Thu·Jul 30, 2020Thursday·July 30, 2020

1. 01*

   Pico-charged particles explaining 511 keV line and XENON1T signal

   Yasaman Farzan🇮🇷 · Meshkat Rajaee🇮🇷

   There is a robust signal for a 511 keV photon line from the galactic center which may originate from dark matter particles with masses of a few MeV. To avoid the bounds from delayed recombination and from the absence of the line from dwarf galaxies, in 2017, we have proposed a model in which dark matter first decays into a pair of intermediate pico-charged particles $C\bar{C}$ with a lifetime much larger than the age of the universe. The galactic magnetic field accumulates the relativistic $C\bar{C}$ that eventually annihilate, producing the $e^{-}{e}^{+}$ pair that give rise to the 511 keV line. The relativistic pico-charged $C$ particles can scatter on the electrons inside the direct dark matter search detectors imparting a recoil energy of $E_r\sim$~keV. We show that this model can account for the electron recoil excess recently reported by the XENON1T experiment. Moreover, we show that the XENON1T electron recoil data sets the most stringent bound on the lifetime of the dark matter within this model.

   hep-phPRD(2020)·29 citations
2. 02*

   QCD resummation on single hadron transverse momentum distribution with the thrust axis

   Zhong-Bo Kang🇺🇸 · Ding Yu Shao🇺🇸 · Fanyi Zhao🇺🇸

   We derive the transverse momentum dependent (TMD) factorization and resummation formula of the unpolarized transverse momentum distribution ($j_T$) for the single hadron production with the thrust axis in electron-positron collision. Two different kinematic regions are considered, including small transverse momentum limit $j_T\ll Q$, and joint transverse momentum and threshold limit $j_T\ll Q(1-z_h)\ll Q$, where $Q$ and $z_h$ are the hard scattering energy and the observed hadron momentum fraction. Using effective theory methods, we resum logarithms $\ln (Q/j_T)$ and $\ln (1-z_h)$ to all orders. In the end we present the differential cross sections and Gaussian widths calculated for the inclusive charged pion production and find that our results are consistent with the measurements reported by the Belle collaboration.

   hep-phhep-exnucl-exnucl-thJHEP(2020)·28 citations
3. 03*

   Monte Carlo event generation of neutrino-electron scattering

   Dmitry Zhuridov🇵🇱 · Jan T. Sobczyk🇵🇱 · Cezary Juszczak🇵🇱 · Kajetan Niewczas🇧🇪

   We describe an extension of the NuWro Monte Carlo neutrino event generator with the neutrino-electron scattering processes. This new dynamical channel includes the charged current and neutral current interactions, together with their interference, for ${\nu }_{\ell }e$ and ${\bar{\nu }}_{\ell }e$ ($\ell =e,\mu ,\tau$) scatterings, resulting in ten possible final states. We illustrate the performance of the new functionality on few physical examples, including an estimation of the background in the T2K ${\nu }_{\mu }\to {\nu }_e$ oscillation experiment. We show that the background events arising from the neutrino-electron interactions occupy mostly a distinct region of the phase space and can be easily separated.

   hep-phJ.Phys.G(2021)·6 citations
4. 04*

   PMNS matrix in a non-universal $U(1{)}_X$ extension to the MSSM with one massless neutrino

   J. S. Alvarado🇨🇴 · R. Martinez🇨🇴

   An anomaly free non-universal $U(1{)}_X$ extension to the Minimal Supersymmetric Standard Model is proposed, where additional two $SU(2)$ doublet superfields and four singlet superfields complement the scalar sector of the model. The fermion sector is extended by considering additional superfields containing three quark singlets, two charged lepton singlet superfields and six neutral leptons. A tree-level massless electron is found so radiative corrections are considered to match the mass spectrum with both SUSY and non-SUSY contributions. Likewise, a massless neutrino is found and analytic expressions for massive mass eigenstates are obtained via inverse-seesaw mechanism, which implies a known neutrino mass spectrum for both normal and inverse ordering. Lastly, a numerical fitting of the model parameters to the PMNS matrix is done.

   hep-ph7 citations
5. 05*

   Scale-Fixed Predictions for $\gamma +{\eta }_c$ production in electron-positron collisions at NNLO in perturbative QCD

   Huai-Min Yu🇨🇳 · Wen-Long Sang🇨🇳 · Xu-Dong Huang🇨🇳 · Jun Zeng🇨🇳 · Xing-Gang Wu🇨🇳 · Stanley J. Brodsky🇺🇸

   In the paper, we present QCD predictions for ${\eta }_c+\gamma$ production at an electron-position collider up to next-to-next-to-leading order (NNLO) accuracy without renormalization scale ambiguities. The NNLO total cross-section for $e^{+}+e^{-}\to \gamma +{\eta }_c$ using the conventional scale-setting approach has large renormalization scale ambiguities, usually estimated by choosing the renormalization scale to be the $e^{+}{e}^{-}$ center-of-mass collision energy $\sqrt{s}$. The Principle of Maximum Conformality (PMC) provides a systematic way to eliminate such renormalization scale ambiguities by summing the nonconformal $\beta$ contributions into the QCD coupling ${\alpha }_s(Q^2)$. The renormalization group equation then sets the value of ${\alpha }_s$ for the process. The PMC renormalization scale reflects the virtuality of the underlying process, and the resulting predictions satisfy all of the requirements of renormalization group invariance, including renormalization scheme invariance. After applying the PMC, we obtain a scale-and-scheme independent prediction, $\sigma {|}_{\mathrm{NNLO},\mathrm{PMC}}\simeq 41.18$ fb for $\sqrt{s}$=10.6 GeV. The resulting pQCD series matches the series for conformal theory and thus has no divergent renormalon contributions. The large $K$ factor which contributes to this process reinforces the importance of uncalculated NNNLO and higher-order terms. Using the PMC scale-and-scheme independent conformal series and the $\mathrm{Pad}\acute{\mathrm{e}}$ approximation approach, we predict $\sigma {|}_{\mathrm{NNNLO},\mathrm{PMC}+\mathrm{Pade}}\simeq 21.36$ fb, which is consistent with the recent BELLE measurement ${\sigma }^{\mathrm{obs}}$=$16.58_{-9.93}^{+10.51}$ fb at $\sqrt{s}\simeq 10.6$ GeV. This procedure also provides a first estimate of the NNNLO contribution.

