Tue·May 4, 2021Tuesday·May 4, 2021

1. 01*

   Doubly charged vector tetraquark $Z_{\mathrm{V}}^{++}=[cu][\overline{s}\overline{d}]$

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

   We explore properties of the doubly charged vector tetraquark $Z_{\mathrm{V}}^{++}=[cu][\overline{s}\overline{d}]$ built of four quarks of different flavors using the QCD sum rule methods. The mass and current coupling of $Z_{\mathrm{V}}^{++}$ are computed in the framework of the QCD two-point sum rule approach by taking into account quark, gluon and mixed vacuum condensates up to dimension $10$. The full width of this tetraquark is saturated by $S$-wave $Z_{\mathrm{V}}^{++}\to {\pi }^{+}{D}_{s1}(2460{)}^{+},{\rho }^{+}{D}_{s0}^{\ast }(2317{)}^{+}$, and $P$-wave $Z_{\mathrm{V}}^{++}\to {\pi }^{+}{D}_s^{+},K^{+}{D}^{+}$ decays. Strong couplings required to find partial widths of aforementioned decays are calculated in the context of the QCD light-cone sum rule method and a soft-meson approximation. Our predictions for the mass $m=(3515\pm 125)\mathrm{MeV}$ and full width ${\Gamma }_{\mathrm{full}}=156_{-30}^{+56}\mathrm{MeV}$ of $Z_{\mathrm{V}}^{++}$ are useful to search for this exotic meson in various processes. Recently, the LHCb collaboration discovered neutral states $X_{0(1)}(2900)$ as resonance-like peaks in $D^{-}{K}^{+}$ invariant mass distribution in the decay $B^{+}\to D^{+}{D}^{-}{K}^{+}$. We argue that mass distribution of $D^{+}{K}^{+}$ mesons in the same $B$ decay can be used to observe the doubly charged scalar $Z_{\mathrm{S}}^{++}$ and vector $Z_{\mathrm{V}}^{++}$ tetraquarks.

   hep-phhep-exhep-latPLB(2021)·20 citations
2. 02*

   Induced Quantized Spin Current in Vacuum

   Chong-Sun Chu🇹🇼 · Chun-Hei Leung🇹🇼

   We uncover a fundamental effect of the QED vacuum in an external electromagnetic (EM) field. We show that the quantized vacuum of electrons is spin polarized by the EM field and manifests as a vacuum spin current. An experiment is proposed to measure the spin torque exerted by the spin current by measuring the twisted angle of the director axis of a nematic liquid crystal.

   hep-phcond-mat.otherhep-exhep-thPRL(2021)·7 citations
3. 03*

   Analysis of the differential cross section and photon beam asymmetry data for $\gamma p\to {\eta }^{\prime }p$

   Yu Zhang🇨🇳 · Ai-Chao Wang🇨🇳 · Neng-Chang Wei🇨🇳 · Fei Huang🇨🇳

   The photoproduction reaction of $\gamma p\to {\eta }^{\prime }p$ is investigated based on an effective Lagrangian approach in the tree-level approximation, with the purpose being to understand the reaction mechanisms and to extract the resonance contents and the associated resonance parameters in this reaction. Apart from the $t$-channel $\rho$ and $\omega$ exchanges, $s$- and $u$-channel nucleon exchanges, and generalized contact term, the exchanges of a minimum number of nucleon resonances in the $s$ channel are taken into account in constructing the reaction amplitudes to describe the experimental data. It is found that a satisfactory description of the available data on both differential cross sections and photon beam asymmetries can be obtained by including in the $s$ channel the exchanges of the $N(1875)3/2^{-}$ and $N(2040)3/2^{+}$ resonances. The reaction mechanisms of $\gamma p\to {\eta }^{\prime }p$ are discussed and a prediction for the target nucleon asymmetries is presented.

   hep-phnucl-thPRD(2021)·7 citations
4. 04*

   Coulomb effects in the decays ${\rm Y}(4S)\to B\bar{B}$

   A.I. Milstein🇷🇺 · S.G. Salnikov🇷🇺

   A simple exactly solvable model is proposed for describing the decays ${\rm Y}(4S)\to B^0{\bar{B}}^0$ and ${\rm Y}(4S)\to B^{+}{B}^{-}$. Our predictions agree with available experimental data. Using this model, we analyze the Coulomb effects in the spectra of these decays. It is shown that the frequently used assumption of factorization of Coulomb effects is not fulfilled. The Coulomb interaction leads to the difference in the positions and heights of the peaks corresponding to the charged and neutral modes. As a result, the ratio of probability of ${\rm Y}(4S)\to B^{+}{B}^{-}$ decay and ${\rm Y}(4S)\to B^0{\bar{B}}^0$ decay is a nontrivial function of energy.

   hep-phnucl-thPRD(2021)·13 citations
5. 05*

   Global Vision of Precision Measurements

   Jens Erler🇩🇪

   I summarize recent developments in electroweak precision physics and global fits. Expectations for future measurements, both at lower energies and the energy frontier, are also discussed.

   hep-phhep-exnucl-ex1 citation
6. 06*

   Determination of perturbative QCD coupling from ALEPH $\tau$ decay data using pinched Borel-Laplace and Finite Energy Sum Rules

