Mon·Dec 14, 2020Monday·December 14, 2020

1. 01*

   Lowering the scale of Pati-Salam breaking through seesaw mixing

   Matthew J. Dolan🇦🇺 · Tomasz P. Dutka🇦🇺 · Raymond R. Volkas🇦🇺

   We analyse the experimental limits on the breaking scale of Pati-Salam extensions of the Standard Model. These arise from the experimental limits on rare-meson decay processes mediated at tree-level by the vector leptoquark in the model. This leptoquark ordinarily couples to to both left- and right-handed SM fermions and therefore the meson decays do not experience a helicity suppression. We find that the current limits vary from $\mathcal{O}(80-2500)$ TeV depending on the choice of matrix structure appearing in the relevant three-generational charged-current interactions. We extensively analyse scenarios where additional fermionic degrees of freedom are introduced, transforming as complete Pati-Salam multiplets. These can lower the scales of Pati-Salam breaking through mass-mixing within the charged-lepton and down-quark sectors, leading to a helicity suppression of the meson decay widths which constrain Pati-Salam breaking. We find four multiplets with varying degrees of viability for this purpose: an $SU(2{)}_{L/R}$ bidoublet, a pair of $SU(4)$ decuplets and either a $SU(2{)}_L$ or $SU(2{)}_R$ triplet all of which contain heavy exotic versions of the SM charged leptons. We find that the Pati-Salam limits can be as low as $\mathcal{O}(5-150)$ TeV with the addition of these four multiplets. We also identify an interesting possible connection between the smallness of the neutrino masses and a helicity suppression of the Pati-Salam limits for three of the four multiplets.

   hep-phJHEP(2021)·17 citations
2. 02*

   Collisional energy loss and the Chiral Magnetic Effect

   Jeremy Hansen🇺🇸 · Kirill Tuchin🇺🇸

   Collisional energy loss of a fast particle in a medium is mostly due to the medium polarization by the electromagnetic fields of the particle. A small fraction of energy is carried away by the Cherenkov radiation. In chiral medium there is an additional contribution to the energy loss due to induction of the anomalous current proportional to the magnetic field. It causes the particle to lose energy mostly in the form of the \emph{chiral} Cherenkov radiation. We employ classical electrodynamics, adequate in a wide range of particle energies, to compute the collisional energy loss by a fast particle in a homogenous chiral plasma and apply the results to Quark-Gluon Plasma and a Weyl semimetal. In the later case photon spectrum is strongly enhanced in the ultraviolet and X-ray regions which makes it amenable to experimental investigation. Our main observation is that while the collisional energy loss in a non-chiral medium is a slow, at most logarithmic, function of energy $E$, the chiral Cherenkov radiation is proportional to $E^2$ when the recoil is neglected and to $E$ when it is taken into account.

   hep-phcond-mat.mes-hallnucl-thPRC(2021)·12 citations
3. 03*

   CP violation in non-leptonic $B_c$ decays to excited final states

   Tian Zhou🇨🇳 · Tianhong Wang🇨🇳 · Hui-Feng Fu🇨🇳 · Zhi-Hui Wang🇨🇳 · Lei Huo🇨🇳 · Guo-Li Wang🇨🇳

   We study the CP violation in two-body nonleptonic decays of $B_c$ meson. We concentrate on the decay channels which contain at least one excited heavy meson in the final states. Specifically, the following channels are considered: $B_c\to c\bar{c}(2S,2P)+\bar{c}q(1S,1P)$, $B_c\to c\bar{c}(1S)+\bar{c}q(2S,2P)$, $B_c\to c\bar{c}(1P)+\bar{c}q(2S)$, $B_c\to c\bar{c}(1D)+\bar{c}q(1S,1P)$, and $B_c\to c\bar{c}(3S)+\bar{c}q(1S)$. The improved Bethe-Salpeter method is applied to calculate the hadronic transition matrix element. Our results show that some decay modes have large branching ratios, which is of the order of $10^{-3}$. The CP violation effect in $B_c\to {\eta }_c(1S)+D(2S)$, $B_c\to {\eta }_c(1S)+D_0^{\ast }(2P)$, and $B_c\to J/\psi +D^{\ast }(2S)$ are most likely to be found. If the detection precision of the CP asymmetry in such channels can reach the $3\sigma$ level, at least $10^7$ $B_c$ events are needed.

