Thu·Dec 14, 2023Thursday·December 14, 2023

1. 01*

   Elliptic and triangular flow of light nuclei in Au+Au collisions in the BES-II energies using the STAR detector

   Rishabh Sharma🇮🇳

   Light nuclei might be formed in heavy-ion collisions by the coalescence of produced (anti-)nucleons or transported nucleons. Due to their low binding energies, they are more likely to form at later stages of the hadronic fireball. In this proceedings, we report the transverse momentum and centrality dependence of elliptic ($v_2$) and triangular ($v_3$) flow of $d$, $t$, and ${}^3$He in Au+Au collisions at $\sqrt{s_{NN}}$ = 14.6 -- 54.4 GeV. The mass number scaling of $v_2(p_T)$ and $v_3(p_T)$ of light nuclei is discussed. We also report the comparison of $v_2(p_T)$ and $v_3(p_T)$ of light nuclei with a transport-plus-coalescence model calculation.

   nucl-exhep-exhep-phEPJ Web Conf.(2024)·1 citation
2. 02*

   Evaluation of the E2/M1 ratio in the $N\to \Delta (1232)$ transition from the $\vec{\gamma }\vec{p}\to p{\pi }^0$ reaction

   E. Mornacchi🇩🇪 · P. Pedroni🇮🇹 · F. Afzal🇩🇪 · Y. Wunderlich🇩🇪 · S. Abt🇨🇭 · P. Achenbach🇩🇪 · J.R.M. Annand🇬🇧 · H.J. Arends🇩🇪 · M. Bashkanov🇬🇧 · M. Biroth🇩🇪 · R. Beck🇩🇪 · N. Borisov🇷🇺 and 50 other authors

   A new data set for the helicity-dependent differential cross section of the single-meson photoproduction reaction $\gamma p\to p{\pi }^0$ was obtained for the photon energy interval 150-400 MeV. The experiment was performed at the A2 tagged photon facility of the Mainz Microtron MAMI using a circularly polarized photon beam and a longitudinally polarized proton target. The reaction products were detected with the large acceptance Crystal Ball/TAPS calorimeter covering 97\% of the full solid angle. These new results, obtained with a fine energy and polar angle binning, greatly increase both the existing quantity and quality of the data available for this observable. A moment analysis, based on a finite expansion in Legendre polynomials, was applied to these data by using a bootstrap-based fitting method to correctly account for their systematic uncertainties. From the resulting decomposition of the differential cross sections, the $E2/M1$ ratio for the $N\to \Delta (1232)$ transition was determined to be $[-2.38\pm 0.16(stat.+sys.)\pm 0.10(model)]\%$. Combining this value with previous results also allowed us to evaluate the most precise available estimate of the $E2/M1$ ratio to be used for all further reference and model comparisons.

   nucl-exPRC(2024)·6 citations
3. 03*

   Shell-Model Description of the Isospin-Symmetry-Breaking Correction to Gamow-Teller $\beta$-Decay Rates and Their Mirror Asymmetries

   Latsamy Xayavong🇰🇷 · Yeunhwan Lim🇰🇷

   The isospin-symmetry breaking correction, denoted as ${\delta }_C$, is introduced for the first time within the shell-model framework to the nuclear matrix element of Gamow-Teller transitions. ${\delta }_C$ is separated into two components: the isospin mixing term, ${\delta }_{C1}$, induced by the Coulomb and nuclear charge-dependent forces in the effective Hamiltonian, and the radial mismatch term, ${\delta }_{C2}$, arising from differences between proton and neutron realistic wave functions. Consequently, the refinement strategy developed for superallowed $0^{+}\to 0^{+}$ Fermi transitions is applied to Gamow-Teller transitions as well. It is demonstrated that, to a given precision level, the shell model calculation of ${\delta }_C$ converges much faster than the calculation of the transition matrix element. Furthermore, higher-order correction terms are investigated and considered for consistent study of our works. Various interesting properties of the leading correction terms are discovered within the two-level model and parentage expansion of the one-body transition densities in angular momentum and isospin spaces. One such property is the dependence of ${\delta }_{C1}$ on the isospin admixture amplitude, $\alpha$, starting from the first order, while the same model yields ${\delta }_{C1}={\alpha }^2$ for Fermi transitions. The calculated ${\delta }_C$ values are then utilized to evaluate the mirror asymmetry of Gamow-Teller transition strengths, which are compared with available experimental data and other theoretical calculations. Due to the refined fitting procedure of the Woods-Saxon potential parameters and the improved convergence as a function of intermediate state number, our results show better agreement on average compared to those of Smirnova and Volpe [Nucl. Phys. {\bf A 714}, 441 (2003)].

   ↳ nucl-thnucl-exPRC(2025)·7 citations
4. 04*

   Nonrelativistic nuclear reduction for tensor couplings in dark matter direct detection and $\mu \to e$ conversion

   Ayala Glick-Magid🇺🇸

   The nonrelativistic effective field theory (NRET) is widely used in dark matter direct detection and charged-lepton flavor violation studies through $\mu \to e$ conversion. However, existing literature has not fully considered tensor couplings. This study fills this gap by utilizing an innovative tensor decomposition method, extending NRET to incorporate previously overlooked tensor interactions. This development is expected to have a significant impact on ongoing experiments seeking physics beyond the Standard Model and on our understanding of the new-physics interactions. Notably, we identify additional operators in $\mu \to e$ conversion that are absent in scalar and vector couplings. To support further research and experimental analyses, comprehensive tables featuring tensor matrix elements and their corresponding operators are provided.

   ↳ hep-phnucl-exnucl-thPRD(2024)·5 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.