Nuclear Theory·nucl-th

Wednesday·March 9, 2016

11 papers—7 primary·4 cross-listed

01
[Submitted on 7 Mar 2016]
Nucleon-deuteron scattering using the adiabatic projection method
Serdar Elhatisari🇩🇪 · Dean Lee🇺🇸 · Ulf-G. Meißner🇩🇪 · Gautam Rupak🇺🇸
In this paper we discuss the adiabatic projection method, a general framework for scattering and reaction calculations on the lattice. We also introduce several new techniques developed to study nucleus-nucleus scattering and reactions on the lattice. We present technical details of the method for large-scale problems. To estimate the systematic errors of the calculations we consider simple two-particle scattering on the lattice. Then we benchmark the accuracy and efficiency of the numerical methods by applying these to calculate fermion-dimer scattering in lattice effective field theory with and without a long-range Coulomb potential. The fermion-dimer calculations correspond to neutron-deuteron and proton-deuteron scattering in the spin-quartet channel at leading order in the pionless effective field theory.
Comments:
26 pages, 17 figures, and 1 table; version published in EPJA
Subjects:
Nuclear Theory (nucl-th); Quantum Gases (cond-mat.quant-gas); High Energy Physics — Lattice (hep-lat)
arXiv:
1603.02333 [pdf]
EPJA(2016)·41 citations
02
[Submitted on 7 Mar 2016]
Evolution to the Quark-Gluon Plasma
Kenji Fukushima🇯🇵
Theoretical studies on the early-time dynamics in the ultra-relativistic heavy-ion collisions are reviewed including pedagogical introductions on the initial condition with small-x gluons treated as a color glass condensate, the bottom-up thermalization scenario, plasma/glasma instabilities, basics of some formulations such as the kinetic equations and the classical statistical simulation. More detailed discussions follow to make an overview of recent developments on the fast isotropization, the onset of hydrodynamics, and the transient behavior of momentum spectral cascades.
Comments:
46 pages, submitted to RoPP Key Issue Review; references added for early works related to aHydro, typos corrected
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1603.02340 [pdf]
Rept.Prog.Phys.(2017)·42 citations
03
[Submitted on 8 Mar 2016]
Probing nuclear bubble configuration by the $π^{-} / π^{+}$ ratio in heavy-ion collisions
Gao-Chan Yong
It is theoretically and experimentally argued that there may exist bubble or toroid-shaped configurations in some nucleus systems. Based on the nuclear transport model, it is shown that compared with the collision of normal nuclei, there is a depletion of central density of compression with bubble configurations in projectile and target nuclei. This depletion of central compression density may affect some observables in heavy-ion collisions.
Comments:
5 pages, 6 figures, accepted by European Physical Journal A
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1603.02364 [pdf]
EPJA(2016)·8 citations
04
[Submitted on 8 Mar 2016]
$K^{+}$ -nucleus potentials from $K^{+}$ -nucleon amplitudes
E. Friedman
Optical potentials for $K^{+}$ -nucleus interactions are constructed from $K^{+}$ -nucleon amplitudes using recently developed algorithm based on $K^{+}$ -N kinematics in the nuclear medium. With the deep penetration of $K^{+}$ mesons into the nucleus at momenta below 800~MeV/c it is possible to test this approach with greater sensitivity than hitherto done with $K^{-}$ and pions. The energy-dependence of experimental reaction and total cross sections on nuclei is better reproduced with this approach compared to fixed-energy amplitudes. The inclusion of Pauli correlations in the medium also improves the agreement between calculation and experiment. The absolute scale of the cross sections is reproduced very well for $^{6}$ Li but for C, Si and Ca calculated cross sections are (23 $\pm 4$ )\% smaller than experiment, in agreement with earlier analyses. Two phenomenological models that produce such missing strength suggest that the imaginary part of the potential needs about 40\% enhancement.
Comments:
15 pages, 6 figures, to appear in Nucl. Phys. A
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1603.02451 [pdf]
NPA(2016)·4 citations
05
[Submitted on 8 Mar 2016]
Challenges in Nuclear Structure Theory
Witold Nazarewicz🇺🇸
