Thu·Apr 1, 2021Thursday·April 1, 2021

1. 01*

   One-loop impact factor for the emission of two gluons

   Marc Canay🇨🇭 · Vittorio Del Duca🇨🇭

   We consider one-loop five-point QCD amplitudes in next-to-multi-Regge kinematics, and evaluate the one-loop impact factor for the emission of two gluons. This is the last ingredient which is necessary to evaluate the gluon-jet impact factor at NNLO accuracy in $\text{as}$. It is also the first instance in which loop-level QCD amplitudes are evaluated in next-to-multi-Regge kinematics, which requires to apply a different reggeisation ansatz to each colour-ordered amplitude.

   hep-phhep-thJHEP(2021)·5 citations
2. 02*

   Mapping the Electromagnetic Fields of Heavy-Ion Collisions with the Breit-Wheeler Process

   James Daniel Brandenburg🇺🇸 · Wangmei Zha🇨🇳 · Zhangbu Xu🇨🇳

   Ultra-relativistic heavy-ion collisions are expected to produce the strongest electromagnetic fields in the known Universe. These highly-Lorentz contracted fields can manifest themselves as linearly polarized quasi-real photons that can interact via the Breit-Wheeler process to produce lepton anti-lepton pairs. The energy and momentum distribution of the produced dileptons carry information about the strength and spatial distribution of the colliding fields. Recently it has been demonstrated that photons from these fields can interact even in heavy-ion collisions with hadronic overlap, providing a purely electromagnetic probe of the produced medium. In this review we discuss the recent theoretical progress and experimental advances for mapping the ultra-strong electromagnetic fields produced in heavy-ion collisions via measurement of the Breit-Wheeler process.

   hep-phnucl-exEPJA(2021)·71 citations
3. 03*

   Gluons, Light and Heavy Quarks in the Instanton Vacuum

   M. Musakhanov🇺🇿 · U. Yakhshiev🇰🇷

   In this review we will concentrate on the nonperturbative effects in the properties of hadrons made from the light-heavy and heavy-heavy quarks in the framework of Instanton Liquid Model (ILM) of QCD vacuum. We briefly discuss the main features of ILM and its applicability in the heavy quark sector. The properties of gluonic systems, light and heavy quark correlators in the instanton background are also analyzed. Consideration of the both, perturbative and nonperturbative, gluon effects in the instanton background for the single heavy quark will lead to the mass shift due to the direct-instanton nonperturbative and ILM modified perturbative contributions, respectively. For the interacting heavy quark-antiquarks, the potential consists the direct instanton induced part and the one-gluon exchange (OGE) perturbative part. OGE interactions are screened at large distances due to the nonperturbative dynamics. We discuss the estimations of instanton contributions in the phenomenological Cornell type potential model. As related to the experimental data we discuss the charmonium properties and the role of instanton effects in their spectra and transitions. We discuss also the main features of heavy-light quarks systems in the ILM. As an example, it is considering the process of pions emission by exited heavy quarkonium states.

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

   Fitting the $Zb\bar{b}$ vertex in the two-Higgs-doublet model and in the three-Higgs-doublet model

   Darius Jurčiukonis🇱🇹 · Luis Lavoura🇵🇹

   We investigate the new contributions to the parameters $g_L$ and $g_R$ of the $Zb\bar{b}$ vertex in a multi-Higgs-doublet model (MHDM). We emphasize that those contributions generally worsen the fit of those parameters to the experimental data. We propose a solution to this problem, wherein $g_R$ has the opposite sign from the one predicted by the Standard Model; this solution, though, necessitates light scalars and large Yukawa couplings in the MHDM.