   hep-phJHEP(2021)·17 citations
6. 06*

   Distinguishing $W^{\prime }$ Signals at Hadron Colliders Using Neural Networks

   Spencer Chang🇺🇸 · Ting-Kuo Chen🇹🇼 · Cheng-Wei Chiang🇹🇼

   We investigate a neural network-based hypothesis test to distinguish different $W^{\prime }$ and charged scalar resonances through the $\ell +\text{require}cancel{\cancel{E}}_T$ channel at hadron colliders. This is traditionally challenging due to a four-fold ambiguity at proton-proton colliders, such as the Large Hadron Collider. Of the neural network approaches we studied, we find a multi-class classifier based on a fully-connected neural network trained upon 2D histograms made from kinematic variables of the final state $\ell$ to be the most powerful. Furthermore, by considering the 1-jet processes, we demonstrate that one can generalize to multiple $2D$ histograms to represent different variable pairs. Finally, as a comparison to traditional approaches, we compare our method with Bayesian hypothesis testing and discuss the pros and cons of each approach. The neural network scheme presented in this paper is a powerful tool that can help probe the properties of charged resonances.

   hep-phPRD(2021)·7 citations
7. 07*

   Signal from sterile neutrino dark matter in extra $U(1)$ model at direct detection experiment

   Osamu Seto🇯🇵 · Takashi Shimomura🇯🇵

   We examine the possibility that direct dark matter detection experiments find decay products from sterile neutrino dark mater in $U(1{)}_{B-L}$ and $U(1{)}_R$ models. This is possible if the sterile neutrino interacts with a light gauge boson and decays into a neutrino and the light gauge boson with a certain lifetime. This decay produces energetic neutrinos scattering off nuclei with a large enough recoil energy in direct dark matter detection experiments. We stress that direct dark matter detection experiments can explore not only WIMP but also sterile neutrino dark matter.

   hep-phastro-ph.COPLB(2020)·21 citations
8. 08*

   Little group generators for Dirac neutrino one-particle states

   R. Romero🇲🇽

   Assuming neutrinos to be of the Dirac type, the little group generators for the one-particle states, created off the vacuum by the field operator, are obtained, both in terms of the one-particle states themselves and in terms of creation/annihilation operators. It is shown that these generators act also as rotation operators in the Hilbert space of the states, providing three types of transformations: a helicity flip, the standard charge conjugation, and a combination of the two, up to phases. The transformations' properties are provided in detail and their physical implications discussed. It is also shown that one of the transformations continues to hold for chiral fields without mixing them.

   hep-phhep-thquant-phRev.Mex.Fis.(2021)·1 citation
9. 09*

   Semileptonic Transition of ${\Lambda }_b$ Baryon

   Kaushal Thakkar🇮🇳

   The semileptonic transition of ${\Lambda }_b$ baryon is studied using the Hypercentral constituent quark model. The six-dimensional hyperradial $Schr\ddot{o}dinger$ equation is solved in the variational approach to get masses and wavefunctions of heavy baryons. The matrix elements of weak decay are written in terms of the overlap integrals of the baryon wave function. The Isgur-Wise function is determined to calculate exclusive semileptonic decay ${\Lambda }_b$ $\to$ ${\Lambda }_c$ $\ell$ $\bar{\nu }$. The calculated decay rate and the branching ratio of ${\Lambda }_b$ baryon are consistent with other theoretical predictions and with the available experimental observations.

   hep-phEPJC(2020)·18 citations
10. 10*

    Thermoelectric transport coefficients of quark matter

    Aman Abhishek🇮🇳 · Arpan Das🇵🇱 · Deepak Kumar🇮🇳 · Hiranmaya Mishra🇮🇳

    A thermal gradient and/or a chemical potential gradient in a conducting medium can lead to an electric field, an effect known as thermoelectric effect or Seebeck effect. In the context of heavy-ion collisions, we estimate the thermoelectric transport coefficients for quark matter within the ambit of the Nambu-Jona Lasinio (NJL) model. We estimate the thermal conductivity, electrical conductivity, and the Seebeck coefficient of hot and dense quark matter. These coefficients are calculated using the relativistic Boltzmann transport equation within relaxation time approximation. The relaxation times for the quarks are estimated from the quark-quark and quark-antiquark scattering through in-medium meson exchange within the NJL model.

    hep-phnucl-thEPJC(2022)·20 citations
11. 11*

    Full resummation analysis of jet quenching and tests of the QCD Equation of State

    Xabier Feal🇺🇸

    Jet quenching has become a fundamental tool to study the hot QCD matter produced in heavy ion collisions. While important theoretical and experimental advances have been made in the last two decades, the extraction of the medium properties and the comparison with finite temperature QCD is still particularly worrisome. In this work we show that improvements in the calculation of the medium-induced gluon spectrum are required for a correct extraction of the parameters without temperature issues. In particular, we employ an improved numerical implementation of multiple hard scatterings that resums all terms in the opacity expansion beyond the Gaussian approximation. We find significant differences in the extracted medium parameters when comparing with two of the most used approximations in phenomenological analyses to date, the first order opacity expansion and the Gaussian approximation. We also make a first attempt to compare the extracted medium parameters with lattice results.