   Cesar Ayala🇨🇱 · Gorazd Cvetic🇨🇱 · Diego Teca🇨🇱

   We present a determination of the perturbative QCD (pQCD) coupling using the V+A channel ALEPH $\tau$-decay data. The determination involves the double-pinched Borel-Laplace Sum Rules and Finite Energy Sum Rules. The theoretical basis is the Operator Product Expansion (OPE) of the V+A channel Adler function in which the higher order terms of the leading-twist part originate from a model based on the known structure of the leading renormalons of this quantity. The applied evaluation methods are contour-improved perturbation theory (CIPT), fixed-order perturbation theory (FOPT), and Principal Value of the Borel resummation (PV). All the methods involve truncations in the order of the coupling. In contrast to the truncated CIPT method, the truncated FOPT and PV methods account correctly for the suppression of various renormalon contributions of the Adler function in the mentioned sum rules. The extracted value of the $\overline{\mathrm{MS}}$ coupling is ${\alpha }_s(m_{\tau }^2)=0.3116\pm 0.0073$ [${\alpha }_s(M_Z^2)=0.1176\pm 0.0010$] for the average of the FOPT and PV methods, which we regard as our main result. On the other hand, if we include in the average also the CIPT method, the resulting values are significantly higher, ${\alpha }_s(m_{\tau }^2)=0.3194\pm 0.0167$ [${\alpha }_s(M_Z^2)=0.1186\pm 0.0021$].

   hep-phEPJC(2021)·27 citations
7. 07*

   Deeply virtual Compton scattering off Helium nuclei with positron beams

   Sara Fucini🇮🇹 · Mohammad Hattawy🇺🇸 · Matteo Rinaldi🇮🇹 · Sergio Scopetta🇮🇹

   Positron initiated deeply virtual Compton scattering (DVCS) off ${}^4$He and ${}^3$He nuclei is described. The way the so-called $d-$term could be obtained from the real part of the relevant Compton form factor is summarized, and the importance and novelty of this measurement is discussed. The measurements addressed for ${}^3$He targets could be very useful even in a standard unpolarized target setup, measuring beam spin and beam charge asymmetries only. The unpolarized beam charge asymmetries for DVCS off ${}^3$He and ${}^4$He are also estimated, at JLab kinematics and, for ${}^4$He, also at a configuration typical at the future Electron-Ion Collider. Incoherent DVCS processes, in particular the ones with tagging the internal target by measuring slow recoiling nuclei, and the unique possibility offered by positron beams for the investigation of Compton form factors of higher twist, are also briefly addressed.

   hep-phEPJA(2021)·8 citations
8. 08*

   Radiative Seesaw Dark Matter

   Ernest Ma🇺🇸 · Valentina De Romeri🇪🇸

   The singlet majoron model of seesaw neutrino mass is appended by one dark Majorana fermion singlet $\chi$ with $L=2$ and one dark complex scalar singlet $\zeta$ with $L=1$. This simple setup allows $\chi$ to obtain a small radiative mass anchored by the same heavy right-handed neutrinos, whereas the one-loop decay of the standard-model Higgs boson to $\chi \chi +\bar{\chi }\bar{\chi }$ provides the freeze-in mechanism for $\chi$ to be the light dark matter of the Universe.

   hep-phPRD(2021)·13 citations
9. 09*

   Constraints on the kinetic mixing parameter ${ϵ}^2$ for the light dark photons from dilepton production in heavy-ion collisions in the few-GeV energy range

   Ida Schmidt (Frankfurt Uni.)🇩🇪 · Elena Bratkovskaya (GSI, Darmstadt, Frankfurt Uni.)🇩🇪 · Malgorzata Gumberidze (GSI, Darmstadt)🇩🇪 · Romain Holzmann (GSI, Darmstadt)🇩🇪

   The vector $U$-bosons, or so called 'dark photons', are one of the possible candidates for the dark matter mediators. They are supposed to interact with the standard matter via a 'vector portal' due to the $U(1)-U(1{)}^{\prime }$ symmetry group mixing which might make them visible in particle and heavy-ion experiments. While there is no confirmed observation of dark photons, the detailed analysis of different experimental data allows to estimate the upper limit for the kinetic mixing parameter ${ϵ}^2$ depending on the mass $M_U$ of $U$-bosons which is also unknown. In this study we present theoretical constraints on the upper limit of ${ϵ}^2(M_U)$ in the mass range $M_U\le 0.6$ GeV from the comparison of the calculated dilepton spectra with the experimental data from the HADES Collaboration at SIS18 energies where the dark photons are not observed. Our analysis is based on the microscopic Parton-Hadron-String Dynamics (PHSD) transport approach which reproduces well the measured dilepton spectra in $p+p$, $p+A$ and $A+A$ collisions. Additionally to the different dilepton channels originating from interactions and decays of ordinary matter particles (mesons and baryons), we incorporate the decay of hypothetical $U$-bosons to dileptons, $U\to e^{+}{e}^{-}$, where the $U$-bosons themselves are produced by the Dalitz decay of pions ${\pi }^0\to \gamma U$, $\eta$-mesons $\eta \to \gamma U$ and Delta resonances $\Delta \to NU$. Our analysis can help to estimate the requested accuracy for future experimental searches of 'light' dark photons by dilepton experiments.

