Mon·Aug 10, 2020Monday·August 10, 2020

1. 01*

   Factorized approach to radiative corrections for inelastic lepton-hadron collisions

   Tianbo Liu🇺🇸 · W. Melnitchouk🇺🇸 · Jian-Wei Qiu🇺🇸 · N. Sato🇺🇸

   We propose a factorized approach to QED radiative corrections for inclusive and semi-inclusive deep-inelastic scattering to systematically account for QED and QCD radiation contributions to both processes on equal footing. This is achieved by utilizing factorization to resum logarithmically enhanced QED radiation into universal lepton distribution and fragmentation (or jet) functions. Numerical simulations suggest that the QED effects induced by the rotational distortion of the hadron transverse momentum, arising from the mismatch between the experimental Breit frame and the true photon-hadron frame, can be as large as 50\% for moderate $Q$, and become increasingly important for large transverse momenta. Our framework provides a uniform treatment of radiative effects for extracting three-dimensional hadron structure from high-energy lepton-hadron scattering at current and future facilities, such as the Electron-Ion Collider.

   hep-phhep-exnucl-exnucl-thPRD(2021)·35 citations
2. 02*

   The emission of electromagnetic radiation from the early stages of relativistic heavy-ion collisions

   Jessica Churchill🇨🇦 · Li Yan🇨🇳 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦

   We estimate the production of electromagnetic radiation (real and virtual photons) from the early, pre-equilibrium, stage of relativistic heavy-ion collisions. The parton dynamics are obtained as a solution of the Boltzmann equation in the Fokker-Planck diffusion limit. The photon and dilepton rates are integrated and the obtained yields are compared with those from standard sources and with available experimental data. Non-equilibrium photon spectra are predicted for Pb+Pb at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV.

   hep-phnucl-exnucl-thPRC(2021)·35 citations
3. 03*

   Exclusive heavy quark dijet cross section

   Chul Kim🇰🇷

   We study the exclusive heavy quark dijet cross section from $e^{+}{e}^{-}$-annihilation using soft-collinear effective theory. In order to resum the large logarithms of small jet veto parameter $\beta$ and jet radius $R$, we factorize the cross section into the hard, hard-soft, collinear, and collinear-soft parts. Compared with the case of a massless quark, the jet sector with the collinear and collinear-soft parts can be modified to include the heavy quark mass. The factorization of the jet sector can be systematically achieved through matching onto the boosted heavy quark effective theory. Heavy quark mass corrections enhance the cross section sizably and cannot be ignored when the quark mass is comparable with the jet size $E_{J}R$. We also analyze the exclusive heavy quark pair production in the limit as $R$ goes to zero. Using the resummed result, the top isolation effects on the cross section are estimated.

   hep-phJ.Korean Phys.Soc.(2020)·7 citations
4. 04*

   Dark matter annihilation into leptons through gravity portals

   Sun Xu-Dong🇨🇳 · Dai Ben-Zhong🇨🇳

   Dark matter (DM) constitutes 85% of the matter in the Universe. However, its specific particle property is still unclear. The fundamentals of DM particles subject to gravitational interaction, and that the lepton excess in cosmic rays may originate from DM particles, inspired us to investigate DM particle properties beyond the standard model. We assume that a leptophilic SU(2) doublet exists in nature as the mediator connecting DM with visible leptons. Since general relativity is not renormalizable at the quantum level, it should be regarded as an effective field theory's leading order term. One species of the next-to-leading-order term should be operators linear to the Ricci scalar and containing scalar fields, such as the Higgs field, scalar DM, or the newly introduced SU(2) scalar doublet. These operators can cause DM annihilation through gravity portals. We analyzed constraints from the cosmic antiproton flux, DM relic abundance, cosmic positron flux, cosmic microwave background, and direct detection experiments. The result shows that there is a vast parameter space that is compatible with current experiments. DM with a mass of electroweak scale is only allowed to annihilate into leptons. We further show that the purely gravitational DM better explains the DArk Matter Particle Explorer cosmic lepton excess. Our work provides a promising mechanism for DM particles to connect with standard model particles.

   hep-phastro-ph.HEJHEP(2021)·7 citations
5. 05*

   Investigating the pion source function in heavy-ion collisions with the EPOS model

   Maria Stefaniak🇵🇱 · Daniel Kincses🇭🇺

   By measuring the momentum correlations of pions created in heavy-ion collisions we can gain information about the space-time geometry of the particle emitting source. Recent experimental results from multiple different collaborations demonstrated that to properly describe the shape of the measured correlation functions, one needs to go beyond the Gaussian approximation. Some studies suggest that the Levy distribution could provide a good description of the source. While there are already many experimental results, there is very little input from the phenomenology side in explanation of the observed non-Gaussian source shapes. The EPOS model is a sophisticated hybrid model where the evolution of the newly-created system is governed by Parton-Based Gribov-Regge theory. It has already proved to be successful in describing many different experimental observations for the systems characterized by baryon chemical potential close to zero, but so far the source shape has not been explored in detail. In this paper we discuss studies of the pion emitting source based on the theoretical approach of the EPOS model.

