HEP Phenomenology·hep-ph

Wed·Jan 13, 2021Wednesday·January 13, 2021

17 papers—13 primary·4 cross-listed·reconstructed*

01*
Quarkonium propagation in the quark gluon plasma
Rishi Sharma🇮🇳
In relativistic heavy ion collisions at RHIC and the LHC, a quark gluon plasma (QGP) is created for a short duration of about 10fm/c. Quarkonia (bound states of $c c ˉ$ and $b b ˉ$ ) are sensitive probes of this phase on length scales comparable to the size of the bound states which are less than 1fm. Observations of quarkonia in these collisions provide us with a lot of information about how the presence of a QGP affects various quarkonium states. This has motivated the development of the theory of heavy quarks and their bound states in a thermal medium, and its application to the phenomenology of quarkonia in heavy ion collisions. We review some of these developments here.
hep-phnucl-thEur.Phys.J.ST(2021)·25 citations
02*
Hierarchical Quark and Lepton Masses with Sequential U(1) Gauge Symmetry
Ernest Ma (UC Riverside)🇺🇸
Instead of right-handed neutrino singlets, the standard model is extended to include lepton triplets $(Σ^{+}, Σ^{0}, Σ^{-})$ . Each quark and lepton family may now transform under an anomaly-free $U (1)_{X}$ gauge symmetry, known already for many years. A new sequential application is presented, using just the one Higgs doublet of the standard model, together with two $U (1)_{X}$ Higgs singlets. The resulting structure has hierarchical quark and lepton masses, as well as a viable seesaw neutrino mass matrix.
hep-phPLB(2021)·2 citations
03*
Dynamic Jet Charge
Zhong-Bo Kang🇺🇸 · Xiaohui Liu🇨🇳 · Sonny Mantry🇺🇸 · M.C. Spraker🇺🇸 · Tyler Wilson🇺🇸
We propose a modified definition of the jet charge, the "dynamic jet charge", where the constant jet momentum fraction weighting parameter, $κ$ , in the standard jet charge definition is generalized to be a function of a dynamical property of the jet or the individual jet constituents. The dynamic jet charge can complement analyses based on the standard definition and give improved discrimination between quark and gluon initiated jets and between jets initiated by different quark flavors. We focus on the specific scenario where each hadron in the jet contributes to the dynamic jet charge with a $κ$ -value dynamically determined by its jet momentum fraction. The corresponding dynamic jet charge distributions have qualitatively distinct features and are typically characterized by a multiple peak structure. For proton-proton collisions, compared to the standard jet charge, the dynamic jet charge gives significantly improved discrimination between quark and gluon initiated jets and comparable discrimination between $u$ - and $d$ -quark initiated jets. In Pythia simulations of heavy ion collisions, the dynamic jet charge is found to have higher jet discrimination power compared to the standard jet charge, remaining robust against the increased contamination from underlying event. We also present phenomenological applications of the dynamic jet charge to probe nuclear flavor structure.
hep-phhep-exnucl-exnucl-thPRD(2021)·21 citations
04*
Angular Distributions in Rare $b$ Decays
Thorsten Feldmann (Univ. Siegen)🇩🇪
We give a brief overview of phenomenological developments in the analysis of angular observables for exclusive decay modes of $B$ mesons and $Λ_{b}$ baryons, with focus on recent results and some important aspects related to the theoretical background (which mostly concern the treatment of hadronic uncertainties).
hep-phhep-exPoS(2021)·3 citations
05*
Quantum vacuum signatures in multi-color laser pulse collisions
Holger Gies🇩🇪 · Felix Karbstein🇩🇪 · Leonhard Klar🇩🇪
Quantum vacuum fluctuations give rise to effective non-linear interactions between electromagnetic fields. A prominent signature of quantum vacuum nonlinearities driven by macroscopic fields are signal photons differing in characteristic properties such as frequency, propagation direction and polarization from the driving fields. We devise a strategy for the efficient tracing of the various vacuum-fluctuation-mediated interaction processes in order to identify the most prospective signal photon channels. As an example, we study the collision of up to four optical laser pulses and pay attention to sum and difference frequency generation. We demonstrate how this information can be used to enhance the signal photon yield in laser pulse collisions for a given total laser energy.
