Tue·Nov 24, 2020Tuesday·November 24, 2020

1. 01*

   Measurements of Nuclear Modification Factors of $B_s^0$ and $B^{+}$ Mesons in PbPb Collisions with the CMS Experiment

   Zhaozhong Shi (on Behalf of CMS Collaboration)🇺🇸

   Beauty quarks are considered as one of the best probes of the strongly interacting medium created in relativistic heavy-ion collisions because they are predominantly produced via initial hard scatterings. Measurements of B meson production provide information about the diffusion of beauty quarks and the flavor dependence of in-medium energy loss. In these studies, clarifying the hadronization mechanism is crucial for understanding the transport properties of beauty quarks. Measurements of $B_s^0$ production can shed light on the mechanisms of beauty recombination in the medium and provide information about strangeness enhancement in the quark-gluon plasma. In this talk, we will present a new measurement of the ratio of $B_s^0$ to $B^{+}$ mesons in PbPb collisions at 5.02 TeV with the CMS detector, using data recorded in 2018.

   nucl-exPoS(2021)·0 citations
2. 02*

   $\mathbf{N}=32$ shell closure below calcium: Low-lying structure of ${}^{50}$Ar

   M. L. Cortés🇯🇵 · W. Rodriguez🇨🇴 · P. Doornenbal🇯🇵 · A. Obertelli🇫🇷 · J. D. Holt🇨🇦 · J. Menéndez🇪🇸 · K. Ogata🇯🇵 · A. Schwenk🇩🇪 · N. Shimizu🇯🇵 · J. Simonis🇩🇪 · Y. Utsuno🇯🇵 · K. Yoshida🇯🇵 and 69 other authors

   Low-lying excited states in the $N=32$ isotope ${}^{50}$Ar were investigated by in-beam $\gamma$-ray spectroscopy following proton- and neutron-knockout, multi-nucleon removal, and proton inelastic scattering at the RIKEN Radioactive Isotope Beam Factory. The energies of the two previously reported transitions have been confirmed, and five additional states are presented for the first time, including a candidate for a 3${}^{-}$ state. The level scheme built using $\gamma \gamma$ coincidences was compared to shell-model calculations in the $sd-pf$ model space, and to ab initio predictions based on chiral two- and three-nucleon interactions. Theoretical proton- and neutron-knockout cross sections suggest that two of the new transitions correspond to $2^{+}$ states, while the previously proposed $4^{+}$ state could also correspond to a $2^{+}$ state.

   nucl-exPRC(2020)·19 citations
3. 03*

   Confirmation of $g_{\mathrm{A}}$ quenching using the revised spectrum-shape method for the analysis of the ${}^{113}$Cd $\beta$-decay as measured with the COBRA demonstrator

   Joel Kostensalo🇫🇮 · Jouni Suhonen🇫🇮 · Juliane Volkmer🇩🇪 · Stefan Zatschler🇩🇪 · Kai Zuber🇩🇪

   In this article we present an updated spectrum-shape analysis of the ${}^{113}$Cd fourfold forbidden non-unique $\beta$-decay transition in order to address the quenching of the weak axial-vector coupling $g_{\mathrm{A}}$ in low-momentum exchange nuclear processes. The experimental data were collected in a dedicated low-threshold run with the COBRA demonstrator at the LNGS and resulted in 44 individual ${}^{113}$Cd spectra. These data are evaluated in the context of three nuclear model frameworks based on a revised version of the spectrum-shape method and the conserved vector current hypothesis. The novel idea devised in the present work is to fit the value of the small relativistic nuclear matrix element (s-NME) driving the nuclear model calculations, which remained essentially as a free parameter in previous studies. This is done by tuning the nuclear structure calculations and making use of the interplay of $g_{\mathrm{A}}$ and the s-NME such that the experimentally known ${}^{113}$Cd half-life gets reproducible by the different frameworks. In this way, a best fit s-NME value can be derived for each of the considered nuclear models, which finally enters the template calculations used to perform the spectrum-shape analysis for each of the obtained ${}^{113}$Cd spectra. The primary analysis strategy results in significantly quenched values of the axial-vector coupling for all three nuclear models: ${\overline{g}}_{\mathrm{A}}(\text{ISM})=0.907\pm 0.064$, ${\overline{g}}_{\mathrm{A}}(\text{MQPM})=0.993\pm 0.063$ and ${\overline{g}}_{\mathrm{A}}(\text{IBFM-2})=0.828\pm 0.140$. Moreover, with our data-driven approach one of the main shortcomings of the spectrum-shape method has been resolved. This achievement is a milestone in the description of strongly forbidden $\beta$-decays and adds to the indications for the existence of a quenching of $g_{\mathrm{A}}$ in low-momentum exchange nuclear processes.

