangle singularities. The $X(4685)$ with $J^P=1^{+}$ cannot be well simulated by the threshold effects in our model, which implies that it may be a genuine resonance.

   hep-phhep-exEPJC(2021)·22 citations
6. 06*

   Lepton flavor violation and leptogenesis in discrete flavor symmetric scotogenic model

   Bichitra Bijay Boruah🇮🇳 · Lavina Sarma🇮🇳 · Mrinal Kumar Das🇮🇳

   We have studied the scotogenic model proposed by Ernest Ma, which is an extension of the Standard Model by three singlet right-handed neutrinos and a scalar doublet. This model proposes that the light neutrinos acquire a non-zero mass at 1-loop level. In this work, the realisation of the scotogenic model is done by using discrete symmetries $A_4\times Z_4$ in which the non-zero ${\theta }_{13}$ is produced by assuming a non-degeneracy in the loop factor. Considering different lepton flavor violating(LFV) processes such as $l_{\alpha }⟶l_{\beta }\gamma$ and $l_{\alpha }⟶3l_{\beta }$, their impact on neutrino phenomenology is studied. We have also analysed $0\nu \beta \beta$ and baryon asymmetry of the Universe (BAU) in this work.

   hep-ph6 citations
7. 07*

   Helical magnetic fields from Riemann coupling lead to baryogenesis

   Ashu Kushwaha🇮🇳 · S. Shankaranarayanan (IIT Bombay)🇮🇳

   The spectrum of energy density fluctuations, baryon asymmetry, and coherent large-scale magnetic fields are the three observables that provide crucial information on physics at very high energies. Inflation can only provide a mechanism to explain the density perturbations, and the origin of primordial magnetic fields and baryon asymmetry require physics beyond the standard models of cosmology and particle physics. In this work, we show that the mechanism that leads to primordial helical fields also leads to baryogenesis at the beginning of the radiation-dominated epoch. The model we consider here consists of mass dimension 6 operators that include Riemann coupling between gravity and electromagnetic field without extending the Standard Model of particle physics. We explicitly show that the generation of primordial helical magnetic fields leads to baryogenesis. We further show that the model predicts the observed amount of baryon asymmetry of the Universe for a range of reheating temperatures consistent with the observations.

   hep-phastro-ph.COgr-qchep-thPRD(2021)·16 citations
8. 08*

   Particle yields in pp interactions at $\sqrt{s}=17.3$ GeV interpreted in the statistical hadronization model

   T. Matulewicz🇵🇱 · K. Piasecki🇵🇱

   The unified set of yields of particles produced in proton-proton collisions at $\sqrt{s}$ = 17.3 GeV (laboratory beam momentum 158 GeV/c) is evaluated, combining the experimental results of the NA49 and NA61/SHINE collaborations at the CERN SPS. With the statistical hadronization code Thermal-Fist we confirm the unacceptably high value of ${\chi }^2$, both in the canonical and grand canonical - strangeness canonical approach, and the common volume for all the hadrons. The use of the energy-dependent width of the Breit-Wigner parametrization for the mass distributions of unstable particles improves the quality of the description of particle yields only slightly. We confirm the observation that exclusion of the $\varphi$ meson yield makes the fit result acceptable. The complete experimental data set of particle yields can be reasonably fitted if the canonical volumes of hadrons without and with open strangeness are allowed to vary independently. The canonical volume of strangeness was found larger than that for non-strange hadrons, which is compatible with the femtoscopy measurements of p+p system at $\sqrt{s}=$ 27.4 MeV and 900 MeV. The model with the best-fit parameters allows to predict the yields of several not yet measured particles emitted from p+p at $\sqrt{s}$ = 17.3 GeV.

   hep-phnucl-thJ.Phys.G(2021)·6 citations
9. 09*

   Bayesian nonparametric inference of neutron star equation of state via neural network