   hep-phEPJC(2021)·9 citations
4. 04*

   Dijet Acoplanarity in CUJET3 as a Probe of the Nonperturbative Color Structure of QCD Perfect Fluids

   M. Gyulassy🇺🇸 · P.M. Jacobs🇺🇸 · J. Liao🇺🇸 · S. Shi🇨🇦 · X.N. Wang🇺🇸 · F.Yuan🇺🇸

   Using the CUJET3=DGLV+VISHNU jet-medium interaction framework, we show that dijet azimuthal acoplanarity in high energy $A+A$ collisions is sensitive to possible non-perturbative enhancement of the jet transport coefficient, $\hat{q}(T,E)$, in the QCD crossover temperature $T\sim 150-300$ MeV range. With jet-medium couplings constrained by global RHIC\& LHC ${\chi }^2$ fits to nuclear modification data on $R_{AA}$, we compare predictions of the medium induced dijet transverse momentum squared, $Q_s^2\sim ⟨\hat{q}L⟩\sim \Delta {\varphi }^2{E}^2$, in two models of the temperature, $T$, and jet energy $E$ dependence of the jet medium transport coefficient, $\hat{q}(T,E)$. In one model, wQGP, only perturbative quark and gluon dof are assumed. In the second model, sQGMP, nonperturbative three component semi-Quark-Gluon and Magnetic Monopole dof are asssumed. We show that the dijet path averaged medium induced azimuthal acoplanarity, $\Delta {\varphi }^2$, in sQGMP is robustly a factor of $\sim 2$ larger than in perturbative wQGP while the radiative energy loss in both models is nearly identical as required to fit the same single jet nuclear modification $R_{AA}$ data. Future A+A dijet acoplanarity measurements correlated with $R_{AA}$ and azimuthal asymmetry $v_n$ measurements therefore appears to be a promising strategy to search for possible signatures of critical opalescence like phenomena in the QCD confinement temperature range.

   hep-phnucl-thNPA(2021)·4 citations
5. 05*

   A Standard Model explanation for the MiniBooNE anomaly

   Ara Ioannisian🇦🇲 · Carlo Giunti🇮🇹 · Gioacchino Ranucci🇮🇹

   We present the results of a new analysis of the data of the MiniBooNE experiment taking into account the additional background of photons. MiniBooNE normalises the rate of photon production to the measured ${\pi }^0$ production rate. We study neutral current (NC) neutrino-induced ${\pi }^0$/photon production (${\nu }_{\mu }+A\to {\nu }_{\mu }+1{\pi }^0/\gamma +X$) on carbon nucleus (A=12). Our conclusion is based on experimental data for photon-nucleus interactions from the A2 collaboration at the Mainz MAMI accelerator. We work in the approximation that decays of the intermediate states (non-resonant N, $\Delta$ resonance, higher resonances) unaffected by its production channel, via photon or Z boson. $1{\pi }^0+X$ production scales as A${}^{2/3}$, the surface area of the nucleus. Meanwhile the photons incoherently created in intermediate states decays will leave the nucleus, and that cross section will be proportional to the atomic number of the nucleus. We also took into account the coherent emission of photons. We show that the new photon background can explain part of the MiniBooNE low-energy excess, thus significantly lowering the number of unexplained MiniBooNE electron-like events from $5.1\sigma$ to $3.6\sigma$.

