Nuclear Theory·nucl-th

Tuesday·March 23, 2021

13 papers—5 primary·8 cross-listed

06
Evolution of Primordial Neutrino Helicities in Cosmic Gravitational Inhomogeneities
Gordon Baym🇺🇸 · Jen-Chieh Peng🇺🇸
Relic neutrinos from the Big Bang decoupled from the hot plasma predominantly in helicity eigenstates. Their subsequent propagation through gravitational inhomogeneities of the Universe alters the helicities of both Dirac and Majorana neutrinos, thus providing an independent probe of the evolving universe. We determine here the probability that relic neutrinos flip their helicity, in terms of the spectrum of density inhomogeneities measured in the Cosmic Microwave Background. As we find, for Dirac neutrinos the gravitational helicity modifications are intermediate between the effects of magnetic fields if the neutrino magnetic moment is of the magnitude predicted in the Standard Model and the much larger effects if the magnetic moment is of the scale consistent with the excess of low energy electron events seen by the XENON1T experiment. We give succinct derivations, within general relativity, of the semi-classical response of a spinning particle to a weak gravitational field in an expanding universe, and estimate the helicity modifications of neutrinos emitted by the Sun caused by the Sun's gravity.
↳ hep-phastro-ph.COnucl-exnucl-thPRD(2021)·21 citations
07
Nuclear-powered X-ray millisecond pulsars
Sudip Bhattacharyya (TIFR, India)
Nuclear-powered X-ray millisecond pulsars are the third type of millisecond pulsars, which are powered by thermonuclear fusion processes. The corresponding brightness oscillations, known as burst oscillations, are observed during some thermonuclear X-ray bursts, when the burning and cooling accreted matter gives rise to an azimuthally asymmetric brightness pattern on the surface of the spinning neutron star. Apart from providing neutron star spin rates, this X-ray timing feature can be a useful tool to probe the fundamental physics of neutron star interior and surface. This chapter presents an overview of the relatively new field of nuclear-powered X-ray millisecond pulsars.
↳ astro-ph.HEnucl-exnucl-thAstrophys.Space Sci.Libr.(2021)·15 citations
08
Functional-renormalization-group approach to classical liquids with short-range repulsion: a scheme without repulsive reference system
Takeru Yokota🇯🇵 · Jun Haruyama🇯🇵 · Osamu Sugino🇯🇵
The renormalization-group approaches for classical liquids in previous works require a repulsive reference such as a hard-core one when applied to systems with short-range repulsion. The need for the reference is circumvented here by using a functional renormalization group approach for integrating the hierarchical flow of correlation functions along a path of variable interatomic coupling. We introduce the cavity distribution functions to avoid the appearance of divergent terms and choose a path to reduce the error caused by the decomposition of higher order correlation functions. We demonstrate using an exactly solvable one-dimensional models that the resulting scheme yields accurate thermodynamic properties and interatomic distribution at various densities when compared to integral-equation methods such as the hypernetted chain and the Percus-Yevick equation, even in the case where our hierarchical equations are truncated with the Kirkwood superposition approximation, which is valid for low-density cases.
↳ cond-mat.stat-mechcond-mat.softhep-thnucl-thPRE(2021)·8 citations
09
Dynamical Phase Transitions in models of Collective Neutrino Oscillations
Alessandro Roggero🇺🇸
Collective neutrino oscillations can potentially play an important role in transporting lepton flavor in astrophysical scenarios where the neutrino density is large, typical examples are the early universe and supernova explosions. It has been argued in the past that simple models of the neutrino Hamiltonian designed to describe forward scattering can support substantial flavor evolution on very short time scales $t \approx lo g (N) / (G_{F} ρ_{ν})$ , with $N$ the number of neutrinos, $G_{F}$ the Fermi constant and $ρ_{ν}$ the neutrino density. This finding is in tension with results for similar but exactly solvable models for which $t \approx N / (G_{F} ρ_{ν})$ instead. In this work we provide a coherent explanation of this tension in terms of Dynamical Phase Transitions (DPT) and study the possible impact that a DPT could have in more realistic models of neutrino oscillations and their mean-field approximation.
