Wed·Jun 10, 2020Wednesday·June 10, 2020

1. 01*

   The soft-gluon limit and the infrared enhancement of the quark-gluon vertex

   Orlando Oliveira🇵🇹 · Tobias Frederico🇧🇷 · Wayne de Paula🇧🇷

   The Schwinger-Dyson quark equation (SDE) combined with results from lattice simulation for the propagators are used to obtain information on the quark-gluon vertex, taking into account the recent full QCD lattice results for the soft-gluon limit. Its inclusion leads to a clear enhancement of the infrared quark-gluon vertex. We also find that the relative contribution of the quark-ghost kernel to the quark-gluon vertex in the infrared region does not follow the rules from the perturbative analysis of the ultraviolet region. This shows that for QCD the intuition based on perturbation theory does not apply to the full momentum range. The framework developed in the current work provides analytical expressions for all the longitudinal components of vertex taken into account.

   hep-phhep-thEPJC(2020)·33 citations
2. 02*

   Cosmological implications of the KOTO excess

   Wolfgang Altmannshofer🇺🇸 · Benjamin V. Lehmann🇺🇸 · Stefano Profumo🇺🇸

   The KOTO experiment has reported an excess of $K_L\to {\pi }^0\nu \bar{\nu }$ events above the Standard Model prediction, in tension with the Grossman-Nir (GN) bound. The GN bound heavily constrains new physics interpretations of an excess in this channel, but another possibility is that the observed events originate from a different process entirely: a decay of the form $K_L\to {\pi }^{0}X$, where $X$ denotes one or more new invisible species. We introduce a class of models to study this scenario with two light scalars playing the role of $X$, and we examine the possibility that the lighter of the two new states may also account for cosmological dark matter (DM). We show that this species can be produced thermally in the presence of additional interactions apart from those needed to account for the KOTO excess. Conversely, in the minimal version of the model, DM must be produced nonthermally. In this case, avoiding overproduction imposes constraints on the structure of the low-energy theory. Moreover, this requirement carries significant implications for the scale of reheating in the early Universe, generically preferring a low but observationally permitted reheating temperature of O(10 MeV). We discuss astrophysical and terrestrial signatures that will allow further tests of this paradigm in the coming years.

   hep-phPRD(2020)·7 citations
3. 03*

   Mapping $pp\to A\to ZH\to l^{+}{l}^{-}b\bar{b}$ and $pp\to H\to ZA\to l^{+}{l}^{-}b\bar{b}$ Current and Future Searches onto 2HDM Parameter Spaces

   Rachid Benbrik (1)🇲🇦 · Henry Day-Hall (2)(3)🇬🇧 · Stefano Moretti (2)🇬🇧 · Souad Semlali (1) ((1) Laboratoire de Physique fondamentale et Appliqée Safi, Faculté Polydisciplinaire de Safi, Sidi Bouzid, Morocco, (2) School of Physics and Astronomy, University of Southampton, United Kingdom, (3) Particle Physics Department, Rutherford Appleton Laboratory, United Kingdom)

   By borrowing the results from a Large Hadron Collider (LHC) analysis performed with $36.1{\text{fb}}^{-1}$ of Run 2 data intended to search for $A$ production followed by $ZH$ decay in turn yielding $l^{+}{l}^{-}b\bar{b}$ ($l=e,\mu$) final states in the context of the standard four Yukawa types of the 2-Higgs Doublet Model (2HDM), we recast it in terms of sensitivity reaches for the similar process $pp\to H\to ZA\to l^{+}{l}^{-}b\bar{b}$. This simple exercise across the two processes, which is possible because the only kinematic difference between these are different widths for the Higgs bosons, in turn affecting minimally the efficiency of an experimental selection, enables us to expand the region of parameter space that can be tested to the case when $m_H\ge m_A+m_Z$. Furthermore, we extrapolate our results to full Run 3 data samples. We conclude that, while the high energy and luminosity stage of the LHC can afford one with increased sensitivity to the 2HDM in general, the recast analysis does not add anything to what already probed through the actual one.

   hep-phhep-exPLB(2020)·3 citations
4. 04*

   New Collider Searches for Axion-like Particles Coupling to Gluons

   Gholamhossein Haghighat🇮🇷 · Daruosh Haji Raissi🇮🇷 · Mojtaba Mohammadi Najafabadi🇮🇷