   hep-phhep-exnucl-thPRD(2021)·10 citations
10. 10*

    The proton charge radius

    Haiyan Gao🇺🇸 · Marc Vanderhaeghen🇩🇪

    Nucleons (protons and neutrons) are the building blocks of atomic nuclei, and are responsible for more than 99\% of the visible matter in the universe. Despite decades of efforts in studying its internal structure, there are still a number of puzzles surrounding the proton such as its spin, and charge radius. Accurate knowledge about the proton charge radius is not only essential for understanding how quantum chromodynamics (QCD) works in the non-perturbative region, but also important for bound state quantum electrodynamics (QED) calculations of atomic energy levels. It also has an impact on the Rydberg constant, one of the most precisely measured fundamental constants in nature. This article reviews the latest situation concerning the proton charge radius in light of the new experimental results from both atomic hydrogen spectroscopy and electron scattering measurements, with particular focus on the latter. We also present the related theoretical developments and backgrounds concerning the determination of the proton charge radius using different experimental techniques. We discuss upcoming experiments, and briefly mention the deuteron charge radius puzzle at the end.

    hep-phnucl-exnucl-thRMP(2022)·162 citations
11. 11*

    Quark model analysis of the Weinberg operator contribution to the nucleon EDM

    Nodoka Yamanaka🇺🇸 · Emiko Hiyama🇯🇵

    The Weinberg operator (chromo-electric dipole moment of gluon) is a CP violating quantity generated in many candidates of new physics beyond the standard model, and it contributes to observables such as the electric dipole moments (EDM) of the neutron or atoms which are currently measured in experiments. In this proceedings contribution, we report on our result of the evaluation of the Weinberg operator contribution to the nucleon EDM in the nonrelativistic quark model using the Gaussian expansion method.

    hep-phnucl-thFew Body Syst.(2021)·0 citations
12. 12*

    Comment on "Dark Matter Annihilation Can Produce a Detectable Antihelium Flux through ${\bar{\Lambda }}_b$ Decays"

    M. Kachelriess🇳🇴 · S. Ostapchenko🇷🇺 · J. Tjemsland🇳🇴

    In a recent Letter, it was suggested that a previously neglected Standard Model process, namely, the production of antihelium-3 nuclei through decays of ${\bar{\Lambda }}_b$ baryons can lead to a flux of antihelium-3 from dark matter annihilations detectable by AMS-02. We show that an essential condition for its detectability -- the introduction of the "${\bar{\Lambda }}_b$ tune" of Pythia -- is excluded by a wealth of measurements of (anti-) baryon and (anti-) meson production at accelerators. Moreover, we argue that Monte Carlo generators like Pythia should not be used to predict branching ratios like $BR({\bar{\Lambda }}_b\to \bar{u}du(u{d}_0))$, which control the formation rate of antihelium-3. In particular, we show that ${\bar{\Lambda }}_b$ decays which proceed via diquark formation are overestimated by Pythia using its standard settings, which are further enhanced in the "${\bar{\Lambda }}_b$ tune".

    hep-ph13 citations
13. 13*

    Vector and Axial-Vector Mesons in Nuclear Matter

    Ralf-Arno Tripolt🇩🇪 · Christopher Jung🇩🇪 · Lorenz von Smekal🇩🇪 · Jochen Wambach🇩🇪

    As a first step towards a realistic phenomenological description of vector and axial-vector mesons in nuclear matter, we calculate the spectral functions of the $\rho$ and the $a_1$ meson in a chiral baryon-meson model as a low-energy effective realization of QCD, taking into account the effects of fluctuations from scalar mesons, nucleons, and vector mesons within the Functional Renormalization Group (FRG) approach. The phase diagram of the effective hadronic theory exhibits a nuclear liquid-gas phase transition as well as a chiral phase transition at a higher baryon-chemical potential. The in-medium $\rho$ and $a_1$ spectral functions are calculated by using the previously introduced analytically-continued FRG (aFRG) method. Our results show strong modifications of the spectral functions in particular near the critical endpoints of both phase transitions which may well be of relevance for electromagnetic rates in heavy-ion collisions or neutrino emissivities in neutron-star merger events.

    hep-phnucl-thPRD(2021)·42 citations
14. 14*

    Inelastic dark matter, small scale problems, and the XENON1T excess

    Seungwon Baek🇰🇷

    We study a generic model in which the dark sector is composed of a Majorana dark matter ${\chi }_1$, its excited state ${\chi }_2$, both at the electroweak scale, and a light dark photon $Z^{\prime }$ with $m_{Z^{\prime }}\sim 10^{-4}$ eV. The light $Z^{\prime }$ enhances the self-scattering elastic cross section ${\chi }_1{\chi }_1\to {\chi }_1{\chi }_1$ enough to solve the small scale problems in the $N$-body simulations with the cold dark matter. The dark matter communicates with the SM via kinetic mixing parameterized by $ϵ$. The inelastic scattering process ${\chi }_1{\chi }_1\to {\chi }_2{\chi }_2$ followed by the prompt decay ${\chi }_2\to {\chi }_1{Z}^{\prime }$ generates energetic $Z^{\prime }$. By setting $\delta \equiv m_{{\chi }_2}-m_{{\chi }_1}\simeq 2.8$ keV and $ϵ\sim 10^{-10}$ the excess in the electron-recoil data at the XENON1T experiment can be explained by the dark-photoelectric effect. The relic abundance of the dark matter can also be accommodated by the thermal freeze-out mechanism via the annihilation ${\chi }_1{\chi }_1({\chi }_2{\chi }_2)\to Z^{\prime }{Z}^{\prime }$ with the dark gauge coupling constant ${\alpha }_X\sim 10^{-3}$.