   hep-phJHEP(2021)·6 citations
5. 05*

   Solar Gamma Ray Constraints on Dark Matter Annihilation to Secluded Mediators

   Nicole F. Bell🇦🇺 · James B. Dent🇺🇸 · Isaac W. Sanderson🇦🇺

   We consider the indirect detection of dark matter that is captured in the Sun and subsequently annihilates to long-lived dark mediators. If these mediators escape the Sun before decaying, they can produce striking gamma ray signals, either via the decay of the mediators directly to photons, or via bremsstrahlung and hadronization of the mediator decay products. Using recent measurements from the HAWC Observatory, we determine model-independent limits on heavy dark matter that are orders of magnitude more powerful than direct detection experiments, for both spin-dependent and spin-independent scattering. We also consider a well-motivated model in which fermionic dark matter annihilates to dark photons. For such a realistic scenario, the strength of the solar gamma ray constraints are reduced, compared to the idealistic case, because the dark matter capture cross section and mediator lifetime are related. Nonetheless, solar gamma ray constraints enable us to exclude a previously unconstrained region of dark photon parameter space.

   hep-phastro-ph.HEastro-ph.SRPRD(2021)·47 citations
6. 06*

   Light front analysis towards the study of thermalisation in pp collisions at $\sqrt{s}=13$ TeV

   Rahul Ramachandran Nair🇵🇱

   An analysis involving the light front variables of inclusively produced hadrons in proton-proton (pp) collisions to study the thermalisation and formation of a QGP-like medium is presented in this paper. Two schemes of analysis are discussed and performed with inclusively produced ${\pi }^{\pm }$, $K^{\pm }$ and $p(\bar{p})$ in the central pp collisions at $\sqrt{s}=13$ TeV simulated using the PYTHIA 8 event generator. It is shown that a group of ${\pi }^{\pm }$ and $K^{\pm }$ falling inside a paraboloid defined by a certain constant value of the light front variable in their respective phase space follows the Bose-Einstein statistics while the $p(\bar{p})$ inside the similar paraboloid in its phase space follows the Fermi-Dirac statistics. It is also shown that for the ${\pi }^{\pm }$, $K^{\pm }$ and $p(\bar{p})$ with transverse momentum $p_T<1$ GeV in these collisions, a polynomial in $p_T$ can be constructed for a specific light front variable of the particle ${\zeta }_c(p_T)$ such that the ${\pi }^{\pm }$ and $K^{\pm }$ with their light front variable ${\zeta }^{\pm }>{\zeta }_c(p_T)$ follows Bose-Einstein statistics while the $p(\bar{p})$ with ${\zeta }^{\pm }>{\zeta }_c(p_T)$ follows the Fermi-Dirac statistics. The analysis can serve as a baseline for an investigation towards the QGP formation and thermalisation in the pp collisions at LHC.

   hep-ph1 citation
7. 07*

   Comprehensive study of light axial vector mesons with the presence of triangle singularity

   Meng-Chuan Du🇨🇳 · Qiang Zhao🇨🇳

   We present a systematic study of the productions and decays of light axial vector mesons with $J^{PC}=1^{+\pm }$ in charmonium decays. In the quark model scenario, the two axial vector nonets are connected with each other by the Gell-Mann-Okubo mass relation through the mixing between two $K_1$ states (i.e. $K_1(1270)$ and $K_1(1400)$) with configurations of ${}^3{P}_1$ and ${}^1{P}_1$. The mixing angles between $f_1$ and $f_1^{\prime }$ (i.e. $f_1(1285)$ and $f_1(1420)$), and between $h_1$ and $h_1^{\prime }$ (i.e. $h_1(1170)$ and $h_1(1415)$) can be reliably constrained. We then introduce the intermediate $K^{\ast }\bar{K}+c.c.$ meson loop transitions in the description of the productions and decays of these axial vector mesons. The presence of the nearby $S$-wave $K^{\ast }\bar{K}+c.c.$ to which these axial vector mesons have strong coupling strengths, turns out to be crucial for understanding many puzzling questions related to their productions and decays. This is because that the $S$-wave $K^{\ast }\bar{K}+c.c.$ rescatterings by the kaon exchange satisfy the triangle singularity (TS) condition in some of these cases and the TS mechanism can introduce special interference effects in the exclusive decays of these light axial vector mesons.