    hep-phnucl-thPoS(2021)·0 citations
12. 12*

    Sub-TeV Singlet Scalar Dark Matter and Electroweak Vacuum Stability with Vector Like Fermions

    Debasish Borah🇮🇳 · Rishav Roshan🇮🇳 · Arunansu Sil🇮🇳

    We study a scalar singlet dark matter (DM) having mass in sub-TeV regime by extending the minimal scalar singlet DM setup by additional vector like fermions. While the minimal scalar singlet DM satisfies the relic and direct detection constraints for mass beyond TeV only, presence of its portal coupling with vector like fermions opens up additional co-annihilation channels. These vector like fermions also help in achieving electroweak vacuum stability all the way up to Planck scale. We find that for one generation of vector like quarks consisting of a $SU(2{)}_L$ doublet and a singlet, scalar singlet DM with mass a few hundred GeV can indeed satisfy relic, direct detection and other relevant constraints while also making the electroweak vacuum absolutely stable. The same can be achieved by introducing vector like leptons too, but with three generations. While the model with vector like quarks is minimal, the three generations of vector like lepton doublet and neutral singlet can also give rise to light neutrino mass at one loop level.

    hep-phPRD(2020)·16 citations
13. 13*

    Neutrinoless Double-Electron Capture

    K. Blaum🇩🇪 · S. Eliseev🇩🇪 · F. A. Danevich🇺🇦 · V. I. Tretyak🇺🇦 · Sergey Kovalenko🇨🇱 · M. I. Krivoruchenko🇷🇺 · Yu. N. Novikov🇷🇺 · J. Suhonen🇫🇮

    Double-beta processes play a key role in the exploration of neutrino and weak interaction properties, and in the searches for effects beyond the Standard Model. During the last half century many attempts were undertaken to search for double-beta decay with emission of two electrons, especially for its neutrinoless mode ($0\nu 2{\beta }^{-}$), the latter being still not observed. Double-electron capture (2EC) was not in focus so far because of its in general lower transition probability. However, the rate of neutrinoless double-electron capture ($0\nu 2$EC) can experience a resonance enhancement by many orders of magnitude in case the initial and final states are energetically degenerate. In the resonant case, the sensitivity of the $0\nu 2$EC process can approach the sensitivity of the $0\nu 2{\beta }^{-}$ decay in the search for the Majorana mass of neutrinos, right-handed currents, and other new physics. We present an overview of the main experimental and theoretical results obtained during the last decade in this field. The experimental part outlines search results of 2EC processes and measurements of the decay energies for possible resonant $0\nu$2EC transitions. An unprecedented precision in the determination of decay energies with Penning traps has allowed one to refine the values of the degeneracy parameter for all previously known near-resonant decays and has reduced the rather large uncertainties in the estimate of the $0\nu 2$EC half-lives. The theoretical part contains an updated analysis of the electron shell effects and an overview of the nuclear structure models, in which the nuclear matrix elements of the $0\nu 2$EC decays are calculated. One can conclude that the decay probability of $0\nu$2EC can experience a significant enhancement in several nuclides.

    hep-phnucl-exnucl-thphysics.atom-phRMP(2020)·68 citations
14. 14*

    Photon radiation from quark-gluon plasma by means of chiral anomalies without magnetic field

    Kirill Tuchin🇺🇸

    We discuss a new channel of photon emission from the quark-gluon plasma, which opens up as photon acquires a tachyonic mass in the presence of the CP-odd topological domains generated by the chiral anomaly. It allows photon radiation through the decay $q\to q\gamma$ and annihilation $q\bar{q}\to \gamma$ processes closely related to the chiral Cherenkov radiation. Unlike previous proposals this mechanism does not require an external magnetic field. The differential photon emission rate per unit volume is computed and shown to be comparable to the rate of photon emission in conventional processes.

    hep-phnucl-thPoS(2021)·0 citations
15. 15*

    Dynamics of QCD Matter -- current status

    Amaresh Jaiswal🇮🇳 · Najmul Haque🇮🇳 · Aman Abhishek🇮🇳 · Raktim Abir🇮🇳 · Aritra Bandyopadhyay🇧🇷 · Khatiza Banu🇮🇳 · Samapan Bhadury🇮🇳 · Sumana Bhattacharyya🇮🇳 · Trambak Bhattacharyya🇷🇺 · Deeptak Biswas🇮🇳 · H. C. Chandola🇮🇳 · Vinod Chandra🇮🇳 and 49 other authors

    In this article, there are 18 sections discussing various current topics in the field of relativistic heavy-ion collisions and related phenomena, which will serve as a snapshot of the current state of the art. Section 1 reviews experimental results of some recent light-flavored particle production data from ALICE collaboration. Other sections are mostly theoretical in nature. Very strong but transient magnetic field created in relativistic heavy-ion collisions could have important observational consequences. This has generated a lot of theoretical activity in the last decade. Sections 2, 7, 9, 10 and 11 deal with the effects of the magnetic field on the properties of the QCD matter. There are several unanswered questions about the QCD phase diagram. Sections 3, 11 and 18 discuss various aspects of the QCD phase diagram and phase transitions. Recent years have witnessed interesting developments in foundational aspects of hydrodynamics and their application to heavy-ion collisions. Sections 12, 15, 16 and 17 of this article probe some aspects of this exciting field. Transport coefficients together with their temperature- and density-dependence, are essential inputs in hydrodynamical calculations. Sections 5, 8 and 14 deal with calculation/estimation of various transport coefficients (shear and bulk viscosity, thermal conductivity, relaxation times, etc.) of quark matter and hadronic matter. Sections 4, 6 and 13 deals with interesting new developments in the field. Section 4 discusses color dipole gluon distribution function at small transverse momentum in the form of a series of Bells polynomials. Section 6 discusses the properties of Higgs boson in the quark gluon plasma using Higgs-quark interaction. Section 13 discusses modification of coalescence model to incorporate viscous corrections and application of this model.

