Fri·Jun 18, 2021Friday·June 18, 2021

1. 01*

   Search for the chiral magnetic effect via charge-dependent azimuthal correlations relative to spectator and participant planes in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV

   STAR Collaboration: M. S. Abdallah · J. Adam · L. Adamczyk · J. R. Adams · J. K. Adkins · G. Agakishiev · I. Aggarwal · M. M. Aggarwal · Z. Ahammed · I. Alekseev · D. M. Anderson · A. Aparin and 377 other authors

   The chiral magnetic effect (CME) refers to charge separation along a strong magnetic field due to imbalanced chirality of quarks in local parity and charge-parity violating domains in quantum chromodynamics. The experimental measurement of the charge separation is made difficult by the presence of a major background from elliptic azimuthal anisotropy. This background and the CME signal have different sensitivities to the spectator and participant planes, and could thus be determined by measurements with respect to these planes. We report such measurements in Au+Au collisions at a nucleon-nucleon center-of-mass energy of 200 GeV at the Relativistic Heavy-Ion Collider. It is found that the charge separation, with the flow background removed, is consistent with zero in peripheral (large impact parameter) collisions. Some indication of finite CME signals is seen in mid-central (intermediate impact parameter) collisions. Significant residual background effects may, however, still be present.

   nucl-exhep-exhep-phnucl-thPRL(2022)·61 citations
2. 02*

   Level Densities from 0-30 MeV

   R.B. Firestone🇺🇸

   Photon strength, $f(E_{\gamma })$, measured in photonuclear reactions, is the product of the average level density per MeV, $\rho (E_x)$, and the average reduced level width, ${\Gamma }_{\gamma }/E_{\gamma }^3$ for levels populated primarily by E1 transitions at an excitation energy $E_x=E_{\gamma }$. It can be calculated with the Brink-Axel (BA) formulation modified to include contributions from the Giant Dipole Resonance (GDR) and higher lying resonances. Level densities and reduced widths have been calculated for 17 nuclei with atomic numbers between Z=14-92. Level densities below the GDR energy were calculated with the CT-JPI model and combined with the BA photon strength to determine the associated reduced widths. The reduced widths varied exponentially with level energy and could be extrapolated up to higher energies. The extrapolated widths were then combined with the BA photon strength to determine the level densities at higher energies. The level densities are found to increase exponentially at low energies, peak near the GDR energy due to the appearance of new states at the $2\hslash \omega$ shell closure, and continue to increase less rapidly up to at least 30 MeV. The average level densities have been compared with the Fermi Gas Level Density (FGLD), Back-Shifted Fermi Gas (BSFG), and Hartree-Fock-Bogoliubov (HFB) models. Good agreement is found with the nearly identical FGLD and BDFG models, while the HFB models gives substantially lower level densities. A universal set of FGLD model parameters were determined as a function of mass and temperature that are applicable to all nuclei.

   ↳ nucl-thnucl-ex1 citation
3. 03*

   Dispersion relation analysis of the radiative corrections to $g_A$ in the neutron $\beta$-decay

   Mikhail Gorchtein🇩🇪 · Chien-Yeah Seng🇩🇪

   We present the first and complete dispersion relation analysis of the inner radiative corrections to the axial coupling constant $g_A$ in the neutron $\beta$-decay. Using experimental inputs from the elastic form factors and the spin-dependent structure function $g_1$, we determine the contribution from the $\gamma W$-box diagram to a precision better than $10^{-4}$. Our calculation indicates that the inner radiative corrections to the Fermi and the Gamow-Teller matrix element in the neutron $\beta$-decay are almost identical, i.e. the ratio $\lambda =g_A/g_V$ is almost unrenormalized. With this result, we predict the bare axial coupling constant to be {${\mathring{g}}_A=-1.2754(13{)}_{\exp }(2{)}_{\mathrm{RC}}$} based on the PDG average $\lambda =-1.2756(13)$

   ↳ hep-phhep-latnucl-exnucl-thJHEP(2021)·45 citations
4. 04*

   Investigations of the linear and non-linear flow harmonics using the A Multi-Phase Transport model

   Niseem Magdy🇺🇸

   The Multi-Phase Transport model (AMPT) is used to study the effects of the parton-scattering cross-sections (${\sigma }_{pp}$) and hadronic re-scattering on the linear contributions to the flow harmonic ${\text{v}}_4$, the non-linear response coefficients, and the correlations between different order flow symmetry planes in Au+Au collisions at 200~GeV. The model results, which agree with current experimental measurements, indicate that the higher-order flow harmonics are sensitive to the ${\sigma }_{pp}$ variations. However, the non-linear response coefficients and the correlations between different order flow symmetry planes are ${\sigma }_{pp}$ independent. These results suggest that further detailed experimental measurements which span a broad range of collision systems and beam energies could serve as an additional constraint for the theoretical models' calculations.

   ↳ nucl-thhep-phnucl-exJ.Phys.G(2022)·10 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.