Tue·Oct 23, 2018Tuesday·October 23, 2018

1. 01*

   Weakly Bound Neutron-Rich Nuclei and Cosmic Phenomena

   Ushasi Datta🇮🇳 · A.Rahaman · S.Chakraborty🇮🇳 · B.K.Agrawal🇮🇳 · T.Aumann🇩🇪 · K.Boretzky🇩🇪 · C.Caesar🇩🇪 · H.Emling🇩🇪 · H.Geissel🇩🇪 · C.Langer🇩🇪 · T.Le Bleis🇩🇪 · Y. Leifels🇩🇪 and 29 other authors

   The single particle and bulk properties of the neutron-rich nuclei constrain fundamental issues in nuclear physics and nuclear astrophysics like the limits of existence of quantum many body systems (atomic nuclei), the equation of state of neutron-rich matter, neutron star, nucleosynthesis, evolution of stars, neutron star merging etc.. The state of the art of Coulomb breakup of the neutron-rich nuclei has been used to explore those properties. Unambiguous information on detailed components of the ground-state wave-function along with quantum numbers of the valence neutron of the nuclei have been obtained from the measurement of threshold strength along with the $\gamma$-rays spectra of the core following Coulomb breakup. The shape of this threshold strength is a finger-print of the quantum numbers of the nucleon. We investigated the ground-state properties of the neutron-rich Na, Mg, Al nuclei around N $\sim$ 20 using this method at GSI, Darmstadt. Very clear evidence has been observed for melting and merging of long cherished magic shell gaps at N = 20, 28. The evanescent neutron-rich nuclei imprint their existence in stellar explosive scenarios (r-process etc.). Coulomb dissociation (CD) is one of the important indirect measurements of the capture cross-section which may provide valuable input to the model for star evolution process, particularly the r-process. Some valuable bulk properties of the neutron-rich nuclei like the density dependent symmetry energy,neutron skin etc. play a key role in understanding cosmic phenomena and these properties have been studied via electromagnetic excitation. Preliminary results of electromagnetic excitation of the neutron-rich nucleus, ${}^{32}$Mg are presented.

   nucl-exnucl-th1 citation
2. 02*

   Ab initio Rayleigh-Schrödinger perturbation calculation including three-body force

   B. S. Hu🇨🇳 · T. Li🇨🇳 · F. R. Xu🇨🇳

   We first derive the Rayleigh-Schrödinger many-body perturbation theory up to third order (RSPT3) for Hamiltonians with three-body interaction. The structure of closed-shell nuclei in a wide mass range from 4He to 48Ca has been investigated by the RSPT3 with explicit NN+3N Hamiltonian. The RSPT3 calculations are performed within Hartree-Fock bases. The perturbative contribution of antisymmetrized Goldstone diagrams (diagrammatic expansion for RSPT) with normal-ordered interaction has been analyzed. We demonstrate that the normal-ordered two-body level (NO2B) approximation which neglects the residual three-body term can catch the main effect of full three-body force in RSPT calculation. We also present rigorous benchmarks for RSPT3 with non-perturbative coupled cluster and in-medium similarity renormalization group using the same chiral NNLOsat NO2B interaction. The three methods are in good agreement with each other for binding energies and radii. However, the RSPT3 provides an alternative that is computationally inexpensive but comparable in accuracy to state-of-the-art non-perturbative many-body methods.

   ↳ nucl-thnucl-exquant-ph4 citations
3. 03*

   $p$-shell hypernuclear structures using the Gogny-interaction shell model

   X. Y. Chen🇨🇳 · Z. Zhou🇨🇳 · W. G. Jiang🇨🇳 · B. S. Hu🇨🇳 · F. R. Xu🇨🇳

   We have systematically investigated the excitation spectra of $p$-shell hypernuclei within the shell model based on the nucleon-nucleon and hyperon-nucleon interactions. For the effective nucleon-nucleon interaction, we adopt the Gogny force instead of the widely-used empirical $p$-shell Cohen-Kurath interaction, while the hyperon-nucleon interaction takes the $\Lambda N$ interaction including the $\Lambda N$-$\Sigma N$ coupling effect. We find that the shell model with the Gogny force can give reasonable descriptions of both spectra and binding energies of the $p$-shell nuclei. With this confidence, combined with the $\Lambda N$ interaction, we have performed shell-model calculations for the $p$-shell hypernuclei. We compare our results with $\gamma$-ray data as well as various theoretical calculations, and explain recent experimental hypernuclear excitation spectra observed at JLab.