   hep-phhep-exPRD(2021)·20 citations
8. 08*

   An issue of determination of the centrality in nucleus-nucleus collisions

   R.M. Djilkibaev🇷🇺

   The accuracy of measuring the total energy of the spectators in the FHCal calorimeter, depending on the fluctuations in the number of nucleons and the hadron shower is obtained. It is shown that, from the point of view of statistics, the process of registering photoelectrons in a photomultiplier (PM) is similar to the process of registering spectator nucleons in a calorimeter. The measurements of single photoelectrons in the PM are in good agreement with the obtained formula for the relative variance of the charge detected by the PM.

   hep-ph1 citation
9. 09*

   Two Real Scalar WIMP Model in the Assisted Freeze-Out Scenario

   Bastián Díaz Sáez🇩🇪 · Kilian Möhling🇩🇪 · Dominik Stöckinger🇩🇪

   We study a simple dark matter model given by two interacting real singlet scalars, with only one of them coupled to the Higgs. The model therefore presents a minimal assisted-freeze-out framework: both scalars contribute to the dark matter relic density, but only one of them takes part in the elastic scattering with nuclei. This reduces the expected interaction rate in direct detection experiments in such a way that the model in some regions of the parameter space may evade XENON1T constraints. We explore the model under theoretical (perturbativity, stability potential and unitarity) and experimental constraints (Higgs to invisible, relic density, direct detection), with the use of the narrow-width-approximation near the Higgs resonance to calculate the average annihilation cross section. We show that the model is viable in the Higgs resonance region and for scalar singlets masses of hundreds of GeV, although the model becomes highly constrained at high energies.

   hep-phJCAP(2021)·30 citations
10. 10*

    A new and gauge-invariant Littlest Higgs model with T-parity

    José Ignacio Illana🇪🇸 · José María Pérez-Poyatos🇪🇸

    We inspect the Littlest Higgs model with T-parity, based on a global symmetry SU(5) spontaneously broken to SO(5), in order to elucidate the pathologies it presents due to the non trivial interplay between the gauge invariance associated to the heavy modes and the discrete T-parity symmetry. In particular, the usual Yukawa Lagrangian responsible for providing masses to the heavy `mirror' fermions is not gauge invariant. This is because it contains an SO(5) quintuplet of right-handed fermions that transforms non-linearly under SU(5), hence involving in general all SO(5) generators when a gauge transformation is performed and not only those associated to its gauge subgroup. Part of the solution to this problem consists of completing the right-handed fermion quintuplet with T-odd `mirror partners' and a gauge singlet, what has been previously suggested for other purposes. Furthermore, we find that the singlet must be T-even, the global symmetry group must be enlarged, an additional non-linear sigma field should be introduced to parametrize the spontaneous symmetry breaking and new extra fermionic degrees of freedom are required to give a mass to all fermions in an economic way while preserving gauge invariance. Finally, we derive the Coleman-Weinberg potential for the Goldstone fields using the background field method.

    hep-phEur.Phys.J.Plus(2022)·11 citations
11. 11*

    Intrinsic Glue and Wilson lines within Dressed Quarks

    C. S. R. Costa🇧🇷 · Adam Freese🇺🇸 · Ian C. Cloët🇺🇸 · Bruno El-Bennich🇧🇷 · Gastão Krein🇧🇷 · Peter C. Tandy🇺🇸

    We construct a quark target model (QTM) to incorporate intrinsic glue into effective low-energy models of QCD, which often contain only quark degrees of freedom. This method guarantees the gauge invariance of observables order-by-order in the strong coupling. The quark and gluon PDFs for the dressed quarks are obtained in the QTM at leading order. We demonstrate gauge invariance of the results by comparing both covariant and light cone gauges, with the former including an explicit Wilson line contribution. A key finding is that in covariant gauges the Wilson line can carry a significant amount of the light cone momentum. With coupling strength ${\alpha }_s=0.5$ and dressed quark mass $M_q=0.4$GeV, we find quark and gluon momentum fractions of ${⟨x⟩}_q=0.81$ and ${⟨x⟩}_g=0.19$, where the Wilson line contribution to the quark momentum fraction is $-0.18$. We use the on-shell renormalization scheme and find that at one-loop this Wilson line contribution does not depend on the covariant gauge but does vanish in light cone gauge as expected. This result demonstrates that it is crucial to account for Wilson line contributions when calculating quantum correlation functions in covariant gauges. We also consider the impact of a gluon mass using the gauge invariant formalism proposed by Cornwall, and combine these QTM results with two quark-level models to obtain quark and gluon PDFs for the pion.

