HEP Phenomenology·hep-ph

Tue·May 5, 2020Tuesday·May 5, 2020

42 papers—30 primary·12 cross-listed·reconstructed*

01*
Effective field theory for double heavy baryons at strong coupling
Joan Soto🇪🇸 · Jaume Tarrús Castellà🇪🇸
We present an effective field theory for doubly heavy baryons that goes beyond the compact heavy diquark approximation. The heavy-quark distance $r$ is only restricted to $m_{Q} ≫ 1/ r ≫ E_{bin}$ , where $m_{Q}$ is the mass of the heavy quark and $E_{bin}$ the typical binding energy. This means that the size of the heavy diquark can be as large as the typical size of a light hadron. We start from Non-Relativistic QCD, and build the effective field theory at next-to-leading in the $1/ m_{Q}$ expansion. At leading order the effective field theory reduces to the Born-Oppenheimer approximation. The BO potentials are obtained from available lattice QCD data. The spectrum for double charm baryons below threshold is compatible with most of the lattice QCD results. We present for the first time the full spin averaged double bottom baryon spectrum below threshold based on QCD. We also present model-independent formulas for the spin splittings.
hep-phhep-exhep-latPRD(2020)·35 citations
02*
Nonrelativistic effective field theory for heavy exotic hadrons
Joan Soto🇪🇸 · Jaume Tarrús Castellà🇪🇸
We propose an effective field theory to describe hadrons with two heavy quarks without any assumption on the typical distance between the heavy quarks with respect to the typical hadronic scale. The construction is based on Non-Relativistic QCD and inspired in the strong coupling regime of Potential Non-Relativistic QCD. We construct the effective theory at leading and next-to-leading order in the inverse heavy-quark mass expansion for arbitrary quantum numbers of the light degrees of freedom. Hence our results hold for hybrids, tetraquarks, double heavy baryons and pentaquarks, for which we also present the corresponding operators at Non-Relativistic level. At leading order, the effective theory enjoys heavy quark spin symmetry and corresponds to the Born-Oppenheimer approximation. At next-to-leading order, spin and velocity dependent terms arise, which produce splittings in the heavy-quark spin symmetry multiplets. A concrete application to double heavy baryons is presented in an accompanying paper.
hep-phhep-exhep-latPRD(2020)·58 citations
03*
SModelS database update v1.2.3
Charanjit K. Khosa🇬🇧 · Sabine Kraml🇫🇷 · Andre Lessa🇧🇷 · Philipp Neuhuber🇦🇹 · Wolfgang Waltenberger🇦🇹
We present an update of the SModelS database with simplified model results from 13 ATLAS and 10 CMS searches for supersymmetry at Run 2. This includes 5 ATLAS and 1 CMS analyses for full Run 2 luminosity, i.e. close to 140/fb of data. In total, 76 official upper limit and efficiency map results have been added. Moreover, 21 efficiency map results have been produced by us using MadAnalysis5, to improve the coverage of gluino-squark production. The constraining power of the new database, v1.2.3, is compared to that of the previous release, v1.2.2. SModelS v1.2.3 is publicly available and can readily be employed for physics studies.
hep-phhep-exLHEP(2020)·56 citations
04*
Dynamical Symmetry Breaking and Fermion Mass Hierarchy in the Scale-Invariant 3-3-1 Model
Alex G. Dias🇧🇷 · Julio Leite🇧🇷 · B. L. Sánchez-Vega🇧🇷 · William C. Vieira🇧🇷
We propose an extension of the Standard Model (SM) based on the $S U (3)_{C} \otimes S U (3)_{L} \otimes U (1)_{X}$ (3-3-1) gauge symmetry and scale invariance. Maintaining the main features of the so-called 3-3-1 models, such as the cancellation of gauge anomalies related to the number of chiral fermion generations, this model exhibits a very compact scalar sector. Only two scalar triplets and one singlet are necessary and sufficient to break the symmetries dynamically via the Coleman-Weinberg mechanism. With the introduction of an Abelian discrete symmetry and assuming a natural hierarchy among the vacuum expectation values of the neutral scalar fields, we show that all particles in the model can get phenomenologically consistent masses. In particular, most of the standard fermion masses are generated via a seesaw mechanism involving some extra heavy fermions introduced for consistency. This mechanism provides a partial solution for the fermion mass hierarchy problem in the SM. Furthermore, the simplicity of the scalar sector allows us to analytically find the conditions for the potential stability up to one-loop level and show how they can be easily satisfied. Some of the new particles, such as the scalars $H$ , $H^{\pm}$ and all the non-SM vector bosons, are predicted to get masses around the TeV scale and, therefore, could be produced at the high-luminosity LHC. Finally, we show that the model features a residual symmetry which leads to the stability of a heavy neutral particle; the latter is expected to show up in experiments as missing energy.
hep-phPRD(2020)·10 citations
05*
Top-quark pair hadroproduction at NNLO: differential predictions with the MSbar mass
Stefano Catani🇮🇹 · Simone Devoto🇨🇭 · Massimiliano Grazzini🇨🇭 · Stefan Kallweit🇮🇹 · Javier Mazzitelli🇩🇪
We consider top-quark pair production at the LHC within the MSbar scheme for the renormalisation of the top-quark mass, and we present predictions for total and differential cross sections at next-to-next-to-leading order (NNLO) in QCD. Our state-of-the-art calculation extends the available differential results by one order in the perturbative expansion, and it is relevant for a precise determination of the top-quark mass, including possible effects of the running mass in the MSbar scheme. We consider variations of the scale at which the MSbar mass of the top quark is evaluated, extending the usual 7-point to a 15-point scale variation. This additional variation is crucial for a reliable estimate of the theoretical uncertainties, especially at low perturbative orders and close to the production threshold of the top-quark pair. We also compute, for the first time, the invariant-mass distribution of the top-quark pair by using a running mass, evaluated at a dynamic scale. Our predictions for the invariant-mass distribution in the MSbar scheme are compared with a recent measurement performed by the CMS Collaboration. We observe that the inclusion of the NNLO corrections improves the agreement with the data, and we discuss effects due to the QCD running of the MSbar mass of the top quark.