   hep-phnucl-thProc.SPIE Int.Soc.Opt.Eng.(2020)·2 citations
6. 06*

   Fractal Structures of Yang-Mills Fields and Non Extensive Statistics: Applications to High Energy Physics

   Airton Deppman🇧🇷 · Eugenio Megias🇪🇸 · Debora P. Menezes🇧🇷

   In this work, we provide an overview of the recent investigations on the non-extensive Tsallis statistics and its applications to high energy physics and astrophysics, including physics at the Large Hadron Collider (LHC), hadron physics, and neutron stars. We review some recent investigations on the power-law distributions arising in high energy physics experiments focusing on a thermodynamic description of the system formed, which~could explain the power-law behavior. The possible connections with a fractal structure of hadrons is also discussed. The main objective of the present work is to delineate the state-of-the-art of those studies and~show some open issues that deserve more careful investigation. We propose several possibilities to test the theory through analyses of experimental data.

   hep-phhep-thnucl-thMDPI Physics(2020)·19 citations
7. 07*

   Cabibbo anomaly versus electroweak precision tests: An exploration of extensions of the Standard Model

   Matthew Kirk🇮🇹

   There is a newly emerging tension between determinations of $V_{us}$ from different sources (known as the Cabibbo anomaly), which is clearly demonstrated by the new $R(V_{us})$ observable. We explore this observable from the perspective of the Standard Model Effective Field Theory and show there is a discrepancy between $R(V_{us})$ and existing electroweak precision observables (EWPO) in a simple single operator dominated scenario. We explore all possible single particle extensions of the Standard Model that can generate the Cabibbo anomaly effect and show how they cannot reconcile the current data. We further examine the future of EWPO at the ILC or FCC-ee experiments and discuss the effect on the tension of a change in specific EW observables.

   hep-phPRD(2021)·77 citations
8. 08*

   Low Scale String Theory Benchmarks for Hidden Photon Dark Matter Interpretations of the XENON1T Anomaly

   Athanasios Karozas🇬🇷 · Stephen F. King🇬🇧 · George K. Leontaris🇬🇷 · Dimitrios K. Papoulias🇬🇷

   An excess of low-energy electronic recoil events over known backgrounds was recently observed in the XENON1T detector, where $285$ events are observed compared to an expected $232\pm 15$ events from the background-only fit to the data in the energy range 1-7 keV. This could be due to the beta decay of an unexpected tritium component, or possibly to new physics. One plausible new physics explanation for the excess is absorption of hidden photon dark matter relics with mass around $2.8$ keV and kinetic mixing of about $10^{-15}$, which can also explain cooling excesses in horizontal-branch (HB) stars. Such small gauge boson masses and couplings can naturally arise from type-IIB low scale string theory. We provide a fit of the XENON1T excess in terms of a minimal low scale type-IIB string theory parameter space and present some benchmark points which provide a good fit to the data. It is also demonstrated how the required transformation properties of the massless spectrum are obtained in intersecting D-brane models.

   hep-phhep-exhep-thPRD(2021)·11 citations
9. 09*

   X-ray Searches for Axions from Super Star Clusters

   Christopher Dessert🇺🇸 · Joshua W. Foster🇺🇸 · Benjamin R. Safdi🇺🇸

   Axions may be produced in abundance inside stellar cores and then convert into observable X-rays in the Galactic magnetic fields. We focus on the Quintuplet and Westerlund 1 super star clusters, which host large numbers of hot, young stars including Wolf-Rayet stars; these stars produce axions efficiently through the axion-photon coupling. We use Galactic magnetic field models to calculate the expected X-ray flux locally from axions emitted from these clusters. We then combine the axion model predictions with archival Nuclear Spectroscopic Telescope Array (NuSTAR) data from 10 - 80 keV to search for evidence of axions. We find no significant evidence for axions and constrain the axion-photon coupling $g_{a\gamma \gamma }\lesssim 3.6\times 10^{-12}$ GeV${}^{-1}$ for masses $m_a\lesssim 5\times 10^{-11}$ eV at 95\% confidence.

   hep-phastro-ph.HEastro-ph.SRPRL(2020)·127 citations
10. 10*

    Secondary Vertex Finding in Jets with Neural Networks

    Jonathan Shlomi🇮🇱 · Sanmay Ganguly🇮🇱 · Eilam Gross🇮🇱 · Kyle Cranmer🇺🇸 · Yaron Lipman🇮🇱 · Hadar Serviansky🇮🇱 · Haggai Maron🇺🇸 · Nimrod Segol🇮🇱

    Jet classification is an important ingredient in measurements and searches for new physics at particle coliders, and secondary vertex reconstruction is a key intermediate step in building powerful jet classifiers. We use a neural network to perform vertex finding inside jets in order to improve the classification performance, with a focus on separation of bottom vs. charm flavor tagging. We implement a novel, universal set-to-graph model, which takes into account information from all tracks in a jet to determine if pairs of tracks originated from a common vertex. We explore different performance metrics and find our method to outperform traditional approaches in accurate secondary vertex reconstruction. We also find that improved vertex finding leads to a significant improvement in jet classification performance.