    hep-phnucl-thPRC(2021)·5 citations
12. 12*

    The Swapland

    Prateek Agrawal🇬🇧 · Hengameh Bagherian🇺🇸 · Cari Cesarotti🇺🇸 · Nicholas DePorzio🇺🇸 · Qianshu Lu · Julian B. Muñoz🇺🇸 · Aditya Parikh🇺🇸 · Matthew Reece🇺🇸 · Weishuang Linda Xu🇺🇸

    All the news that's (un)fit to publish.

    hep-phastro-ph.COhep-th0 citations
13. 13*

    Toward the existence of odderon as a three-gluon bound state

    Hua-Xing Chen🇨🇳 · Wei Chen🇨🇳 · Shi-Lin Zhu🇨🇳

    Inspired by the evidence of the odderon exchange recently observed by the D0 and TOTEM Collaborations, a QCD sum rule investigation is performed to study the odderon as a three-gluon bound state. There may exist six lowest-lying three-gluon odderons with the quantum numbers $J^{PC}=1/2/3^{\pm -}$. We systematically construct their interpolating currents, and calculate their mass spectra. To verify their existence, we propose to search for the spin-3 odderons in their $VVV$ and $VVP$ decay channels directly at LHC, with $V$ and $P$ light vector and pseudoscalar mesons respectively.

    hep-phhep-exhep-latPRD(2021)·21 citations
14. 14*

    Future searches for light sterile neutrinos at nuclear reactors

    Jeffrey M. Berryman🇺🇸 · Luis A. Delgadillo🇺🇸 · Patrick Huber🇺🇸

    We study the optimization of a green-field, two-baseline reactor experiment with respect to the sensitivity for electron antineutrino disappearance in search of a light sterile neutrino. We consider both commercial and research reactors and identify as key factors the distance of closest approach and detector energy resolution. We find that a total of 5 tons of detectors deployed at a commercial reactor with a closest approach of 25 m can probe the mixing angle ${\sin }^{2}2\theta$ down to $\sim 5\times 10^{-3}$ around $\Delta m^2\sim 1$ eV${}^2$. The same detector mass deployed at a research reactor can be sensitive up to $\Delta m^2\sim 20-30$ eV${}^2$ assuming a closest approach of 3 m and excellent energy resolution, such as that projected for the Taishan Antineutrino Observatory. We also find that lithium doping of the reactor could be effective in increasing the sensitivity for higher $\Delta m^2$ values.

    hep-phPRD(2022)·9 citations
15. 15*

    Spinning Gluons from the QCD Light-Ray OPE

    Hao Chen🇨🇳 · Ian Moult🇺🇸 · Hua Xing Zhu🇨🇳

    We study the transverse spin structure of the squeezed limit of the three-point energy correlator, $⟨\mathcal{E}({\vec{n}}_1)\mathcal{E}({\vec{n}}_2)\mathcal{E}({\vec{n}}_3)⟩$. To describe its all orders perturbative behavior, we develop the light-ray operator product expansion (OPE) in QCD. At leading twist the iterated OPE of $\mathcal{E}({\vec{n}}_i)$ operators closes onto light-ray operators ${\mathbb{O}}^{[J]}(\vec{n})$ with spin $J$, and transverse spin $j=0,2$. We compute the $\mathcal{E}({\vec{n}}_1)\mathcal{E}({\vec{n}}_2)$, $\mathcal{E}({\vec{n}}_1){\mathbb{O}}^{[J]}({\vec{n}}_2)$ and ${\mathbb{O}}^{[J_1]}({\vec{n}}_1){\mathbb{O}}^{[J_2]}({\vec{n}}_2)$ OPEs as analytic functions of $J$, which allows for the description of arbitrary squeezed limits of $N$-point correlators in QCD. We use these results with $J=3$ to reproduce the perturbative expansion in the squeezed limit of the three-point correlator, as well as to resum the leading twist singular structure for both quark and gluon jets, including transverse spin contributions, as required for phenomenological applications. Finally, we briefly comment on the transverse spin structure at higher twists, and show that to all orders in the twist expansion the highest transverse spin contributions are universal between quark and gluon jets, and are descendants of the leading twist transverse spin-2 operator, allowing their resummation into a simple two-dimensional Euclidean conformal block. Due to the general applicability of our results to arbitrary correlation functions of energy flow operators, we anticipate that they can be widely applied to improving our understanding of jet substructure at the LHC.