   Ming-Zhe Han🇨🇳 · Jin-Liang Jiang🇨🇳 · Shao-Peng Tang🇨🇳 · Yi-Zhong Fan🇨🇳

   We develop a new nonparametric method to reconstruct the Equation of State (EoS) of Neutron Star with multimessenger data. As an universal function approximator, the Feed-Forward Neural Network (FFNN) with one hidden layer and a sigmoidal activation function can approximately fit any continuous function. Thus we are able to implement the nonparametric FFNN representation of the EoSs. This new representation is validated by its capabilities of fitting the theoretical EoSs and recovering the injected parameters. Then we adopt this nonparametric method to analyze the real data, including mass-tidal deformability measurement from the Binary Neutron Star (BNS) merger Gravitational Wave (GW) event GW170817 and mass-radius measurement of PSR J0030+0451 by {\it NICER}. We take the publicly available samples to construct the likelihood and use the nested sampling to obtain the posteriors of the parameters of FFNN according to the Bayesian theorem, which in turn can be translated to the posteriors of EoS parameters. Combining all these data, for a canonical 1.4 $M_{\odot }$ neutron star, we get the radius $R_{1.4}=11.83_{-1.08}^{+1.25}$ km and the tidal deformability ${\Lambda }_{1.4}=323_{-165}^{+334}$ (90\% confidence interval).Furthermore, we find that in the high density region ($\ge 3{\rho }_{\mathrm{sat}}$), the 90\% lower limits of the $c_{\mathrm{s}}^2/c^2$ ($c_{\mathrm{s}}$ is the sound speed and $c$ is the velocity of light in the vacuum) are above $1/3$, which means that the so-called conformal limit (i.e., $c_{\mathrm{s}}^2/c^2<1/3$) is not always valid in the neutron stars.

   hep-phastro-ph.HEgr-qcnucl-thApJ(2021)·56 citations
10. 10*

    Impact of intrinsic charm amount in the nucleon and saturation effects on the prompt atmospheric ${\nu }_{\mu }$ flux for IceCube

    Victor P. Goncalves🇧🇷 · Rafal Maciula🇵🇱 · Antoni Szczurek🇵🇱

    The predictions for the atmospheric neutrino flux at high energies strongly depend on the contribution of prompt neutrinos, which are determined by the production of charmed meson in the atmosphere at very forward rapidities. In this paper we estimate the related cross sections taking into account the presence of an intrinsic charm (IC) component in the proton wave function and the QCD dynamics modified by the onset of saturation effects. The impact on the predictions for the prompt neutrino flux is investigated assuming different values for the probability to find the IC in the nucleon. Comparison with the IceCube data is performed and conclusions are drawn.

    hep-phhep-exEPJC(2022)·18 citations
11. 11*

    Newly observed resonance $X(4685)$: diquark-antidiquark picture

    A. Türkan🇹🇷 · J.Y. Süngü🇹🇷 · E. Veli Veliev🇹🇷

    In this work, the mass and pole residue of $X(4685)$ state with spin-parity $J^P=1^{+}$ are computed by the QCD sum rule approaches up to operator dimension seven based on the diquark-antidiquark configuration. For its mass we get $m_{X_{cs}}=4607_{-22}^{+36}$ MeV and pole residue ${\lambda }_{X_{cs}}=6.19_{-0.24}^{+0.32}\times 10^{-2}\mathrm{Ge}{\mathrm{V}}^5$, which may be checked via other nonperturbative approaches as well as future experiments. As a by product, the mass of the hidden-bottom partner state of the $X(4685)$ is extracted to be both around $m_{X_{bs}}=(10604-10924)$ MeV and ${\lambda }_{X_{bs}}=(42.2-53.7)\times 10^{-2}\mathrm{Ge}{\mathrm{V}}^5$, which can be searched in the ${\rm Y}\varphi$ invariant mass distribution.

    hep-ph5 citations
12. 12*

    Pole-Induced Higgs Inflation With Hyperbolic Kaehler Geometries

    C. Pallis🇬🇷

    We present novel realizations of Higgs inflation within Supergravity which are largely tied to the existence of a pole of order two in the kinetic term of the inflaton field. This pole arises due to the selected Kaehler potentials which parameterize the (SU(1,1)/U(1))^2 or SU(2,1)/(SU(2)xU(1)) manifolds with scalar curvatures R_{(11)^2}=-4/N or R_{21}=-3/N respectively. The associated superpotential includes, in addition to the Higgs superfields, a stabilizer superfield, respects the gauge and an R symmetries and contains the first allowed nonrenormalizable term. If the coefficient of this term is almost equal to that of the renormalizable terms within about 10^-5 and N=1, the inflationary observables can be done compatible with the present data and the scale M of gauge-symmetry breaking may assume its value within MSSM. Increasing M beyond this value, though, inflation may be attained with less tuning. Modifications to the Kaehler potentials associated with the manifolds above allow for inflation, realized with just renormalizable terms, resulting to higher tensor-to-scalar ratios as N approaches its maximum at N=40.