    hep-phhep-exnucl-thIJMPE(2021)·39 citations
16. 16*

    Higgs inflation in Einstein-Cartan gravity

    Mikhail Shaposhnikov🇨🇭 · Andrey Shkerin🇨🇭 · Inar Timiryasov🇨🇭 · Sebastian Zell🇨🇭

    We study inflation driven by the Higgs field in the Einstein-Cartan formulation of gravity. In this theory, the presence of the Holst and Nieh-Yan terms with the Higgs field non-minimally coupled to them leads to three additional coupling constants. For a broad range of parameters, we find that inflation is both possible and consistent with observations. In most cases, the spectral index is given by $n_s=1-2/N_{\star }$ (with $N_{\star }$ the number of e-foldings) whereas the tensor-to-scalar ratio $r$ can vary between about $10^{-10}$ and $1$. Thus, there are scenarios of Higgs inflation in the Einstein-Cartan framework for which the detection of gravitational waves from inflation is possible in the near future. In certain limits, the known models of Higgs inflation in the metric and Palatini formulations of gravity are reproduced. Finally, we discuss the robustness of inflationary dynamics against quantum corrections due to the scalar and fermion fields.

    hep-phastro-ph.COgr-qchep-thJCAP(2021)·100 citations
17. 17*

    Dark Matter Spectra from the Electroweak to the Planck Scale

    Christian W. Bauer🇺🇸 · Nicholas L. Rodd🇺🇸 · Bryan R. Webber🇬🇧

    We compute the decay spectrum for dark matter (DM) with masses above the scale of electroweak symmetry breaking, all the way to the Planck scale. For an arbitrary hard process involving a decay to the unbroken standard model, we determine the prompt distribution of stable states including photons, neutrinos, positrons, and antiprotons. These spectra are a crucial ingredient in the search for DM via indirect detection at the highest energies as being probed in current and upcoming experiments including IceCube, HAWC, CTA, and LHAASO. Our approach improves considerably on existing methods. For example, we include all relevant electroweak interactions. The importance of these effects grow with DM mass, and by an EeV our spectra can differ by orders of magnitude from existing results.

    hep-phastro-ph.COastro-ph.HEJHEP(2021)·174 citations
18. 18*

    Boosted Neutrinos and Relativistic Dark Particles as Messengers from Reheating

    Joerg Jaeckel🇩🇪 · Wen Yin🇯🇵

    Usually information from early eras such as reheating is hard to come by. In this paper we argue that, given the right circumstances, right-handed sterile neutrinos decaying to left-handed active ones at relatively late times can carry information from reheating by propagating freely over the thermal history. For not too small mixing angles, suitable right-handed neutrino masses are around $\mathcal{O}$(MeV-GeV). We identify the typical spectra and argue that they provide information on the ratio of the inflaton mass to the reheating temperature. This primordial neutrino signal can be strong enough that it can be detected in IceCube. More speculatively, for a reheating temperature and inflaton mass satisfying $T_R=\mathcal{O}(1-100)\mathrm{MeV}$, and $m_{\varphi }=\mathcal{O}(10^{16-19})$GeV they may even explain the observed PeV events. Also more general relativistic dark particles can play the role of such messengers, potentially not only allowing for the PeV events but also alleviating the $H_0$-tension .

    hep-phastro-ph.COJCAP(2021)·36 citations
19. 19*

    $\chi$aro$\nu$: a tool for neutrino flux generation from WIMPs

    Qinrui Liu🇺🇸 · Jeffrey Lazar🇺🇸 · Carlos A. Argüelles🇺🇸 · Ali Kheirandish🇺🇸

    Indirect searches for signatures of corpuscular dark matter have been performed using all cosmic messengers: gamma rays, cosmic rays, and neutrinos. The search for dark matter from neutrinos is of particular importance since they are the only courier that can reach detectors from dark matter processes in dense environments, such as the core of the Sun or Earth, or from the edge of the observable Universe. In this work, we introduce $\chi$aro$\nu$, a software package that, in the spirit of its mythological Greek namesake $\chi \acute{\alpha }\rho \omega \nu$, bridges the dark sector and Standard Model by predicting neutrino fluxes from different celestial dark matter agglomerations. The flux at the point of production is either computed internally by $\chi$aro$\nu$ or is taken from user supplied tables. $\chi$aro$\nu$ then propagates this flux through vacuum or dense media and returns the expected neutrino yield at an observer's location. In developing $\chi$aro$\nu$, we have revisited and updated the production of neutrinos in dense media, updated the propagation of high-energy neutrinos, and studied the sources of uncertainty in neutrino transport. This package is coupled to a new calculation that includes electroweak corrections resulting in the most up-to-date and complete repository of neutrino fluxes from dark matter decay and annihilation over the energy range of 1 GeV to 10 PeV coming from the Earth, the Sun, and the Galactic halo.