   Axion-like particles (ALPs) are pseudo Nambu-Goldstone bosons associated with spontaneously broken global symmetries emerging in many extensions of the Standard Model. Assuming the most general effective Lagrangian up to dimension-5 operators for an ALP interacting with the SM fields, we investigate for the first time the sensitivity of the LHC13 to the ALP production in association with a di-jet. This study is focused on light ALPs which appear as invisible particles at the detector. Performing a realistic detector simulation and deploying a multivariate technique to best discriminate the signal from backgrounds, we set expected upper bounds on the ALP coupling to gluons. A comprehensive set of background processes is considered, and it is shown that this process provides significant sensitivity to the ALP-gluon coupling and the resulting bound is more stringent than those already obtained at the LHC. We also present prospects for the HE-LHC27 and FCC-hh100 and show that these future colliders are able to improve the limits from the LHC by roughly one order of magnitude.

   hep-phPRD(2020)·34 citations
5. 05*

   Triangle Singularity as the Origin of the $a_1(1420)$

   G.D. Alexeev · M.G. Alexeev · A. Amoroso · V. Andrieux · V. Anosov · A. Antoshkin · K. Augsten · W. Augustyniak · C.D.R. Azevedo · B. Badelek · F. Balestra · M. Ball and 186 other authors

   The COMPASS experiment recently discovered a new isovector resonance-like signal with axial-vector quantum numbers, the $a_1(1420)$, decaying to $f_0(980)\pi$. With a mass too close to and a width smaller than the axial-vector ground state $a_1(1260)$, it was immediately interpreted as a new light exotic meson, similar to the $X$, $Y$, $Z$ states in the hidden-charm sector. We show that a resonance-like signal fully matching the experimental data is produced by the decay of the $a_1(1260)$ resonance into $K^{\ast }(\to K\pi )\bar{K}$ and subsequent rescattering through a triangle singularity into the coupled $f_0(980)\pi$ channel. The amplitude for this process is calculated using a new approach based on dispersion relations. The triangle-singularity model is fitted to the partial-wave data of the COMPASS experiment. Despite having less parameters, this fit shows a slightly better quality than the one using a resonance hypothesis and thus eliminates the need for an additional resonance in order to describe the data. We thereby demonstrate for the first time in the light-meson sector that a resonance-like structure in the experimental data can be described by rescattering through a triangle singularity, providing evidence for a genuine three-body effect.

   hep-phhep-exPRL(2021)·63 citations
6. 06*

   NLO QCD corrections to $J/\psi$ pair production in photon-photon collision

   Hao Yang🇨🇳 · Zi-Qiang Chen🇨🇳 · Cong-Feng Qiao🇨🇳

   We calculate the next-to-leading order (NLO) quantum chromodynamics (QCD) correction to the exclusive process $\gamma +\gamma \to J/\psi +J/\psi$ in the framework of non-relativistic QCD (NRQCD) factorization formalism. The cross sections at the SuperKEKB electron-positron collider, as well as at the future colliders, like the Circular Electron Positron Collider (CEPC) and the International Linear Collider (ILC), are evaluated. Numerical result indicates that the process will be hopefully to be seen by the Belle II detector within the next decade.

   hep-ph3 citations
7. 07*

   Evolution of the $B$-Meson Light-Cone Distribution Amplitude in Laplace Space

   Anne Mareike Galda (U. Mainz)🇩🇪 · Matthias Neubert (U. Mainz & Cornell U.)🇩🇪

   The $B$-meson light-cone distribution amplitude is a central quantity governing non-perturbative hadronic dynamics in exclusive $B$ decays. We show that the information needed to describe such processes at leading power in ${\Lambda }_{\mathrm{QCD}}/m_b$ is most directly contained in its Laplace transform ${\tilde{\varphi }}_{+}(\eta )$. We derive the renormalization-group (RG) equation satisfied by this function and present its exact solution. We express the RG-improved QCD factorization theorem for the decay $B^{-}\to \gamma {\ell }^{-}\bar{\nu }$ in terms of ${\tilde{\varphi }}_{+}(\eta )$ and show that it is explicitly independent of the factorization scale. We propose an unbiased parameterization of ${\tilde{\varphi }}_{+}(\eta )$ in terms of a small set of uncorrelated hadronic parameters.

   hep-phhep-thPRD(2020)·29 citations
8. 08*

   Lattice Calculation of Pion Form Factor with Overlap Fermions

   Gen Wang🇺🇸 · Jian Liang🇺🇸 · Terrence Draper🇺🇸 · Keh-Fei Liu🇺🇸 · Yi-Bo Yang (chiQCD Collaboration)🇨🇳