    hep-phhep-exhep-thnucl-ex+1JHEP(2022)·84 citations
16. 16*

    Leptoquarks facing flavour tests and $b\to s\ell \ell$ after Moriond 2021

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

    In view of the emerging hints for the violation of lepton flavour universality in several $B$-meson decays, we conduct a model-independent study (effective field theory approach) of several well-motivated new physics scenarios. Taking into account the most recent LHCb data, we provide updates to Wilson coefficient fits for numerous popular new physics hypotheses. We also consider a promising model of vector leptoquarks, which in addition to explaining the $B$-meson decay anomalies ($R_{K^{(\ast )}}$ and $R_{D^{(\ast )}}$) would have an extensive impact for numerous flavour observables. We identify promising decay modes allowing to (indirectly) probe such an extension: these include positive signals (at Belle II or LHCb) for $\tau \to \varphi \mu$, $B_{(s)}$-meson decays to ${\tau }^{+}{\tau }^{-}$ and ${\tau }^{+}{\mu }^{-}$ (${\tau }^{+}{e}^{-}$) final states, as well as an observation of certain charged lepton flavour violation transitions at COMET and Mu2e. We also argue how the evolution of the experimental determination of $R_{D^{(\ast )}}$ can prove instrumental in falsifying a vector leptoquark explanation of the anomalous $B$-meson decay data.

    hep-phhep-ex21 citations
17. 17*

    Boosted dark matter from diffuse supernova neutrinos

    Anirban Das🇺🇸 · Manibrata Sen🇺🇸

    The XENON collaboration recently reported an excess of electron recoil events in the low energy region with a significance of around $3.3\sigma$. An explanation of this excess in terms of thermal dark matter seems challenging. We propose a scenario where dark matter in the Milky Way halo gets boosted as a result of scattering with the diffuse supernova neutrino background. This interaction can accelerate the dark-matter to semi-relativistic velocities, and this flux, in turn, can scatter with the electrons in the detector, thereby providing a much better fit to the data. We identify regions in the parameter space of dark-matter mass and interaction cross-section which satisfy the excess. Furthermore, considering the data only hypothesis, we also impose bounds on the dark-matter scattering cross-section, which are competitive with bounds from other experiments.

    hep-phastro-ph.COPRD(2021)·85 citations
18. 18*

    Geodesic deviation equation in Brans-Dicke theory in arbitrary dimensions

    S. M. M. Rasouli🇵🇹 · F. Shojai🇮🇷

    In this paper, we study the geodesic deviation equation (GDE) within the context of the Brans-Dicke (BD) theory in $D$ dimensions. Then, we restrict our attention to the GDE for the fundamental observers and null vector field past directed. Concerning the latter, in order to apply the retrieved GDE for the cosmological models as well as examining exact solutions, we study some cosmological models in general relativity (GR) and in the context of the BD theory. For the BD framework, we provide two appropriate settings for dynamical system, which can be considered as the most extended case scenarios with respect to those studied previously. Then, we investigate a few well-known BD cosmological models, for which we present the modified and corrected exact solutions. Moreover, we show that the retrieved formalism of the GDE can also be properly applicable for the modified BD theory (MBDT), whose matter and potential emerge from the geometry. For all of our herein cosmological models, we investigate the energy conditions and depict the behavior of the deviation vector and observer area distance. We demonstrate that why the MBDT can be considered as a more appropriate candidate to describe the universe in accordance with the observational data as well as from theoretical viewpoint.