    hep-phastro-ph.COhep-thJCAP(2021)·19 citations
13. 13*

    Are the CKM anomalies induced by vector-like quarks? Limits from flavor changing and Standard Model precision tests

    Benedetta Belfatto🇮🇹 · Zurab Berezhiani🇮🇹

    Recent high precision determinations of $V_{us}$ and $V_{ud}$ indicate towards anomalies in the first row of the CKM matrix. Namely, determination of $V_{ud}$ from superallowed beta decays and of $V_{us}$ from kaon decays imply a violation of first row unitarity at about $4\sigma$ level. Moreover, there is tension between determinations of $V_{us}$ obtained from leptonic $K\mu 2$ and semileptonic $K\ell 3$ kaon decays. These discrepancies can be explained if there exist extra vector-like quarks at the TeV scale, which have large enough mixings with the lighter quarks. In particular, extra vector-like weak singlets quarks can be thought as a solution to the CKM unitarity problem and an extra vector-like weak doublet can in principle resolve all tensions. The implications of this kind of mixings are examined against the flavour changing phenomena and SM precision tests. We consider separately the effects of an extra down-type isosinglet, up-type isosinglet and an isodoublet containing extra quarks of both up and down type, and determine available parameter spaces for each case. We find that the experimental constraints on flavor changing phenomena become more stringent with larger masses, so that the extra species should have masses no more than few TeV. Moreover, only one type of extra multiplet cannot entirely explain all the discrepancies, and some their combination is required. We show that these scenarios are testable with future experiments. Namely, if extra vector-like quarks are responsible for CKM anomalies, then at least one of them should be found at scale of few TeV, and anomalous weak isospin violating $Z$-boson couplings with light quarks should be detected if the experimental precision on $Z$ hadronic decay rate is improved by a factor of $2$ or so.

    hep-phhep-exnucl-exnucl-thJHEP(2021)·77 citations
14. 14*

    Charming Charm, Beautiful Bottom, and Quark-Gluon Plasma in the Large Hadron Collider Era

    Santosh K. Das🇮🇳 · Raghunath Sahoo🇮🇳

    After a few microseconds of the creation of our Universe through the Big Bang, the primordial matter was believed to be a soup of the fundamental constituents of matter -- quarks and gluons. This is expected to be created in the laboratory by colliding heavy nuclei at ultra-relativistic speeds. A plasma of quarks and gluons, called Quark-Gluon Plasma (QGP) can be created at the energy and luminosity frontiers in the Relativistic Heavy Ion Collider (RHIC), at Brookhaven National Laboratory, New York, USA, and the Large Hadron Collider (LHC) at CERN, Geneva, Switzerland. Heavy quarks, namely the charm and bottom quarks, are considered as novel probes to characterize QGP, and hence the produced Quantum Chromodynamics (QCD) matter. Heavy quark transport coefficients play a significant role in understanding the properties of QGP. Experimental measurements of nuclear suppression factor and elliptic flow can constrain the heavy quark transport coefficients, which are key ingredients for phenomenological studies, and they help to disentangle different energy loss mechanisms. We give a general perspective of the heavy quark drag and diffusion coefficients in QGP and discuss their potentials as probes to disentangle different hadronization mechanisms, as well as to probe the initial electromagnetic fields produced in non-central heavy-ion collisions. Experimental perspectives on future measurements are discussed with special emphasis on heavy-flavors as next-generation probes in view of new technological developments.