   We present a precise calculation of the pion form factor using overlap fermions on seven ensembles of 2+1-flavor domain-wall configurations with pion masses varying from 139 to 340 MeV. Taking advantage of the fast Fourier transform and other techniques to access many combinations of source and sink momenta, we find the pion mean square charge radius to be $⟨r_{\pi }^2⟩=0.430(5)(13)\mathrm{f}{\mathrm{m}}^2$, which agrees well with the experimental result, and includes the systematic uncertainties from chiral extrapolation, lattice spacing and finite-volume dependence. We also find that $⟨r_{\pi }^2⟩$ depends on both the valence and sea quark masses strongly and predict the pion form factor up to $Q^2=1.0\mathrm{Ge}{\mathrm{V}}^2$ which agrees with experiments very well.

   hep-phhep-latPRD(2021)·63 citations
9. 09*

   Finding Wombling Boundaries in LHC Data with Voronoi and Delaunay Tessellations

   Konstantin T. Matchev🇺🇸 · Alexander Roman🇺🇸 · Prasanth Shyamsundar🇺🇸

   We address the problem of finding a wombling boundary in point data generated by a general Poisson point process, a specific example of which is an LHC event sample distributed in the phase space of a final state signature, with the wombling boundary created by some new physics. We discuss the use of Voronoi and Delaunay tessellations of the point data for estimating the local gradients and investigate methods for sharpening the boundaries by reducing the statistical noise. The outcome from traditional wombling algorithms is a set of boundary cell candidates with relatively large gradients, whose spatial properties must then be scrutinized in order to construct the boundary and evaluate its significance. Here we propose an alternative approach where we simultaneously form and evaluate the significance of all possible boundaries in terms of the total gradient flux. We illustrate our method with several toy examples of both straight and curved boundaries with varying amounts of signal present in the data.

   hep-phhep-exphysics.comp-phphysics.data-anJHEP(2020)·3 citations
10. 10*

    Searches for heavy Higgs bosons in the framework of 2HDM model

    Tetiana Obikhod🇺🇦 · Ievgenii Petrenko🇺🇦

    The searches for heavy neutral and charged Higgs bosons are performed through the calculations of production cross sections using MadGraph5aMC@NLO program with ansatz of Yukawa coupling and the restricted parameter space connected with LHC Run 2 data. The searches for heavy resonances are performed in the framework of 2HDM model over the mass range 0.1 - 1 TeV for the $pp\to At\bar{b}$, $pp\to H^{+}b\bar{t}$ , $pp\to H^{+}t\bar{t}$ , $pp\to HHZ$ decay modes. The presented data demonstrate the jump in the production cross section of $H^{+}b\bar{t}$ and $HHZ$ production processes in the mass range of 100-200 GeV and 100-300 GeV accordingly at energy of 14 TeV.

    hep-phPhys.Part.Nucl.(2023)·0 citations
11. 11*

    The nonperturbative functional renormalization group and its applications

    N. Dupuis🇫🇷 · L. Canet🇫🇷 · A. Eichhorn🇩🇰 · W. Metzner🇩🇪 · J. M. Pawlowski🇩🇪 · M. Tissier🇫🇷 · N. Wschebor🇺🇾

    The renormalization group plays an essential role in many areas of physics, both conceptually and as a practical tool to determine the long-distance low-energy properties of many systems on the one hand and on the other hand search for viable ultraviolet completions in fundamental physics. It provides us with a natural framework to study theoretical models where degrees of freedom are correlated over long distances and that may exhibit very distinct behavior on different energy scales. The nonperturbative functional renormalization-group (FRG) approach is a modern implementation of Wilson's RG, which allows one to set up nonperturbative approximation schemes that go beyond the standard perturbative RG approaches. The FRG is based on an exact functional flow equation of a coarse-grained effective action (or Gibbs free energy in the language of statistical mechanics). We review the main approximation schemes that are commonly used to solve this flow equation and discuss applications in equilibrium and out-of-equilibrium statistical physics, quantum many-particle systems, high-energy physics and quantum gravity.