hep-phhep-exJHEP(2020)·59 citations
06*
Probing Exotic Charged Higgs Decays in the Type-II 2HDM through Top Rich Signal at a Future 100 TeV pp Collider
Shuailong Li🇺🇸 · Huayang Song🇺🇸 · Shufang Su🇺🇸
The exotic decay modes of non-Standard Model Higgs bosons are efficient in probing the hierarchical Two Higgs Doublet Models (2HDM). In particular, the decay mode $H^{\pm} \to H W^{\pm}$ serves as a powerful channel in searching for charged Higgses. In this paper, we analyzed the reach for $H^{\pm} \to H W^{\pm} \to t t ˉ W$ at a 100 TeV $pp$ collider, and showed that it extends the reach of the previously studied $τ τ W$ final states once above the top threshold. Top tagging technique is used, in combination with the boosted decision tree classifier. Almost the entire hierarchical Type-II 2HDM parameter space can be probed via the combination of all channels at low $tan β$ region.
hep-phJHEP(2020)·16 citations
07*
Neutron Decay to a Non-Abelian Dark Sector
Fatemeh Elahi🇮🇷 · Mojtaba Mohammadi Najafabadi🇮🇷
According to the Standard Model (SM), we expect to find a proton for each decaying neutron. However, the experiments counting the number of decayed neutrons and produced protons have a disagreement. This discrepancy suggests that neutrons might have an exotic decay to a Dark Sector (DS). In this paper, we explore a scenario where neutrons decay to a dark Dirac fermion $χ$ and a non-abelian dark gauge boson $W^{'}$ . We discuss the cosmological implications of this scenario assuming DS particles are produced via freeze-in. In our proposed scenario, DS has three portals with the SM sector: (1) the fermion portal coming from the mixing of the neutron with $χ$ , (2) a scalar portal, and (3) a non-renormalizable kinetic mixing between photon and dark gauge bosons which induces a vector portal between the two sectors. We show that neither the fermion portal nor the scalar portal should contribute to the production of the particles in the early universe. Specifically, we argue that the maximum temperature of the universe must be low enough to prevent the production of $χ$ in the early universe. In this paper, we rely on the vector portal to connect the two sectors, and we discuss the phenomenological bounds on the model. The main constraints come from ensuring the right relic abundance of dark matter and evading the neutron star bounds. When dark gauge boson is very light, measurements of the Big Bang Nucleosynthesis impose a stringent constraint as well.
hep-phPRD(2020)·20 citations
08*
Imprint of a new light particle at KOTO?
Yi Liao (Nankai Uni and CHEP Peking Uni)🇨🇳 · Hao-Lin Wang (Nankai Uni)🇨🇳 · Chang-Yuan Yao (Nankai Uni)🇨🇳 · Jian Zhang (Nankai Uni)🇨🇳
Recently, the KOTO experiment reported their new preliminary result of searching for the decay $K_{L} \to π^{0} ν ν ˉ$ . Three candidate events were observed in the signal region, which exceed significantly the expectation based on the standard model. On the other hand, the new NA62 and previous BNL-E949 experiments yielded a consistent result and confirmed the standard model prediction in the charged meson decay $K^{+} \to π^{+} ν ν ˉ$ . Furthermore, the two decays are bound by a well-motivated relation from an analysis of isospin symmetry that is hard to break by the new physics of heavy particles. In this work, we study the issue by a systematic effective field theory approach with three of the simplest scenarios, in which the $K_{L}$ may decay into a new light neutral particle $X$ , i.e., $K_{L} \to π^{0} X$ , $K_{L} \to γ γ X$ , or $K_{L} \to π^{0} X X$ . We assess the feasibility of the scenarios by simulations and by incorporating constraints coming from NA62 and other relevant experiments. Our main conclusion is that the scenario $K \to π X X$ for a long lived scalar $X$ seems more credible than the other two when combining distributions and other experimental constraints while the region below the KOTO's blind box provides a good detection environment to search for all three scenarios for a relatively heavy $X$ .
hep-phhep-exPRD(2020)·18 citations
09*
On the mixing angle of the vector mesons $ω (782)$ and $ϕ (1020)$
M. K. Volkov🇷🇺 · A. A. Pivovarov🇷🇺 · K. Nurlan🇷🇺
In the present work, the mixing angle of the vector $ω (782)$ and $ϕ (1020)$ mesons is estimated in the framework of Nambu--Jona-Lasinio model. The decay $ϕ \to π^{0} γ$ is considered as a basic process to determine this angle. The obtained value is compared with the results of the other authors. Besides, the width of the decay $ϕ \to 3 π$ and the cross-section of the process $e^{+} e^{-} \to π^{0} ϕ$ are calculated by using this angle.
hep-phMod.Phys.Lett.A(2020)·8 citations
10*
Quark and lepton flavors with common modulus $τ$ in $A_{4}$ modular symmetry
Hiroshi Okada🇰🇷 · Morimitsu Tanimoto🇯🇵
We study quark and lepton mass matrices with the common modulus $τ$ in the $A_{4}$ modular symmetry. The viable quark mass matrices are composed of modular forms of weights $2$ , $4$ and $6$ . It is remarked that the modulus $τ$ is close to $i$ , which is a fixed point in the fundamental region of SL $(2, Z)$ , and the CP symmetry is not violated. Indeed, the observed CP violation is reproduced at $τ$ which is deviated a little bit from $τ = i$ . The charged lepton mass matrix is also given by using modular forms of weights $2$ , $4$ and $6$ , where five cases have been examined. The neutrino mass matrix is generated in terms of the modular forms of weight $4$ through the Weinberg operator. Lepton mass matrices are also consistent with the observed mixing angles at $τ$ close to $i$ for NH of neutrino masses. Allowed regions of $τ$ of quarks and leptons overlap each other for all cases of the charged lepton mass matrix. However, the sum of neutrino masses is crucial to test the common $τ$ for quarks and leptons. The minimal sum of neutrino masses $\sum m_{i}$ is $140$ meV at the common $τ$ . The inverted hierarchy of neutrino masses is unfavorable in our framework. It is emphasized that our result suggests the residual symmetry $Z_{2}^{S} = {I, S}$ in the quark and lepton mass matrices.
