Nuclear Theory·nucl-th

Monday·January 18, 2016

9 papers—4 primary·5 cross-listed

01
[Submitted on 14 Jan 2016]
Unified ab initio approaches to nuclear structure and reactions
Petr Navratil🇨🇦 · Sofia Quaglioni🇺🇸 · Guillaume Hupin🇫🇷 · Carolina Romero-Redondo🇺🇸 · Angelo Calci🇨🇦
The description of nuclei starting from the constituent nucleons and the realistic interactions among them has been a long-standing goal in nuclear physics. In addition to the complex nature of the nuclear forces, with two-, three- and possibly higher many-nucleon components, one faces the quantum-mechanical many-nucleon problem governed by an interplay between bound and continuum states. In recent years, significant progress has been made in ab initio nuclear structure and reaction calculations based on input from QCD-employing Hamiltonians constructed within chiral effective field theory. After a brief overview of the field, we focus on ab initio many-body approaches - built upon the No-Core Shell Model - that are capable of simultaneously describing both bound and scattering nuclear states, and present results for resonances in light nuclei, reactions important for astrophysics and fusion research. In particular, we review recent calculations of resonances in the $^{6}$ He halo nucleus, of five- and six-nucleon scattering, and an investigation of the role of chiral three-nucleon interactions in the structure of $^{9}$ Be. Further, we discuss applications to the $^{7}$ Be $(p, γ)^{8}$ B radiative capture. Finally, we highlight our efforts to describe transfer reactions including the $^{3}$ H $(d, n)^{4}$ He fusion.
Comments:
Contribution to the Special Physica Scripta Edition - 40 year anniversary - Nobel Prize '75, 71 pages, 29 figures
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex)
arXiv:
1601.03765 [pdf]
Phys.Scripta(2016)·235 citations
02
[Submitted on 15 Jan 2016]
Photoproduction of $K Λ$ on the proton
Dalibor Skoupil🇨🇿 · Petr Bydzovsky🇨🇿
Kaon photoproduction on the proton is studied in the resonance region using an isobar model. The higher-spin nucleon (3/2 and 5/2) and hyperon (3/2) resonances were included in the model utilizing the consistent formalism by Pascalutsa and they were found to play an important role in data description. The spin-1/2 and spin-3/2 hyperon resonances in combination with the Born terms contribute significantly to the background part of the amplitude. Various forms of the hadron form factor were considered in the construction and the dipole and multidipole forms were selected as those most suitable for the data description. Model parameters were fitted to new experimental data from CLAS, LEPS, and GRAAL collaborations and two versions of the model, BS1 and BS2, were chosen. Both models provide a good overall description of the data for the c.m. energies from the threshold up to 2.4 GeV. Predicted cross sections of the models at very small kaon angles being consistent with results of the Saclay-Lyon model indicate that the models could be also successful in predicting the hypernucleus production cross sections. Although kaon photoproduction takes place in the third-resonance region with many resonant states, the total number of included resonances, 15 and 16, is quite moderate and it is comparable with numbers of resonances in other models. The set of chosen nucleon resonances overlaps well with the set of the most probable contributing states determined in the Bayesian analysis with the Regge-plus-resonance model. Particularly, we confirm that the missing resonances $P_{13} (1900)$ and $D_{13} (1875)$ do play important role in the description of data. However, the spin-1/2 state $P_{11} (1880)$ included in the Bayesian analysis was replaced in our analysis with the near-mass spin-5/2 state $N^{*} (1860)$ , recently considered by the Particle Data Group.
Comments:
28 pages, 11 figures, 2 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1601.03840 [pdf]
PRC(2016)·50 citations
03
[Submitted on 15 Jan 2016]
What can we learn from the directed flow in heavy-ion collisions at BES RHIC energies?
Yu. B. Ivanov🇷🇺 · A. A. Soldatov🇷🇺
Analysis of directed flow ( $v_{1}$ ) of protons, antiprotons and pions in heavy-ion collisions is performed in the range of collision energies $s_{N N}$ = 2.7--39 GeV. Simulations have been done within a three-fluid model employing a purely hadronic equation of state (EoS) and two versions of the EoS with deconfinement transitions: a first-order phase transition and a smooth crossover transition. The crossover EoS is unambiguously preferable for the description of the most part of experimental data in this energy range. The directed flow indicates that the crossover deconfinement transition takes place in semicentral Au+Au collisions in a wide range of collision energies 4 \lsim\sqrt{s_{NN}}\lsim$ 30 GeV. The obtained results suggest that the deconfinement EoS's in the quark-gluon sector should be stiffer at high baryon densities than those used in the calculation. The latter finding is in agreement with that discussed in astrophysics.
Comments:
6 pages, 4 figures, the paper extends results of arXiv:1412.1669
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1601.03902 [pdf]
EPJA(2016)·35 citations
04
[Submitted on 15 Jan 2016]
Initial conditions from the shadowed Glauber model for Pb+Pb at $s_{NN} = 2.76$ TeV
Snigdha Ghosh🇮🇳 · Sushant K. Singh🇮🇳 · Sandeep Chatterjee🇮🇳 · Jane Alam🇮🇳 · Sourav Sarkar🇮🇳
We study the initial conditions for Pb+Pb collisions at $s_{NN} = 2.76$ TeV using the two component Monte-Carlo Glauber model with shadowing of the nucleons in the interior by the leading ones. The model parameters are fixed by comparing to the multiplicity data of p+Pb and Pb+Pb at $s_{NN} = 5.02$ and $2.76$ TeV respectively. We then compute the centrality dependence of the eccentricities upto the fourth order as well as their event by event distributions. The inclusion of shadowing brings the Monte-Carlo Glauber model predictions in agreement with data as well as with results from other dynamical models of initial conditions based on gluon saturation at high energy nuclear collisions. Further, we find that the shadowed Glauber model provides the desired relative magnitude between the ellipticity and triangularity of the initial energy distribution required to explain the data on the even and odd flow harmonics $v_{2}$ and $v_{3}$ respectively at the LHC.
Comments:
version accepted for publication in Physical Review C
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1601.03971 [pdf]
PRC(2016)·14 citations

Affiliations

first authorsco-authorsvia INSPIRE

Unified ab initio approaches to nuclear structure and reactions

Photoproduction of KΛ on the proton

What can we learn from the directed flow in heavy-ion collisions at BES RHIC energies?

Initial conditions from the shadowed Glauber model for Pb+Pb at sNN​​=2.76 TeV

Affiliations

Photoproduction of $K Λ$ on the proton

Initial conditions from the shadowed Glauber model for Pb+Pb at $s_{NN} = 2.76$ TeV