    hep-phJHEP(2021)·7 citations
15. 15*

    Distinguishing Different BSM Signatures at Present and Future Colliders

    Saunak Dutta🇮🇳 · Priyotosh Bandyopadhyay🇮🇳 · Anirban Karan🇮🇳

    We show how angular distributions can distinguish different scenarios beyond the standard model by characterising particles of different spins at the LHC. We illustrate the idea with scalar and vector leptoquarks along with the heavy fermions in Type-III seesaw as spin zero, spin one and spin half examples respectively. On the other hand, zeros of single photon tree level amplitude can separate different particles according their electromagnetic charges. This phenomenon can be used to distinguish leptoquarks of different gauge representations, even different excitations of same $SU(2{)}_L$ gauge group, within the same spin frame work. We explore electron-photon and electron-hadron colliders to discern such scenarios in the context of the leptoquark models by means of zeros in scattering amplitudes. We found that the discerning effect in these two colliders are complementary to each other and both of them are required for an exhaustive analysis of leptoquark models. The analyses are carried out for different leptoquark masses and centre of mass energies of the collisions which involve a PYTHIA based simulation.

    hep-phCERN Proceedings - International Conferen…·3 citations
16. 16*

    Calculation of the contribution to muon $g-2$ due to the effective anomalous three boson interaction and the new experimental result

    B.A. Arbuzov🇷🇺 · I.V. Zaitsev🇷🇺

    Using the approach based on Bogoliubov compensation principle is applied to calculation of a contribution to the muon $g-2$. Using the previous results on spontaneous generation of the effective anomalous three-boson interaction we calculate the contribution, which proves to agree with the well-known discrepancy. The calculated quantity contains no adjusting parameters but the experimental values for the muon and the W-boson masses. The result can be considered as a confirmation of the approach.

    hep-phInt.J.Mod.Phys.A(2021)·4 citations
17. 17*

    Damping and polarization rates in near equilibrium state

    Ziyue Wang🇨🇳 · Pengfei Zhuang🇨🇳

    The collision terms in spin transport theory are analyzed in Kadanoff-Baym formalism for systems close to equilibrium. The non-equilibrium fluctuations in spin distribution include both damping and polarization, with the latter arising from the exchange between orbital and spin angular momenta. The damping and polarization rates or the relaxation times are expressed in terms of various Dirac components of the self-energy. Unlike the usually used Anderson-Witting relaxation time approximation assuming a single time scale for different degrees of freedom, the polarization effect is induced by the thermal vorticity and its time scale of thermalization is different from the damping. The numerical calculation in the Nambu--Jona-Lasinio model shows that, charge is thermalized earlier and spin is thermalized later.

    hep-ph29 citations
18. 18*

    $U(1{)}_A$ axial anomaly, ${\eta }^{\prime }$, and topological susceptibility in the holographic soft-wall model

    Floriana Giannuzzi🇮🇹 · Stefano Nicotri🇮🇹

    The singlet pseudoscalar sector of light mesons is investigated in the soft-wall model, a bottom-up approach to the AdS/QCD correspondence. The ${\eta }^{\prime }$ mass results from the mixing among the fields dual to the axial current, pseudoscalar current and the $G\tilde{G}$ operator. The topological susceptibility is computed for any quark mass, and the Witten-Veneziano relation is obtained in the large $N_c$ limit.

    hep-phPRD(2021)·10 citations
19. 19*

    The $pp\to W(\to l\nu )+\gamma$ process at next-to-next-to-leading order

    John M. Campbell🇺🇸 · Giuseppe De Laurentis🇩🇪 · R. Keith Ellis🇬🇧 · Satyajit Seth🇮🇳

    We present details of the calculation of the $pp\to W(\to l\nu )\gamma$ process at next-to-next-to-leading order in QCD, calculated using the jettiness slicing method. The calculation is based entirely on analytic amplitudes. Because of the radiation zero, the NLO QCD contribution from the $gq$ channel is as important as the contribution from the Born $q\bar{q}$ process, disrupting the normal counting of leading and sub-leading contributions. We also assess the importance of electroweak (EW) corrections, including the EW corrections to both the six-parton channel $0\to \bar{u}d\nu e^{+}\gamma g$ and the five-parton channel $0\to \bar{u}d\nu e^{+}\gamma$. Previous experimental results have been shown to agree with theoretical predictions, taking into account the large experimental errors. With the advent of run II data from the LHC, the statistical errors on the data will decrease, and will be competitive with the error on theoretical predictions for the first time. We present numerical results for $\sqrt{s}=7$ and 13 TeV. Analytic results for the one-loop six-parton QCD amplitude and the tree-level seven-parton QCD amplitude are presented in appendices.