    hep-phastro-ph.HEJCAP(2020)·54 citations
20. 20*

    Impact of fermionic operators on the Higgs width measurement

    Eduardo da Silva Almeida🇧🇷 · Oscar J. P. Éboli🇧🇷 · M. C. Gonzalez-Garcia🇺🇸

    The off-shell Higgs production in pp -> ZZ at LHC provides at present the most direct measurement of the Higgs width in the absence of beyond the standard model contributions. Here, we analyze the impact of anomalous Z couplings to fermions on the Higgs width determination. We show that, despite these couplings being strongly constrained by the available electroweak precision data, they can substantially affect the Higgs width determination at the LHC Runs 2 and 3. Conversely, in larger integrated luminosities runs, such as those foreseen at the high luminosity LHC and high energy LHC setups, the effect of such anomalous interactions in the Higgs width measurement is minimal.

    hep-phPRD(2020)·1 citation
21. 21*

    Fully exclusive heavy quark-antiquark pair production from a colourless initial state at NNLO in QCD

    Gábor Somogyi🇭🇺 · Francesco Tramontano🇮🇹

    We present a local subtraction scheme for computing next-to-next-to-leading order QCD corrections to the production of a massive quark-antiquark pair from a colourless initial state. The subtraction terms are built following the CoLoRFulNNLO method and refined in such a way that their integration gives rise to compact, fully analytic expressions. All ingredients necessary for a numerical implementation of our subtraction scheme are provided in detail. As an example, we calculate the fully differential decay rate of the Standard Model Higgs boson to massive bottom quarks at next-to-next-to-leading order accuracy in perturbative QCD.

    hep-phhep-thJHEP(2020)·20 citations
22. 22*

    Anomalies and accidental symmetries: charging the scalar leptoquark under $L_{\mu }$-$L_{\tau }$

    Joe Davighi🇬🇧 · Matthew Kirk🇮🇹 · Marco Nardecchia🇮🇹

    While the $S_3$ scalar leptoquark presents a possible tree-level explanation of the $b\to s\ell \ell$ flavour anomalies, it suffers from two conceptual problems which are often disregarded by model-builders. Firstly, the quantum numbers of the $S_3$ allow for a renormalisable diquark operator that would trigger rapid proton decay unless its coupling were tuned away. Secondly, one expects the leptoquark to have generic couplings to leptons, which require tuning to avoid stringent experimental bounds on lepton flavour violation. By gauging a $U(1)$ current that acts as $L_{\mu }-L_{\tau }$ on the Standard Model (SM) fermions, and under which the leptoquark has charge $-1$, one can remedy both these problems. The additional $U(1)$, which is spontaneously broken at some high scale, is associated with a massive $Z^{\prime }$ gauge boson and a scalar SM singlet $\Phi$, which play no direct role in mediating the anomalous $B$ meson decays. By computing one- and two-loop mass corrections, we show that this pair of particles can be hidden away at much higher mass scales without destabilising either the Higgs or the leptoquark masses. The only low-energy relic of gauging $L_{\mu }-L_{\tau }$ is thus the accidental global symmetry structure of the lagrangian. On the other hand, we find quite generally that an $S_3$ leptoquark that mediates the $b\to s\ell \ell$ anomalies cannot be much heavier than a few TeV without itself inducing large Higgs mass corrections.

    hep-phJHEP(2020)·38 citations
23. 23*

    The LPM effect in sequential bremsstrahlung: nearly complete results for QCD

    Peter Arnold🇺🇸 · Tyler Gorda🇺🇸 · Shahin Iqbal🇨🇳

    The splitting processes of bremsstrahlung and pair production in a medium are coherent over large distances in the very high energy limit, which leads to a suppression known as the Landau-Pomeranchuk-Migdal (LPM) effect. We continue study of the case when the coherence lengths of two consecutive splitting processes overlap (which is important for understanding corrections to standard treatments of the LPM effect in QCD), avoiding soft-emission approximations. Previous work has computed overlap effects for double splitting $g\to gg\to ggg$. To make use of those results, one also needs calculations of related virtual loop corrections to single splitting $g\to gg$ in order to cancel severe (power-law) infrared (IR) divergences. This paper provides calculations of nearly all such processes involving gluons and discusses how to organize the results to demonstrate the cancellation. In the soft emission limit, our results reproduce the known double-log behavior of earlier authors who worked in leading-log approximation. We also present a first (albeit numerical and not yet analytic) investigation of sub-leading, single IR logarithms. Ultraviolet divergences appearing in our calculations correctly renormalize the coupling ${\alpha }_{\mathrm{s}}$ in the usual LPM result for leading-order $g\to gg$.

    hep-phnucl-thJHEP(2020)·46 citations
24. 24*

    Precision Higgs Couplings in Neutral Naturalness Models: an Effective Field Theory Approach

    Lucien Heurtier🇺🇸 · Hao-Lin Li🇨🇳 · Huayang Song🇺🇸 · Shufang Su🇺🇸 · Wei Su🇦🇺 · Jiang-Hao Yu🇨🇳

    The Higgs sector in neutral naturalness models provides a portal to the hidden sectors, and thus measurements of Higgs couplings at current and future colliders play a central role in constraining the parameter space of the model. We investigate a class of neutral naturalness models, in which the Higgs boson is a pseudo-Goldstone boson from the universal SO(N)/SO(N-1) coset structure. Integrating out the radial mode from the spontaneous global symmetry breaking, we obtain various dimension-six operators in the Standard Model effective field theory, and calculate the low energy Higgs effective potential with radiative corrections included. We perform a chi-square fit to the Higgs coupling precision measurements at current and future colliders and show that the new physics scale could be explored up to 2.7 (2.8) TeV without (with) the Higgs invisible decay channels at future Higgs factories.