    hep-phhep-exnucl-exnucl-thCurr.Sci.(2021)·3 citations
15. 15*

    Detecting long-lived multi-charged particles in neutrino mass models with MoEDAL

    Martin Hirsch🇪🇸 · Rafał Masełek🇵🇱 · Kazuki Sakurai🇵🇱

    A certain class of neutrino mass models predicts long-lived particles whose electric charge is four or three times larger than that of protons. Such particles, if they are light enough, may be produced at the LHC and detected. We investigate the possibility of observing those long-lived multi-charged particles with the MoEDAL detector, which is sensitive to long-lived particles with low velocities ($\beta$) and a large electric charge ($Z$) with $\Theta \equiv \beta /Z\lesssim 0.15$. We demonstrate that multi-charged scalar particles with a large $Z$ give three-fold advantage for MoEDAL; reduction of $\Theta$ due to strong interactions with the detector, and enhancement of the photon-fusion process, which not only increases the production cross-section but also lowers the average production velocity, reducing $\Theta$ further. To demonstrate the performance of MoEDAL on multi-charged long-lived particles, two concrete neutrino mass models are studied. In the first model, the new physics sector is non-coloured and contains long-lived particles with electric charges 2, 3 and 4. A model-independent study finds MoEDAL can expect more than 1 signal event at the HL-LHC ($L=300$ fb${}^{-1}$) if these particles are lighter than 600, 1100 and 1430 GeV, respectively. These compare with the current ATLAS limits 650, 780 and 920 GeV for $L=36$ fb${}^{-1}$. The second model has a coloured new physics sector, which possesses long-lived particles with electric charges 4/3, 7/3 and 10/3. The corresponding MoEDAL's mass reaches at the HL-LHC are 1400, 1650 and 1800 GeV, respectively, which compare with the current CMS limits 1450, 1480 and 1510 GeV for $L=36$ fb${}^{-1}$. In a model-specific study we explore the parameter space of neutrino mass generation models and identify the regions that can be probed with MoEDAL at the end of Run-3 and the High-Luminosity LHC.

    hep-phhep-exEPJC(2021)·27 citations
16. 16*

    Muon $g-2$ in two Higgs doublet models with vectorlike leptons

    Radovan Dermisek🇺🇸 · Keith Hermanek🇺🇸 · Navin McGinnis🇨🇦

    We calculate contributions to the anomalous magnetic moment of the muon from heavy neutral and charged Higgs bosons and new leptons in two Higgs doublet models extended by vectorlike leptons. We present detailed predictions of two models with type-II couplings to standard model fermions, motivated by a $Z_2$ symmetry and supersymmetry. In addition, we compare the results with the standard model extended by vectorlike leptons. We find that the model motivated by a $Z_2$ symmetry can generate much larger contributions to the magnetic moment compared to the standard model, even by two orders of magnitude due to ${\tan }^2\beta$ enhancement, while satisfying current constraints. As a consequence, the standard model explanation of the anomaly requires much larger corrections to muon couplings making this model easier to probe at future precision machines. Additionally, we find that the model with couplings motivated by supersymmetry typically leads to much smaller contributions to the anomaly as a result of cancellations. However, we identify interesting scenarios where contributions from the charged Higgs boson can fully explain the anomaly.

    hep-phPRD(2021)·64 citations
17. 17*

    Avoided Deconfinement in Randall-Sundrum Models

    Prateek Agrawal🇬🇧 · Michael Nee🇬🇧

    We study first order phase transitions in Randall-Sundrum models in the early universe dual to confinement in large-$N$ gauge theories. The transition rate to the confined phase is suppressed by a factor $\exp (-N^2)$, and may not complete for $N\gg 1$, instead leading to an eternally inflating phase. To avoid this fate, the resulting constraint on $N$ makes the RS effective field theory only marginally under control. We present a mechanism where the IR brane remains stabilized at very high temperature, so that the theory stays in the confined phase at all times after inflation and reheating. We call this mechanism avoided deconfinement. The mechanism involves adding new scalar fields on the IR brane which provide a stablilizing contribution to the radion potential at finite temperature, in a spirit similar to Weinberg's symmetry non-restoration mechanism. Avoided deconfinement allows for a viable cosmology for theories with parametrically large $N$. Early universe cosmological phenomena such as WIMP freeze-out, axion abundance, baryogenesis, phase transitions, and gravitational wave signatures are qualitatively modified.

    hep-phhep-thJHEP(2021)·30 citations
18. 18*

    Light Dirac neutrino portal dark matter with observable $\Delta N_{\mathrm{eff}}$

