Tue·Sep 13, 2022Tuesday·September 13, 2022

1. 01*

   QCD Phase Structure and Interactions at High Baryon Density: Continuation of BES Physics Program with CBM at FAIR

   D. Almaalol🇺🇸 · M. Hippert🇺🇸 · J. Noronha-Hostler🇺🇸 · J. Noronha🇺🇸 · E. Speranza🇺🇸 · G. Basar🇺🇸 · S. Bass🇺🇸 · D. Cebra🇺🇸 · V. Dexheimer🇺🇸 · D. Keane🇺🇸 · S. Radhakrishnan🇺🇸 · A.I. Sheikh🇺🇸 and 32 other authors

   We advocate for an active US participation in the international collaboration of the CBM experiment that will allow the US nuclear physics program to build on its successful exploration of the QCD phase diagram, use the expertise gained at RHIC to make complementary measurements at FAIR, and contribute to achieving the scientific goals of the beam energy scan (BES) program.

   nucl-exnucl-th40 citations
2. 02*

   (Anti)nucleosynthesis in heavy-ion collisions and (anti)nuclei as "baryonmeter" of the collision

   Mario Ciacco (for the ALICE Collaboration)🇮🇹

   The production mechanism of light (anti)nuclei in heavy-ion collisions has been extensively studied experimentally and theoretically. Two competing (anti)nucleosynthesis models are typically used to describe light (anti)nuclei yields and their ratios to other hadrons in heavy-ion collisions: the statistical hadronization model (SHM) and the nucleon coalescence model. The possibility to distinguish these phenomenological models calls for new experimental observables. Given their large baryon number, light (anti)nuclei have a high sensitivity to the baryon chemical potential (${\mu }_{\mathrm{B}}$) of the system created in the collision. In this talk, the first measurement of event-by-event antideuteron number fluctuations in heavy-ion collisions is presented and compared with expectations of the SHM and coalescence model. In addition, the antinuclei-to-nuclei ratios are used to obtain a measurement of ${\mu }_{\mathrm{B}}$ in heavy-ion collisions with unprecedented precision.

   nucl-exEPJ Web Conf.(2023)·0 citations
3. 03*

   Microscopic aspects of $\gamma$-softness in atomic nuclei

   Nazira Nazir · S. Jehangir · S.P. Rouoof · G.H. Bhat · J. A. Sheikh · N. Rather · S.Frauendorf

   The microscopic origin of the $\gamma$-softness (fluctuations in the triaxiality parameter $\gamma$ of the nuclear shape) observed in atomic nuclei is studied in the framework of the triaxial projected shell model approach, which is based on the deformed mean-field picture with multi-quasiparticle configuration space. It is demonstrated that the coupling to quasiparticle excitations drives the system from a $\gamma$-rigid to a $\gamma$-soft pattern. As an illustrative example for a $\gamma$-soft nucleus, a detailed study has been performed for the ${}^{104}$Ru nucleus. The experimental energies and a large sample of measured $E2$ matrix elements available for this nucleus are reproduced quite accurately. The shape invariant analysis of the calculated $E2$ matrix elements elucidates the $\gamma$-soft nature of ${}^{104}$Ru.

   ↳ nucl-thnucl-ex15 citations
4. 04*

   Global and local polarization of $\Lambda$ ($\bar{\Lambda }$) hyperons in Pb--Pb collisions in ALICE at the LHC

   Debojit Sarkar🇺🇸

   The global polarization of the $\Lambda$ and $\bar{\Lambda }$ hyperons ($P_{\mathrm{H}}$) has been measured in Pb--Pb collisions at $\text{sNN}=$ 2.76 TeV and 5.02 TeV in ALICE at the Large Hadron Collider (LHC). The hyperon global polarization is found to be consistent with zero at both collision energies. The local polarization of the $\Lambda$ and $\bar{\Lambda }$ hyperons along the beam ($z$) direction, $P_{\mathrm{z}}$, has also been measured in Pb--Pb collisions at $\text{sNN}=5.02$ TeV. The $P_{\mathrm{z}}$, measured as a function of the hyperon emission angle relative to the second harmonic symmetry plane, exhibits a second harmonic sine modulation, as expected due to elliptic flow. The measurements of global and local hyperon polarization are reported for different collision centralities and as a function of transverse momentum in semicentral collisions. These results show the first experimental evidence of a non-zero hyperon $P_{\mathrm{z}}$ in Pb--Pb collisions at the LHC.