    hep-phhep-exJHEP(2021)·2 citations
25. 25*

    Heavy flavor and jet studies for the future Electron-Ion Collider

    Xuan Li🇺🇸

    The proposed high luminosity high energy Electron-Ion Collider (EIC) will explore the proton/nuclear structure in a wide Bjorken-x ($x_{BJ}$) and $Q^2$ phase space. Heavy flavor products are generated in initial collisions and have their hadronization influenced by the nuclear medium. Heavy flavor hadron and jet measurements at the future EIC will allow us to better constrain the nPDFs especially in the poorly constrained high $x_{BJ}$ region, precisely determine the quark/gluon fragmentation processes and directly study the quark/gluon energy loss within the nuclear medium. These measurements can constrain the cold nuclear medium effects for previous and ongoing heavy ion measurements at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). Silicon vertex/tracking detectors are essential to realize the heavy flavor and jet measurements at the EIC. Feasibility studies in simulation for proposed heavy flavor and jet observable with evaluated detector performance at the future EIC will be discussed.

    ↳ hep-exhep-phnucl-exPoS(2021)·7 citations
26. 26*

    The Large Hadron-Electron Collider at the HL-LHC

    P. Agostini🇪🇸 · H. Aksakal🇹🇷 · S. Alekhin🇩🇪 · P. P. Allport🇬🇧 · N. Andari🇫🇷 · K. D. J. Andre🇬🇧 · D. Angal-Kalinin🇬🇧 · S. Antusch🇨🇭 · L. Aperio Bella🇨🇳 · L. Apolinario🇵🇹 · R. Apsimon🇬🇧 · A. Apyan🇦🇲 and 325 other authors

    The Large Hadron electron Collider (LHeC) is designed to move the field of deep inelastic scattering (DIS) to the energy and intensity frontier of particle physics. Exploiting energy recovery technology, it collides a novel, intense electron beam with a proton or ion beam from the High Luminosity--Large Hadron Collider (HL-LHC). The accelerator and interaction region are designed for concurrent electron-proton and proton-proton operation. This report represents an update of the Conceptual Design Report (CDR) of the LHeC, published in 2012. It comprises new results on parton structure of the proton and heavier nuclei, QCD dynamics, electroweak and top-quark physics. It is shown how the LHeC will open a new chapter of nuclear particle physics in extending the accessible kinematic range in lepton-nucleus scattering by several orders of magnitude. Due to enhanced luminosity, large energy and the cleanliness of the hadronic final states, the LHeC has a strong Higgs physics programme and its own discovery potential for new physics. Building on the 2012 CDR, the report represents a detailed updated design of the energy recovery electron linac (ERL) including new lattice, magnet, superconducting radio frequency technology and further components. Challenges of energy recovery are described and the lower energy, high current, 3-turn ERL facility, PERLE at Orsay, is presented which uses the LHeC characteristics serving as a development facility for the design and operation of the LHeC. An updated detector design is presented corresponding to the acceptance, resolution and calibration goals which arise from the Higgs and parton density function physics programmes. The paper also presents novel results on the Future Circular Collider in electron-hadron mode, FCC-eh, which utilises the same ERL technology to further extend the reach of DIS to even higher centre-of-mass energies.

    ↳ hep-exhep-phnucl-exnucl-thJ.Phys.G(2021)·442 citations
27. 27*

    Strange hadron production in a quark combination model in Au+Au collisions at RHIC energies

    Jun Song🇨🇳 · Xiao-feng Wang🇨🇳 · Hai-hong Li🇨🇳 · Rui-qin Wang🇨🇳 · Feng-lan Shao🇨🇳

    We apply a quark combination model to study yield densities and transverse momentum ($p_T$) spectra of strange (anti-)hadrons at mid-rapidity in central Au+Au collisions at $\sqrt{s_{NN}}=$ 7.7, 11.5, 19.6, 27, 39 and 200 GeV. We show that experimental data for $p_T$ spectra of (anti-)hadrons in these collisions can be systematically described by the equal velocity combination of constituent quarks and antiquarks at hadronization. We obtain $p_T$ spectra of quarks and antiquarks at hadronization and study their collision energy dependence. We also reproduce the yield densities of hadrons and anti-hadrons. In particular, we demonstrate that yield ratios of anti-hadrons to hadrons $K^{-}/K^{+}$, $\bar{p}/p$, $\bar{\Lambda }/\Lambda$, ${\bar{\Xi }}^{+}/{\Xi }^{-}$ and ${\bar{\Omega }}^{+}/{\Omega }^{-}$ simply correlate with each other and their experimental data except ${\bar{\Omega }}^{+}/{\Omega }^{-}$ at $\sqrt{s_{NN}}=$ 7.7 GeV are systematically described by the model. These results suggest that the equal velocity combination mechanism for quarks and antiquarks at hadronization plays an important role in Au+Au collisions at low RHIC energies ($\sqrt{s_{NN}}\ge$ 11.5 GeV).

    ↳ nucl-thhep-phPRC(2021)·13 citations
28. 28*

    Reproductive Freeze-In of Self-Interacting Dark Matter

    John March-Russell🇬🇧 · Hannah Tillim🇬🇧 · Stephen M. West🇬🇧

    We present a mechanism for dark matter (DM) production involving a self-interacting sector that at early times is ultra-relativistic but far-underpopulated relative to thermal equilibrium (such initial conditions often arise, e.g., from inflaton decay). Although elastic scatterings can establish kinetic equilibrium we show that for a broad variety of self-interactions full equilibrium is never established despite the DM yield significantly evolving due to $2\to k$ ($k>2$) processes (the DM carries no conserved quantum number nor asymmetry). During the active phase of the process, the DM to Standard Model temperature ratio falls rapidly, with DM kinetic energy being converted to DM mass, the inverse of the recently-discussed `cannibal DM mechanism'. Potential observables and applications include self-interacting DM signatures in galaxies and clusters, dark acoustic oscillations, the alteration of free-streaming constraints, and possible easing of ${\sigma }_8$ and Hubble tensions.

