Wed·Jul 13, 2022Wednesday·July 13, 2022

1. 01*

   Measurement of global polarization of {\Lambda} hyperons in few-GeV heavy-ion collisions

   R. Abou Yassine · J. Adamczewski-Musch · C. Asal · M. Becker · A. Belounnas · A. Blanco · C. Blume · L. Chlad · P. Chudoba · I. Ciepal · M. Cordts · J. Dreyer and 96 other authors

   The global polarization of {\Lambda} hyperons along the total orbital angular momentum of a relativistic heavy-ion collision is presented based on the high statistics data samples collected in Au+Au collisions at \sqrt{s_{NN}} = 2.4 GeV and Ag+Ag at 2.55 GeV with the High-Acceptance Di-Electron Spectrometer (HADES) at GSI, Darmstadt. This is the first measurement below the strangeness production threshold in nucleon-nucleon collisions. Results are reported as a function of the collision centrality as well as a function of the hyperon transverse momentum (p_T) and rapidity (y_{CM}) for the range of centrality 0--40%. We observe a strong centrality dependence of the polarization with an increasing signal towards peripheral collisions. For mid-central (20--40%) collisions the polarization magnitudes are <P_{\Lambda}>(%) = 6.8 \pm 1.3 (stat.) \pm 2.1 (syst.) for Au+Au and <P_{\Lambda}>(%) = 6.2 \pm 0.4 (stat.) \pm 0.6 (syst.) for Ag+Ag, which are the largest values observed so far. This observation thus provides a continuation of the increasing trend previously observed by STAR and contrasts expectations from recent theoretical calculations predicting a maximum in the region of collision energies about 3 GeV. The observed polarization is of a similar magnitude as predicted by 3D fluid dynamics and the UrQMD plus thermal vorticity model and significantly above results from the AMPT model.

   nucl-exPLB(2022)·86 citations
2. 02*

   Determining the Proton's Gluonic Gravitational Form Factors

   B. Duran🇺🇸 · Z. -E. Meziani🇺🇸 · S. Joosten🇺🇸 · M. K. Jones🇺🇸 · S. Prasad🇺🇸 · C. Peng🇺🇸 · W. Armstrong🇺🇸 · H. Atac🇺🇸 · E. Chudakov🇺🇸 · H. Bhatt🇺🇸 · D. Bhetuwal🇺🇸 · M. Boer🇺🇸 and 43 other authors

   The proton is one of the main building blocks of all visible matter in the universe. Among its intrinsic properties are its electric charge, mass, and spin. These emerge from the complex dynamics of its fundamental constituents, quarks and gluons, described by the theory of quantum chromodynamics (QCD). Using electron scattering, its electric charge and spin, shared among the quark constituents, have been the topic of active investigation. An example is the novel precision measurement of the proton's electric charge radius. In contrast, little is known about the proton's inner mass density, dominated by the energy carried by the gluons, which are hard to access through electron scattering since gluons carry no electromagnetic charge. Here, we chose to probe this gluonic gravitational density using a small color dipole, the $J/\psi$ particle, through its threshold photoproduction. From our data, we determined, for the first time, the proton's gluonic gravitational form factors. We used a variety of models and determined, in all cases, a mass radius that is notably smaller than the electric charge radius. In some cases, the determined radius, although model dependent, is in excellent agreement with first-principle predictions from lattice QCD. This work paves the way for a deeper understanding of the salient role of gluons in providing gravitational mass to visible matter.

   nucl-exhep-exhep-phNature(2023)·191 citations
3. 03*

   Neutrinoless $\beta \beta$-decay nuclear matrix elements from two-neutrino $\beta \beta$-decay data

   Lotta Jokiniemi🇪🇸 · Beatriz Romeo🇪🇸 · Pablo Soriano🇪🇸 · Javier Menéndez🇪🇸

   We study two-neutrino ($2\nu \beta \beta$) and neutrinoless double-$\beta$ ($0\nu \beta \beta$) decays in the nuclear shell model and proton-neutron quasiparticle random-phase approximation (pnQRPA) frameworks. Calculating the decay half-life of several dozens of nuclei ranging from calcium to xenon with the shell model, and of $\beta \beta$ emitters with a wide range of proton-neutron pairing strengths in the pnQRPA, we observe good linear correlations between $2\nu \beta \beta$- and $0\nu \beta \beta$-decay nuclear matrix elements for both methods. We then combine the correlations with measured $2\nu \beta \beta$-decay half-lives to predict $0\nu \beta \beta$-decay matrix elements with theoretical uncertainties based on our systematic calculations. Our results include two-body currents and the short-range $0\nu \beta \beta$-decay operator.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2023)·54 citations
4. 04*

   Systematics of fully heavy dibaryons

   Xin-Zhen Weng🇮🇱 · Shi-Lin Zhu🇨🇳

   We systematically study the mass spectra of the fully heavy dibaryons in an extended chromomagnetic model, which includes both the colorelectric and chromomagnetic interactions. We find no stable state below the corresponding baryon-baryon thresholds. Besides the masses, we also estimate the relative width ratios of the two-body decay channels. We hope our study will be of help for future experiments.