   ↳ hep-exhep-phnucl-exphysics.data-anEPJ Web Conf.(2022)·2 citations
5. 05*

   Empirical determination of the Bohr-Weisskopf effect in cesium and improved tests of precision atomic theory in searches for new physics

   G. Sanamyan🇦🇺 · B. M. Roberts🇦🇺 · J. S. M. Ginges🇦🇺

   The finite distribution of the nuclear magnetic moment across the nucleus gives a contribution to the hyperfine structure known as the Bohr-Weisskopf (BW) effect. We have obtained an empirical value of -0.24(18)% for this effect in the ground and excited s states of atomic Cs-133. This value is found from historical muonic-atom measurements in combination with our muonic-atom and atomic many-body calculations. The effect differs by 0.5% in the hyperfine structure from the value found using the uniform magnetization distribution, which has been commonly employed in the precision heavy-atom community over the last several decades. We also deduce accurate values for the BW effect in other isotopes and states of cesium. These results enable cesium atomic wave functions to be tested in the nuclear region at an unprecedented 0.2% level, and are needed for the development of precision atomic many-body methods. This is important for increasing the discovery potential of precision atomic searches for new physics, in particular for atomic parity violation in cesium.

   ↳ physics.atom-phhep-phnucl-exnucl-thPRL(2023)·17 citations
6. 06*

   Nucleonic metamodelling in light of multimessenger, PREX-II and CREX data

   Chiranjib Mondal🇫🇷 · Francesca Gulminelli🇫🇷

   The need of reconciling our understanding of the behavior of hadronic matter across a wide range of densities, especially at the time when data from multimessenger observations and novel experimental facilities are flooding in, has provided new challenges to the nuclear models. Particularly, the density dependence of the isovector channel of the nuclear energy functionals seems hard to pin down if experiments like PREX-II (or PREX) and CREX are required to be taken on the same footing. We put to test this anomaly in a semi-agnostic modelling technique, by performing a full Bayesian analysis of static properties of neutron stars, together with global properties of nuclei as binding energy, charge radii and neutron skin calculated at the semi-classical level. Our results show that the interplay between bulk and surface properties, and the importance of high order empirical parameters that effectively decouple the subsaturation and the supersaturation density regime, might partially explain the tension between the different measurements and observations. If the surface behaviors, however, are decoupled from the bulk properties, we found a rather harmonious situation among experimental and observational data.

   ↳ nucl-thastro-ph.HEnucl-exPRC(2023)·54 citations
7. 07*

   Enhanced dilepton emission from a phase transition in dense matter

   O. Savchuk🇺🇦 · A. Motornenko🇩🇪 · J. Steinheimer🇩🇪 · V. Vovchenko🇺🇸 · M. Bleicher🇩🇪 · M. Gorenstein🇺🇦 · T. Galatyuk🇩🇪

   It is demonstrated that the presence of a phase transition in heavy ion collisions, at beam energies that probe dense QCD matter, leads to a significant enhancement of the dilepton yield per produced pion due to the extended emission time. In addition, the temperature of low mass dileptons shows a modest decrease due to the mixed phase. The emission of dileptons in the SIS18-SIS100 beam energies range is studied by augmenting the UrQMD transport model with a realistic density dependent equation of state, as well as two different phase transitions. This is achieved by extending the molecular dynamics interaction part of the UrQMD model to a density dependent interaction potential with a high density minimum leading to a phase transition and metastable coexisting high density states. Together with a high precision measurement these simulations will be able to constrain the existence of a phase transition in QCD up to densities of several times nuclear saturation density.

   ↳ nucl-thhep-exhep-phnucl-exJ.Phys.G(2023)·29 citations
8. 08*

   Accessing GPDs through the exclusive photoproduction of a $\gamma$-meson pair

   Goran Duplančić🇭🇷 · Saad Nabeebaccus🇫🇷 · Kornelija Passek-Kumerički🇭🇷 · Bernard Pire🇫🇷 · Lech Szymanowski🇵🇱 · Samuel Wallon🇫🇷

   We consider the exclusive photo-production of a photon-meson pair with a large invariant mass, working in the QCD factorisation framework. Explicitly, we consider a $\rho$-meson or a charged $\pi$ in the final state. This process gives access both to chiral-even GPDs and chiral-odd GPDs, which are not well-known experimentally, especially the latter ones. The computation is performed at leading order and leading twist. We discuss the prospects of measuring them in experiments, focusing on the kinematics at the JLab 12-GeV experiment, and pPb ultra-peripheral collisions at LHC. In particular, the latter gives access to the small $\xi$ regime of GPDs.

   ↳ hep-phhep-exnucl-exnucl-th2 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.