Tue·Mar 23, 2021Tuesday·March 23, 2021

1. 01*

   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
2. 02*

   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
3. 03*

   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 $\xi$, 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 $J/\psi$ 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
4. 04*

   NRQCD analysis of charmonium production with pion and proton beams at fixed-target energies

   Chia-Yu Hsieh🇹🇼 · Yu-Shiang Lian🇹🇼 · Wen-Chen Chang🇹🇼 · Jen-Chieh Peng🇺🇸 · Stephane Platchkov🇫🇷 · Takahiro Sawada🇯🇵

   We present an analysis of hadroproduction of $J/\psi$ and $\psi (2S)$ at fixed-target energies in the framework of non-relativistic QCD (NRQCD). Using both pion- and proton-induced data, a new determination of the color-octet long-distance matrix elements (LDMEs) is obtained. Compared with previous results, the contributions from the $q\bar{q}$ and color-octet processes are significantly enhanced, especially at lower energies. A good agreement between the pion-induced $J/\psi$ production data and NRQCD calculations using the newly obtained LDMEs is achieved. We find that the pion-induced charmonium production data are sensitive to the gluon density of pions, and favor pion PDFs with relatively large gluon contents at large $x$.

   ↳ hep-phhep-exnucl-exChin.J.Phys.(2021)·15 citations
5. 05*

   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 $\approx 3\sigma$ significance, and the CMS result can be correlated and commonly explained in a model independent way by the operator $[Q_{\ell q}^{(3)}{]}_{1111}=({\bar{\ell }}_1{\gamma }^{\mu }{\sigma }^I{\ell }_1)({\bar{q}}_1{\gamma }_{\mu }{\sigma }^I{q}_1)$. 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 $R(\pi )=\pi \to \mu \nu /\pi \to e\nu$. We find a combined preference for the new physics hypothesis of $4.5\sigma$ and predict $1.0004<R(\pi )<1.0009$ (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
6. 06*

   Cluster structure of 21Ne and 21Na

   R. Bijker🇲🇽 · F. Iachello🇺🇸

   We study the cluster structure of 21Ne and 21Na within the framework of the cluster shell model (CSM) and show that they have a complex cluster structure with the coexistence of a 20Ne+n, 20}Ne+p structure and a 19Ne+2n, 19}F+2p structure. Seven rotational bands are identified in 21Ne and four in 21Na and assigned to single-particle cluster states, single-hole cluster states and vibrational states. The single-particle states are associated with the 20Ne+n and 20Ne+p cluster structure, while the single-hole states are associated with the 19Ne+2n and 19F+2p structure.

   ↳ nucl-thnucl-exNPA(2021)·7 citations
7. 07*

   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

* 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.