hep-phPhys.Dark Univ.(2023)·102 citations
11*
Corrections to Yukawa couplings from higher dimensional operators in a natural SUSY $SO (10)$ and HL-LHC implications
Amin Aboubrahim🇩🇪 · Pran Nath🇺🇸 · Raza M. Syed🇦🇪
We consider a class of unified models based on the gauge group $SO (10)$ which with appropriate choice of Higgs representations generate in a natural way a pair of light Higgs doublets needed to accomplish electroweak symmetry breaking. In this class of models higher dimensional operators of the form matter-matter-Higgs-Higgs in the superpotential after spontaneous breaking of the GUT symmetry generate contributions to Yukawa couplings which are comparable to the ones from cubic interactions. Specifically we consider an $SO (10)$ model with a sector consisting of $126 + 126 + 210$ of heavy Higgs which breaks the GUT symmetry down to the standard model gauge group and a sector consisting of $2 \times 10 + 120$ of light Higgs fields. In this model we compute the corrections from the quartic interactions to the Yukawa couplings for the top and the bottom quarks and for the tau lepton. It is then shown that inclusion of these corrections to the GUT scale Yukawas allows for consistency of the top, bottom and tau masses with experiment for low $tan β$ with a value as low as $tan β$ of 5 $-$ 10. We compute the sparticle spectrum for a set of benchmarks and find that satisfaction of the relic density is achieved via a compressed spectrum and coannihilation and three sets of coannihilations appear: chargino-neutralino, stop-neutralino and stau-neutralino. We investigate the chargino-neutralino coannihilation in detail for the possibility of observation of the light chargino at the high luminosity LHC (HL-LHC) and at the high energy LHC (HE-LHC) which is a possible future 27 TeV hadron collider. It is shown that all benchmark models but one can be discovered at HL-LHC and all would be discoverable at HE-LHC. The ones discoverable at both machines require a much shorter time scale and a lower integrated luminosity at HE-LHC.
hep-phJHEP(2021)·6 citations
12*
Effect of magnetic field on the charge and thermal transport properties of hot and dense QCD matter
Shubhalaxmi Rath🇮🇳 · Binoy Krishna Patra🇮🇳
We have studied the effect of strong magnetic field on the charge and thermal transport properties of hot QCD matter at finite chemical potential. For this purpose, we have calculated the electrical ( $σ_{el}$ ) and thermal ( $κ$ ) conductivities using kinetic theory in the relaxation time approximation, where the interactions are subsumed through the distribution functions within the quasiparticle model at finite temperature, strong magnetic field and finite chemical potential. This study helps to understand the impacts of strong magnetic field and chemical potential on the local equilibrium by the Knudsen number ( $Ω$ ) through $κ$ and on the relative behavior between thermal conductivity and electrical conductivity through the Lorenz number ( $L$ ) in the Wiedemann-Franz law. We have observed that, both $σ_{el}$ and $κ$ get increased in the presence of strong magnetic field, and the additional presence of chemical potential further increases their magnitudes, where $σ_{el}$ shows decreasing trend with the temperature, opposite to its increasing behavior in the isotropic medium, whereas $κ$ increases slowly with the temperature, contrary to its fast increase in the isotropic medium. The variation in $κ$ explains the decrease of the Knudsen number with the increase of the temperature. However, in the presence of strong magnetic field and finite chemical potential, $Ω$ gets enhanced and approaches unity, thus, the system may move slightly away from the equilibrium state. The Lorenz number ( $κ / (σ_{el} T))$ in the abovementioned regime of strong magnetic field and finite chemical potential shows linear enhancement with the temperature and has smaller magnitude than the isotropic one, thus, it describes the violation of the Wiedemann-Franz law for the hot and dense QCD matter in the presence of a strong magnetic field.
hep-phhep-thnucl-thEPJC(2020)·27 citations
13*
Leptogenesis in the minimal gauged U(1) $_{L_{μ} - L_{τ}}$ model and the sign of the cosmological baryon asymmetry
Kento Asai🇯🇵 · Koichi Hamaguchi🇯🇵 · Natsumi Nagata🇯🇵 · Shih-Yen Tseng🇯🇵
The minimal gauged U(1) $_{L_{μ} - L_{τ}}$ model is a simple extension of the Standard Model and has a strong predictive power for the neutrino sector. In particular, the mass spectrum and couplings of heavy right-handed neutrinos are determined as functions of three neutrino Dirac Yukawa couplings, with which we can evaluate the baryon asymmetry of the Universe generated through their decay, i.e., leptogenesis. In this letter, we study leptogenesis in the minimal gauged U(1) $_{L_{μ} - L_{τ}}$ model. It turns out that the sign of the resultant baryon asymmetry for the case with the Dirac CP phase, $δ$ , larger than $π$ is predicted to be opposite to that for $δ < π$ . In addition, if lepton asymmetry is dominantly produced by the decay of the lightest right-handed neutrino, then the correct sign of baryon asymmetry is obtained for $δ > π$ , which is favored by the current neutrino-oscillation experiments, whilst the wrong sign is obtained for $δ < π$ . We further investigate a non-thermal leptogenesis scenario where the U(1) $_{L_{μ} - L_{τ}}$ breaking field plays the role of inflaton and decays into right-handed neutrinos, as a concrete example. It is found that this simple framework offers a successful inflation that is consistent with the CMB observation. We then show that the observed amount of baryon asymmetry can be reproduced in this scenario, with its sign predicted to be positive in most of the parameter space.