    Anirban Biswas🇮🇳 · Debasish Borah🇮🇳 · Dibyendu Nanda🇮🇳

    We propose a Dirac neutrino portal dark matter scenario by minimally extending the particle content of the Standard Model (SM) with three right handed neutrinos (${\nu }_R$), a Dirac fermion dark matter candidate ($\psi$) and a complex scalar ($\varphi$), all of which are singlets under the SM gauge group. An additional ${\mathbb{Z}}_4$ symmetry has been introduced for the stability of dark matter candidate $\psi$ and also ensuring the Dirac nature of light neutrinos at the same time. Both the right handed neutrinos and the dark matter thermalise with the SM plasma due to a new Yukawa interaction involving ${\nu }_R$, $\psi$ and $\varphi$ while the latter maintains thermal contact via the Higgs portal interaction. The decoupling of ${\nu }_R$ occurs when $\varphi$ loses its kinetic equilibrium with the SM plasma and thereafter all three ${\mathbb{Z}}_4$ charged particles form an equilibrium among themselves with a temperature $T_{{\nu }_R}$. The dark matter candidate $\psi$ finally freezes out within the dark sector and preserves its relic abundance. We have found that in the present scenario, some portion of low mass dark matter ($M_{\psi }\lesssim 10$ GeV) is already excluded by the Planck 2018 data for keeping ${\nu }_R$s in the thermal bath below a temperature of 600 MeV and thereby producing an excess contribution to $N_{\mathrm{eff}}$. The next generation experiments like CMB-S4, SPT-3G etc. will have the required sensitivities to probe the entire model parameter space of this minimal scenario, especially the low mass range of $\psi$ where direct detection experiments are still not capable enough for detection.

    hep-phastro-ph.COJCAP(2021)·52 citations
19. 19*

    Soft interactions in cold quark matter

    Tyler Gorda🇩🇪 · Aleksi Kurkela🇳🇴 · Risto Paatelainen🇫🇮 · Saga Säppi🇮🇹 · Aleksi Vuorinen🇫🇮

    Accurate knowledge of the thermodynamic properties of zero-temperature, high-density quark matter plays an integral role in attempts to constrain the behavior of the dense QCD matter found inside neutron-star cores, irrespective of the phase realized inside the stars. In this Letter, we consider the weak-coupling expansion of the dense QCD equation of state and compute the next-to-next-to-next-to-leading-order contribution arising from the non-Abelian interactions among long-wavelength, dynamically screened gluonic fields. Accounting for these interactions requires an all-loop resummation, which can be performed using hard-thermal-loop (HTL) kinematic approximations. Concretely, we perform a full two-loop computation using the HTL effective theory, valid for the long-wavelength, or soft, modes. We find that the soft sector is well-behaved within cold quark matter, contrary to the case encountered at high temperatures, and find that the new contribution decreases the renormalization-scale dependence of the equation of state at high density.

    hep-phnucl-thPRL(2021)·166 citations
20. 20*

    Explicit Kink Solutions in Several One-Parameter Family of Higher Order Field Theory Models

    Avinash Khare🇮🇳 · Ayhan Duzgun🇺🇸 · Avadh Saxena🇺🇸

    We present several one-parameter family of higher order field theory models some of which admit explicit kink solutions with an exponential tail while others admit explicit kink solutions with a power-law tail. Various properties of these families of kink solutions are examined in detail. In particular for models harboring kink solutions with a power-law tail, we show that there is no gap between the zero mode and the beginning of the continuum in the kink stability potential. Further, by applying the recent Manton formalism, we provide estimates for the kink-kink and antikink-kink acceleration and hence the ratio of the corresponding antikink-kink and kink-kink forces.

    ↳ nlin.PShep-phhep-thmath-ph+1Int.J.Mod.Phys.B(2021)·6 citations
21. 21*

    Strange stars with a mirror-dark-matter core confronting with the observations of compact stars

    Shu-Hua Yang🇨🇳 · Chun-Mei Pi🇨🇳 · Xiao-Ping Zheng🇨🇳

    We investigate the structure and the tidal deformability of strange stars (SSs) with a mirror-dark-matter (MDM) core for the standard MIT bag model. We find that to explain the observations of PSR J0740+6620, PSR J0030+0451 and GW170817 simultaneously, SSs in GW170817 should have a MDM core although it is unnecessary for PSR J0740+6620 and PSR J0030+0451 to contain a MDM core. Our study leads to the result that for the standard MIT bag model, the observations of compact stars mentioned above confirm the existence of a dark-matter core inside SSs.

