Tue·Jun 13, 2023Tuesday·June 13, 2023

1. 01*

   Evidence against a strong first-order phase transition in neutron star cores: impact of new data

   Len Brandes🇩🇪 · Wolfram Weise🇩🇪 · Norbert Kaiser🇩🇪

   With the aim of exploring the evidence for or against phase transitions in cold and dense baryonic matter, the inference of the sound speed and equation-of-state for dense matter in neutron stars is extended in view of recent new observational data. The impact of the heavy (2.35 $M_{\odot }$) black widow pulsar PSR J0952-0607 and of the unusually light supernova remnant HESS J1731-347 is inspected. In addition a detailed re-analysis is performed of the low-density constraint based on chiral effective field theory and of the perturbative QCD constraint at asymptotically high densities, in order to clarify the influence of these constraints on the inference procedure. The trace anomaly measure, $\Delta =1/3-P/\epsilon$, is also computed and discussed. A systematic Bayes factor assessment quantifies the evidence (or non-evidence) of low averaged sound speeds $(c_s^2\le 0.1)$, a prerequisite for a phase transition, within the range of densities realized in the core of neutron stars. One of the consequences of including PSR J0952-0607 in the data base is a further stiffening of the equation-of-state, resulting for a 2.1 solar-mass neutron star in a reduced central density of less than five times the equilibrium density of normal nuclear matter at the 68\% level. The evidence against small sound speeds in neutron star cores is further strengthened. Within the inferred 68\% posterior credible bands, only a weak first-order phase transition with a coexistence density interval $\Delta n/n\lesssim 0.2$ would be compatible with the observed data.

   ↳ nucl-thastro-ph.HEgr-qchep-ph+1PRD(2023)·92 citations
2. 02*

   Prediction of the neutron drip line in oxygen isotopes using quantum computation

   Chandan Sarma🇮🇳 · Olivia Di Matteo🇨🇦 · Abhishek Abhishek🇨🇦 · Praveen C. Srivastava🇮🇳

   In the noisy intermediate-scale quantum era, variational algorithms have become a standard approach to solving quantum many-body problems. Here, we present variational quantum eigensolver (VQE) results of selected oxygen isotopes within the shell model description. The aim of the present work is to locate the neutron drip line of the oxygen chain using unitary coupled cluster (UCC) type ansatze with different microscopic interactions (DJ16, JISP16, and N3LO), in addition to a phenomenological USDB interaction. While initially infeasible to execute on contemporary quantum hardware, the size of the problem is reduced significantly using qubit tapering techniques in conjunction with custom circuit design and optimization. The optimal values of ansatz parameters from classical simulation are taken for the DJ16 interaction, and the tapered circuits are run on IonQ's Aria, a trapped-ion quantum computer. After applying gate error mitigation for three isotopes, we reproduced exact ground state energies within a few percent error. The post-processed results from hardware also clearly show ${}^{24}$O as the drip line nucleus of the oxygen chain. Future improvements in quantum hardware could make it possible to locate drip lines of heavier nuclei.

   ↳ nucl-thnucl-exquant-phPRC(2023)·39 citations
3. 03*

   $\Lambda$ hypernuclear potentials beyond linear density dependence

   E. Friedman🇮🇱 · A. Gal🇮🇱

   In a recent paper [PLB 837 (2023) 137669] we showed that all measured ($1s_{\Lambda }$, $1p_{\Lambda }$) pairs of $\Lambda$ binding energies in $\Lambda$-hypernuclei across the periodic table, $12\le A\le 208$, can be obtained from a $\Lambda$-nucleus optical potential with only two adjustable $\Lambda N$ and $\Lambda NN$ parameters, associated with leading linear and quadratic terms in the nuclear density, derived by fitting ${}_{\Lambda }^{16}$N binding energies. Here we extend the previous analysis by performing least-squares fits to the full set of data points. Consequences of suppressing $\Lambda NN$ interactions between `core' nucleons and `excess' neutrons are studied and related predictions are made for ($1s_{\Lambda }$, $1p_{\Lambda }$) binding energies in ${}_{\Lambda }^{40,48}$K, obtainable from upcoming ${}^{40,48}$Ca($e,e^{\prime }{K}^{+}$) JLab experiments. We find $\Lambda$-nucleus partial potential depths of $D_{\Lambda }^{(2)}=-38.6\pm 0.8$~MeV ($\Lambda N$) and $D_{\Lambda }^{(3)}=11.3\pm 1.4$~MeV ($\Lambda NN$), with a total depth $D_{\Lambda }=-27.3\pm 0.6$~MeV at nuclear-matter density ${\rho }_0$=0.17~fm${}^{-3}$, consistently with our previous results. Extrapolation to higher nuclear densities and possible relevance to the `hyperon puzzle' in neutron-star matter are discussed.

   ↳ nucl-thhep-phnucl-exNPA(2023)·26 citations
4. 04*

   Derivation of transition density from the observed 4He(e,e')4He(0^+_2) form factor raising the alpha-particle monopole puzzle

   Masayasu Kamimura

   Recently, the monopole transition form factor of the electron-scattering excitation of the 0^+_2 state (E_x=20.21 MeV) of the 4He nucleus was observed over a broad momentum transfer range (0.5 < q^2 < 5.0 fm^-2) with dramatically improved preision compared with older sets of data; modern nuclear forces, including those derived from the chiral effective field theory, failed to reproduce the form factor, which is called the alpha-particle monopole puzzle. To resolve this puzzle by improving the study of spatial structure of the 0^+_2 state, we derive in this letter a possible 0^+_1 --> 0^+_2 transition density \rho_tr(r) for r > 1 fm from the observed form factor. The shape of the transition density is significantly different from that obtained theoretically in the literature

   ↳ nucl-thnucl-exPTEP(2023)·2 citations
5. 05*

   Neutron-Gamma Pulse Shape Discrimination for Organic Scintillation Detector using 2D CNN based Image Classification

   Annesha Karmakar · Anikesh Pal🇮🇳 · G. Anil Kumar · Bhavika · V. Anand · Mohit Tyagi

   This study shows an implementation of neutron-gamma pulse shape discrimination (PSD) using a two-dimensional convolutional neural network. The inputs to the network are snapshots of the unprocessed, digitized signals from a BC501A detector. By exposing a BC501A detector to a Cf-252 source, neutron and gamma signals were collected to create a training dataset. The realistic datasets were created using a data-driven approach for labeling the digitized signals, having classified snapshots of neutron and gamma pulses. Our algorithm was able to successfully differentiate neutrons and gammas with similar accuracy as the CI approach. Additionally, the independent dataset accuracy for our suggested 2D CNN-based PSD approach is 99%. In contrast to the traditional charge integration method, our suggested algorithm with data augmentation, is capable of extracting features from snapshots of the raw data based on the signal structures, making it computationally more efficient and also appropriate for other types of neutron detectors.

   ↳ physics.ins-detnucl-exAppl.Radiat.Isot.(2025)·1 citation

* 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.