hep-phJCAP(2020)·22 citations
14*
Medium modifications of girth distributions for inclusive jets and $Z^{0} + jet$ in relativistic heavy-ion collisions at the LHC
Jun Yan🇨🇳 · Shi-Yong Chen🇨🇳 · Wei Dai🇨🇳 · Ben-Wei Zhang🇨🇳 · Enke Wang🇨🇳
In this paper we investigate the medium modifications of girth distributions for inclusive jets and $Z^{0}$ tagged jets with small radius ( $R = 0.2$ ) in Pb+Pb collisions with $s = 2.76$ TeV at the LHC. The partonic spectrum in the initial hard scattering of elementary collisions are obtained by a event generator POWHEG+PYTHIA, which matches the next-to-leading (NLO) matrix elements with parton showering, and energy loss of faster parton traversing in hot/dense QCD medium is calculated by Monte Carlo simulation within Higher-Twist formalism of jet quenching in heavy-ion collisions. We present the model calculations of event normalized girth distributions for inclusive jets in p+p and Pb+Pb collisions at $s = 2.76$ TeV, which give nice descriptions of ALICE measurements. It is shown that the girth distributions of inclusive jets in Pb+Pb are shifted to lower girth region relative to that in p+p. Thus the nuclear modification factor of girth distributions for inclusive jets is larger than unity at small girth region, while smaller than one at large girth region. This behavior results from more soft fragments inside a jet as well as the fraction alteration of gluon/quark initiated jets in heavy-ion collisions. We further predict the girth distributions for $Z^{0}$ boson tagged jets in Pb+Pb collisions at $s = 2.76$ TeV, and demonstrate that the medium modification on girth distributions for $Z^{0}$ tagged jets is less pronounced as compared to that for inclusive jets because the dominant components of $Z^{0}$ tagged jets are quark-initiated jets.
hep-phnucl-thCPC(2021)·22 citations
15*
Hidden Signals of New Physics within the Yukawa Couplings of the Higgs boson
M. A. Arroyo-Ureña🇲🇽 · J. Lorenzo Diaz-Cruz🇲🇽
The Large Hadron Collider (LHC) has measured the Higgs boson couplings with the heavier particles of the Standard Model (SM), and they seem to lay on a single line as function of the particle mass, as predicted in the SM. However a complete test of this property must involve the lighter generations, and the coming measurements at LHC, or future colliders, may reveal hidden patterns associated with physics beyond the SM. In renormalizable multi-Higgs models, the Higgs-fermion couplings could still be linear, but they could lay on multiple lines. Then, the angle subtended by these lines, with respect to the SM line, can be used to characterize different models, as it is shown here for the Two-Higgs doublet Model (2HDM). Models where fermion masses arise from higher-dimensional operators, may also result in large deviations from the SM values for the Higgs couplings, which would show an irregular pattern as a function of the fermion masses. In the case of neutrino masses, when they arise from the see-saw mechanism, one finds that the Higgs Yukawa couplings will show a non-linear mass relation.
hep-phPLB(2020)·12 citations
16*
Rephasing invariant quartets in texture zero neutrino mass matrix and CP violation
Madan Singh🇮🇳
In the quark sector, Jarlskog rephasing invariant $J_{CP}$ has important implications for the CP violation as well as phase structure of the quark mass matrices. In fact all CP violating effects in this sector are proportional to the magnitude of the imaginary part of $J_{CP}$ . With the observation of non-zero and relatively large reactor mixing angle $θ_{13}$ , it is widely believed that CP might be violated in the lepton sector. The recent global best fits of neutrino oscillation indicates the preference of CP violation over CP conservation at relatively large confidence level. These experimental observations warrant to re-investigate the CP-odd weak basis invariants at low energies, and also explore their implications for CP violation in the context of texture two zero neutrino mass matrix.
hep-ph0 citations
17*
Muon pair production in the process $e^{+} + e^{-} \to e^{+} + e^{-} + μ^{+} + μ^{-}$ by the two-photon collisions $γ γ \to μ^{+} μ^{-}$ at high energies. The transverse momentum distributions
A.I. Ahmadov🇷🇺
In this present paper, we investigate the muon pairs production in the interaction between two quasireal photons in $e^{+} e^{-}$ collision. The total and differential cross section of the process $γ γ \to μ^{+} μ^{-}$ at a beam energy of photons from 3 GeV to 40 GeV in the center-of-mass and for different values of muon transverse momentum and the muon rapidity and the muon angle are calculated. We also study the total cross section, as a function of the $e^{+} e^{-}$ center-of-mass energy $s$ in the region 5 GeV $\leq s \leq$ 209 GeV process of the $e^{+} + e^{-} \to e^{+} + e^{-} + μ^{+} + μ^{-}$ by the two-photon mechanism. The obtained our results are in satisfactory agreement with the experimental data.
hep-ph0 citations
18*
Covariant kinetic theory and transport coefficients for Gribov plasma
Amaresh Jaiswal🇮🇳 · Najmul Haque🇮🇳
Gribov quantization is a method to improve the infrared dynamics of Yang-Mills theory. We study the thermodynamics and transport properties of a plasma consisting of gluons whose propagator is improved by the Gribov prescription. We first construct thermodynamics of Gribov plasma using the gauge invariant Gribov dispersion relation for interacting gluons. When the Gribov parameter in the dispersion relation is temperature dependent, one expects a mean field correction to the Boltzmann equation. We formulate covariant kinetic theory for the Gribov plasma and determine the mean-field contribution in the Boltzmann equation. This leads to a quasiparticle like framework with a bag correction to pressure and energy density which mimics confinement. The temperature dependence of the Gribov parameter and bag pressure is fixed by matching with lattice results for a system of gluons. Finally we calculate the temperature dependence of the transport coefficients, i.e., bulk and shear viscosities.
hep-phhep-thnucl-thPLB(2020)·28 citations
19*
Mixed QCD $\otimes$ QED corrections to exclusive Drell Yan production using the $q_{T}$ -subtraction method
Leandro Cieri🇮🇹 · Daniel de Florian🇦🇷 · Manuel Der🇩🇪 · Javier Mazzitelli🇩🇪
In this work we extend the $q_{T}$ -subtraction formalism, originally developed for QCD corrections, to the case of mixed QCD $\otimes$ QED corrections, and apply it to the fully exclusive calculation of the $O (α_{s} α)$ contribution to the production of an off-shell $Z$ boson in hadronic collisions. We present explicit results for the subtraction term and the hard factor, therefore providing all the ingredients needed for the application of the formalism up to $O (α_{s} α)$ . To study the phenomenological impact we consider the decay of the off-shell $Z$ boson into a pair of neutrinos, and present kinematical distributions for the final-state leptons at LHC energies.