    hep-phJHEP(2021)·16 citations
20. 20*

    Gravitational waves from a dark $U(1{)}_D$ phase transition in the light of NANOGrav 12.5 yr data

    Debasish Borah🇮🇳 · Arnab Dasgupta🇰🇷 · Sin Kyu Kang🇰🇷

    We study a possibility of a strong first-order phase transition (FOPT) taking place below the electroweak scale in the context of $U(1{)}_D$ gauge extension of the standard model. As pointed out recently by the NANOGrav collaboration, gravitational waves from such a phase transition with appropriate strength and nucleation temperature can explain their 12.5 yr data. We first find the parameter space of this minimal model consistent with NANOGrav findings considering only a complex singlet scalar and $U(1{)}_D$ vector boson. Existence of a singlet fermion charged under $U(1{)}_D$ can give rise to dark matter in this model, preferably of non-thermal type, while incorporating additional fields can also generate light neutrino masses through typical low scale seesaw mechanisms like radiative or inverse seesaw.

    hep-phastro-ph.COPRD(2021)·28 citations
21. 21*

    Applications of pT-xR Variables in Describing Inclusive Cross Sections at the LHC

    Frank E. Taylor🇺🇸

    Invariant inclusive single particle/jet cross sections in p-p collisions can be factorized in terms of two separable pT dependences, a [pT - sqrt(s)] sector and an [xR - pT - sqrt(s)] sector, where xR = E/Emax is the radial scaling variable. Here, we extend our earlier work by analyzing more extensive data to explore various s-dependent attributes and other systematics of inclusive jet, photon and single particle inclusive reactions. Approximate power laws in sqrt(s), pT and xR are found. Physical arguments are given which relate observations to the underlying physics of parton - parton hard scattering and the parton distribution functions in the proton. We show that the A(sqrt(s), pT)-function, introduced in our earlier publication to describe the pT-dependence of the inclusive cross section, is directly related to the underlying hard parton-parton scattering for jet production with little influence from soft physics. In addition to the A-function, we introduce another function, the F(sqrt(s), xR)-function, which obeys radial scaling for inclusive jets that offers another test of the underlying parton physics. An application to heavy ion physics is given where we use our variables to determine the transparency of cold nuclear matter to penetrating heavy mesons through the lead nucleus.

    hep-phUniverse(2021)·0 citations
22. 22*

    An Effective Model for Glueballs and Dual Superconductivity at Finite Temperature

    Adamu Issifu🇧🇷 · Francisco A. Brito🇧🇷

    The glueballs lead to gluon and QCD monopole condensations as by-products of color confinement. A color dielectric function $G(|\varphi |)$ coupled with Abelian gauge field is properly defined to mediate the glueball interactions at confining regime after {\it spontaneous symmetry breaking} (SSB) of the gauge symmetry. The particles are expected to form through quark gluon plasma (QGP) hadronization phase where the free quarks and gluons start clamping together to form hadrons. The QCD-like vacuum $⟨{\eta }^2{m}_{\eta }^2{F}^{\mu \nu }{F}_{\mu \nu }⟩$, confining potential $V_c(r)$, string tension $\sigma$, penetration depth $\lambda$, superconducting and normal monopole densities ($n_s{n}_n$) and the effective masses ($m_{\eta }^2$ and $m_A^2$) will be investigated at finite temperature $T$. We also calculate the strong `running' coupling ${\alpha }_s$ and subsequently the QCD $\beta$-function. {\it Dual superconducting} nature of the QCD vacuum will be investigated based on monopole condensation.

    hep-phhep-thAdv.High Energy Phys.(2021)·6 citations
23. 23*

    Extending light-front holographic QCD using the 't Hooft Equation

    Mohammad Ahmady🇨🇦 · Harleen Dahiya🇮🇳 · Satvir Kaur🇮🇳 · Chandan Mondal🇨🇳 · Ruben Sandapen🇨🇦 · Neetika Sharma🇵🇰

    We show the 't Hooft Equation and the light-front holographic Schrödinger Equation are complementary to each other in governing the transverse and longitudinal dynamics of colour confinement in quark-antiquark mesons. Together, they predict remarkably well the light, heavy-light and heavy-heavy meson spectroscopic data. The universal emerging hadronic scale of light-front holography, $\kappa \approx 0.5$ GeV, controls the transverse dynamics of confinement in all mesons. In heavy-heavy mesons, it also coincides numerically with the 't Hooft coupling which governs longitudinal confinement, thus reflecting the restoration of manifest 3-dimensional rotational symmetry

    hep-phPLB(2021)·28 citations
24. 24*

    Impact of gauge fixing on angular momentum operators of the covariantly quantized electromagnetic field