hep-phphysics.opticsquant-phPRD(2021)·21 citations
06*
Quantum Anomalous Energy Effects on the Nucleon Mass
Xiangdong Ji🇺🇸 · Yizhuang Liu🇨🇳
Apart from the quark and gluon kinetic and potential energies, the nucleon mass includes a novel energy of pure quantum origin resulting from anomalous breaking of scale symmetry. We demonstrate the effects of this quantum anomalous energy (QAE) in QED, as well as in a toy 1+1 dimensional non-linear sigma model where it contributes non-perturbatively, in a way resembling the Higgs mechanism for the masses of matter particles in electro-weak theory. The QAE contribution to the nucleon mass can be explained using a similar mechanism, in terms of a dynamical response of the gluonic scalar field through Higgs-like couplings between the nucleon and scalar resonances. In addition, the QAE sets the scale for other energies in the nucleon through a relativistic virial theorem, and contributes a negative pressure to confine the colored quarks.
hep-phhep-latnucl-exnucl-thSCPMA(2021)·40 citations
07*
Unification of Neutrino-Neutrino and Neutrino-Antineutrino Oscillations
Keiichi Kimura🇯🇵 · Akira Takamura🇯🇵
In the case of two-generation Majorana neutrinos, we derive the oscillation probabilities for $ν \leftrightarrow ν$ , $ν^{c} \leftrightarrow ν^{c}$ , and $ν \leftrightarrow ν^{c}$ within a unified framework using a relativistic equation. We demonstrate that the Majorana phase arises not from lepton number violation but from chirality change. Additionally, we verify the conservation of unitarity. Notably, we find that the oscillation probabilities for $ν \leftrightarrow ν^{c}$ derived in this paper differ significantly from previous results, particularly in the absence of zero-distance effects and direct CP violation.
hep-ph8 citations
08*
A comparison of optimisation algorithms for high-dimensional particle and astrophysics applications
The DarkMachines High Dimensional Sampling Group: Csaba Balázs🇦🇺 · Melissa van Beekveld🇬🇧 · Sascha Caron🇳🇱 · Barry M. Dillon🇩🇪 · Ben Farmer🇦🇺 · Andrew Fowlie🇨🇳 · Eduardo C. Garrido-Merchán🇪🇸 · Will Handley🇬🇧 · Luc Hendriks🇳🇱 · Gu{\dh}laugur Jóhannesson🇮🇸 · Adam Leinweber🇦🇺 · Judita Mamužić🇪🇸 and 8 other authors
Optimisation problems are ubiquitous in particle and astrophysics, and involve locating the optimum of a complicated function of many parameters that may be computationally expensive to evaluate. We describe a number of global optimisation algorithms that are not yet widely used in particle astrophysics, benchmark them against random sampling and existing techniques, and perform a detailed comparison of their performance on a range of test functions. These include four analytic test functions of varying dimensionality, and a realistic example derived from a recent global fit of weak-scale supersymmetry. Although the best algorithm to use depends on the function being investigated, we are able to present general conclusions about the relative merits of random sampling, Differential Evolution, Particle Swarm Optimisation, the Covariance Matrix Adaptation Evolution Strategy, Bayesian Optimisation, Grey Wolf Optimisation, and the PyGMO Artificial Bee Colony, Gaussian Particle Filter and Adaptive Memory Programming for Global Optimisation algorithms.
hep-phphysics.comp-phJHEP(2021)·34 citations
09*
3D tomography of the nucleon: transverse-momentum-dependent gluon distributions
Francesco Giovanni Celiberto🇮🇹
We perform explorative analyses of the 3D gluon content of the proton via a study of (un)polarized twist-2 gluon TMDs, calculated in a spectator model for the parent nucleon. Our approach encodes a flexible parametrization for the spectator-mass density, suited to describe both moderate and small- $x$ effects. All these prospective developments are relevant in the investigation of the gluon dynamics inside nucleons and nuclei, which constitutes one of the major goals of new-generation colliding machines, as the EIC, the HL-LHC and NICA.