hep-phJHEP(2020)·52 citations
20*
An Improved Hadronic Model for Pion Electroproduction
Robert J. Perry🇹🇼 · Ayse Kızılersu🇦🇺 · Anthony W. Thomas🇦🇺
Current measurements of the high energy behavior of the pion form factor are obtained from pion electroproduction data. These values are model dependent, utilizing the Vanderhaeghen, Guidal and Laget Regge (VGL) Model for their extraction. Recent work which examined the implementation of gauge invariance in that model suggested that it might lead to extracted pion form factors larger than the true values. Here we introduce a new model which preserves the successes of the VGL Model but implements gauge invariance in a new way. To demonstrate the validity of this new approach, we first use it to extract the pion form factor in a simple toy model. When compared with the previous extraction method, the improved model leads to a more reliable extraction. The success in this simple model leads us to reanalyse the electroproduction cross section data, where we obtain comparable values for the pion form factor to those obtained using the VGL procedure.
hep-phhep-latnucl-thPLB(2020)·5 citations
21*
Generating spin polarization from vorticity through nonlocal collisions
Nora Weickgenannt🇩🇪 · Enrico Speranza🇩🇪 · Xin-li Sheng🇨🇳 · Qun Wang🇨🇳 · Dirk H. Rischke🇩🇪
We derive the collision term in the Boltzmann equation using the equation of motion for the Wigner function of massive spin-1/2 particles. To next-to-lowest order in $ℏ$ it contains a nonlocal contribution, which is responsible for the conversion of orbital into spin angular momentum. In a proper choice of pseudo-gauge the antisymmetric part of the energy-momentum tensor arises solely from this nonlocal contribution. We show that the collision term vanishes only in global equilibrium and that the spin potential is then equal to the thermal vorticity. In the nonrelativistic limit, the equations of motion for the energy-momentum and spin tensors reduce to the well-known form for hydrodynamics for micropolar fluids.
hep-phnucl-thPRL(2021)·214 citations
22*
The Dark Photon
Marco Fabbrichesi🇮🇹 · Emidio Gabrielli🇮🇹 · Gaia Lanfranchi🇮🇹
The dark photon is a new gauge boson whose existence has been conjectured. It is dark because it arises from a symmetry of a hypothetical dark sector comprising particles completely neutral under the Standard Model interactions. Dark though it is, this new gauge boson can be detected because of its kinetic mixing with the ordinary, visible photon. We review its physics from the theoretical and the experimental point of view. We discuss the difference between the massive and the massless case. We explain how the dark photon enters laboratory, astrophysical and cosmological observations as well as dark matter physics. We survey the current and future experimental limits on the parameters of the massless and massive dark photons together with the related bounds on milli-charged fermions.
hep-phhep-exSpringerBriefs in Physics 2020·588 citations
23*
The X(3872) as a mass distribution
E. Ruiz Arriola🇪🇸 · P. Garcia Ortega🇪🇸
All existing experimental evidence of the bound state nature of the X(3872) relies on considering its decay products with a finite experimental spectral mass resolution which is typically $Δ m \geq 2$ MeV and much larger than its alleged binding energy, $B_{X} = 0.00 (18)$ MeV. On the other hand, there is a neat cancellation in the $1^{++}$ channel for the invariant $D D ˉ^{*}$ mass around the threshold between the continuum and bound state contribution. We discuss the impact of this effect for X(3872) at finite temperature, in prompt production in pp collisions data with a finite $p_{T}$ or the lineshapes of specific production experiments of exotic states involving triangle singularities
hep-phnucl-thActa Phys.Polon.Supp.(2021)·2 citations
24*
General neutrino interactions with sterile neutrinos in light of coherent neutrino-nucleus scattering and meson invisible decays
Tong Li🇨🇳 · Xiao-Dong Ma🇹🇼 · Michael A. Schmidt🇦🇺
In this work we study the current bounds from the CE{\nu}NS process and meson invisible decays on generic neutrino interactions with sterile neutrinos in effective field theories. The interactions between quarks and left-handed SM neutrinos and/or right-handed neutrinos are first described by the low-energy effective field theory (LNEFT) between the electroweak scale and the chiral symmetry breaking scale. We complete the independent operator basis for the LNEFT up to dimension-6 by including both the lepton-number-conserving (LNC) and lepton-number-violating (LNV) operators involving right-handed neutrinos. We translate the bounds on the LNEFT Wilson coefficients from the COHERENT observation and calculate the branching fractions of light meson invisible decays. The bounds on LNEFT are then mapped onto the SM effective field theory with sterile neutrinos (SMNEFT) to constrain new physics above the electroweak scale. We find that the meson invisible decays can provide the only sensitive probe for {\tau} neutrino flavor component and s quark component in the quark-neutrino interactions involving two (one) active neutrinos and for the effective operators without any active neutrino fields. The CE{\nu}NS process places the most stringent bound on all other Wilson coefficients. By assuming one dominant Wilson coefficient at a time in SMNEFT and negligible sterile neutrino mass, the most stringent limits on the new physics scale are 2.7 - 10 TeV from corresponding dipole operator in LNEFT and 0.5 - 1.5 TeV from neutrino-quark operator in LNEFT.
hep-phhep-exJHEP(2020)·63 citations
25*
A holographic relation between the deconfinement temperature and gluon condensate
S. S. Afonin🇷🇺
We derive a holographic prediction of the deconfinement temperature $T_{c}$ at vanishing chemical potential within a simplest AdS/QCD model with dynamical dilaton. Our analysis leads to a linear relation between $T_{c}^{4}$ and the gluon condensate. After normalizing this relation to the lattice data for $S U (3)$ pure gauge theory, the standard phenomenological value of gluon condensate from QCD sum rules leads to the prediction $T_{c} = 156$ MeV which is in a perfect agreement with the modern lattice results and freeze-out temperature measured by the ALICE Collaboration.
