Nuclear Theory·nucl-th

Thursday·January 6, 2022

8 papers—5 primary·3 cross-listed

01
[Submitted on 4 Jan 2022]
The $^{1}$ S $_{0}$ pairing gap in neutron matter
S. Gandolfi · G. Palkanoglou · J. Carlson · A. Gezerlis · K. E. Schmidt
We report ab initio calculations of the S wave pairing gap in neutron matter calculated using realistic nuclear Hamiltonians that include two- and three-body interactions. We use a trial state, properly optimized to capture the essential pairing correlations, from which we extract ground state properties by means of auxiliary field diffusion Monte Carlo simulations. We extrapolate our results to the thermodynamic limit by studying the finite-size effects in the symmetry-restored projected Bardeen-Cooper-Schrieffer (PBCS) theory and compare our results to other ab initio studies done in the past. Our quantum Monte Carlo results for the pairing gap show a modest suppression with respect to the mean-field BCS values. These results can be connected to cold atom experiments, via the unitarity regime where fermionic superfluidity assumes a unified description, and they are important in the prediction of thermal properties and the cooling of neutron stars.
Comments:
14 pages, 7 figures; v2 corresponds to published version
Subjects:
Nuclear Theory (nucl-th); Quantum Gases (cond-mat.quant-gas)
arXiv:
2201.01308 [pdf]
Condens.Mat.(2022)·31 citations
02
[Submitted on 5 Jan 2022]
Determination of neutron-skin thickness using configurational information entropy
Chunwang Ma · Yipu Liu · Huiling Wei · Jie Pu · Kaixuan Cheng · Yuting Wang
Configurational information entropy (CIE) theory was employed to determine the neutron skin thickness of neutron-rich calcium isotopes. The nuclear density distributions and fragment cross-sections in 350 MeV/u $^{40 - 60}$ Ca + $^{9}$ Be projectile fragmentation reactions were calculated using a modified statistical abrasion-ablation model. CIE quantities were determined from the nuclear density, isotopic, mass, and charge distributions. The linear correlations between the CIE determined using the isotopic, mass, and charge distributions and the neutron skin thickness of the projectile nucleus show that CIE provides new methods to extract the neutron skin thickness of neutron-rich nuclei.
Comments:
7 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2201.01442 [pdf]
Nucl.Sci.Tech.(2022)·19 citations
03
[Submitted on 5 Jan 2022]
The $Λ (1405)$ resonance as a genuine three-quark or molecular state
B. Golli🇸🇮 · H. Osmanović🇧🇦 · S. Širca🇸🇮
The mechanism for the formation of the $Λ (1405)$ resonance is studied in a chiral quark model that includes quark-meson as well as contact (four point) interactions. The negative-parity $S$ -wave scattering amplitudes for strangeness $- 1$ and $1$ are calculated within a unified coupled-channel framework that includes the $K N$ , $K ˉ N$ , $π Σ$ , $η Λ$ , $K Ξ$ , $π Λ$ , and $η Σ$ channels and possible genuine three-quark bare singlet and octet states corresponding to $\frac{1}{2}^{-}$ resonances. We show that in order to reproduce the scattering amplitudes in the $S_{01}$ partial wave it is important to include the pertinent three-quark octet states as well as the singlet state, while the inclusion of the contact term is not mandatory. The Laurent-Pietarinen expansion is used to determine the $S$ -matrix poles. Following their evolution as a function of increasing interaction strength, the mass of the singlet state is strongly reduced due to the attractive self-energy in the $π Σ$ and $K ˉ N$ channels; when it drops below the $K N$ threshold, the state acquires a dominant $K ˉ N$ component which can be identified with a molecular state. The attraction between the kaon and the nucleon is generated through the $K ˉ N Λ^{*}$ interaction rather than by meson-nucleon forces.