   hep-phPoS(2021)·0 citations
6. 06*

   Revisiting electroweak radiative corrections to $b\to s\ell \ell$ in SMEFT

   Motoi Endo🇯🇵 · Satoshi Mishima🇯🇵 · Daiki Ueda🇯🇵

   We revisit electroweak radiative corrections to Standard Model Effective Field Theory (SMEFT) operators which are relevant for the $B$-meson semileptonic decays. The one-loop matching formulae onto the low-energy effective field theory are provided without imposing any flavor symmetry. The on-shell conditions are applied especially in dealing with quark-flavor mixings. Also, the gauge independence is shown explicitly in the $R_{\xi }$ gauge.

   hep-phhep-exhep-thJHEP(2021)·8 citations
7. 07*

   Chiral and effective $U(1{)}_{\mathrm{A}}$ symmetry restoration in QCD

   Jens Braun🇩🇪 · Marc Leonhardt🇩🇪 · Jan M. Pawlowski🇩🇪 · Daniel Rosenblüh🇩🇪

   The nature and location of the QCD phase transition close to the chiral limit restricts the phase structure of QCD with physical pion masses at non-vanishing density. At small pion masses, explicit $U(1{)}_{\mathrm{A}}$-breaking, as induced by a non-trivial topological density, is of eminent importance. It triggers the 't Hooft interactions and also manifests itself in the interplay of four-quark interactions at low momentum scales. In the present work, we perform a Fierz-complete analysis of the emergence of four-quark interactions from the QCD dynamics at finite temperature, subject to a given 't Hooft coupling at large momentum scales. The variation of the latter allows us to test the robustness of our findings. Taking an estimate of the effect of the topological running of the 't Hooft coupling into account, our analysis suggests that the chiral transition in QCD with two massless quark flavours falls into the $O(4)$ universality class.

   hep-ph25 citations
8. 08*

   Calculation of binding energy and wave function for exotic hidden-charm pentaquark

   F. Chezani Sharahi🇮🇷 · M. Monemzadeh🇮🇷

   In this study, pentaquark Pc(4380) composed of a baryon sigma_c and a D_* meson is considered. Pentaquark is as a bound state of two-body systems composed of a baryon and a meson. The calculated potential will be expanded and replaced in the Schrodinger equation until tenth sentences of expansion. Solving the Schrodinger equation with the expanded potential of Pentaquark leads to an analytically complete approach. As a consequence, the binding energy EB of pentaquark Pc and wave function are obtained. The results EB will presented in the form of tables so that we can review the existence of pentaquark Pc. Then, the wave function will be shown on diagrams. Finally, the calculated results are compared with another obtained results and the mass of observing pentaquark Pc and the radius of pentaquark are estimated.

   hep-phAdv.High Energy Phys.(2021)·1 citation
9. 09*

   A combined explanation of the $B$-meson decay anomalies with a single vector leptoquark

   J. Kriewald🇫🇷 · C. Hati🇩🇪 · J. Orloff🇫🇷 · A. M. Teixeira🇫🇷

   Motivated by the recent experimental progress on the $R_{D^{(\ast )}}$ and $R_{K^{(\ast )}}$ anomalies in $B$-decays, we consider an extension of the Standard Model by a single vector leptoquark field. We study how one can achieve the required lepton flavour non-universality, starting from a priori universal gauge couplings. While the unitary coupling flavour structure, induced by the mass misalignment of quarks and leptons after $SU(2{)}_L$ breaking, does not allow to comply with stringent bounds from lepton flavour violating processes, we find that effectively non-unitary couplings, due to mixings with heavy vector-like fermions, hold the key to simultaneously address the $R_{K^{(\ast )}}$ and $R_{D^{(\ast )}}$ anomalies. Furthermore, in the near future, the expected progress in the sensitivity on charged lepton flavour violating observables should allow to probe a large region of the preferred parameter space in this class of vector leptoquark models.

   hep-phPoS(2021)·2 citations
10. 10*

    Production of ${\nu }_{\tau }$ neutrinos and ${\overline{\nu }}_{t}au$ antineutrinos -- elaborate calculation for a fixed target experiment SHiP