↳ hep-phastro-ph.HEnucl-thPRD(2021)·54 citations
10
QCD Analysis of Near-Threshold Photon-Proton Production of Heavy Quarkonium
Yuxun Guo🇺🇸 · Xiangdong Ji🇺🇸 · Yizhuang Liu🇩🇪
The near threshold photo or electroproduction of heavy vector quarkonium off the proton is studied in quantum chromodynamics. Similar to the high-energy limit, the production amplitude can be factorized in terms of gluonic Generalized Parton Distributions and the quarkonium distribution amplitude. At the threshold, the threshold kinematics has a large skewness parameter $ξ$ , leading to the dominance of the spin-2 contribution over higher-spin twist-2 operators. Thus threshold production data are useful to extract the gluonic gravitational form factors, allowing studying the gluonic contributions to the quantum anomalous energy, mass radius, spin and mechanical pressure in the proton. We use the recent GlueX data on the $J / ψ$ photoproduction to illustrate the potential physics impact from the high-precision data from future JLab 12 GeV and EIC physics program.
↳ hep-phhep-latnucl-exnucl-thPRD(2021)·112 citations
11
Thermal impacts on the properties of nuclear matter and young neutron star
Ankit Kumar🇮🇳 · H. C. Das🇮🇳 · M. Bhuyan🇲🇾 · S. K. Patra🇮🇳
We present a methodical study of the thermal and nuclear properties for the hot nuclear matter using relativistic-mean field theory. We examine the effects of temperature on the binding energy, pressure, thermal index, symmetry energy, and its derivative for the symmetric nuclear matter using temperature-dependent relativistic mean-field formalism for the well-known G2 $^{*}$ and recently developed IOPB-I parameter sets. The critical temperature for the liquid-gas phase transition in an asymmetric nuclear matter system has also been calculated and collated with the experimentally available data. We investigate the approach of the thermal index as a function of nucleon density in the wake of relativistic and non-relativistic formalism. The computation of neutrino emissivity through the direct Urca process for the supernovae remnants has also been performed, which manifests some exciting results about the thermal stabilization and evolution of the newly born proto-neutron star. The central temperature and the maximum mass of the proto-neutron star have also been calculated for different entropy values.
↳ hep-phastro-ph.HEnucl-thNPA(2021)·3 citations
12
Correlating Non-Resonant Di-Electron Searches at the LHC to the Cabibbo-Angle Anomaly and Lepton Flavour Universality Violation
Andreas Crivellin🇨🇭 · Claudio Andrea Manzari🇨🇭 · Marc Montull🇨🇭
In addition to the existing strong indications for lepton flavour university violation (LFUV) in low energy precision experiments, CMS recently released an analysis of non-resonant di-lepton pairs which could constitute the first sign of LFUV in high-energy LHC searches. In this article we show that the Cabibbo angle anomaly, an (apparent) violation of first row and column CKM unitarity with $\approx 3 σ$ significance, and the CMS result can be correlated and commonly explained in a model independent way by the operator $[Q_{ℓ q}^{(3)}]_{1111} = (ℓ ˉ_{1} γ^{μ} σ^{I} ℓ_{1}) (q ˉ_{1} γ_{μ} σ^{I} q_{1})$ . This is possible without violating the bounds from the non-resonant di-lepton search of ATLAS (which interestingly also observed slightly more events than expected in the electron channel) nor from $R (π) = π \to μν / π \to e ν$ . We find a combined preference for the new physics hypothesis of $4.5 σ$ and predict $1.0004 < R (π) < 1.0009$ (95\%~CL) which can be tested in the near future with the forthcoming results of the PEN experiment.
↳ hep-phhep-exhep-thnucl-ex+1PRD(2021)·36 citations
13
Perturbative QCD Analysis of Near Threshold Heavy Quarkonium Photoproduction at Large Momentum Transfer
Peng Sun🇨🇳 · Xuan-Bo Tong🇨🇳 · Feng Yuan🇺🇸
We apply perturbative QCD to investigate the near threshold heavy quarkonium photoproduction at large momentum transfer. From an explicit calculation, we show that the conventional power counting method will be modified and the three quark Fock state with nonzero orbital angular momentum dominates the near threshold production. It carries a power behavior of $1/ (- t)^{5}$ for the differential cross section. We further comment on the impact of our results on the interpretation of the experiment measurement in terms of the gluonic gravitational form factors of the proton.
↳ hep-phhep-exnucl-exnucl-thPLB(2021)·58 citations

Affiliations

first authorsco-authorsvia INSPIRE