    ↳ astro-ph.COhep-phPRD(2020)·19 citations
29. 29*

    Constraints on Primordial Power Spectrum from Galaxy Luminosity Functions

    Shintaro Yoshiura🇦🇺 · Masamune Oguri🇯🇵 · Keitaro Takahashi🇯🇵 · Tomo Takahashi🇯🇵

    We derive constraints on primordial power spectrum, for the first time, from galaxy UV luminosity functions (LFs) at high redshifts. Since the galaxy LFs reflect an underlying halo mass function which depends on primordial fluctuations, one can constrain primordial power spectrum, particularly on small scales. We perform a Markov Chain Monte Carlo analysis by varying parameters for primordial power spectrum as well as those describing astrophysics. We adopt the UV LFs derived from Hubble Frontier Fields data at $z=6-10$, which enable us to probe primordial fluctuations on the scales of $k\sim 10-10^3{\mathrm{Mpc}}^{-1}$. Our analysis also clarifies how the assumption on cosmology such as primordial power spectrum affects the determination of astrophysical parameters.

    ↳ astro-ph.COgr-qchep-phPRD(2020)·25 citations
30. 30*

    Detecting the Diffuse Supernova Neutrino Background in the future Water-based Liquid Scintillator Detector Theia

    Julia Sawatzki🇩🇪 · Michael Wurm🇩🇪 · Daniel Kresse🇩🇪

    A large-scale neutrino observatory based on Water-based Liquid Scintillator (WbLS) will be excellently suited for a measurement of the Diffuse Supernova Neutrino Background (DSNB). The WbLS technique offers high signal efficiency and effective suppression of the otherwise overwhelming background from neutral-current interactions of atmospheric neutrinos. To illustrate this, we investigate the DSNB sensitivity for two configurations of the future Theia detector by developing the expected signal and background rejection efficiencies along a full analysis chain. Based on a statistical analysis of the remaining signal and background rates, we find that a rather moderate exposure of 190kt$\cdot$yrs will be sufficient to claim a ($5\sigma$) discovery of the faint DSNB signal for standard model assumptions. We conclude that, in comparison with other experimental techniques, WbLS offers the highest signal efficiency of more than 80\% and best signal significance over background.

    ↳ physics.ins-detastro-ph.IMhep-exhep-phPRD(2021)·37 citations
31. 31*

    Gauging scale symmetry and inflation: Weyl versus Palatini gravity

    D. M. Ghilencea🇷🇴

    We present a comparative study of inflation in two theories of quadratic gravity with {\it gauged} scale symmetry: 1) the original Weyl quadratic gravity and 2) the theory defined by a similar action but in the Palatini approach obtained by replacing the Weyl connection by its Palatini counterpart. These theories have different vectorial non-metricity induced by the gauge field ($w_{\mu }$) of this symmetry. Both theories have a novel spontaneous breaking of gauged scale symmetry, in the absence of matter, where the necessary scalar field is not added ad-hoc to this purpose but is of geometric origin and part of the quadratic action. The Einstein-Proca action (of $w_{\mu }$), Planck scale and metricity emerge in the broken phase after $w_{\mu }$ acquires mass (Stueckelberg mechanism), then decouples. In the presence of matter (${\varphi }_1$), non-minimally coupled, the scalar potential is similar in both theories up to couplings and field rescaling. For small field values the potential is Higgs-like while for large fields inflation is possible. Due to their $R^2$ term, both theories have a small tensor-to-scalar ratio ($r\sim 10^{-3}$), larger in Palatini case. For a fixed spectral index $n_s$, reducing the non-minimal coupling (${\xi }_1$) increases $r$ which in Weyl theory is bounded from above by that of Starobinsky inflation. For a small enough ${\xi }_1\le 10^{-3}$, unlike the Palatini version, Weyl theory gives a dependence $r(n_s)$ similar to that in Starobinsky inflation, while also protecting $r$ against higher dimensional operators corrections.

    ↳ hep-thastro-ph.COgr-qchep-phEPJC(2021)·83 citations
32. 32*

    Simple relativistic quark models

    Sirajudheen Kuthini Kunhammed🇺🇸 · W. N. Polyzou🇺🇸

    A class of phenomenological relativistic models of hadronic systems motivated by QCD that have dual representations as models of mesons and nucleons or quarks and gluons is investigated. These models are designed to provided qualitative insight into the role of sea quarks in hadronic structure and reactions. The model assumption is that the Hamiltonian can be divided into two parts; one that involves degrees of freedom in the same connected local and global color singlet and the remaining interactions that allow the connected local and global color singlets to interact. The first class of interactions results in infinite towers of bare "particles" with hadronic quantum numbers. All but a finite number of these remain stable when the second class of interactions is included. The model interactions are expressed in terms of sub-hadronic degrees of freedom, which determine the bare hadronic spectrum and the interactions involving the bare hadrons in terms of a small number of sub-hadronic model parameters. As a first test, this paper considers the simplest case of mesons that interact via a string-breaking interaction. One virtue of this model is that all of the bare meson masses and eigenfunctions can be computed analytically. In addition, the string breaking interaction leads to production vertices that can also be computed analytically. The relativistic wave functions have a light-front kinematic symmetry. The goal is to find a simple relativistic quantum mechanical model based on sub-hadronic degrees of freedom that can provide an efficient, qualitatively consistent description of hadronic masses, lifetimes, cross sections, sea quark effects, and electromagnetic properties. The simplicity of the model makes it a potentially useful tool to study the impact of sea quarks on hadronic structure and reactions.