    ↳ astro-ph.HEhep-phPRD(2021)·25 citations
22. 22*

    The Higgs mechanism in nonlocal field theory

    Leonardo Modesto🇨🇳

    We provide an example of nonlocal scalar electrodynamics that allows the same Higgs mechanism so successful in local field theory. The nonlocal action is structured in order to have the same exact solutions and the same equations of motion for perturbations of the local theory, at any perturbative order. Therefore, the perturbative degrees of freedom that propagate in the unstable vacuum are reshuffled when the stable vacuum is replaced in the EoM, but their number does not change at any perturbative order, and their properties are the same like in the usual local theory. Finally, the theory is super-renormalizable or finite at quantum level.

    ↳ hep-thgr-qchep-phJHEP(2021)·22 citations
23. 23*

    A curvature bound from gravitational catalysis in thermal backgrounds

    Holger Gies🇩🇪 · Abdol Sabor Salek🇩🇪

    We investigate the phenomenon of gravitational catalysis, i.e., curvature-induced chiral symmetry breaking and fermion mass generation, at finite temperature. Using a scale-dependent analysis, we derive a thermal bound on the curvature of local patches of spacetime. This bound quantifies regions in parameter space that remain unaffected by gravitational catalysis and thus are compatible with the existence of light fermions as observed in Nature. While finite temperature generically relaxes the curvature bound, we observe a comparatively strong dependence of the phenomenon on the details of the curvature. Our bound can be applied to scenarios of quantum gravity, as any realistic candidate has to accommodate a sufficient number of light fermions. We argue that our bound therefore represents a test for quantum gravity scenarios: a suitably averaged spacetime in the (trans-)Planckian regime that satisfies our curvature bound does not induce correspondingly large Planckian fermion masses by gravitational catalysis. The temperature dependence derived in this work facilitates to follow the fate of gravitational catalysis during the thermal history of the (quantum) universe. In an application to the Asymptotic Safety scenario of quantum gravity, our bound translates into a temperature-dependent upper bound on the number of fermion flavors.

    ↳ hep-thgr-qchep-phPRD(2021)·22 citations
24. 24*

    Precision Nucleon Charges and Form Factors Using 2+1-flavor Lattice QCD

    Sungwoo Park🇺🇸 · Rajan Gupta🇺🇸 · Boram Yoon🇺🇸 · Santanu Mondal🇺🇸 · Tanmoy Bhattacharya🇺🇸 · Yong-Chull Jang🇺🇸 · Bálint Joó🇺🇸 · Frank Winter🇺🇸

    We present high statistics results for the isovector nucleon charges and form factors using seven ensembles of 2+1-flavor Wilson-clover fermions. The axial and pseudoscalar form factors obtained on each ensemble satisfy the PCAC relation once the lowest energy $N\pi$ excited state is included in the spectral decomposition of the correlation functions used for extracting the ground state matrix elements. Similarly, we find evidence that the $N\pi \pi$ excited state contributes to the correlation functions with the vector current, consistent with the vector meson dominance model. The resulting form factors are consistent with the Kelly parameterization of the experimental electric and magnetic data. Our final estimates for the isovector charges are $g_A^{u-d}=1.31(06)(05{)}_{sys}$, $g_S^{u-d}=1.06(10)(06{)}_{sys}$, and $g_T^{u-d}=0.95(05)(02{)}_{sys}$, where the first error is the overall analysis uncertainty and the second is an additional combined systematic uncertainty. The form factors yield: (i) the axial charge radius squared, ${⟨r_A^2⟩}^{u-d}=0.428(53)(30{)}_{sys}{\mathrm{fm}}^2$, (ii) the induced pseudoscalar charge, $g_P^{\ast }=7.9(7)(9{)}_{sys}$, (iii) the pion-nucleon coupling $g_{\pi \mathrm{NN}}=12.4(1.2)$, (iv) the electric charge radius squared, ${⟨r_E^2⟩}^{u-d}=0.85(12)(19{)}_{sys}{\mathrm{fm}}^2$, (v) the magnetic charge radius squared, ${⟨r_M^2⟩}^{u-d}=0.71(19)(23{)}_{\mathrm{sys}}{\mathrm{fm}}^2$, and (vi) the magnetic moment ${\mu }^{u-d}=4.15(22)(10{)}_{\mathrm{sys}}$. All our results are consistent with phenomenological/experimental values but with larger errors. Lastly, we present a Padé parameterization of the axial, electric and magnetic form factors over the range $0.04<Q^2<1$ GeV${}^2$ for phenomenological studies.

    ↳ hep-lathep-phPRD(2022)·154 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.