    ↳ hep-exhep-phEPJC(2021)·46 citations
11. 11*

    Scattering of two and three physical pions at maximal isospin from lattice QCD

    Matthias Fischer🇩🇪 · Bartosz Kostrzewa🇩🇪 · Liuming Liu🇨🇳 · Fernando Romero-López🇪🇸 · Martin Ueding🇩🇪 · Carsten Urbach🇩🇪

    We present the first direct $N_f=2$ lattice QCD computation of two- and three-${\pi }^{+}$ scattering quantities that includes an ensemble at the physical point. We study the quark mass dependence of the two-pion phase shift, and the three-particle interaction parameters. We also compare to phenomenology and chiral perturbation theory (ChPT). In the two-particle sector, we observe good agreement to the phenomenological fits in $s$- and $d$-wave, and obtain $M_{\pi }{a}_0=-0.0481(86)$ at the physical point from a direct computation. In the three-particle sector, we observe reasonable agreement at threshold to the leading order chiral expansion, i.e.\@ a mildly attractive three-particle contact term. In contrast, we observe that the energy-dependent part of the three-particle quasilocal scattering quantity is not well described by leading order ChPT.

    ↳ hep-lathep-phEPJC(2021)·94 citations
12. 12*

    Constructing Canonical Feynman Integrals with Intersection Theory

    Jiaqi Chen🇨🇳 · Xuhang Jiang🇨🇳 · Xiaofeng Xu🇨🇭 · Li Lin Yang🇨🇳

    Canonical Feynman integrals are of great interest in the study of scattering amplitudes at the multi-loop level. We propose to construct $d\log$-form integrals of the hypergeometric type, treat them as a representation of Feynman integrals, and project them into master integrals using intersection theory. This provides a constructive way to build canonical master integrals whose differential equations can be solved easily. We use our method to investigate both the maximally cut integrals and the uncut ones at one and two loops, and demonstrate its applicability in problems with multiple scales.

    ↳ hep-thhep-phPLB(2021)·75 citations
13. 13*

    Extracting ${\sigma }_{\pi N}$ from pionic atoms

    Eliahu Friedman · Avraham Gal

    We discuss a recent extraction of the $\pi N$ $\sigma$ term ${\sigma }_{\pi N}$ from a large-scale fit of pionic-atom strong-interaction data across the periodic table. The value thus derived, ${\sigma }_{\pi N}^{\mathrm{FG}}=57\pm 7$ MeV, is directly connected via the Gell-Mann--Oakes--Renner expression to the medium-renormalized $\pi N$ isovector scattering amplitude near threshold. It compares well with the value derived recently by the Bern-Bonn-Jülich group, ${\sigma }_{\pi N}^{\mathrm{RS}}=58\pm 5$ MeV, using the Roy-Steiner equations to control the extrapolation of the vanishingly small near threshold $\pi N$ isoscalar scattering amplitude to zero pion mass.

    ↳ nucl-thhep-phActa Phys. Pol. B 51 (2020) 45 and AIP Co…
14. 14*

    Statistically-Anisotropic Tensor Bispectrum from Inflation

    Takashi Hiramatsu🇯🇵 · Kai Murai🇯🇵 · Ippei Obata🇩🇪 · Shuichiro Yokoyama🇯🇵

    We develop a possibility of generating tensor non-Gaussianity in a kind of anisotropic inflation, where a $U(1)$ gauge field is kinetically coupled to a spectator scalar field. Owing to this coupling, the coherent mode of the electric field appears and softly breaks the isotropy of the Universe. We compute the bispectrum of linearly-polarized tensor perturbations sourced by the gauge field and find that it is strongly red-tilted and has distinctive statistical anisotropies including higher-order multipole moments. Interestingly, the tensor bispectra with the specific combinations of linear polarization modes are dominant, and their amplitudes depend on the different sets of multipole moments. This new type of statistically-anisotropic tensor non-Gaussianity can be potentially testable with the upcoming cosmic microwave background B-mode polarization experiments.

    ↳ astro-ph.COhep-phJCAP(2021)·7 citations
15. 15*

    Nuclear and dark matter heating in massive white dwarf stars

    C. J. Horowitz🇺🇸

    Recently, Cheng et al. identified a number of massive white dwarfs (WD) that appear to have an additional heat source providing a luminosity near $\approx 10^{-3}{L}_{\odot }$ for multiple Gyr. In this paper we explore heating from electron capture and pycnonuclear reactions. We also explore heating from dark matter annihilation. WD stars appear to be too small to capture enough dark matter for this to be important. Finally, if dark matter condenses to very high densities inside a WD this could ignite nuclear reactions. We calculate the enhanced central density of a WD in the gravitational potential of a very dense dark matter core. While this might start a supernova, it seems unlikely to provide modest heating for a long time. We conclude that electron capture, pycnonuclear, and dark matter reactions are unlikely to provide significant heating in the massive WD that Cheng considers.

    ↳ astro-ph.SRastro-ph.HEhep-phnucl-thPRD(2020)·23 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.