    Rafal Maciula🇵🇱

    We discuss cross sections for ${\nu }_{\tau }$ and ${\overline{\nu }}_{\tau }$ production from the direct $D_s^{\pm }\to {\nu }_{\tau }/{\overline{\nu }}_{\tau }$ and chain $D_s^{\pm }\to {\tau }^{+}/{\tau }^{-}\to {\nu }_{\tau }/{\overline{\nu }}_{\tau }$ decays in $p{+}^{96}\mathrm{Mo}$ scattering with proton beam $E_{\mathrm{lab}}$ = 400 GeV \textit{i.e.} at ${\sqrt{s}}_{NN}$ = 27.4 GeV. In our calculations we include $D_s^{\pm }$ from charm fragmentation $c\to D_s^{+}$ and $\bar{c}\to D_s^{-}$ as well as those from subleading fragmentation of strange quarks/antiquarks $s\to D_s^{-}$ and $\bar{s}\to D_s^{+}$. The different contributions to $D_s^{\pm }$ and ${\nu }_{\tau }/{\overline{\nu }}_{\tau }$ production rates are shown explicitly. Estimates of a number of observed ${\nu }_{\tau }/{\overline{\nu }}_{\tau }$ in the ${\nu }_{\tau }/{\overline{\nu }}_{\tau }{+}^{208}\mathrm{Pb}$ reaction, with 2m long target are given.

    hep-phPoS(2021)·0 citations
11. 11*

    The charmed mesons in the region above 3.0 GeV

    A.M. Badalian🇷🇺 · B.L.G. Bakker🇳🇱

    The masses of excited charmed mesons are shown to decrease by $\sim (50-150)$~MeV due to a flattening of the confining potential at large distances, which effectively takes into account open decay channels. The scale of the mass shifts is similar to that in charmonium for $\psi (4660)$ and ${\chi }_{c0}(4700)$. The following masses of the first excitations: $M(2{}^3{P}_0)=2874$~MeV, $M(2{}^3{P}_2)=2968$~MeV, $M(2{}^3{D}_1)=3175$~MeV, and $M(2{}^3{D}_3)=3187$~MeV, and second excitations: $M(3{}^1{S}_0)=3008$~MeV, $M(3{}^3{S}_1)=3062$~MeV, $M(3{}^3{P}_0)=3229$~MeV, and $M(3{}^3{P}_2)=3264$~MeV, are predicted. The other states with $L=0,1,2$ and $n_r\ge 3$ have their masses in the region $M(nL)\ge 3.3$~GeV.

    hep-phhep-exPhys.Atom.Nucl.(2021)·5 citations
12. 12*

    Hard gluon evolution in the last stage of the bottom-up thermalization

    F. G. Ben🇧🇷 · M. V. T. Machado🇧🇷

    The study of how fast thermalization in heavy ion collisions occurs has been one of the central topics in the heavy ion community. In the weak coupling picture this thermalization occurs from "the bottom up": high energy partons, formed early in the collision, radiate low energy gluons which then proceed to equilibrate among themselves, forming a thermal bath that brings the high energy sector to equilibrium. In this scheme we apply a model on parton energy loss to discuss the effects of medium expansion on the thermalization problem and estimate the average transverse momentum diffusivity for thermalization in a Bjorken expanding medium.

    hep-phJ.Phys.G(2022)·2 citations
13. 13*

    Three-flavour order parameters of chiral symmetry in low-energy QCD

    Marián Kolesár🇨🇿 · Jiří Novotný🇨🇿

    The current state of knowledge of the order parameters of the spontaneously broken chiral symmetry, the quark condensate and the pseudoscalar decay constant in the chiral limit, is briefly reviewed, based on available phenomenological fits and lattice QCD calculations. We argue that while the theory is pretty well understood in the two-flavour case, there is still a gap in the knowledge of the characteristics of the QCD vacuum in the three-flavour one. Our constraints for the three-flavour parameters obtained by a Bayesian statistical analysis of the decays of eta to three pions are presented. Possible implications of a new analysis of subthreshold parameters of pion-pion scattering is outlined.

    hep-phPoS(2021)·0 citations
14. 14*

    Thermomagnetic Properties of QCD

    Christoph P. Hofmann🇲🇽

    We explore the low-energy regime of quantum chromodynamics subjected to an external magnetic field by deriving the two-loop representations for the entropy density and the magnetization within chiral perturbation theory (CHPT). At fixed temperature, the entropy density drops when the magnetic field becomes stronger. The magnetization induced at finite temperature is negative in the entire parameter region accessible by CHPT. We also point out that the enhancement of the finite-temperature part in the quark condensate is correlated with the decrease of the entropy density.