    Bogdan Damski🇵🇱

    Covariant quantization of the electromagnetic field imposes the so-called gauge-fixing modification on the Lagrangian density. As a result of that, the total angular momentum operator receives at least one gauge-fixing-originated contribution, whose presence causes some confusion in the literature. The goal of this work is to discuss in detail why such a contribution, having no classical interpretation, is actually indispensable. For this purpose, we divide canonical and Belinfante-Rosenfeld total angular momentum operators into different components and study their commutation relations, their role in generation of rotations of quantum fields, and their action on states from the physical sector of the theory. Then, we examine physical matrix elements of operators having gauge-fixing-related contributions, illustrating problems that one may encounter due to careless employment of the resolution of identity during their evaluation. The resolution of identity, in the indefinite-metric space of the covariantly-quantized electromagnetic field, is extensively discussed because it takes a not-so-intuitive form if one insists on explicit projection onto states from the physical sector of the theory. Our studies are carried out in the framework of the Gupta-Bleuler theory of the free electromagnetic field. Relevant remarks about interacting systems, described by covariantly-quantized electrodynamics, are given.

    hep-phhep-thquant-phPRD(2021)·6 citations
25. 25*

    ALP-SMEFT Interference

    Anne Mareike Galda (U. Mainz)🇩🇪 · Matthias Neubert (U. Mainz)🇩🇪 · Sophie Renner (SISSA)🇮🇹

    The Standard Model Effective Field Theory (SMEFT) offers a powerful theoretical framework for parameterizing the low-energy effects of heavy new particles with masses far above the scale of electroweak symmetry breaking. Additional light degrees of freedom extend the effective theory. We show that light new particles that are weakly coupled to the SM via non-renormalizable interactions induce non-zero Wilson coefficients in the SMEFT Lagrangian via renormalization-group evolution. For the well-motivated example of axions and axion-like particles (ALPs) interacting with the SM via classically shift-invariant dimension-5 interactions, we calculate how these interactions contribute to the one-loop renormalization of the dimension-6 SMEFT operators, and how this running sources additional contributions to the Wilson coefficients on top of those expected from heavy new states. As an application, we study the ALP contributions to the magnetic dipole moment of the top quark and comment on implications of electroweak precision constraints on ALP couplings.

    hep-phhep-thJHEP(2021)·52 citations
26. 26*

    Spectra of Heavy Quarkonia in a Magnetized-Hot Medium in the Framework of Fractional Non-relativistic Quark Model

    M. Abu-shady🇪🇬 · A. I. Ahmadov🇦🇿 · H. M. Fath-Allah🇪🇬 · V. H. Badalov🇦🇿

    In the fractional nonrelativistic potential model, the decomposition of heavy quarkonium in a hot magnetized medium is investigated. The analytical solution of the fractional radial Schrodinger equation for the hot-magnetized interaction potential is displayed by using the conformable fractional Nikiforov-Uvarov method. Analytical expressions for the energy eigenvalues and the radial wave function are obtained for arbitrary quantum numbers. Next, we study the charmonium and bottmonium binding energies for different magnetic field values in the thermal medium. The effect of the fractional parameter on the decomposition temperature is also analyzed for charmonium and bottomonium in the presence of hot magnetized media. We conclude that the dissociation of heavy quarkonium in the fractional nonrelativistic potential model is more practical than the classical nonrelativistic potential model.

    hep-phJ.Theor.Appl.Phys.(2022)·9 citations
27. 27*

    Constraining free parameters of a color superconducting non-local Nambu-Jona-Lasinio model using Bayesian analysis of neutron stars mass and radius measurements

    Mahboubeh Shahrbaf🇵🇱 · Sofija Antić🇦🇺 · A. Ayriyan🇷🇺 · David Blaschke🇵🇱 · Ana Gabriela Grunfeld🇦🇷

    We provide a systematic study of hybrid neutron star equations of state (EoS) consisting of a relativistic density functional for the hadronic phase and a covariant nonlocal Nambu--Jona-Lasinio (nlNJL) model to describe the color superconducting quark matter phase. Changing the values of the two free parameters, the dimensionless vector and diquark coupling strengths ${\eta }_V$ and ${\eta }_D$ results in a set of EoS with varying stiffness and deconfinement onset. The favorable parameters are obtained from a systematic Bayesian analysis for which the multi-messenger constraint on the neutron star radius at $1.4$M${}_{\odot }$ and the combined mass-radius constraint for PSR J0740+6620 from NICER experiment are used as the constraints. Additionally, the transition from hadronic matter to deconfined quark matter is constrained to occur above nuclear saturation density. Hybrid stars modeled with these favorable parameters are compatible with the NICER results for the radius of the highest known mass neutron star, PSR J0740+6620. Three new observations interesting for neutron star phenomenology are reported: 1) We show that the constant sound speed (CSS) EoS provides an excellent fit to that of the nlNJL model which implies the squared speed of sound at high densities to be about $0.5$ for the optimized parameters; 2) we give a simple functional form for the mapping between the parameter spaces of these two models valid for the whole range of relevant chemical potentials and 3) we observe that the special point property of hybrid EoS based on CSS quark matter generalizes to a set of lines consisting of special points when two EoS parameters are varied instead of one. A lower limit for the maximum mass of hybrid stars as a function of the vector coupling strength is obtained.

