Thu·Aug 4, 2022Thursday·August 4, 2022

1. 01*

   The splitting of directed flow for identified light hadrons ($K$ and $p$) and strange baryons ($\Xi$ and $\Omega$) in Au+Au collisions at STAR

   Ashik Ikbal Sheikh (for the STAR Collaboration)🇺🇸

   The first measurements for rapidity-odd directed flow of $\Xi$ and $\Omega$ in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=$ 27 and 200 GeV are reported. The coalescence sum rule is examined with various combinations of hadrons where all constituent quarks are produced, such as $K^{{}^{-}}(\bar{u}s)$, $\bar{p}(\bar{u}\bar{u}\bar{d})$, $\bar{\Lambda }(\bar{u}\bar{d}\bar{s})$, $\varphi (s\bar{s})$, ${\bar{\Xi }}^{+}(\bar{d}\bar{s}\bar{s})$, ${\Omega }^{-}(sss)$, and ${\bar{\Omega }}^{+}(\bar{s}\bar{s}\bar{s})$. For such combinations, a systematic violation of the sum rule is observed with increasing difference in the electric charge and the strangeness content of the combinations. Measurements are compared with the calculations of A Multi-Phase Transport (AMPT) model and Parton-Hadron String Dynamics (PHSD) model with electromagnetic (EM) field. The PHSD model with EM field agrees with the measurements within uncertainties.

   nucl-exhep-exhep-phnucl-thActa Phys.Polon.Supp.(2023)·1 citation
2. 02*

   Model-independent determination of the dipole response of ${}^{66}$Zn using quasi-monoenergetic and linearly-polarized photon beams

   D. Savran🇩🇪 · J. Isaak🇩🇪 · R. Schwengner · R. Massarczyk🇺🇸 · M. Scheck · W. Tornow🇺🇸 · G. Battaglia · T. Beck🇩🇪 · S. W. Finch🇺🇸 · C. Fransen🇩🇪 · U. Friman-Gayer🇸🇪 · R. Gonzalez and 14 other authors

   [Background] Photon strength functions are an important ingredient in calculations relevant for the nucleosynthesis of heavy elements. The relation to the photoabsorption cross section allows to experimentally constrain photon strength functions by investigating the photo-response of atomic nuclei. [Purpose] We determine the photoresponse of ${}^{66}$Zn in the energy region of 5.6 MeV to 9.9 MeV and analyze the contribution of the "elastic" decay channel back to the ground state. In addition, for the elastic channel electric and magnetic dipole transitions were separated. [Methods] Nuclear resonance fluorescence experiments were performed using a linearly-polarized quasi-monoenergetic photon beam at the High Intensity $\gamma$-ray Source. Photon beam energies from 5.6 to 9.9 MeV with an energy spread of about 3% were selected in steps of 200-300 keV. Two High Purity Germanium detectors were used for the subsequent $\gamma$-ray spectroscopy. [Results] Full photoabsorption cross sections are extracted from the data making use of the monoenergetic character of the photon beam. For the ground-state decay channel, the average contribution of electric and magnetic dipole strengths is disentangled. The average branching ratio back to the ground state is determined as well. [Conclusions] The new results indicate lower cross sections when compared to the values extracted from a former experiment using bremsstrahlung on ${}^{66}$Zn. In the latter, the average branching ratio to the ground state is estimated from statistical-model calculations in order to analyze the data. Corresponding estimates from statistical-model calculations underestimate this branching ratio compared to the values extracted from the present analysis, which would partly explain the high cross sections determined from the bremsstrahlung data.

   nucl-exPRC(2022)·9 citations
3. 03*

   Advances and new ideas for neutron-capture astrophysics experiments at CERN n_TOF

   C. Domingo-Pardo · V. Babiano-Suarez · J. Balibrea-Correa · L. Caballero · I. Ladarescu · J. Lerendegui-Marco · J.L. Tain · A. Tarifeño-Saldivia · O. Aberle · V. Alcayne · S. Altieri · S. Amaducci and 127 other authors

   This article presents a few selected developments and future ideas related to the measurement of $(n,\gamma )$ data of astrophysical interest at CERN n_TOF. The MC-aided analysis methodology for the use of low-efficiency radiation detectors in time-of-flight neutron-capture measurements is discussed, with particular emphasis on the systematic accuracy. Several recent instrumental advances are also presented, such as the development of total-energy detectors with $\gamma$-ray imaging capability for background suppression, and the development of an array of small-volume organic scintillators aimed at exploiting the high instantaneous neutron-flux of EAR2. Finally, astrophysics prospects related to the intermediate $i$ neutron-capture process of nucleosynthesis are discussed in the context of the new NEAR activation area.