Comments:
13 pages, 9 figures. Updated results and discussion of dynamical generation of resonances
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2201.01489 [pdf]
EPJA(2022)·0 citations
04
[Submitted on 5 Jan 2022]
Nucleon momentum gap in asymmetric nuclear matter
Gao-Chan Yong
For more than half a century, nucleons are considered to move continuously in the nuclei. Recent electron-scattering experiments indicate about 20 $\sim$ 25\% nucleons in heavier nuclei are involved in the neutron-proton short-range correlations. Nucleons in the nuclei thus have abnormal behavior unlike those in the non-interaction fermi gas. In the neutron-rich nuclei, around the Fermi momentum, the neutron-proton short-range correlations lead to a momentum gap in the proton momentum distribution, which is circumstantially supported by the pionic experimental data. Likewise, there should also be a neutron momentum gap in the proton-rich nuclei. Nucleon momentum gap is thought to have profound and extensive implications in the studies ranging from particle physics to neutron stars as well as ultra-cold atomic gases.
Comments:
5 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2201.01550 [pdf]
PRC(2022)·5 citations
05
[Submitted on 5 Jan 2022]
A Chiral Mean-Field Equation-of-State in UrQMD: Effects on the Heavy Ion Compression Stage
Manjunath Omana Kuttan🇩🇪 · Anton Motornenko🇩🇪 · Jan Steinheimer🇩🇪 · Horst Stoecker🇩🇪 · Yasushi Nara🇯🇵 · Marcus Bleicher🇩🇪
It is shown that the initial compression in central heavy ion collisions at beam energies of $E_{lab} = 1 - 10 A$ ~GeV depends dominantly on the underlying equation of state and only marginally on the model used for the dynamical description. To do so, a procedure to incorporate any equation of state in the UrQMD transport model is introduced. In particular we compare the baryon density, temperature and pressure evolution as well as produced entropy in a relativistic ideal hydrodynamics approach and the UrQMD transport model, where the same equation of state is used in both approaches. Not only is the compression similar if the same equation of state is used in either dynamical model, but it also strongly depends on the actual equation of state. These results indicate that the equation of state can be studied with observables which are sensitive to the initial compression phase and maximum compression achieved in heavy ion collisions at these beam energies.
Comments:
11 pages, 7 figures, version accepted by: The European Physical Journal C
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2201.01622 [pdf]
EPJC(2022)·32 citations
06
[Submitted on 5 Jan 2022] (cross-list from hep-ph)
Hyperon production in quasielastic $ν ˉ_{τ} -$ nucleon scattering
A. Fatima🇮🇳 · M. Sajjad Athar🇮🇳 · S. K. Singh🇮🇳
The theoretical results for the total cross sections and polarization components of the $τ^{+}$ lepton produced in the charged current induced $∣Δ S ∣ = 1$ quasielastic $ν ˉ_{τ} - N$ scattering leading to hyperons ( $Λ, Σ$ ) have been presented assuming T invariance. The theoretical uncertainties arising due to the use of different vector, axial vector and pseudoscalar form factors as well as the effect of SU(3) symmetry breaking have been studied. We have also presented, for the first time, a comparison of the total cross sections for the production of $e, μ, τ$ leptons to facilitate the implications of lepton flavor universality~(LFU) in the $∣Δ S ∣ = 1$ quasielastic reactions induced by the antineutrinos of all flavors i.e., $ν_{l}; l = e, μ, τ$ .
Comments:
23 pages, 15 figures and 1 table. arXiv admin note: text overlap with arXiv:2010.10311
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2201.01474 [pdf]
PRD(2022)·5 citations
07