    ↳ nucl-thastro-ph.HEhep-phPRD(2023)·34 citations
28. 28*

    From Veltman's conditions to Finite Unification

    Myriam Mondragón🇲🇽 · Gregory Patellis🇬🇷 · George Zoupanos🇬🇷

    First we review Veltman's suggestion to attack the naturalness problem in the Standard model by requiring absence of quadratic divergences and the resulting mass formula. Then we emphasise the influence of Veltman's suggestion in strengthening the belief that supersymmetry is the natural playground for solving the problem of quadratic divergences. Going further, we recall few sporadic suggestions concerning the cancellation of the logarithmic divergences too, which in the framework of supersymmetry has led to the construction of all-loop Finite Theories with the use of the idea of reduction of couplings. Eventually, we concentrate on a specific Finite Unified Theory and its successful predictions for the top and Higgs mass, among others, and the prospects of its final justification in future collider searches.

    ↳ hep-thhep-phActa Phys.Polon.B(2021)·1 citation
29. 29*

    Dependence of the amplitude of gravitational waves from preheating on the inflationary energy scale

    Rong-Gen Cai🇨🇳 · Zong-Kuan Guo🇨🇳 · Pei-Ze Ding🇨🇳 · Cheng-Jie Fu🇨🇳 · Jing Liu🇨🇳

    Stochastic gravitational wave backgrounds (SGWBs) receive increasing attention and provide a new possibility to directly probe the early Universe. In the preheating process at the end of inflation, parametric resonance can generate large energy density perturbations and efficiently produce gravitational waves (GWs) which carry unique information about inflation. Since the peak frequency of such GWs is approximately proportional to the inflationary energy scale, ${\Lambda }_{\inf }$, GWs from preheating are expected to be observed by interferometer GW detectors in low-scale inflationary models. We investigate the dependence of the amplitude of such GWs on ${\Lambda }_{\inf }$, and find that the present energy spectrum of these GWs does not depend on ${\Lambda }_{\inf }$ only in the case of ${\Lambda }_{\inf }$ is above a critical value ${\Lambda }_c$, a parameter depending on the resonance strength. We numerically obtain ${\Lambda }_c$ in terms of the model parameters in linear approximation and then conduct lattice simulations to verify this result. For ${\Lambda }_{\inf }\lesssim {\Lambda }_c$, the amplitude of GWs quickly decreases with ${\Lambda }_{\inf }$ and becomes challenging to observe. In turn, observing such GWs in interferometer detectors also helps to determine ${\Lambda }_{\inf }$ and the resonance strength during the preheating.

    ↳ astro-ph.COgr-qchep-phPRD(2022)·5 citations
30. 30*

    Recommended conventions for reporting results from direct dark matter searches

    D. Baxter🇺🇸 · I. M. Bloch🇮🇱 · E. Bodnia🇺🇸 · X. Chen🇨🇳 · J. Conrad🇸🇪 · P. Di Gangi🇮🇹 · J. E. Y. Dobson🇬🇧 · D. Durnford🇨🇦 · S. J. Haselschwardt🇺🇸 · A. Kaboth🇬🇧 · R. F. Lang🇺🇸 · Q. Lin🇨🇳 and 14 other authors

    The field of dark matter detection is a highly visible and highly competitive one. In this paper, we propose recommendations for presenting dark matter direct detection results particularly suited for weak-scale dark matter searches, although we believe the spirit of the recommendations can apply more broadly to searches for other dark matter candidates, such as very light dark matter or axions. To translate experimental data into a final published result, direct detection collaborations must make a series of choices in their analysis, ranging from how to model astrophysical parameters to how to make statistical inferences based on observed data. While many collaborations follow a standard set of recommendations in some areas, for example the expected flux of dark matter particles (to a large degree based on a paper from Lewin and Smith in 1995), in other areas, particularly in statistical inference, they have taken different approaches, often from result to result by the same collaboration. We set out a number of recommendations on how to apply the now commonly used Profile Likelihood Ratio method to direct detection data. In addition, updated recommendations for the Standard Halo Model astrophysical parameters and relevant neutrino fluxes are provided. The authors of this note include members of the DAMIC, DarkSide, DARWIN, DEAP, LZ, NEWS-G, PandaX, PICO, SBC, SENSEI, SuperCDMS, and XENON collaborations, and these collaborations provided input to the recommendations laid out here. Wide-spread adoption of these recommendations will make it easier to compare and combine future dark matter results.

    ↳ hep-exhep-phEPJC(2021)·298 citations
31. 31*

    Sensitivity of SKA to dark matter induced radio emission

    Zhanfang Chen🇨🇳 · Yue-Lin Sming Tsai🇨🇳 · Qiang Yuan🇨🇳

    Conventionally, one can constrain the dark matter (DM) interaction with DM mass heavier than GeV by searching for DM induced synchrotron emission in the radio frequency band. However, an MeV DM can also generate detectable radio emission if electrons and positrons produced by DM annihilation or decay undergoes inverse Compton scattering (ICS) with the cosmic microwave background. The upcoming radio telescope Square Kilometre Array (SKA) is designed to operate with extremely high sensitivity. We investigate the capability of the SKA to detect DM particles in a board mass range from MeV to TeV, for both annihilation and decay scenarios. In this paper, we consider the sensitivities of the future SKA first and second phase (SKA1 and SKA2). As a comprehensive study, we systematically study the impacts on the DM-induced signal computation from the magnetic field strengths and particle diffusion coefficients. We compare the detection potential of four very different sources: two dwarf spheroidal galaxies (Draco and Segue 1), one radio-poor cluster (A2199), and one DM-rich ultra-diffuse galaxy (Dragonfly 44). We project the SKA1 and SKA2 sensitivities with the exposure of 100 hours on the annihilation cross section and decay time for DM mass from MeV to TeV by considering two different leptonic final states $e^{+}{e}^{-}$ and ${\mu }^{+}{\mu }^{-}$.