The goal of nuclear structure theory is to build a comprehensive microscopic framework in which properties of nuclei and extended nuclear matter, and nuclear reactions and decays can all be consistently described. Due to novel theoretical concepts, breakthroughs in the experimentation with rare isotopes, increased exchange of ideas across different research areas, and the progress in computer technologies and numerical algorithms, nuclear theorists have been quite successful in solving various bits and pieces of the nuclear many-body puzzle and the prospects are exciting. This article contains a brief, personal perspective on the status of the field.
Comments:
16 pages, 7 figures, Appeared in J. Phys. G Focus Issue on 40 years of research in Journal of Physics G
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1603.02490 [pdf]
J.Phys.G(2016)·31 citations
06
[Submitted on 8 Mar 2016]
A systematic study of the initial state in heavy ion collisions based on the quark participant assumption
Liang Zheng🇨🇳 · Zhongbao Yin🇨🇳
We investigate the initial state geometric quantities of heavy ion collisions based on the quark participant assumption in the Glauber multiple scattering approach. A systematic comparison to the nucleon participant assumption has been presented and confronted with the charged multiplicity measurements in various collision systems. It is found that the quark participant based assumption can be important to understand the data in multiplicity production and the initial spatial eccentricity in small systems.
Comments:
7 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1603.02515 [pdf]
EPJA(2016)·23 citations
07
[Submitted on 8 Mar 2016]
The link between rare earth peak formation and the astrophysical site of the $r$ process
M. R. Mumpower · G. C. McLaughlin · R. Surman · A. W. Steiner
The primary astrophysical source of the rare earth elements is the rapid neutron capture process ( $r$ process). The rare earth peak that is seen in the solar $r$ -process residuals has been proposed to originate as a pile-up of nuclei during the end of the $r$ process. We introduce a new method utilizing Monte Carlo studies of nuclear masses in the rare earth region, that includes self-consistently adjusting $β$ -decay rates and neutron capture rates, to find the mass surfaces necessary for the formation of the rare earth peak. We demonstrate our method with two types of astrophysical scenarios, one corresponding conditions typical of core-collapse supernova winds and one corresponding to conditions typical of the ejection of the material from the tidal tails of neutron star mergers. In each type of astrophysical conditions, this method successfully locates a region of enhanced stability in the mass surface that is responsible for the rare earth peak. For each scenario, we find that the change in the mass surface has qualitatively different features, thus future measurements can shed light on the type of environment in which the $r$ process occurred.
Comments:
5 pages, 4 figures, submitted
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR)
arXiv:
1603.02600 [pdf]
ApJ(2016)·22 citations
08
[Submitted on 8 Mar 2016] (cross-list from hep-ph)
Coupled channel analysis of molecule picture of $P_{c} (4380)$
Yuki Shimizu🇯🇵 · Daiki Suenaga🇯🇵 · Masayasu Harada🇯🇵
We construct a potential obtained by one-pion exchange for the coupled channel $Σ_{c}^{*}$ $D ˉ$ - $Σ_{c}$ $D ˉ^{*}$ , and solve the coupled Schrödinger equations to determine the binding energy. We find that there exists one or two bound states with the binding energy of several MeV below the threshold of $Σ_{c}^{*}$ and $D ˉ$ , dominantly made from a $Σ_{c}^{*}$ baryon and a $D ˉ$ meson, with the size of about $1.5$ fm for wide parameter region. We also study the pentaquark states including a $b$ quark and/or an anti- $b$ quark. We show that there exist pentaquarks including $c b ˉ$ , $b c ˉ$ and $b b ˉ$ , all of which lie at about $10$ MeV below the corresponding threshold and have size of about $1.5$ fm.
Comments:
7 pages, 9 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1603.02376 [pdf]
PRD(2016)·82 citations
09
[Submitted on 8 Mar 2016] (cross-list from hep-ph)
On the pole content of coupled channels chiral approaches used for the $K ˉ N$ system
A. Cieplý🇨🇿 · M. Mai🇩🇪 · Ulf-G. Meißner🇩🇪 · J. Smejkal🇨🇿
Several theoretical groups describe the antikaon-nucleon interaction at low energies within approaches based on the chiral SU(3) dynamics and including next-to-leading order contributions. We present a comparative analysis of the pertinent models and discuss in detail their pole contents. It is demonstrated that the approaches lead to very different predictions for the $K^{-} p$ amplitude extrapolated to subthreshold energies as well as for the $K^{-} n$ amplitude. The origin of the poles generated by the models is traced to the so-called zero coupling limit, in which the inter-channel couplings are switched off. This provides new insights into the pole contents of the various approaches. In particular, different concepts of forming the $Λ (1405)$ resonance are revealed and constraints related to the appearance of such poles in a given approach are discussed.