hep-phNuovo Cim.C(2021)·64 citations
10*
Diabatic description of charmoniumlike mesons II: mass corrections and strong decay widths
R. Bruschini🇪🇸 · P. González🇪🇸
From a diabatic bound state approach to $J^{P C} = 1^{--}$ and $(0, 1, 2)^{++}$ charmoniumlike resonances below $4.1$ GeV, formulated in terms of $c c$ and closed meson-meson channels, we calculate mass shifts and widths due to open meson-meson channels. This calculation does not involve any new free parameter, so comparison of our predictions with existing data provides a direct test of our approach. Further mass corrections are also estimated and good agreement with the measured masses comes out. As for the calculated widths, overall reasonable, they point out to the need of some refinement of our current bound state approximation for an accurate description of data. These results give additional support to the diabatic approach in QCD as an adequate framework for a complete unified description of conventional and unconventional charmoniumlike resonances. In this respect, the experimental discovery of a predicted $2^{++}$ resonance with a mass around $4$ GeV would be of special relevance.
hep-phPRD(2021)·18 citations
11*
Simultaneous Monte Carlo analysis of parton densities and fragmentation functions
E. Moffat🇺🇸 · W. Melnitchouk🇺🇸 · T. C. Rogers🇺🇸 · N. Sato🇺🇸
We perform a comprehensive new Monte Carlo analysis of high-energy lepton-lepton, lepton-hadron and hadron-hadron scattering data to simultaneously determine parton distribution functions (PDFs) in the proton and parton to hadron fragmentation functions (FFs). The analysis includes all available semi-inclusive deep-inelastic scattering and single-inclusive $e^{+} e^{-}$ annihilation data for pions, kaons and unidentified charged hadrons, which allows the flavor dependence of the fragmentation functions to be constrained. Employing a new multi-step fitting strategy and more flexible parametrizations for both PDFs and FFs, we assess the impact of different data sets on sea quark densities, and confirm the previously observed suppression of the strange quark distribution. The new fit, which we refer to as "JAM20-SIDIS", will allow for improved studies of universality of parton correlation functions, including transverse momentum dependent (TMD) distributions, across a wide variety of process, and the matching of collinear to TMD factorization descriptions.
hep-phhep-exnucl-thPRD(2021)·145 citations
12*
Positronia' clouds in Universe
I.M. Dremin🇷🇺
The intense emission of 511 keV photons from the Galactic center and within terrestrial thunderstorms is attributed to the formation of parapositronia' clouds. Unbound electron-positron pairs and positronia can be created by strong electromagnetic fields produced in interactions of electrically charged objects, in particular, in collisions of heavy nuclei. Kinematics of this process favours abundant creation of the unbound electron-positron pairs with very small masses and the confined parapositronia states which decay directly to two 511 keV quanta. Therefore we propose to consider interactions of electromagnetic fields of colliding heavy ions as a source of low-mass pairs which can transform to 511 keV quanta. Intensity of their creation is enlarged by the factor Z $^{4}$ (Z is the electric charge of a heavy ion) compared to protons with Z=1. These processes are especially important at very high energies of nuclear collisions because their cross sections increase proportionally to cube of the logarithm of energy and can even exceed the cross sections of strong interactions which may not increase faster than the squared logarithm of energy. Moreover, production of extremely low-mass $e^{+} e^{-}$ -pairs in ultraperipheral nuclear collisions is strongly enhanced due to the Sommerfeld-Gamow-Sakharov (SGS) factor which accounts for mutual Coulomb attraction of non-relativistic electrons to positrons in case of low pair-masses. This attraction may lead to their annihilation and, therefore, to the increased intensity of 511 keV photons. It is proposed to confront the obtained results to forthcoming experimental data at NICA collider.
hep-phastro-ph.HEUniverse(2021)·3 citations
13*
Electric dipole moment in storage ring experiments
Peter I Porshnev🇧🇾
The measurement of electric dipole moment in storage rings can potentially exceed the sensitivity of tests with neutral systems. The spin dynamics under such conditions is described by the Bargmann-Michel-Telegdi equation. It can be derived in the semiclassical approximation under several assumptions one of which is the zero pseudoscalar bilinear. However, many promising extensions to the standard model consider scalar-pseudoscalar couplings which assume nonzero electron pseudoscalar. We re-derive the spin precession equation under conditions that do not assume that pseudoscalar is zero. It leads to a correction term that might be required for matching the storage ring measurements with QFT evaluations.