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

    Axial vector transition form factors in holographic QCD and their contribution to the muon $g-2$

    Josef Leutgeb🇦🇹 · Anton Rebhan🇦🇹

    Whereas the theoretical results for the dominant contributions to hadronic light-by-light scattering coming from pseudoscalar meson exchange have converged over the past years, the various published estimates of the contribution due to axial vector meson exchange differ wildly. Since holographic AdS/QCD models have proved to provide rather good models of singly and doubly virtual pion transition form factors, which reproduce remarkably well the known low-energy data and also the asymptotic leading-order pQCD behavior, it is of interest to consider their predictions for axial vector transition form factors. Indeed, we find that these reproduce also very well existing data from the L3 experiment for $f_1\to \gamma {\gamma }^{\ast }$. Including the full infinite tower of axial vector mesons of the AdS/QCD models we moreover show that the Melnikov-Vainshtein short-distance constraint can be satisfied, while almost all existing models for hadronic light-by-light scattering fail to incorporate it. The contribution to $g-2$, which is dominated by the first few resonances, turns out to be significantly larger than estimated previously.

    hep-phhep-thPoS(2021)·0 citations
16. 16*

    Universal Scale Factors: A Bridge Between Chiral Lagrangians and QCD Sum-Rules

    Amir H. Fariborz🇺🇸 · J. Ho🇺🇸 · T.G. Steele🇨🇦

    Chiral Lagrangian mesonic fields can be connected to QCD quark operators via matrix operators containing scale factors. These scale factor matrices are shown to be constrained by chiral symmetry, resulting in a universal scale factor for each Chiral Lagrangian nonet. QCD sum-rules, combined with mixing angles from Chiral Lagrangian analyses, are used to determine the scale factors for the $a_0$ isotriplet and $K_0^{\ast }$ isodoublet scalar mesons. The resulting scale factors verify the universality property, providing a validation of the scale factor matrices connecting Chiral Lagrangian mesonic fields and quark operators.

    hep-phNucl.Part.Phys.Proc.(2021)·0 citations
17. 17*

    The DFSZ axion in the CMB

    Ricardo Z. Ferreira🇸🇪 · Alessio Notari🇪🇸 · Fabrizio Rompineve🇺🇸

    We perform for the first time a dedicated analysis of cosmological constraints on DFSZ QCD axion models. Such constructions are especially interesting in light of the recent Xenon-1T excess and of hints from stellar cooling. In DFSZ models, for $m_a\gtrsim 0.1$ eV, scatterings of pions and muons can produce a sizable cosmic background of thermal axions, that behave similarly to massive neutrinos. However, the pion coupling depends on the alignment between the vevs of two Higgs doublets, and can be significantly suppressed or enhanced with respect to the KSVZ scenario. Using the latest Planck and BAO data, we find $m_a\le 0.2\text{eV}$ at $95\%$ C.L., when the axion coupling to pions $c_{a\pi }$ is maximal. Constraints on $m_a$, instead, can be significantly relaxed when $c_{a\pi }$ is small. In particular, we point out that in the so-called DFSZ-II model, where the axion coupling to leptons does not vanish simultaneously with $c_{a\pi }$, production via muons gives $m_a\le 0.6\text{eV}$ at $95\%$ C.L., whereas in the DFSZ-I model bounds on $m_a$ can be fully lifted. We then combine cosmological data with recent hints of a DFSZ axion coupled to electrons from the Xenon-1T experiment, finding in this case that the axion mass is constrained to be in the window $0.07\text{eV}\lesssim m_a\lesssim 1.8(0.3)\text{eV}$ for the DFSZ-I (DFSZ-II) model. A similar analysis with stellar cooling hints gives $3\text{meV}\lesssim m_a\lesssim 0.2\text{eV}$ for DFSZ-II, while no constraint arises in the DFSZ-I case. Forthcoming CMB Stage 4 experiments will be able to further test such scenarios; for instance the Xenon-1T window should be fully probed at $2\sigma$ for a DFSZ-I axion.