   nucl-exnucl-thPLB(2021)·30 citations
4. 04*

   QCD equations of state and speed of sound in neutron stars

   Toru Kojo🇨🇳

   Neutron stars are cosmic laboratories to study dense matter in Quantum Chromodynamics (QCD). The observable mass-radius relations of neutron stars are determined by QCD equations of state, and can reflect the properties of QCD phase transitions. In the last decade there have been historical discoveries in neutron stars, the discoveries of two-solar mass neutron stars and neutron star merger events, which have imposed tight constraints on equations of state. While a number of equations of state are constructed to satisfy these constraints, a theoretical challenge is how to reconcile those constructions with the microphysics expected from the hadron physics and in-medium calculations. In this short article we briefly go over recent observations and discuss their implications for dense QCD matter, referring to QCD constraints in the low and high density limits, QCD-like theories, and lattice QCD results for baryon-baryon interactions.

   ↳ nucl-thastro-ph.HEhep-phnucl-exAAPPS Bull.(2021)·98 citations
5. 05*

   Deep exclusive electroproduction of ${\pi }^0$ at high $Q^2$ in the quark valence regime

   The Jefferson Lab Hall A Collaboration: M. Dlamini (Ohio University) · B. Karki (Ohio University) · S.F. Ali (Catholic University of America) · P-J. Lin (Universite Paris-Saclay) · F. Georges (Universite Paris-Saclay) · H-S Ko (Universite Paris-Saclay) · N. Israel (Ohio University) · M.N.H. Rashad (Old Dominion University) · A. Stefanko (Carnegie Mellon University) · D. Adikaram (Thomas Jefferson National Accelerator Facility) · Z. Ahmed (University of Regina) · H. Albataineh (Texas A&M University) and 146 other authors

   We report measurements of the exclusive neutral pion electroproduction cross section off protons at large values of $x_B$ (0.36, 0.48 and 0.60) and $Q^2$ (3.1 to 8.4 GeV${}^2$) obtained from Jefferson Lab Hall A experiment E12-06-014. The corresponding structure functions $d{\sigma }_L/dt+ϵd{\sigma }_T/dt$, $d{\sigma }_{TT}/dt$, $d{\sigma }_{LT}/dt$ and $d{\sigma }_{L{T}^{\prime }}/dt$ are extracted as a function of the proton momentum transfer $t-t_{min}$. The results suggest the amplitude for transversely polarized virtual photons continues to dominate the cross-section throughout this kinematic range. The data are well described by calculations based on transversity Generalized Parton Distributions coupled to a helicity flip Distribution Amplitude of the pion, thus providing a unique way to probe the structure of the nucleon.

   ↳ hep-exnucl-exPRL(2021)·26 citations
6. 06*

   Impact of scale, nuclear PDF and temperature variations on the interpretation of medium-modified jet production data from the LHC

   A. Andronic🇩🇪 · J. Honermann🇩🇪 · M. Klasen🇩🇪 · C. Klein-Bösing🇩🇪 · J. Salomon🇩🇪

   In this paper we present a study of in-medium jet modifications performed with JEWEL and PYTHIA 6.4, focusing on the uncertainties related to variations of the perturbative scales and nuclear parton distribution functions (PDFs) and on the impact of the initial and crossover temperature variations of the medium. The simulations are compared to LHC data for the jet spectrum and the nuclear modification factor. We assess the interplay between the choice of nuclear PDFs and different medium parameters and study the impact of nuclear PDFs and the medium on the jet structure via the Lund plane.