hep-phPhys.Scripta(2021)·4 citations
14*
Simulations of Axion Minihalos
Huangyu Xiao🇺🇸 · Ian Williams🇺🇸 · Matthew McQuinn🇺🇸
The axion, motivated as a solution to the strong CP problem, is also a viable dark matter candidate. We use N-body simulations to study the formation of substructures from white-noise density fluctuations. The density profiles of our relaxed axion minihalos can be described by the Navarro-Frenk-White profile, and the minihalos' concentration number agrees well with a simple, physically-motivated model. We develop a semi-analytic formula to fit the mass function from our simulation, which agrees broadly at different redshifts and only differs at factor of two level from classic halo mass functions. This analytic mass function allows us to consider uncertainties in the post-inflation axion scenario, as well as extrapolate our high-redshift simulations results to the present. Our work estimates the present-day abundance of axion substructures, as is necessary for predicting their effect on cosmological microlensing caustics and pulsar timing. Our calculations suggest that if pulsar timing and microlensing probes can reach recent sensitivity forecasts, they may be sensitive to the post-inflation axion dark matter scenario, even when accounting for uncertainties pertaining to axion strings. For pulsar timing, the most significant caveat is whether axion minihalos are disrupted by stars, which our estimates show is mildly important at the most relevant masses. Finally, as our gravitational simulations are scale invariant, the results can be extended to models where the dark matter is comprised of other axion-like particles and even clusters of primordial black holes.
↳ astro-ph.COhep-phPRD(2021)·91 citations
15*
Testing High-latitude Curvature Effect of Gamma-Ray Bursts with {\it Fermi} Data: Evidence of Bulk Acceleration in Prompt Emission
Liang Li🇮🇹 · Bing Zhang🇺🇸
When a gamma-ray burst (GRB) emitter stops emission abruptly, the observer receives rapidly fading emission from high latitudes with respect to the line of sight, known as the ``curvature effect''. Identifying such emission from GRB prompt-emission lightcurves would constrain the radius of prompt emission from the central engine and the composition of GRB jets. We perform a dedicated search of high-latitude emission (HLE) through spectral and temporal analyses of a sample of single-pulse bursts detected by the Gamma-ray Burst Monitor on board the {\it Fermi} satellite. We identify HLE from a subsample of bursts and constrain the emission radius to be $R_{GRB} \sim (1 0^{15} - 1 0^{16})$ cm from the central engine. Some bursts have the HLE decay faster than predicted by a constant Lorentz factor jet, suggesting that the emission region is undergoing acceleration during prompt emission. This supports the Poynting-flux-dominated jet composition for these bursts. The conclusion is consistent with previous results drawn from spectral-lag modeling of prompt emission and HLE analysis of X-ray flares.
↳ astro-ph.HEhep-phAstrophys.J.Suppl.(2021)·27 citations
16*
Invariant Differential Forms on Complexes of Graphs and Feynman Integrals
Francis Brown🇬🇧
We study differential forms on an algebraic compactification of a moduli space of metric graphs. Canonical examples of such forms are obtained by pulling back invariant differentials along a tropical Torelli map. The invariant differential forms in question generate the stable real cohomology of the general linear group, as shown by Borel. By integrating such invariant forms over the space of metrics on a graph, we define canonical period integrals associated to graphs, which we prove are always finite and take the form of generalised Feynman integrals. Furthermore, canonical integrals can be used to detect the non-vanishing of homology classes in the commutative graph complex. This theory leads to insights about the structure of the cohomology of the commutative graph complex, and new connections between graph complexes, motivic Galois groups and quantum field theory.
↳ math.AGhep-phmath.QASIGMA(2021)·13 citations
17*
Fractional dark energy
Ricardo G. Landim🇩🇪
In this paper we introduce the fractional dark energy model, in which the accelerated expansion of the Universe is driven by a nonrelativistic gas (composed by either fermions or bosons) with a noncanonical kinetic term. The kinetic energy is inversely proportional to the cube of the absolute value of the momentum for a fluid with an equation of state parameter equal to minus one, and whose corresponding energy density mimics the one of the cosmological constant. In the general case, the dark energy equation of state parameter (times three) is precisely the exponent of the momentum in the kinetic term. We show that this inverse momentum operator appears in fractional quantum mechanics and it is the inverse of the Riesz fractional derivative. The observed vacuum energy can be obtained through the integral of the Fermi-Dirac (or Bose-Einstein) distribution and the lowest allowed energy of the particles. Finally, a possible thermal production and fate of fractional dark energy is investigated.
↳ astro-ph.COgr-qchep-phPRD(2021)·26 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.