    ↳ nucl-thhep-phPRC(2020)·4 citations
33. 33*

    Strangeonium-like hybrids on the lattice

    Yunheng Ma🇨🇳 · Ying Chen🇨🇳 · Ming Gong🇨🇳 · Zhaofeng Liu🇨🇳

    The strangeonium-like $s\bar{s}g$ hybrids are investigated from lattice QCD in the quenched approximation. In the Coulomb gauge, spatially extended operators are constructed for $1^{--}$ and $(0,1,2{)}^{-+}$ states with the color octet $s\bar{s}$ component being separated from the chromomagnetic field strength by spatial distances $r$, whose matrix elements between the vacuum and the corresponding states are interpreted as Bethe-Salpeter (BS) wave functions. In each of the $(1,2{)}^{-+}$ channels, the masses and the BS wave functions are reliably derived. The $1^{-+}$ ground state mass is around 2.1-2.2 GeV, and that of $2^{-+}$ is around 2.3-2.4 GeV, while the masses of the first excited states are roughly 1.4 GeV higher. This mass splitting is much larger than the expectation of the phenomenological flux-tube model or constituent gluon model for hybrids, which is usually a few hundred MeV. The BS wave functions with respect to $r$ show clear radial nodal structures of non-relativistic two-body system, which imply that $r$ is a meaningful dynamical variable for these hybrids and motivate a color halo picture of hybrids that the color octet $s\bar{s}$ is surrounded by gluonic degrees of freedom. In the $1^{--}$ channel, the properties of the lowest two states comply with those of $\varphi (1020)$ and $\varphi (1680)$. We have not obtained convincing information relevant to $\varphi (2170)$ yet, however, we argue that whether $\varphi (2170)$ is a conventional $s\bar{s}$ meson or a $s\bar{s}g$ hybrid within the color halo scenario, the ratio of partial decay widths $\Gamma (\varphi \eta )$ and $\Gamma (\varphi {\eta }^{\prime })$ observed by BESIII can be understood by the mechanism of hadronic transition of a strangeonium-like meson along with the $\eta -{\eta }^{\prime }$ mixing.

    ↳ hep-lathep-exhep-phCPC(2021)·21 citations
34. 34*

    A GPU based multidimensional amplitude analysis to search for tetraquark candidates

    Nairit Sur🇮🇳 · Leonardo Cristella🇮🇹 · Adriano Di Florio🇮🇹 · Vincenzo Mastrapasqua🇮🇹

    The demand for computational resources is steadily increasing in experimental high energy physics as the current collider experiments continue to accumulate huge amounts of data and physicists indulge in more complex and ambitious analysis strategies. This is especially true in the fields of hadron spectroscopy and flavour physics where the analyses often depend on complex multidimensional unbinned maximum-likelihood fits, with several dozens of free parameters, with an aim to study the internal structure of hadrons. Graphics processing units (GPUs) represent one of the most sophisticated and versatile parallel computing architectures that are becoming popular toolkits for high energy physicists to meet their computational demands. GooFit is an upcoming open-source tool interfacing ROOT/RooFit to the CUDA platform on NVIDIA GPUs that acts as a bridge between the MINUIT minimization algorithm and a parallel processor, allowing probability density functions to be estimated on multiple cores simultaneously. In this article, a full-fledged amplitude analysis framework developed using GooFit is tested for its speed and reliability. The four-dimensional fitter framework, one of the firsts of its kind to be built on GooFit, is geared towards the search for exotic tetraquark states in the $B^0\to J/\psi K\pi$ decays and can also be seamlessly adapted for other similar analyses. The GooFit fitter, running on GPUs, shows a remarkable improvement in the computing speed compared to a ROOT/RooFit implementation of the same analysis running on multi-core CPU clusters. Furthermore, it shows sensitivity to components with small contributions to the overall fit. It has the potential to be a powerful tool for sensitive and computationally intensive physics analyses.

    ↳ physics.data-anhep-exhep-phJ.Big Data(2021)·0 citations
35. 35*

    Effective anisotropic stresses of the relic gravitons

    Massimo Giovannini🇨🇭

    The effective anisotropic stresses induced by the scalar modes of the geometry depend on the coordinate system so that the comparison of the competing results is ultimately determined by the evolution of the pivotal variables in each particular gauge. After arguing that the only reasonable physical coordinate systems for this problem are the ones where the gauge freedom is completely fixed (like the longitudinal and the uniform curvature gauges), we propose a novel gauge-invariant strategy for the comparison of gauge-dependent results. Instead of employing the pivotal variables of a given coordinate system, the effective anisotropic stress is solely expressed in terms of the gravitating normal modes of the plasma and in terms of their conformal time derivatives. The new approach is explicitly gauge-invariant and when the wavelengths of the normal modes are either shorter or larger than the sound horizon, the physical limits of the anisotropic stresses are determined without relying on the specific details of the background evolution. The relevance of the proposed strategy is discussed in the general situation where the scalar anisotropic stress and the non-adiabatic pressure fluctuations are simultaneously present. We finally argue that the anisotropic stress can be most efficiently obtained from the second-order effective action of the curvature inhomogeneities.

    ↳ hep-thastro-ph.COgr-qchep-phInt.J.Mod.Phys.D(2020)·6 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.