hep-phhep-thPLB(2020)·8 citations
26*
Exclusive tensor meson photoproduction
JPAC Collaboration: V. Mathieu🇪🇸 · A. Pilloni🇮🇹 · M. Albaladejo🇺🇸 · L. Bibrzycki🇵🇱 · A. Celentano🇮🇹 · C. Fernandez-Ramirez🇲🇽 · A.P. Szczepaniak🇺🇸
We study tensor meson photoproduction outside of the resonance region, at beam energies of few GeVs. We build a model based on Regge theory that includes the leading vector and axial exchanges. We consider two determinations of the unknown helicity couplings, and fit to the recent a2 photoproduction data from CLAS. Both choices give a similar description of the a2 cross section, but result in different predictions for the parity asymmetries and the f2 photoproduction cross section. We conclude that new measurements of f2 photoproduction in the forward region are needed to pin down the correct production mechanism. We also extend our predictions to the 8.5 GeV beam energy, where current experiments are running.
hep-phnucl-exnucl-thPRD(2020)·28 citations
27*
Dirac neutrinos and $N_{eff}$
Xuheng Luo🇨🇳 · Werner Rodejohann🇩🇪 · Xun-Jie Xu🇩🇪
If neutrinos are Dirac particles the existence of light right-handed neutrinos $ν_{R}$ is implied. Those would contribute to the effective number of relativistic neutrino species $N_{eff}$ in the early Universe. With pure standard model interactions, the contribution is negligibly small. In the presence of new interactions, however, the contribution could be significantly enhanced. We consider the most general effective four-fermion interactions for neutrinos (scalar, pseudo-scalar, vector, axial-vector and tensor), and compute the contribution of right-handed neutrinos to $N_{eff}$ . Taking the Planck 2018 measurement of $N_{eff}$ , strong constraints on the effective four-fermion coupling are obtained, corresponding to interaction strengths of $1 0^{- 5} \sim 1 0^{- 3}$ in units of the Fermi constant. This translates in new physics scales of up to 43 TeV and higher. Future experiments such as CMB-S4 can probe or exclude the existence of effective 4-neutrino operators for Dirac neutrinos. Ways to avoid this conclusion are discussed.
hep-phastro-ph.COhep-exJCAP(2020)·89 citations
28*
Physics results from the first COHERENT observation of CE $ν$ NS in argon and their combination with cesium-iodide data
M. Cadeddu🇮🇹 · F. Dordei🇮🇹 · C. Giunti🇮🇹 · Y.F. Li🇨🇳 · E. Picciau🇮🇹 · Y.Y. Zhang🇨🇳
We present the results on the radius of the neutron distribution in $^{40} Ar$ , on the low-energy value of the weak mixing angle, and on the electromagnetic properties of neutrinos obtained from the analysis of the coherent neutrino-nucleus elastic scattering data in argon recently published by the COHERENT collaboration, taking into account proper radiative corrections. We present also the results of the combined analysis of the COHERENT argon and cesium-iodide data for the determination of the low-energy value of the weak mixing angle and the electromagnetic properties of neutrinos. In particular, the COHERENT argon data allow us to improve significantly the only existing laboratory bounds on the electric charge $q_{μμ}$ of the muon neutrino and on the transition electric charge $q_{μτ}$ .
hep-phPRD(2020)·95 citations
29*
Freeze-in Dark Matter from Secret Neutrino Interactions
Yong Du🇺🇸 · Fei Huang🇨🇳 · Hao-Lin Li🇨🇳 · Jiang-Hao Yu🇨🇳
We investigate a simplified freeze-in dark-matter model in which the dark matter only interacts with the standard-model neutrinos via a light scalar. The extremely small coupling for the freeze-in mechanism is naturally realized in several neutrino-portal scenarios with the secret neutrino interactions. We study possible evolution history of the dark sector: the dark sector would undergo pure freeze-in production if the interactions between the dark-sector particles are negligible, while thermal equilibrium within the dark sector could occur if the reannihilation of the dark matter and the scalar mediator is rapid enough. We investigate the relic abundance in the freeze-in and dark freeze-out regimes, calculate evolution of the dark temperature, and study its phenomenological aspects on BBN and CMB constraints, the indirect-detection signature, as well as the potential to solve the small scale structure problem.
hep-phastro-ph.COJHEP(2020)·23 citations
30*
Complete leading-order standard model corrections to quantum leptogenesis
Paul Frederik Depta🇩🇪 · Andreas Halsch🇩🇪 · Janine Hütig🇩🇪 · Sebastian Mendizabal🇨🇱 · Owe Philipsen🇩🇪
Thermal leptogenesis, in the framework of the standard model with three additional heavy Majorana neutrinos, provides an attractive scenario to explain the observed baryon asymmetry in the universe. It is based on the out-of-equilibrium decay of Majorana neutrinos in a thermal bath of standard model particles, which in a fully quantum field theoretical formalism is obtained by solving Kadanoff-Baym equations. So far, the leading two-loop contributions from leptons and Higgs particles are included, but not yet gauge corrections. These enter at three-loop level but, in certain kinematical regimes, require a resummation to infinite loop order for a result to leading order in the gauge coupling. In this work, we apply such a resummation to the calculation of the lepton number density. The full result for the simplest "vanilla leptogenesis" scenario is by $O (1)$ increased compared to that of quantum Boltzmann equations, and for the first time permits an estimate of all theoretical uncertainties. This step completes the quantum theory of leptogenesis and forms the basis for quantitative evaluations, as well as extensions to other scenarios.
