Fri·Mar 19, 2021Friday·March 19, 2021

1. 01*

   Photoneutron Reactions ${}^{181}\mathrm{Ta}(\gamma ,\text{x}\mathrm{n};\text{x}=1÷8{)}^{181-\text{x}}\mathrm{Ta}$ AT $E_{\gamma \max }$ = 80 $÷$ 95 MeV

   A.N. Vodin🇺🇦 · O.S. Deiev🇺🇦 · I.S. Timchenko🇺🇦 · S.N. Olejnik🇺🇦 · M.I. Ayzatskiy🇺🇦 · V.A. Kushnir🇺🇦 · V.V. Mitrochenko🇺🇦 · S.A. Perezhogin🇺🇦

   The bremsstrahlung flux-averaged cross-sections $⟨\sigma (E_{\gamma \max })⟩$ for the ${}^{181}\mathrm{Ta}(\gamma ,\text{x}\mathrm{n};\text{x}=1÷8{)}^{181-\text{x}}\mathrm{Ta}$ photoneutron reactions have been measured at end-point bremsstrahlung energies ranging from 80 MeV to 95 MeV. The measurements were performed with the beam from the NSC KIPT electron linear accelerator LUE-40 using the residual $\gamma$-activity method. The theoretical $⟨\sigma (E_{\gamma \max })⟩$ values were computed using the cross-sections $\sigma (E)$ from TALYS1.9 code. A comparison between the measured cross-sections $⟨\sigma (E_{\gamma \max })⟩$ and the theoretical values has demostrated their good agreement for the reactions with escape of up to 6 neutrons, and substantial differences for the $(\gamma ,7\mathrm{n})$ and $(\gamma ,8\mathrm{n})$ reactions. Isomeric ratios of the average cross-sections $d(E_{\gamma \max })$ have been found for the ${}^{181}\mathrm{Ta}(\gamma ,3n{)}^{178g,\mathrm{m}}\mathrm{Ta}$ reaction products. The results have been compared with the literature data and the computations based on TALYS1.9 code.

   nucl-exhep-ex4 citations
2. 02*

   Revisit the Chiral Magnetic Effect Expectation in Isobaric Collisions at the Relativistic Heavy Ion Collider

   Yicheng Feng🇺🇸 · Yufu Lin🇨🇳 · Jie Zhao🇺🇸 · Fuqiang Wang🇺🇸

   Isobaric ${}_{44}^{96}$Ru+${}_{44}^{96}$Ru and ${}_{40}^{96}$Zr+${}_{40}^{96}$Zr collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV have been conducted at the Relativistic Heavy Ion Collider to circumvent the large flow-induced background in searching for the chiral magnetic effect (CME), predicted by the topological feature of quantum chromodynamics (QCD). Considering that the background in isobar collisions is approximately twice that in Au+Au collisions (due to the smaller multiplicity) and the CME signal is approximately half (due to the weaker magnetic field), we caution that the CME may not be detectable with the collected isobar data statistics, within $\sim$2$\sigma$ significance, if the axial charge per entropy density ($n_5/s$) and the QCD vacuum transition probability are system independent. This expectation is generally verified by the Anomalous-Viscous Fluid Dynamics (AVFD) model. While our estimate provides an approximate "experimental" baseline, theoretical uncertainties on the CME remain large.

   nucl-exnucl-thPLB(2021)·22 citations
3. 03*

   Exploring theoretical uncertainties in the hydrodynamic description of relativistic heavy-ion collisions

   Cheng Chiu🇺🇸 · Chun Shen🇺🇸

   We explore theoretical uncertainties in the hydrodynamic description of relativistic heavy-ion collisions by examining the full non-linear causality conditions and quantifying the second-order transport coefficients' role on flow observables. The causality conditions impose physical constraints on the maximum allowed values of inverse Reynolds numbers during the hydrodynamic evolution. Including additional second-order gradient terms in the Denicol-Niemi-Molnár-Rischke (DNMR) theory significantly shrinks the casual regions compared to those in the Israel-Stewart hydrodynamics. For Au+Au collisions, we find the variations of flow observables are small with and without imposing the necessary causality conditions, suggesting a robust extraction of the Quark-Gluon Plasma's transport coefficients in previous model-to-data comparisons. However, sizable sensitivity is present in small p+Au collisions, which poses challenges to study the small systems' collectivity.

   ↳ nucl-thhep-phnucl-exPRC(2021)·53 citations
4. 04*

   The KOALA Experiment for (anti)proton-proton Elastic Scattering

   Yong Zhou🇩🇪 · Huagen Xu🇨🇳 · Ulf Bechstedt🇩🇪 · Jürgen Böker🇩🇪 · Nils Demary🇩🇪 · Frank Goldenbaum🇩🇪 · Dieter Grzonka🇩🇪 · Jan Hetzel🇩🇪 · Alfons Khoukaz🇩🇪 · Franz Klehr🇩🇪 · Thomas Krings🇩🇪 · Lukas Lessmann🇩🇪 and 8 other authors

   The KOALA experiment measures the differential cross section of (anti)proton-proton elastic scattering over a wide range of four-momentum transfer squared 0.0008 < |t| < 0.1 (GeV/c)${}^2$ . The forward scattering parameters and the absolute luminosity can be deduced by analyzing the characteristic shape of the differential cross-section spectrum. The experiment is based on fixed target kinematics and uses an internal hydrogen cluster jet target. The wide range of |t| is achieved by measuring the total kinetic energy of the recoil protons near 90{\deg} with a recoil detector, which consists of silicon and germanium single-sided strip sensors. The energy resolution of the recoil detector is better than 30 keV (FWHM). A forward detector consisting of two layers of plastic scintillators measures the elastically scattered beam particles in the forward direction close to the beam axis. It helps suppress the large background at small recoil angles and improves the identification of elastic scattering events in the low |t| range. The KOALA setup has been installed and commissioned at COSY in order to validate the detector by measuring the proton-proton elastic scattering. The results from this commissioning are presented here.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2021)·2 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.