    hep-phastro-ph.COPRD(2021)·59 citations
18. 18*

    Explainable machine learning of the underlying physics of high-energy particle collisions

    Yue Shi Lai🇺🇸 · Duff Neill🇺🇸 · Mateusz Płoskoń🇺🇸 · Felix Ringer🇺🇸

    We present an implementation of an explainable and physics-aware machine learning model capable of inferring the underlying physics of high-energy particle collisions using the information encoded in the energy-momentum four-vectors of the final state particles. We demonstrate the proof-of-concept of our White Box AI approach using a Generative Adversarial Network (GAN) which learns from a DGLAP-based parton shower Monte Carlo event generator. We show, for the first time, that our approach leads to a network that is able to learn not only the final distribution of particles, but also the underlying parton branching mechanism, i.e. the Altarelli-Parisi splitting function, the ordering variable of the shower, and the scaling behavior. While the current work is focused on perturbative physics of the parton shower, we foresee a broad range of applications of our framework to areas that are currently difficult to address from first principles in QCD. Examples include nonperturbative and collective effects, factorization breaking and the modification of the parton shower in heavy-ion, and electron-nucleus collisions.

    hep-phnucl-exnucl-thPLB(2022)·36 citations
19. 19*

    Interference and Oscillation in Nambu Quantum Mechanics

    Djordje Minic🇺🇸 · Tatsu Takeuchi🇺🇸 · Chia Hsiung Tze🇺🇸

    Nambu Quantum Mechanics, proposed in Phys. Lett. B536, 305 (2002), is a deformation of canonical Quantum Mechanics in which only the time-evolution of the "phases" of energy eigenstates is modified. We discuss the effect this theory will have on oscillation phenomena, and place a bound on the deformation parameters utilizing the data on the atmospheric neutrino mixing angle ${\theta }_{23}$.

    hep-phquant-phPRD(2021)·9 citations
20. 20*

    Hydrogen Mixing as a Novel Mechanism for Colder Baryons in 21 cm Cosmology

    Lucas Johns🇺🇸 · Seth Koren🇺🇸

    The anomalous 21 cm absorption feature reported by EDGES has galvanized the study of scenarios in which dark matter (DM) siphons off thermal energy from the Standard Model (SM) gas. In a departure from the much-discussed models that achieve cooling by DM scattering directly with SM particles, we show that the same end can be achieved through neutral atomic hydrogen $H$ mixing with a degenerate dark sector state $H^{\prime }$. An analysis of in-medium $H$-$H^{\prime }$ oscillations reveals viable parameter space for generic types of $H^{\prime }$-DM interactions to provide the requisite cooling. This strategy stands in stark contrast to other proposals in many respects, including its cosmological dynamics, model building implications, and complementary observational signatures.