hep-phastro-ph.COhep-thJHEP(2020)·9 citations
31*
Adversarial domain adaptation to reduce sample bias of a high energy physics classifier
Jose M. Clavijo🇩🇪 · Paul Glaysher🇩🇪 · Judith M. Katzy🇩🇪 · Jenia Jitsev🇩🇪
We apply adversarial domain adaptation in unsupervised setting to reduce sample bias in a supervised high energy physics events classifier training. We make use of a neural network containing event and domain classifier with a gradient reversal layer to simultaneously enable signal versus background events classification on the one hand, while on the other hand minimising the difference in response of the network to background samples originating from different MC models via adversarial domain classification loss. We show the successful bias removal on the example of simulated events at the LHC with $t t ˉ H$ signal versus $t t ˉ b b ˉ$ background classification and discuss implications and limitations of the method
↳ stat.MLcs.LGhep-exhep-phMach.Learn.Sci.Tech.(2022)·30 citations
32*
On mass distribution of coalescing black holes
A. D. Dolgov (Novosibirsk U., ITEP Moscow)🇷🇺 · A.G. Kuranov (Sternberg Astron. Inst.)🇷🇺 · N.A. Mitichkin (Faculty of Physics, Moscow U.)🇷🇺 · S. Porey (Novosibirsk U.)🇷🇺 · K.A. Postnov🇷🇺 · O.S. Sazhina (Sternberg Astron. Inst.)🇷🇺 · I.V. Simkin (Bauman Technical U., Moscow)🇷🇺
Available data on the chirp mass distribution of the coalescing black hole binaries in O1-O3 LIGO/Virgo runs are analyzed and compared statistically with the distribution calculated under the assumption that these black holes are primordial with a log-normal mass spectrum. The theoretically calculated chirp mass distribution with the inferred best acceptable mass spectrum parameters, $M_{0} = 17 M_{⊙}$ and $γ = 0.9$ , perfectly describes the data. The value of $M_{0}$ very well agrees with the theoretically expected one. On the opposite, the chirp mass distribution of black hole binaries originated from massive binary star evolution requires additional model adjustments to reproduce the observed chirp mass distribution
↳ astro-ph.COhep-phJCAP(2020)·51 citations
33*
On the graceful exit problem in warm inflation
Suratna Das🇮🇳 · Rudnei O. Ramos🇧🇷
A seemingly simple question, how does warm inflation exit gracefully?, has a more complex answer than in a cold paradigm. It has been highlighted here that whether warm inflation exits gracefully depends on three independent choices: The form of the potential, the choice of the warm inflation model (i.e., on the form of its dissipative coefficient) and the regime, of weak or strong dissipation, characterizing the warm inflation dynamics. Generic conditions on slow-roll parameters and several constraints on the different model parameters required for warm inflation to exit gracefully are derived.
↳ gr-qcastro-ph.COhep-phhep-thPRD(2021)·31 citations
34*
Probing nucleon strange and charm distributions with lattice QCD
Rui Zhang🇺🇸 · Huey-Wen Lin🇺🇸 · Boram Yoon🇺🇸
We present the first lattice-QCD calculation of the unpolarized strange and charm parton distribution functions using large-momentum effective theory (LaMET). We use a lattice ensemble with 2+1+1 flavors of highly improved staggered quarks (HISQ) generated by MILC collaboration, with lattice spacing $a \approx 0.12$ fm and $M_{π} \approx 310$ MeV, and clover valence fermions with two valence pion masses: 310 and 690 MeV. We use momentum-smeared sources to improve the signal up to nucleon boost momentum $P_{z} = 2.18$ GeV, and determine nonperturbative renormalization factors in RI/MOM scheme. We compare our lattice results with the matrix elements obtained from matching the PDFs from CT18NNLO and NNPDF3.1NNLO global fits. Our data support the assumptions of strange-antistrange and charm-anticharm symmetry that are commonly used in global PDF fits, and we find smaller than expected parton distribution at mid to small $x$ .
↳ hep-lathep-phnucl-thPRD(2021)·48 citations
35*
Hubble Hullabaloo and String Cosmology
Luis A. Anchordoqui🇺🇸
The discrepancy in measurements of the Hubble constant indicates new physics in dark energy, dark matter, or both. Drawing inspiration from string theory, we explore possible solutions to overcome the $H_{0}$ problem. We investigate the interplay between the cosmological determination of $Δ N_{eff}$ and $Z^{'}$ searches at the LHC Run3.
↳ astro-ph.COhep-ph13 citations
36*
Gravitational memory effects and Bondi-Metzner-Sachs symmetries in scalar-tensor theories
Shaoqi Hou🇨🇳 · Zong-Hong Zhu🇨🇳
The relation between gravitational memory effects and Bondi-Metzner-Sachs symmetry of the asymptotically flat spacetimes is studied in the scalar-tensor theory. For this purpose, the solutions to the equations of motion near the future null infinity are obtained in the generalized Bondi-Sachs coordinates with a suitable determinant condition. It turns out that the Bondi-Metzner-Sachs group is also a semi-direct product of an infinitesimal dimensional supertranslation group and the Lorentz group as in general relativity. There are also degenerate vacua in both the tensor and the scalar sectors in the scalar-tensor theory. The supertranslation relates the vacua in the tensor sector, while in the scalar sector, it is the Lorentz transformation that transforms the vacua to each other. So there are the tensor memory effect similar to the one in general relativity, and the scalar memory effect, which is new. The evolution equations for the Bondi mass and angular momentum aspects suggest that the null energy fluxes and the angular momentum fluxes across the null infinity induce the transition among the vacua in the tensor and the scalar sectors, respectively.
↳ gr-qchep-phhep-thJHEP(2021)·54 citations
37*
Second virial coefficients of light nuclear clusters and their chemical freeze-out in nuclear collisions
K. A. Bugaev🇺🇦 · O. V. Vitiuk🇺🇦 · B. E. Grinyuk🇺🇦 · V. V. Sagun🇺🇦 · N. S. Yakovenko🇺🇦 · O. I. Ivanytskyi🇺🇦 · G. M. Zinovjev🇺🇦 · D. B. Blaschke🇵🇱 · E. G. Nikonov🇷🇺 · L. V. Bravina🇳🇴 · E. E. Zabrodin🇳🇴 · S. Kabana🇨🇱 and 4 other authors
Here we develop a new strategy to analyze the chemical freeze-out of light (anti)nuclei produced in high energy collisions of heavy atomic nuclei within an advanced version of the hadron resonance gas model. It is based on two different, but complementary approaches to model the hard-core repulsion between the light nuclei and hadrons. The first approach is based on an approximate treatment of the equivalent hard-core radius of a roomy nuclear cluster and pions, while the second approach is rigorously derived here using a self-consistent treatment of classical excluded volumes of light (anti)nuclei and hadrons. By construction, in a hadronic medium dominated by pions, both approaches should give the same results. Employing this strategy to the analysis of hadronic and light (anti)nuclei multiplicities measured by ALICE at $s_{N N} = 2.76$ TeV and by STAR at $s_{N N} = 200$ GeV, we got rid of the existing ambiguity in the description of light (anti)nuclei data and determined the chemical freeze-out parameters of nuclei with high accuracy and confidence. At ALICE energy the nuclei are frozen prior to the hadrons at the temperature $T = 175. 1_{- 3.9}^{+ 2.3}$ MeV, while at STAR energy there is a single freeze-out of hadrons and nuclei at the temperature $T = 167.2 \pm 3.9$ MeV. We argue that the found chemical freeze-out volumes of nuclei can be considered as the volumes of quark-gluon bags that produce the nuclei at the moment of hadronization.