   ↳ hep-phhep-exhep-latnucl-ex+1EPJC(2024)·16 citations
5. 05*

   Energy Dependence of the Breit-Wheeler process in Heavy-Ion Collisions and its Application to Nuclear Charge Radius Measurements

   Xiaofeng Wang🇨🇳 · James Daniel Brandenburg🇺🇸 · Lijuan Ruan🇺🇸 · Fenglan Shao🇨🇳 · Zhangbu Xu🇺🇸 · Chi Yang🇨🇳 · Wangmei Zha🇨🇳

   The collision energy dependence of the cross section and the transverse momentum distribution of dielectrons from the Breit-Wheeler process in heavy-ion collisions are computed in the lowest-order QED and found to be sensitive to the nuclear charge distribution and the infrared-divergence of the ultra-Lorentz boosted Coulomb field. Within a given experimental kinematic acceptance, the cross section is found to increase while the pair transverse momentum ($\sqrt{⟨p_T^2⟩}$) decreases with increasing beam energy. We demonstrate that the transverse-momentum component of Weizsacker-Williams photons is due to the finite extent of the charge source and electric field component in the longitudinal direction. We further clarify the connection between the nuclear charge distribution and the kinematics of produced $e^{+}{e}^{-}$ from the Breit-Wheeler process, and propose a criterion for the validity of the Breit-Wheeler process in relativistic heavy-ion collisions. Following this approach we demonstrate that the experimental measurements of the Breit-Wheeler process in ultra-relativistic heavy-ion collisions can be used to quantitatively constrain the nuclear charge radius. The extracted parameters show sensitivity to the impact parameter dependence, and can be used to study the initial-state and final-state effects in hadronic interactions.

   ↳ nucl-thhep-phnucl-exPRC(2023)·27 citations
6. 06*

   Measurement of Charmonium Production in $p+p$ and $p+d$ Interactions in the Fermilab SeaQuest Experiment

   Ching Him Leung (for the SeaQuest Collaboration)🇺🇸

   The Fermilab SeaQuest experiment has measured dimuon events from the interactions of 120GeV proton beam on liquid hydrogen and deuterium targets with dimuon mass between 2 and 9GeV. These dimuon events contain both the Drell-Yan process and the charmonium ($J/\psi$ and ${\psi }^{\prime }$) production. Unlike the Drell-Yan process which probes the antiquark distributions in the nucleons, the charmonium production is sensitive to both quark and gluon distributions. SeaQuest has extracted the ${\sigma }^{pd}/2{\sigma }^{pp}$ ratio as well as the differential cross sections for charmonium production in the kinematic region of $0.4<x_F<0.9$. The ${\sigma }^{pd}/2{\sigma }^{pp}$ ratio for charmonium production are found to be significantly different from that of the Drell-Yan process. The measured differential cross sections for charmonium production are compared with theoretical calculations using Color Evaporation Model and Non-Relativistic QCD model.

   ↳ hep-exnucl-ex0 citations
7. 07*

   Main Parameters of the MC and FCC/SppC/LHC/RHIC based Muon-Nucleus Colliders

   Burak Dagli🇹🇷 · Bora Ketenoglu🇹🇷 · Arif Ozturk🇹🇷 · Saleh Sultansoy🇹🇷

   Construction of future Muon Collider (or dedicated mu-ring) tangential to nucleus colliders will give opportunity to realize mu-A collisions at multi-TeV center of mass energies at a luminosity of order of 10^29-10^30 cm^-2s^-1. Obviously, such colliders will essentially enlighten fundamentals of strong interactions from quark to nucleus levels as well as clarify QCD basics. This paper is devoted to estimation of main parameters of the FCC, SppC, HL-LHC, HE-LHC and RHIC based muon-nucleus collider proposals by the software AloHEP.

   ↳ physics.acc-phhep-exnucl-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.