    ↳ cond-mat.stat-mechgr-qchep-phhep-thPhys.Rept.(2021)·678 citations
12. 12*

    Transverse Chiral Magnetic Photocurrent Induced by Linearly Polarized Light in Mirror-Symmetric Weyl Semimetals

    Sahal Kaushik🇺🇸 · Dmitri E. Kharzeev🇺🇸 · Evan John Philip🇺🇸

    A new class of photocurrents is predicted to occur in both type-I and type-II Weyl semimetals. Unlike the previously studied photocurrents in chiral materials, the proposed current requires neither circularly polarized light, nor an absence of symmetry with respect to a plane of reflection. We show that if a Weyl semimetal has a broken inversion symmetry then linearly polarized light can induce a photocurrent transverse to the direction of an applied magnetic field, in spite of the symmetry with respect to a reflection plane and the time reversal symmetry. The class of materials in which we expect this to occur is sufficiently broad and includes the transition metal monopnictides such as TaAs. The effect stems from the dynamics of Weyl chiral quasi-particles in a magnetic field, restricted by the symmetries described above; because the resulting current is transverse to the direction of magnetic field, we call it the transverse chiral magnetic photocurrent. The magnitude of the resulting photocurrent is predicted to be significant in the THz frequency range, about $0.75\mu \mathrm{A}$ for type-I and $2.5\mu \mathrm{A}$ for type-II Weyl semimetals. This opens the possibility to utilize the predicted transverse chiral magnetic photocurrent for sensing unpolarized THz radiation.

    ↳ cond-mat.mes-hallhep-phPRResearch(2020)·14 citations
13. 13*

    Gradient effects on false vacuum decay in gauge theory

    Wen-Yuan Ai🇧🇪 · Juan S. Cruz🇩🇪 · Bjorn Garbrecht🇩🇪 · Carlos Tamarit🇩🇪

    We study false vacuum decay for a gauged complex scalar field in a polynomial potential with nearly degenerate minima. Radiative corrections to the profile of the nucleated bubble as well as the full decay rate are computed in the planar thin-wall approximation using the effective action. This allows to account for the inhomogeneity of the bounce background and the radiative corrections in a self-consistent manner. In contrast to scalar or fermion loops, for gauge fields one must deal with a coupled system that mixes the Goldstone boson and the gauge fields, which considerably complicates the numerical calculation of Green's functions. In addition to the renormalization of couplings, we employ a covariant gradient expansion in order to systematically construct the counterterm for the wave-function renormalization. The result for the full decay rate however does not rely on such an expansion and accounts for all gradient corrections at the chosen truncation of the loop expansion. The ensuing gradient effects are shown to be of the same order of magnitude as non-derivative one-loop corrections.

    ↳ hep-thhep-phPRD(2020)·23 citations
14. 14*

    White-dwarf asteroseismology with the Kepler space telescope

    Alejandro H. Córsico🇦🇷

    In the course of their evolution, white-dwarf stars go through at least one phase of variability in which the global pulsations they undergo allow astronomers to peer into their interiors, this way making possible to shed light on their deep inner structure and evolutionary stage by means of asteroseismology. The study of pulsating white dwarfs has witnessed substantial progress in the last decade, and this has been so largely thanks to the arrival of continuous observations of unprecedented quality from space, like those of the CoRoT, Kepler, and TESS missions. This, along with the advent of new detailed thoretical models and the development of improved asteroseismological techniques, has helped to unravel the internal chemical structure of many pulsating white dwarfs, and, at the same time, has opened new questions that challenge theoreticians. In particular, uninterrupted monitoring of white-dwarf stars for months has allowed discovering phenomena impossible to detect with ground-based observations, despite admirable previous efforts like the Whole Earth Telescope (WET). Here, we start by reviewing the essential properties of white-dwarf and pre-white dwarf stars and their pulsations, and then, we go through the different families of pulsating objects known to date. Finally, we review the most outstanding findings about pulsating white dwarfs and pre-white dwarfs made possible with the unprecedented-quality observations of the Kepler space telescope, although we envisage that future analyzes of space data from this mission that still await to be examined may reveal new secrets of these extremely interesting variable stars.