   ↳ nucl-thhep-exnucl-exJ.Phys.G(2019)·3 citations
4. 04*

   Bounds on ortho-positronium and $J/\psi$-${\rm Y}$ quarkonia invisible decays and constraints on hidden braneworlds in a $SO(3,1)$-broken 5D bulk

   Michael Sarrazin🇫🇷 · Coraline Stasser🇧🇪

   While our visible Universe could be a 3-brane, some cosmological scenarios consider that other 3-branes could be hidden in the extra-dimensional bulk. Matter disappearance toward a hidden brane is mainly discussed for neutron - both theoretically and experimentally - but other particles are poorly studied. Recent experimental results offer new constraints on positronium or quarkonium invisible decays. In the present work, we show how a two-brane Universe allows for such invisible decays. We put this result in the context of the recent experimental data to constrain the brane energy scale $M_B$ (or effective brane thickness $M_B^{-1}$) and the interbrane distance $d$ for a relevant two-brane Universe in a $SO(3,1)$-broken 5D bulk. Quarkonia present poor bounds compared to results deduced from previous passing-through-walls-neutron experiments for which scenarios with $M_B<2.5\times 10^{17}$ GeV and $d>0.5$ fm are excluded. By contrast, positronium experiments can compete with neutron experiments depending on the matter content of each brane. To constrain scenarios up to the Planck scale, positronium experiments in vacuum cavity should be able to reach $\text{Br}(\text{o-Ps}\to \text{invisible})\approx 10^{-6}$.

   ↳ hep-phhep-exnucl-exInt.J.Mod.Phys.A(2020)·1 citation
5. 05*

   Electroweak properties of pions in a nuclear medium

   Parada T. P. Hutauruk🇰🇷 · Yongseok Oh🇰🇷 · K. Tsushima🇧🇷

   The charge form factor and weak decay constant of the pion as well as the pion-quark coupling constant in symmetric nuclear matter are explored in the framework of the Nambu--Jona-Lasinio model, where the pion is described as a bound state of dressed quark-antiquark pair obtained by the Bethe-Salpeter equation. For the in-medium current quark properties, we adopt the quark-meson coupling model, which describes successfully many hadron properties in a nuclear medium. The pion decay constant and the pion-quark coupling constant are found to decrease with increasing density as well as the magnitude of the light quark condensate. But the pion mass is found to be insensitive to density up to $1.25$ times the normal nuclear density. The pion charge form factor in the space-like region is also explored and is found to have a similar $Q^2$ dependence as the form factor in vacuum showing $1/Q^2$-behavior in large $Q^2$ region, where $Q^2$ is the negative of the four-momentum transfer squared. The modifications of the charge radius of the charged pion in nuclear matter are then estimated and the root-mean-square radius at the normal nuclear density is predicted to be larger than that in vacuum by about 20\%.

   ↳ nucl-thhep-phnucl-exPRC(2019)·30 citations
6. 06*

   Machine Learning Methods for Track Classification in the AT-TPC

   Michelle P. Kuchera🇺🇸 · Raghuram Ramanujan · Jack Z. Taylor · Ryan R. Strauss🇩🇪 · Daniel Bazin🇺🇸 · Joshua Bradt · Ruiming Chen

   We evaluate machine learning methods for event classification in the Active-Target Time Projection Chamber detector at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. An automated method to single out the desired reaction product would result in more accurate physics results as well as a faster analysis process. Binary and multi-class classification methods were tested on data produced by the ${}^{46}$Ar(p,p) experiment run at the NSCL in September 2015. We found a Convolutional Neural Network to be the most successful classifier of proton scattering events for transfer learning. Results from this investigation and recommendations for event classification in future experiments are presented.

   ↳ cs.CVcs.LGnucl-exNucl.Instrum.Meth.A(2019)·39 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.