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
05
[Submitted on 12 Jan 2016] (cross-list from hep-ph)
Hidden-charm Pentaquark States in Heavy Ion Collisions at the Large Hadron Collider
Rui-Qin Wang🇨🇳 · Jun Song🇨🇳 · Kai-Jia Sun🇨🇳 · Lie-Wen Chen🇨🇳 · Gang Li🇨🇳 · Feng-Lan Shao🇨🇳
In the framework of the quark combination, we derive the yield formulas and study the yield ratios of the hidden-charm pentaquark states in ultra-relativistic heavy ion collisions. We propose some interesting yield ratios which clearly exhibit the production relationships between different hidden-charm pentaquark states. We show how to employ a specific quark combination model to evaluate the yields of exotic $P_{c}^{+} (4380)$ , $P_{c}^{+} (4450)$ and their partners on the basis of reproducing the yields of normal identified hadrons, and execute the calculations in central Pb+Pb collisions at $s_{N N} = 2.76$ TeV as an example.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1601.02835 [pdf]
PRC(2016)·19 citations
06
[Submitted on 14 Jan 2016] (cross-list from hep-ph)
Transport coefficients of heavy baryons
Laura Tolos🇪🇸 · Juan M. Torres-Rincon🇫🇷 · Santosh K. Das🇮🇹
We compute the transport coefficients (drag and momentum diffusion) of the low-lying heavy baryons $Λ_{c}$ and $Λ_{b}$ in a medium of light mesons formed at the later stages of high-energy heavy-ion collisions. We employ the Fokker-Planck approach to obtain the transport coefficients from unitarized baryon-meson interactions based on effective field theories that respect chiral and heavy-quark symmetries. We provide the transport coefficients as a function of temperature and heavy-baryon momentum, and analyze the applicability of certain nonrelativistic estimates. Moreover we compare our outcome for the spatial diffusion coefficient to the one coming from the solution of the Boltzmann-Uehling-Uhlenbeck transport equation and we find a very good agreement between both calculations. The transport coefficients for $Λ_{c}$ and $Λ_{b}$ in a thermal bath will be used in a subsequent publication as input in a Langevin evolution code for the generation and propagation of heavy particles in heavy-ion collisions at LHC and RHIC energies.
Comments:
26 pages, 12 figures. Title changed. Small additions and corrections. Version accepted for publication by Physical Review D journal
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1601.03743 [pdf]
PRD(2016)·22 citations
07
[Submitted on 15 Jan 2016] (cross-list from hep-ph)
How to retrieve additional information from the multiplicity distributions
Grzegorz Wilk🇵🇱 · Zbigniew Włodarczyk🇵🇱
Multiplicity distributions $P (N)$ measured in multiparticle production processes are most frequently described by the Negative Binomial Distribution (NBD). However, with increasing collision energy some systematic discrepancies become more and more apparent. They are usually attributed to the possible multi-source structure of the production process and described using a multi-NBD form of the multiplicity distribution. We investigate the possibility of keeping a single NBD but with its parameters depending on the multiplicity $N$ . This is done by modifying the widely known clan model of particle production leading to the NBD form of $P (N)$ . This is then confronted with the approach based on the so-called cascade-stochastic formalism which is based on different types of recurrence relations defining $P (N)$ . We demonstrate that a combination of both approaches allows the retrieval of additional valuable information from the multiplicity distributions, namely the oscillatory behavior of the counting statistics apparently visible in the high energy data.
Comments:
A few cosmetical changes. Version accepted for publication by J.Phys. G
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1601.03883 [pdf]
J.Phys.G(2017)·24 citations
08
[Submitted on 15 Jan 2016] (cross-list from hep-ph)
Weak decays of heavy hadrons into dynamically generated resonances
Eulogio Oset🇨🇳 · Wei-Hong Liang🇨🇳 · Melahat Bayar🇹🇷 · Ju-Jun Xie🇨🇳 · Lian Rong Dai🇨🇳 · Miguel Albaladejo🇪🇸 · Marina Nielsen🇧🇷 · Takayasu Sekihara🇯🇵 · Fernando Navarra🇧🇷 · Luis Roca🇪🇸 · Maxim Mai🇩🇪 · Juan Nieves🇪🇸 and 15 other authors
In this review we give a perspective of the theoretical work done recently on the interpretation of results from $B$ , $D$ , $Λ_{b}$ , $Λ_{c}$ weak decays into final states that contain interacting hadrons, and how it is possible to obtain additional valuable information that is increasing our understanding of hadron interactions and the nature of many hadronic resonances. The novelty of these processes is that one begins with a clean picture at the quark level which allows one to select the basic mechanisms by means of which the process proceeds. Finally, one has a final state described in terms of quarks. To make contact with the experiments, where mesons and baryons are observed, one must hadronize, creating pairs of $q q ˉ$ and writing the new states in terms of mesons and baryons. This concludes the primary hadron production in these processes. After that, the interaction of these hadrons takes place, offering a rich spectrum of resonances and special features from where it is possible to learn much about the interaction of these hadrons and the nature of many resonances in terms of the components of their wave functions.
Comments:
Review paper comissioned for International Journal of Modern Physics E
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1601.03972 [pdf]
IJMPE(2016)·160 citations
09
[Submitted on 15 Jan 2016] (cross-list from nucl-ex)
Coulomb breakup of neutron-rich $^{29, 30}$ Na isotopes near the island of inversion
A . Rahaman · Ushasi Datta · T. Aumann · S. Beceiro-Novo · K. Boretzky · C. Caesar · B.V. Carlson · W.N. Catford · S. Chakraborty · M. Chartier · D. Cortina-Gil · G. De. Angelis and 41 other authors
First results are reported on the ground state configurations of the neutron-rich $^{29, 30}$ Na isotopes, obtained via Coulomb dissociation (CD) measurements as a method of the direct probe. The invariant mass spectra of those nuclei have been obtained through measurement of the four-momentum of all decay products after Coulomb excitation on a $^{208} P b$ target at energies of 400-430 MeV/nucleon using FRS-ALADIN-LAND setup at GSI, Darmstadt. Integrated Coulomb-dissociation cross-sections (CD) of 89 $(7)$ mb and 167 $(13)$ mb up to excitation energy of 10 MeV for one neutron removal from $^{29}$ Na and $^{30}$ Na respectively, have been extracted. The major part of one neutron removal, CD cross-sections of those nuclei populate core, in its' ground state. A comparison with the direct breakup model, suggests the predominant occupation of the valence neutron in the ground state of $^{29}$ Na $(3/ 2^{+})$ and $^{30}$ Na $(2^{+})$ is the $d$ orbital with small contribution in the $s$ -orbital which are coupled with ground state of the core. The ground state configurations of these nuclei are as $^{28}$ Na $_{gs (1^+)\otimes\nu_{s,d}$ and $^{29}$ Na $_{g s} (3/ 2^{+}) \otimes ν_{s, d}$ , respectively. The ground state spin and parity of these nuclei, obtained from this experiment are in agreement with earlier reported values. The spectroscopic factors for the valence neutron occupying the $s$ and $d$ orbitals for these nuclei in the ground state have been extracted and reported for the first time. A comparison of the experimental findings with the shell model calculation using MCSM suggests a lower limit of around 4.3 MeV of the sd-pf shell gap in $^{30}$ Na.
Comments:
Modified version of the manuscript is accepted for publication in Journal of Physics G, Jan., 2017
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1601.04002 [pdf]
J.Phys.G(2017)·7 citations

Affiliations

first authorsco-authorsvia INSPIRE