    hep-phastro-ph.CO4 citations
21. 21*

    The Hydrogen Mixing Portal, Its Origins, and Its Cosmological Effects

    Lucas Johns🇺🇸 · Seth Koren🇺🇸

    Hydrogen oscillation into a dark-sector state $H^{\prime }$ has recently been proposed as a novel mechanism through which hydrogen can be cooled during the dark ages -- without direct couplings between the Standard Model and dark matter. In this work we demonstrate that the requisite mixing can appear naturally from a microphysical theory, and argue that the startling deviations from standard cosmology are nonetheless consistent with observations. A symmetric mirror model enforces the necessary degeneracy between $H$ and $H^{\prime }$, and an additional twisted $B+L^{\prime }$ symmetry dictates that $H$-$H^{\prime }$ mixing is the leading connection between the sectors. We write down a UV completion where $\sim$ TeV-scale leptoquarks generate the partonic dimension-12 mixing operator, thus linking to the energy frontier. With half of all $H$ atoms oscillating into $H^{\prime }$, the composition of the universe is scandalously different during part of its history. We qualitatively discuss structure formation: both the modifications to it in the Standard Model sector and the possibility of it in the mirror sector, which has recently been proposed as a resolution to the puzzle of early supermassive black holes. While the egregious loss of SM baryons mostly self-erases during reionization, to our knowledge this is the first model that suggests there should be missing baryons in the late universe, and highly motivates a continued, robust observational program of high-precision searches for cosmic baryons.

    hep-phastro-ph.CO13 citations
22. 22*

    Experimental hint for gravitational CP violation

    V. Gharibyan🇦🇲

    An equality of particle and antiparticle gravitational interactions holds in general relativity and is supported by indirect observations. Gravity dependence on rotation or spin direction is experimentally constrained for non-relativistic matter. Here a method based on high energy Compton scattering is developed to measure the gravitational interaction of accelerated charged particles. Within that formalism the Compton spectra measured at HERA rule out the speculated anti-gravity possibility for antimatter at a confidence level close to 100%. The same data, however, imply a gravitational CP violation around 13 GeV energies, by a maximal amount of 9 +/- 2 ppt for the charge and 13 +/- 3 ppt for the space parity. The detected asymmetry hints for a stronger gravitational coupling to left helicity electrons relative to right helicity positrons.

    hep-phhep-exMod.Phys.Lett.A(2020)·2 citations
23. 23*

    Contribution of Secondary Neutrinos from Line-of-sight Cosmic Ray Interactions to the IceCube Diffuse Astrophysical Flux

    Alina Kochocki🇺🇸 · Volodymyr Takhistov🇯🇵 · Alexander Kusenko🇯🇵 · Nathan Whitehorn🇺🇸

    In ten years of observations, the IceCube neutrino observatory has revealed a neutrino sky in tension with previous expectations for neutrino point source emissions. Astrophysical objects associated with hadronic processes might act as production sites for neutrinos, observed as point sources at Earth. Instead, a nearly isotropic flux of astrophysical neutrinos is observed up to PeV energies, prompting a reassessment of the assumed transport and production physics. This work applies a new physical explanation for neutrino production from populations of active galactic nuclei (AGN) and starburst galaxies to three years of public IceCube point source data. Specifically, cosmic rays (CRs) produced at such sources might interact with extragalactic background light and gas along the line of sight, generating a secondary neutrino flux. This model is tested alongside a number of typical flux weighting schemes, in all cases the all-sky flux contribution being constrained to percent levels of the reported IceCube diffuse astrophysical flux.

    ↳ astro-ph.HEhep-phApJ(2021)·7 citations
24. 24*

    Strong coupling constant from moments of quarkonium correlators revisited

    Peter Petreczky🇺🇸 · Johannes Heinrich Weber🇩🇪

    We revisit previous determination of the strong coupling constant from moments of quarkonium correlators in (2+1)-flavor QCD. We use previously calculated moments obtained with Highly Improved Staggered Quark (HISQ) action for five different quark masses and several lattice spacings. We perform a careful continuum extrapolations of the moments and from the comparison of these to the perturbative result we determine the QCD Lambda parameter, ${\Lambda }_{\overline{MS}}^{n_f=3}=332\pm 17\pm 2(scale)$ MeV. This corresponds to ${\alpha }_s^{n_f=5}(\mu =M_Z)=0.1177(12)$.

    ↳ hep-lathep-phEPJC(2022)·33 citations
25. 25*

    Relativistic potential of a hydrogen-like system in Poincare invariant quantum mechanics

    V.V. Andreev🇧🇾

    To describe a relativistic hydrogen atom we used the Poincare-covariant model of a two particle system with gauge invariant potential. The kernel of the radial integral equation is obtained which describes a system of two fermions with electromagnetic interaction.