   ↳ hep-phhep-exnucl-exnucl-thJHEP(2021)·3 citations
7. 07*

   Femtoscopy of the Origin of the Nucleon Mass

   G. Krein🇧🇷 · T.C. Peixoto🇧🇷

   We study the prospects of using femtoscopic low-momentum correlation measurements at the Large Hadron Collider to access properties of the J/psi-nucleon interaction. The QCD multipole expansion in terms of the J/psi chromopolarizability relates the forward scattering amplitude to a key matrix element to the origin of the nucleon mass problem, the average chromoelectric gluon distribution in the nucleon. We use information on the J/psi-nucleon interaction provided by lattice QCD simulations and phenomenological models to compute J/psi-nucleon correlation functions. The computed correlation functions show clear sensitivity to the interaction, in particular to the J/psi chromopolarizability.

   ↳ hep-phhep-exhep-latnucl-ex+1Few Body Syst.(2020)·24 citations
8. 08*

   Neutron skin $r_{\mathrm{skin}}^{48}$ determined from reaction cross section of proton+${}^{48}$Ca scattering

   Shingo Tagami🇯🇵 · Maya Takechi🇩🇪 · Jun Matsui · Tomotsugu Wakasa🇯🇵 · Masanobu Yahiro🇯🇵

   {\bf Background:} Using the chiral (Kyushu) $g$-matrix folding model with the densities calculated with GHFB+AMP, we determined $r_{\mathrm{skin}}^{208}=0.25$fm from the central values of ${\sigma }_{\mathrm{R}}$ of p+${}^{208}$Pb scattering in $E_{\mathrm{in}}=40-81$MeV. The high-resolution $E1$ polarizability experiment ($E1$pE) yields $r_{\mathrm{skin}}^{48}(E1\mathrm{pE})=0.14-0.20$fm. The data on ${\sigma }_{\mathrm{R}}$ are available as a function of $E_{\mathrm{in}}$ for $p$+${}^{48}$Ca scattering. {\bf Aim:} Our aim is to determine $r_{\mathrm{skin}}^{48}$ from the central values of ${\sigma }_{\mathrm{R}}$ for $p$+${}^{48}$Ca scattering by using the folding model. {\bf Results:} As for ${}^{48}$Ca, we determine $r_n(E1\mathrm{pE})=3.56$fm from the central value 0.17fm of $r_{\mathrm{skin}}^{48}(E1\mathrm{pE})$ and $r_p(\mathrm{EXP})=3.385$fm of electron scattering, and evaluate $r_m(E1\mathrm{pE})=3.485$fm from the $r_n(E1\mathrm{pE})$ and the $r_p(\mathrm{EXP})$ of electron scattering. The folding model with GHFB+AMP densities reproduces ${\sigma }_{\mathrm{R}}$ in $23\le E_{\mathrm{in}}\le 25.3$ MeV in one-$\sigma$ level, but slightly overestimates the central values of ${\sigma }_{\mathrm{R}}$ there. In $23\le E_{\mathrm{in}}\le 25.3$MeV, the small deviation allows us to scale the GHFB+AMP densities to the central values of $r_p(\mathrm{EXP})$ and $r_n(E1\mathrm{pE})$. The ${\sigma }_{\mathrm{R}}(E1\mathrm{pE})$ obtained with the scaled densities almost reproduce the central values of ${\sigma }_{\mathrm{R}}$ when $E_{\mathrm{in}}=23-25.3$MeV, so that the ${\sigma }_{\mathrm{R}}(\mathrm{GHFB}+\mathrm{AMP})$ and the ${\sigma }_{\mathrm{R}}(E1\mathrm{pE})$ are in 1-$\sigma$ of ${\sigma }_{\mathrm{R}}$ there. In $E_{\mathrm{in}}=23-25.3$MeV, we determine the $r_m(\mathrm{EXP})$ from the central values of ${\sigma }_{\mathrm{R}}$ and take the average for the $r_m(\mathrm{EXP})$. The averaged value is $r_m(\mathrm{EXP})=3.471$fm. Eventually, we obtain $r_{\mathrm{skin}}^{48}(\mathrm{EXP})=0.146$fm from $r_m(\mathrm{EXP})=3.471$fm and $r_p(\mathrm{EXP})=3.385$fm.

   ↳ nucl-thnucl-ex2 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.