Tue·Apr 18, 2023Tuesday·April 18, 2023

1. 01*

   Properties of First-Order Hadron-Quark Phase Transition from Inverting Neutron Star Observables

   Nai-Bo Zhang🇨🇳 · Bao-An Li🇺🇸

   By inverting the observational data of several neutron star observables in the three dimensional parameter space of the constant speed of sound (CSS) model while fixing all hadronic Equation of State parameters at their currently known most probable values, we constrain the three parameters of the CSS model and their correlations. Using two lower radius limits of $R_{2.01}=11.41$ km and $R_{2.01}=12.2$ km for PSR J0740+6620 obtained from two independent analyses using different approaches by the Neutron Star Interior Composition Explorer (NICER) Collaboration, the speed of sound squared $c_{\mathrm{QM}}^2$ in quark matter is found to have a lower limit of $0.35$ and $0.43$ in unit of $c^2$, respectively, above its conformal limit of $c_{\mathrm{QM}}^2<1/3$. An approximately linear correlation between the first-order hadron-quark transition density ${\rho }_t$ and its strength $\Delta \epsilon$ is found. Moreover, the presence of twin star is deemed improbable by the present work.

   ↳ nucl-thastro-ph.HEnucl-exPRC(2023)·18 citations
2. 02*

   Structure of neutron-rich He $\Lambda$ hypernuclei using the cluster orbital shell model

   Takayuki Myo🇯🇵 · Emiko Hiyama🇯🇵

   We calculated the energy spectra of the neutron-rich He $\Lambda$ hypernuclei with $A=6$ to 9 within the framework of an $\alpha +\Lambda +Xn$ ($X=1$--4) cluster model using the cluster orbital shell model. The employed constituent particles reproduce their observed properties. For resonant states of core nuclei such as ${}^5$He, ${}^6$He, and ${}^7$He, the complex scaling method is employed to obtain energies and decay widths. The calculated ground states of ${}_{\Lambda }^6$He and ${}_{\Lambda }^7$He are in good agreement with published data. The energy levels of ${}_{\Lambda }^8$He and ${}_{\Lambda }^9$He are predicted. In ${}_{\Lambda }^9$He, we find one deeply bound state and two excited resonant states, which are proposed to be produced at the Japan proton accelerator research complex (J-PARC) by the double-charge-exchange reaction $({\pi }^{-},K^{+})$ using a ${}^9$Be target.

   ↳ nucl-thnucl-exPRC(2023)·11 citations
3. 03*

   Classifier for centrality determination with Zero Degree Calorimeter at the Cooling-Storage-Ring External-target Experiment

   Biao Zhang · Li-Ke Liu · Hua Pei · Shusu Shi · Nu Xu · Yaping Wang

   The Zero Degree Calorimeter (ZDC) plays a crucial role in determining centrality at the Cooling-Storage-Ring External-target Experiment (CEE) in the Heavy Ion Research Facility in Lanzhou (HIRFL). A Boosted Decision Trees (BDT) multi-classification algorithm is employed to classify the centrality of the collision events based on the raw features from ZDC such as the number of fired channels and deposited energy. The data from simulated ${}^{238}\mathrm{U}$ + ${}^{238}\mathrm{U}$ collisions at 500 $MeV/u$, generated by the IQMD event generator and subsequently modeled through the GEANT4 package, is employed to train and test the BDT model. The results showed the high accuracy of the multi-classification model adopted in ZDC for centrality determination, which is robust against variations in different factors of detector geometry and response. The study demonstrates a good performance of the CEE-ZDC for determining the centrality in nucleus-nucleus collisions.

   ↳ physics.ins-detnucl-exNucl.Sci.Tech.(2023)·12 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.