    ↳ quant-phhep-ph1 citation
26. 26*

    Gluons in charmoniumlike states

    Wei Sun🇨🇳 · Ying Chen🇨🇳 · Peng Sun🇨🇳 · Yi-Bo Yang🇨🇳

    The mass components of charmoniumlike states are investigated through the decomposition of QCD energy-momentum tensor (EMT) on lattice. The quark mass contribution $⟨H_m⟩$ and the momentum fraction $⟨x⟩$ of valence charm quark and antiquark are calculated for conventional $1S,1P,1D$ charmonia and the exotic $1^{-+}$ charmoniumlike state, based on the $N_f=2+1$ gauge configurations generated by the RBC/UKQCD collaboration. It is found that $⟨H_m⟩$ is close to each other and around 2.0 to 2.2 GeV for these states, which implies that the mass splittings among these states come almost from the gluon contribution of QCD trace anomaly. The $⟨x⟩$ of the $1^{-+}$ state is only around 0.55, while that in conventional charmonia is around 0.7 to 0.8. This difference manifests that the proportion of light quarks and gluons in the $1^{-+}$ charmoniumlike state is significantly larger than conventional states.

    ↳ hep-lathep-exhep-phPRD(2021)·9 citations
27. 27*

    Fire streaks, electromagnetic effects, directed flow and lifetime of the plasma at SPS energies

    Vitalii Ozvenchuk🇵🇱 · Antoni Szczurek🇵🇱 · Andrzej Rybicki🇵🇱

    We present our calculation of electromagnetic effects, induced by the spectator charge on Feynman-$x_F$ distributions of charged pions in peripheral $Pb+Pb$ collisions at CERN SPS energies, including realistic initial space-time-momentum conditions for pion emission. The calculation is performed in the framework of a specific implementation of the fire-streak model, adopted to the production of both ${\pi }^{-}$ and ${\pi }^{+}$ mesons. Isospin effects are included to take into account the asymmetry in production of ${\pi }^{+}$ and ${\pi }^{-}$ at high rapidity. A comparison to a simplified model from the literature is made. We obtain a good description of the NA49 data on the $x_F$- and $p_T$-dependence of the ratio of cross sections ${\pi }^{+}/{\pi }^{-}$. The experimental data favors short times ($0.5<\tau <2$~fm/$c$) for fast pion creation in the local fire-streak rest frame. The possibility of the expansion of the spectators is considered in our calculation, and its influence on the electromagnetic effect observed for the ${\pi }^{+}/{\pi }^{-}$ ratio is discussed. The influence of directed and elliptic flow, and vorticity on the observed effect is also estimated. We conclude that the fire-streak model, which properly describes the centrality dependence of ${\pi }^{-}$ rapidity spectra at CERN SPS energies, also provides realistic initial conditions for pion production. Consequently, it provides a quantitative description of the electromagnetic effect on the ${\pi }^{+}/{\pi }^{-}$ ratio as a function of $x_F$.

    ↳ nucl-thhep-phPoS(2021)·1 citation
28. 28*

    Vector meson mass in the chiral symmetry restored vacuum

    Jisu Kim🇰🇷 · Su Houng Lee🇰🇷

    We calculate the mass of the vector meson in the chiral symmetry restored vacuum. This is accomplished by separating the four quark operators appearing in the vector and axial vector meson sum rules into chiral symmetric and symmetry breaking parts depending on the contribution of the fermion zero modes. We then identify each part from the fit to the vector and axial vector meson masses. By taking the chiral symmetry breaking part to be zero while keeping the symmetric operator to the vacuum value, we find that the chiral symmetric part of the vector and axial vector meson mass to be between 550 and 600 MeV. This demonstrates that chiral symmetry breaking, while responsible for the mass difference between chiral partner, accounts only for a small fraction of the symmetric part of the mass.

    ↳ nucl-thhep-phnucl-exPRD(2021)·19 citations

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