    ↳ astro-ph.HEhep-exhep-phJCAP(2021)·14 citations
32. 32*

    Inflation by Variation of the Strong Coupling Constant: update for Planck 2018

    M. AlHallak (Damascus Univ.)🇸🇾 · A. AlRakik (Damascus Univ.)🇸🇾 · S. Bitar (HIAST)🇸🇾 · N. Chamoun (HIAST)🇸🇾 · M. S. Eldaher (Damascus Univ.)🇸🇾

    We apply the "systematic" $1^{st}$ order cosmological perturbation theory method to re-derive the formulation of an inflationary model generated by variation of constants, then to study the case where it is non-minimally coupled to gravity within both the "Metric" and "Palatini" formulations. Accommodating Planck 2018 data with a length scale $\ell$ larger than Planck Length $L_{pl}$ requires amending the model. First, we assume $f(R)$ gravity where we show that an $R^2$-term within Palatini formulation is able to make the model viable. All along the discussions, we elucidate the origin of the difference between the "Metric" and "Palatini" formalisms, and also highlight the terms dropped when applying the shortcut "potential formulae method", unlike the "systematic' method", for the observable parameters. Second, another variant of the model, represented by a two-exponentials potential, fits also the data with $\ell >L_{pl}$.

    ↳ astro-ph.COhep-phInt.J.Mod.Phys.A(2021)·5 citations
33. 33*

    The Ostrogradsky instability can be overcome by quantum physics

    John F Donoghue🇺🇸 · Gabriel Menezes🇧🇷

    In theories with higher time derivatives, the Hamiltonian analysis of Ostrogradsky predicts an instability. However, this Hamiltonian treatment does not correspond the way that these theories are treated in quantum field theory, and the instability may be avoided in at least some cases. We present a very simple model which illustrates these features.

    ↳ hep-thgr-qchep-phPRD(2021)·77 citations
34. 34*

    Storage Rings and Gravitational Waves: Summary and Outlook

    A. Berlin🇺🇸 · M. Brüggen🇩🇪 · O. Buchmueller🇬🇧 · P. Chen🇹🇼 · R.T. D'Agnolo🇫🇷 · R. Deng🇨🇳 · J.R. Ellis🇬🇧 · S. Ellis🇫🇷 · G. Franchetti🇩🇪 · A. Ivanov🇦🇹 · J.M. Jowett🇨🇭 · A.P. Kobushkin🇺🇦 and 8 other authors

    We report some highlights from the ARIES APEC workshop on ``Storage Rings and Gravitational Waves'' (SRGW2021), held in virtual space from 2 February to 18 March 2021, and sketch a tentative landscape for using accelerators and associated technologies for the detection or generation of gravitational waves.

    ↳ physics.acc-phgr-qchep-exhep-ph9 citations
35. 35*

    Cosmology at the top of the ${\alpha }^{\prime }$ tower

    Jerome Quintin🇩🇪 · Heliudson Bernardo🇨🇦 · Guilherme Franzmann🇸🇪

    The cosmology of the fully ${\alpha }^{\prime }$-corrected duality-invariant action for the Neveu-Schwarz sector of string theory is revisited, with special emphasis on its coupling to matter sources. The role of the duality covariant pressure and dilatonic charge of the matter sector is explored in various contexts, from the low-curvature regime to non-perturbative solutions in ${\alpha }^{\prime }$. We comment on how an infinite tower of ${\alpha }^{\prime }$ corrections allows for fixed-dilaton de Sitter solutions, even in vacuum. We further investigate the necessary conditions for accelerated expansion in the Einstein frame, as well as for non-singular bounces that could resolve the big bang singularity. In particular, explicit examples are constructed, which show that the tower of ${\alpha }^{\prime }$ corrections may support an Einstein-frame non-singular cosmological bouncing background, even when the matter sector respects the null energy condition.

    ↳ hep-thastro-ph.COgr-qchep-phJHEP(2021)·22 citations
36. 36*

    Kalb-Ramond scalar QED multiple vacua

    Anais Smailagic🇮🇹 · Euro Spallucci🇮🇹

    We study a model of interacting vector and Kalb-Ramond gauge fields in a non-trivial Higgs vacuum generated by a charged and a neutral scalar field. The system admits different vacua for different v.e.v. of the two Higgs fields. Our primary interest in this paper regards the "mixed phase" where both the photon and the Kalb-Ramond acquire a mass. In this phase we compute the interaction potential energy between static test charges. It turns out that the limit in which the photon becomes massless, while the Kalb-Ramond remains massive, leads to a Cornell confining potential between test charges.

    ↳ hep-thhep-phJ.Phys.G(2021)·7 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.