Comments:
24 pages, 15 figures, to appear in Nuclear Physics A special issue on Strangeness and Charm Nuclear Physics; v2 - several paragraphs modified or extended, version accepted for publication
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1603.02531 [pdf]
NPA(2016)·116 citations
10
[Submitted on 8 Mar 2016] (cross-list from nucl-ex)
From the stable to the exotic: clustering in light nuclei
C. Beck🇫🇷
A great deal of research work has been undertaken in alpha-clustering study since the pioneering discovery of 12C+12C molecular resonances half a century ago. Our knowledge on physics of nuclear molecules has increased considerably and nuclear clustering remains one of the most fruitful domains of nuclear physics, facing some of the greatest challenges and opportunities in the years ahead. The occurrence of "exotic" shapes in light N=Z alpha-like nuclei is investigated. Various approaches of the superdeformed and hyperdeformed bands associated with quasimolecular resonant structures are presented. Evolution of clustering from stability to the drip-lines is examined: clustering aspects are, in particular, discussed for light exotic nuclei with large neutron excess such as neutron-rich Oxygen isotopes with their complete spectroscopy.
Comments:
15 pages, 5 figures, Presented at the International Symposium on "New Horizons in Fundamental Physics - From Neutrons Nuclei via Superheavy Elements and Supercritical Fields to Neutron Stars and Cosmic Rays" held at Makutsi Safari Farm, South Africa, December 23-29, 2015. arXiv admin note: substantial text overlap with arXiv:1402.6590, arXiv:1303.0960, arXiv:1408.0684, arXiv:1011.3423
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1603.02574 [pdf]
FIAS Interdisc.Sci.Ser.(2017)·4 citations
11
[Submitted on 8 Mar 2016] (cross-list from astro-ph.HE)
Influence of the stiffness of the equation of state and in-medium effects on the cooling of compact stars
H. Grigorian🇷🇺 · D. N. Voskresensky🇷🇺 · D. Blaschke🇷🇺
Measurements demonstrate the existence of compact stars with masses in a broad range from 1.2 to 2 $M_{⊙}$ . The most massive of these objects might be hybrid stars. To fulfill the constraint $M_{max} > 2 M_{⊙}$ with a reserve we exploit the stiff DD2 hadronic equation of state (EoS) without and with excluded volume (DD2vex) correction, which produce maximum neutron star masses of $M_{max} = 2.43 M_{⊙}$ and $2.70 M_{⊙}$ , respectively. We show that the stiffness of the EoS does not preclude an explanation of the whole set of cooling data within "nuclear medium cooling" scenario for compact stars by a variation of the star masses. We select appropriate proton gap profiles from those exploited in the literature and allow for a variation of the effective pion gap controlling the efficiency of the medium modified Urca process. However, we suppress the possibility of pion condensation. In general, the stiffer the EoS the steeper a decrease with density of the effective pion gap is required. Results are compared with previously obtained ones for the HDD EoS for which $M_{max} = 2.06 M_{⊙}$ . The cooling of the compact star in the supernova remnant Cassiopeia A (Cas A) is explained mainly by an efficient medium modified Urca process. With the DD2vex EoS and using an effective pion gap steeper decreasing with the density and/or a proton gap shifted to smaller densities we are also able to reproduce both a strong decline compatible with ACIS-S data and HRC-S instrument data. The mass of Cas A is estimated as $1.6 - 1.9 M_{⊙}$ , above the value $1.5 M_{⊙}$ , which we have evaluated with the softer HDD equation of state. Different mass choices for the hottest object XMMU J173203.3-344518 are discussed. We make general remarks also on hybrid star cooling and on its dependence on the stiffness of the hadronic EoS.
Comments:
25 pages, 21 figures, to appear in the EPJA Topical Issue on "Exotic Matter in Neutron Stars"; a strongly abridged version of this work has been presented as eConf C140926 in the Proceedings of the Conference "Compact Stars in the QCD Phase Diagram IV", Prerow, September 26 - 30, 2014; arxiv:1507.04656
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
1603.02634 [pdf]
EPJA(2016)·40 citations

Affiliations

first authorsco-authorsvia INSPIRE