↳ nucl-thhep-phEPJA(2020)·19 citations
38*
Adversarially Learned Anomaly Detection on CMS Open Data: re-discovering the top quark
Oliver Knapp🇨🇭 · Guenther Dissertori🇨🇭 · Olmo Cerri🇺🇸 · Thong Q. Nguyen🇺🇸 · Jean-Roch Vlimant🇺🇸 · Maurizio Pierini🇨🇭
We apply an Adversarially Learned Anomaly Detection (ALAD) algorithm to the problem of detecting new physics processes in proton-proton collisions at the Large Hadron Collider. Anomaly detection based on ALAD matches performances reached by Variational Autoencoders, with a substantial improvement in some cases. Training the ALAD algorithm on 4.4 fb-1 of 8 TeV CMS Open Data, we show how a data-driven anomaly detection and characterization would work in real life, re-discovering the top quark by identifying the main features of the t-tbar experimental signature at the LHC.
↳ hep-excs.LGhep-phEur.Phys.J.Plus(2021)·95 citations
39*
Symmetries from Locality. I. Electromagnetism and Charge Conservation
Mark P. Hertzberg🇺🇸 · Jacob A. Litterer🇺🇸
It is well known that a theory of the (i) Lorentz invariant and (ii) locally interacting (iii) two degrees of freedom of a massless spin 1 particle, the photon, leads uniquely to electromagnetism at large distances. In this work, we remove the assumption of (i) Lorentz boost invariance, but we still demand (ii) and (iii). We consider several broad classes of theories of spin 1, which in general explicitly violate Lorentz symmetry. We restrict to the familiar two degrees of freedom of the photon. We find that most theories lead to non-locality and instantaneous signaling at a distance. By demanding a mild form of locality (ii), namely that the tree-level exchange action is manifestly local, we find that the photon must still be sourced by a conserved charge with an associated internal symmetry. This recovers the central features of electromagnetism, although it does not by itself impose Lorentz boost symmetry. The case of gravitation dramatically improves the final conclusion and is reported in detail in our accompanying paper Part 2.
↳ hep-thgr-qchep-phPRD(2020)·8 citations
40*
Massive Conformal Symmetry and Integrability for Feynman Integrals
Florian Loebbert🇩🇪 · Julian Miczajka🇩🇪 · Dennis Müller🇩🇰 · Hagen Münkler🇨🇭
In the context of planar holography, integrability plays an important role for solving certain massless quantum field theories such as N=4 SYM theory. In this letter we show that integrability also features in the building blocks of massive quantum field theories. At one-loop order we prove that all massive n-gon Feynman integrals in generic spacetime dimensions are invariant under a massive Yangian symmetry. At two loops similar statements can be proven for graphs built from two n-gons. At generic loop order we conjecture that all graphs cut from regular tilings of the plane with massive propagators on the boundary are invariant. We support this conjecture by a number of numerical tests for higher loops and legs. The observed Yangian extends the bosonic part of the massive dual conformal symmetry that was found a decade ago on the Coulomb branch of N=4 SYM theory. By translating the Yangian level-one generators from dual to original momentum space, we introduce a massive generalization of momentum space conformal symmetry. Even for non-dual conformal integrals this novel symmetry persists. The Yangian can thus be understood as the closure of massive dual conformal symmetry and this new massive momentum space conformal symmetry, which suggests an interpretation via AdS/CFT. As an application of our findings, we bootstrap the hypergeometric building blocks for examples of massive Feynman integrals.
↳ hep-thhep-phmath-phmath.MPPRL(2020)·50 citations
41*
Axionlike Origin of the Primordial Density Perturbation
Takeshi Kobayashi🇯🇵
We show that an axionlike field coupled to a new confining gauge group can generate the primordial density perturbation in the post-inflation universe. The axion decay constant and strong coupling scale are uniquely determined by observations of the density perturbation, which further suggest a temporal deconfinement of the gauge group after inflation. The resulting temperature-dependent axion potential, together with its periodic nature, gives rise to the red-tilted density perturbation, with a positive local-type non-Gaussianity of order unity.
↳ astro-ph.COhep-phhep-thPRL(2020)·6 citations
42*
Symmetries from Locality. II. Gravitation and Lorentz Boosts
Mark P. Hertzberg🇺🇸 · Jacob A. Litterer🇺🇸 · McCullen Sandora🇺🇸
It is known that local, Lorentz invariant, unitary theories involving particles with spin 1 demand that the matter sector they couple to are organized by internal physical symmetries and the associated charge conservation, while spin 3/2 demands supersymmetry. However, the introduction of a spin 2 graviton does not obviously demand new symmetries of the matter sector (although it does demand a universal coupling). In this work we relax the assumption of Lorentz boost symmetry, while maintaining a basic notion of locality that there is no instantaneous signaling at a distance. This extends and complements our accompanying work in Part 1 on related issues for spin 1 particles in electromagnetism. In order to avoid potential problems with longitudinal modes of the graviton, we choose to project them out, leaving only two degrees of freedom. We study large classes of theories that a priori may violate Lorentz boost invariance. By requiring the tree-level exchange action be local, we find that consistency demands that the Lorentz boost symmetry must be satisfied by the graviton and the matter sector, and in turn we recover general relativity at this order of analysis.
↳ hep-thastro-ph.COgr-qchep-phPRD(2020)·13 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.