[Submitted on 5 Jan 2022] (cross-list from nucl-ex)
The structure of $^{36}$ Ca under the Coulomb magnifying glass
L. Lalanne🇫🇷 · O. Sorlin🇫🇷 · A. Poves🇪🇸 · M. Assié🇫🇷 · F. Hammache🇫🇷 · S. Koyama🇯🇵 · F. Flavigny🇯🇵 · V. Girard-Alcindor🇫🇷 · A. Lemasson🇫🇷 · A. Matta🇫🇷 · T. Roger🇫🇷 · D. Beaumel🇫🇷 and 19 other authors
Detailed spectroscopy of the neutron-deficient nucleus $^{36}$ Ca was obtained up to 9 MeV using the $^{37}$ Ca( $p$ , $d$ ) $^{36}$ Ca and the $^{38}$ Ca( $p$ , $t$ ) $^{36}$ Ca transfer reactions. The radioactive nuclei, produced by the LISE spectrometer at GANIL, interacted with the protons of the liquid Hydrogen target CRYPTA, to produce light ejectiles (the deuteron $d$ or triton $t$ ) that were detected in the MUST2 detector array, in coincidence with the heavy residues %identified by a zero degree detection system. %States have been measured up to 9 MeV. Our main findings are: i) a similar shift in energy for the 1 $_{1}^{+}$ and 2 $_{1}^{+}$ states by about -250 keV, as compared to the mirror nucleus $^{36}$ S, ii) the discovery of an intruder 0 $_{2}^{+}$ state at 2.83(13) MeV, which appears below the first 2 $^{+}$ state, in contradiction with the situation in $^{36}$ S, and iii) a tentative 0 $_{3}^{+}$ state at 4.83(17) MeV, proposed to exhibit a bubble structure with two neutron vacancies in the 2s $_{1/2}$ orbit. The inversion between the 0 $_{2}^{+}$ and 2 $_{1}^{+}$ states is due to the large mirror energy difference (MED) of -516(130) keV for the former. This feature is reproduced by Shell Model (SM) calculations, using the $s d$ - $p f$ valence space, predicting an almost pure intruder nature for the 0 $_{2}^{+}$ state, with two protons (neutrons) being excited across the $Z$ =20 magic closure in $^{36}$ Ca ( $^{36}$ S). This mirror system has the largest MEDs ever observed, if one excludes the few cases induced by the effect of the continuum.
Comments:
Paper of 5 pages, 3 figures. Contains also a supplementary material of 3 pages and 4 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2201.01513 [pdf]
PRL(2022)·24 citations
08
[Submitted on 5 Jan 2022] (cross-list from hep-ph)
Neural network reconstruction of the dense matter equation of state from neutron star observables
Shriya Soma🇩🇪 · Lingxiao Wang🇩🇪 · Shuzhe Shi🇨🇦 · Horst Stöcker🇩🇪 · Kai Zhou🇩🇪
The Equation of State (EoS) of strongly interacting cold and hot ultra-dense QCD matter remains a major challenge in the field of nuclear astrophysics. With the advancements in measurements of neutron star masses, radii, and tidal deformabilities, from electromagnetic and gravitational wave observations, neutron stars play an important role in constraining the ultra-dense QCD matter EoS. In this work, we present a novel method that exploits deep learning techniques to reconstruct the neutron star EoS from mass-radius (M-R) observations. We employ neural networks (NNs) to represent the EoS in a model-independent way, within the range of $\sim$ 1-7 times the nuclear saturation density. The unsupervised Automatic Differentiation (AD) framework is implemented to optimize the EoS, so as to yield through TOV equations, an M-R curve that best fits the observations. We demonstrate that this method works by rebuilding the EoS on mock data, i.e., mass-radius pairs derived from a randomly generated polytropic EoS. The reconstructed EoS fits the mock data with reasonable accuracy, using just 11 mock M-R pairs observations, close to the current number of actual observations.
Comments:
24 pages, 14 figures, https://github.com/ss-fias/nn-eos
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Instrumentation and Methods for Astrophysics (astro-ph.IM); Nuclear Theory (nucl-th)
arXiv:
2201.01756 [pdf]
JCAP(2022)·57 citations

Affiliations

first authorsco-authorsvia INSPIRE