   nucl-exEPJA(2023)·23 citations
4. 04*

   Modeling the electric dipole strength of neutron-rich ${}^8$He: Prediction of multineutron collective excitations

   Takayuki Myo🇯🇵 · Kiyoshi Kato

   We investigate the multineutron excitations of neutron-rich ${}^8$He in the electric dipole strength using a ${}^4$He+$n$+$n$+$n$+$n$ five-body model. Many-body unbound states of ${}^8$He are obtained in the complex scaling method. We found that the different excitation modes coexist in the dipole strength below the excitation energy of 20 MeV. The strength below 10 MeV comes from the ${}^7$He+$n$ channel, indicating the sequential breakup of ${}^8$He via the ${}^7$He resonance to ${}^6$He+$n$+$n$. Above 10 MeV, the strength is obtained from many-body continuum states with strong configuration mixings, suggesting a new collective motion of four neutrons with the dipole oscillation against ${}^4$He.

   ↳ nucl-thnucl-exPRC(2022)·12 citations
5. 05*

   Jet cone radius dependence of $R_{AA}$ and $v_2$ at PbPb 5.02 TeV from JEWEL+${\mathrm{T}}_{\mathrm{R}}\mathrm{ENTo}$+v-USPhydro

   Leonardo Barreto🇧🇷 · Fabio M. Canedo🇧🇷 · Marcelo G. Munhoz🇧🇷 · Jorge Noronha🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸

   We combine, for the first time, event-by-event ${\mathrm{T}}_{\mathrm{R}}\mathrm{ENTo}$ initial conditions with the relativistic viscous hydrodynamic model v-USPhydro and the Monte Carlo event generator JEWEL to make predictions for the nuclear modification factor $R_{AA}$ and jet azimuthal anisotropies $v_n\left\{2\right\}$ in $\sqrt{s_{NN}}=5.02\mathrm{TeV}$ PbPb collisions for multiple centralities and values of the jet cone radius $R$. The $R$-dependence of $R_{AA}$ and $v_2\left\{2\right\}$ strongly depends on the presence of recoiling scattering centers. We find a small jet $v_3\left\{2\right\}$ in mid-central collisions and consistent results in wide jet $p_T$ regions and centralities with ATLAS data.

   ↳ nucl-thhep-phnucl-exPLB(2025)·18 citations
6. 06*

   Nuclear physics uncertainties in light hypernuclei

   D. Gazda🇨🇿 · T. Yadanar Htun🇹🇭 · C. Forssén🇸🇪

   The energy levels of light hypernuclei are experimentally accessible observables that contain valuable information about the interaction between hyperons and nucleons. In this work we study strangeness $S=-1$ systems ${}_{\Lambda }^{3,4}$H and ${}_{\Lambda }^{4,5}$He using the ab initio no-core shell model (NCSM) with realistic interactions obtained from chiral effective field theory ($\chi$EFT). In particular, we quantify the finite precision of theoretical predictions that can be attributed to nuclear physics uncertainties. We study both the convergence of the solution of the many-body problem (method uncertainty) and the regulator- and calibration data-dependence of the nuclear $\chi$EFT Hamiltonian (model uncertainty). For the former, we implement infrared correction formulas and extrapolate finite-space NCSM results to infinite model space. We then use Bayesian parameter estimation to quantify the resulting method uncertainties. For the latter, we employ a family of 42 realistic Hamiltonians and measure the standard deviation of predictions while keeping the leading-order hyperon-nucleon interaction fixed. Following this procedure we find that model uncertainties of ground-state $\Lambda$ separation energies amount to $\sim 20(100)$ keV in ${}_{\Lambda }^3$H(${}_{\Lambda }^4$H,He) and $\sim 400$ keV in ${}_{\Lambda }^5$He. Method uncertainties are comparable in magnitude for the ${}_{\Lambda }^4$H,He $1^{+}$ excited states and ${}_{\Lambda }^5$He, which are computed in limited model spaces, but otherwise much smaller. This knowledge of expected theoretical precision is crucial for the use of binding energies of light hypernuclei to infer the elusive hyperon-nucleon interaction.

   ↳ nucl-thhep-phnucl-exPRC(2022)·20 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.