    ↳ astro-ph.SRhep-ph3 citations
15. 15*

    Spoon or slide? The non-linear matter power spectrum in the presence of massive neutrinos

    Steen Hannestad🇩🇰 · Amol Upadhye🇦🇺 · Yvonne Y. Y. Wong🇦🇺

    Numerical simulations of massive neutrino cosmologies consistently find a spoon-like feature in the non-linear matter power spectrum ratios of cosmological models that differ only in the neutrino mass fraction f_N. Typically, the ratio approaches unity at low wave numbers k, decreases by ~ 10 f_N at k ~ 1 h/Mpc, and turns up again at large k. Using the halo model of large-scale structure, we show that this spoon feature originates in the transition from the two-halo power spectrum to the one-halo power spectrum. The former's sensitivity to f_N rises with k, while that of the latter decreases with k. The presence of this spoon feature is robust with respect to different choices of the halo mass function and the halo density profile, and does not require any parameter tuning within the halo model. We demonstrate that a standard halo model calculation is already able to predict the depth, width, and position of this spoon as well as its evolution with redshift z with remarkable accuracy. Predictions at z >= 1 can be further improved using non-linear perturbative inputs.

    ↳ astro-ph.COhep-phJCAP(2020)·37 citations
16. 16*

    QED calculation of ionization energies of $1snd$ states in helium

    Vladimir A. Yerokhin🇷🇺 · Vojtěch Patkóš🇨🇿 · Mariusz Puchalski🇵🇱 · Krzysztof Pachucki🇵🇱

    Quantum electrodynamical (QED) calculations of ionization energies of the $1sndD$ states are performed for the helium atom. We reproduce the previously known relativistic and QED effects up to order $m{\alpha }^5$ and extend the theory by calculating the complete $m{\alpha }^6$ correction. The total contribution of the $m{\alpha }^6$ effects is shown to be much smaller than previously estimated, due to a large cancelation between the radiative and non-radiative parts of this correction. As a result of our calculations, we confirm the previously reported deviations between measured transition energies and theoretical predictions for the $nD$--$2S$ and $nD$--$2P$ transitions. Possible reasons for this discrepancy are analyzed.

    ↳ physics.atom-phhep-phPRA(2020)·11 citations
17. 17*

    First lattice calculation of radiative leptonic decay rates of pseudoscalar mesons

    A. Desiderio🇮🇹 · R. Frezzotti🇮🇹 · M.Garofalo🇮🇹 · D. Giusti🇩🇪 · M. Hansen🇩🇰 · V. Lubicz🇮🇹 · G.Martinelli🇮🇹 · C.T. Sachrajda🇬🇧 · F. Sanfilippo🇮🇹 · S.Simula🇮🇹 · N.Tantalo🇮🇹

    We present a non-perturbative lattice calculation of the form factors which contribute to the amplitudes for the radiative decays $P\to \ell {\bar{\nu }}_{\ell }\gamma$, where $P$ is a pseudoscalar meson and $\ell$ is a charged lepton. Together with the non-perturbative determination of the corrections to the processes $P\to \ell {\bar{\nu }}_{\ell }$ due to the exchange of a virtual photon, this allows accurate predictions at $O({\alpha }_{em})$ to be made for leptonic decay rates for pseudoscalar mesons ranging from the pion to the $D_s$ meson. We are able to separate unambiguously and non-pertubatively the point-like contribution, from the structure-dependent, infrared-safe, terms in the amplitude. The fully non-perturbative $O(a)$ improved calculation of the inclusive leptonic decay rates will lead to the determination of the corresponding Cabibbo-Kobayashi-Maskawa (CKM) matrix elements also at $O({\alpha }_{em})$. Prospects for a precise evaluation of leptonic decay rates with emission of a hard photon are also very interesting, especially for the decays of heavy $D$ and $B$ mesons for which currently only model-dependent predictions are available to compare with existing experimental data.

    ↳ hep-lathep-phPRD(2021)·73 citations
18. 18*

    Effective Field Theory for Acoustic and Pseudo-Acoustic Phonons in Solids

    Angelo Esposito🇨🇭 · Emma Geoffray🇩🇪 · Tom Melia🇯🇵

    We present a relativistic effective field theory for the interaction between acoustic and gapped phonons in the limit of a small gap. We show that, while the former are the Goldstone modes associated with the spontaneous breaking of spacetime symmetries, the latter are pseudo-Goldstones associated with some (small) explicit breaking. We hence dub them "pseudo-acoustic" phonons. In this first investigation, we build our effective theory for the cases of one and two spatial dimensions, two atomic species, and assuming large distance isotropy. As an illustrative example, we show how the theory can be applied to compute the total lifetime of both acoustic and pseudo-acoustic phonons. This construction can find applications that range from the physics of bilayer graphene to sub-GeV dark matter detectors.

    ↳ hep-thcond-mat.otherhep-phPRD(2020)·9 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.