    ↳ gr-qchep-phhep-thphysics.class-phPhys.Dark Univ.(2021)·11 citations
19. 19*

    Beta-decay formulas revisited (I): Gamow--Teller and spin-dipole contributions to allowed and first-forbidden transitions

    W. Horiuchi🇯🇵 · T. Sato🇯🇵 · Y. Uesaka🇯🇵 · K. Yoshida🇯🇵

    We propose formulas of the nuclear beta-decay rate that are useful in a practical calculation. The decay rate is determined by the product of the lepton and hadron current densities. A widely used formula relies upon the fact that the low-energy lepton wave functions in a nucleus can be well approximated by a constant and linear to the radius for the $s$-wave and $p$-wave wave functions, respectively. We find, however, the deviation from such a simple approximation is evident for heavy nuclei with large $Z$ by numerically solving the Dirac equation. In our proposed formulas, the neutrino wave function is treated exactly as a plane wave, while the electron wave function is obtained by iteratively solving the integral equation, thus we can control the uncertainty of the approximate wave function. The leading-order approximation gives a formula equivalent to the conventional one and overestimates the decay rate. We demonstrate that the next-to-leading-order formula reproduces well the exact result for a schematic transition density as well as a microscopic one obtained by a nuclear energy-density functional method.

    ↳ nucl-thhep-phPTEP(2021)·8 citations
20. 20*

    Determination of the Collins-Soper Kernel from Lattice QCD

    Maximilian Schlemmer🇩🇪 · Alexey Vladimirov🇩🇪 · Christian Zimmermann🇩🇪 · Michael Engelhardt🇺🇸 · Andreas Schäfer🇩🇪

    We present lattice results for the non-perturbative Collins-Soper (CS) kernel, which describes the energy-dependence of transverse momentum-dependent parton distributions (TMDs). The CS kernel is extracted from the ratios of first Mellin moments of quasi-TMDs evaluated at different nucleon momenta.The analysis is done with dynamical $N_f=2+1$ clover fermions for the CLS ensemble H101 ($a=0.0854\mathrm{fm}$, $m_{\pi }=m_K=422\mathrm{MeV}$). The computed CS kernel is in good agreement with experimental extractions and previous lattice studies.

    ↳ hep-lathep-phJHEP(2021)·105 citations
21. 21*

    Quark flavor physics and lattice QCD

    Matthew Wingate🇬🇧

    For a long time, investigation into the weak interactions of quarks has guided us toward understanding the Standard Model we know today. Now in the era of high precision, these studies are still one of the most promising avenues for peering beyond the Standard Model. This is a large-scale endeavour with many tales and many protagonists. In these pages I follow a few threads of a complex story, those passing through the realm of lattice gauge theory.

    ↳ hep-lathep-phEPJA(2021)·11 citations
22. 22*

    Evidence of TeV Halos Around Millisecond Pulsars

    Dan Hooper🇺🇸 · Tim Linden🇸🇪

    Using data from the HAWC gamma-ray Telescope, we have studied a sample of 37 millisecond pulsars (MSPs), selected for their spindown power and proximity. From among these MSP, we have identified four which favor the presence of very high-energy gamma-ray emission at a level of $(2\Delta \ln \mathcal{L}{)}^{1/2}\ge 2.5$. Adopting a correlation between the spindown power and gamma-ray luminosity of each pulsar, we performed a stacked likelihood analysis of these 37 MSPs, finding that the data supports the conclusion that these sources emit very high-energy gamma-rays at a level of $(2\Delta \ln \mathcal{L}{)}^{1/2}=4.24$. Among sets of randomly selected sky locations within HAWC's field-of-view, less than 1\% of such realizations yielded such high statistical significance. Our analysis suggests that MSPs produce very high-energy gamma-ray emission with a similar efficiency to that observed from the Geminga TeV-halo, ${\eta }_{\mathrm{MSP}}=(0.39-1.08)\times {\eta }_{\mathrm{Geminga}}$. This conclusion poses a significant challenge for pulsar interpretations of the Galactic Center gamma-ray excess, as it suggests that any population of MSPs potentially capable of producing the GeV excess would also produce TeV-scale emission in excess of that observed by HESS from this region. Future observations by CTA will be able to substantially clarify this situation.

    ↳ astro-ph.HEastro-ph.GAhep-phPRD(2022)·35 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.