Nuclear Theory·nucl-th

Friday·June 30, 2017

10 papers—4 primary·6 cross-listed

01
[Submitted on 28 Jun 2017]
Lambda hyperon polarization in relativistic heavy ion collisions from the chiral kinetic approach
Yifeng Sun🇺🇸 · Che Ming Ko🇺🇸
Based on the chiral kinetic approach using initial conditions from a multiphase transport model, we study the spin polarizations of quarks and antiquarks in non-central heavy ion collisions at the Relativistic Heavy Ion Collider. Because of the non-vanishing vorticity field in these collisions, quarks and antiquarks are found to acquire appreciable spin polarizations in the direction perpendicular to the reaction plane. Converting quarks and antiquarks to hadrons via the coalescence model, we further calculate the spin polarizations of Lambda and anti-Lambda hyperons and find their values comparable to those measured in experiments by the STAR Collaboration.
Comments:
6 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1706.09467 [pdf]
PRC(2017)·175 citations
02
[Submitted on 29 Jun 2017]
New successive variational method of tensor-optimized antisymmetrized molecular dynamics for nuclear many-body systems
Takayuki Myo🇯🇵 · Hiroshi Toki🇯🇵 · Kiyomi Ikeda🇯🇵 · Hisashi Horiuchi🇯🇵 · Tadahiro Suhara🇯🇵
We recently proposed a new variational theory of "tensor-optimized antisymmetrized molecular dynamics" (TOAMD), which treats the strong interaction explicitly for finite nuclei [T. Myo et al., Prog. Theor. Exp. Phys. 2015, 073D02 (2015)]. In TOAMD, the correlation functions for the tensor force and the short-range repulsion and their multiple products are successively operated to the AMD state. The correlated Hamiltonian is expanded into many-body operators by using the cluster expansion and all the resulting operators are taken into account in the calculation without any truncation. We show detailed results for TOAMD with the nucleon-nucleon interaction AV8 $^{'}$ for $s$ -shell nuclei. The binding energy and the Hamiltonian components are successively converged to exact values of the few-body calculations. We also apply TOAMD to the Malfliet-Tjon central potential having a strong short-range repulsion. TOAMD can treat the short-range correlation and provided accurate energies of $s$ -shell nuclei, reproducing the results of few-body calculations. It turns out that the numerical accuracy of TOAMD with double products of the correlation functions is beyond the variational Monte Carlo method with Jastrow's product-type correlation functions.
Comments:
25 pages, 24 figures, corrected typos
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1706.09560 [pdf]
PTEP(2017)·17 citations
03
[Submitted on 29 Jun 2017]
Structural effects of $^{34}$ Na in the $^{33}$ Na(n, $γ)^{34}$ Na radiative capture reaction
G. Singh🇮🇳 · Shubhchintak🇺🇸 · R. Chatterjee🇮🇳
The path towards the production of \textit{r}-process seed nuclei follows a course where the neutron-rich light and medium mass nuclei play a crucial role. The neutron capture rates for these exotic nuclei could dominate over their $α$ -capture rates, thereby enhancing their abundances at or near the drip line. We calculate the radiative neutron capture cross-section for the $^{33}$ Na(n, $γ)^{34}$ Na reaction via the Coulomb dissociation of $^{34}$ Na as it undergoes elastic breakup on $^{208}$ Pb when directed at a beam energy of 100 MeV/u using the entirely quantum mechanical theory of finite range distorted wave Born approximation upgraded to incorporate deformation effects. The non-resonant one neutron radiative capture cross-section for $^{33}$ Na(n, $γ)^{34}$ Na is calculated and is found to increase with increasing deformation of $^{34}$ Na. An analytic scrutiny of the capture cross-section with neutron separation energy as a parameter is also done at different energy ranges. The calculated reaction rate is compared with the rate of the $^{33}$ Na( $α$ ,n) $^{36}$ Al reaction (deduced from the Hauser-Feshbach theory), and is found to be significantly higher below a temperature of $T_{9} = 2$ . Further, at the equilibrium temperature of $T_{9} = 0.62$ , the rate for the neutron capture had a small but non-negligible dependence on the structural parameters of $^{34}$ Na. In addition, this neutron capture rate exceeded that of the $α$ -capture reaction by orders of magnitude, indicating that the $α$ -process should not break the (n, $γ$ ) \textit{r-}process path at the $^{33}$ Na isotope, thus, effectively pushing the abundance of sodium isotopes towards the neutron drip line.
Comments:
14 pages, 9 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1706.09687 [pdf]
PRC(2017)·16 citations
04
[Submitted on 28 Jun 2017]
The $d^{*} (2380)$ in neutron stars - a new degree of freedom?
I. Vidaña🇵🇹 · M. Bashkanov🇬🇧 · D.P. Watts🇬🇧 · A. Pastore🇬🇧
Elucidating the appropriate microscopic degrees of freedom within neutron stars remains an open question which impacts nuclear physics, particle physics and astrophysics. The recent discovery of the first non-trivial dibaryon, the $d^{*} (2380)$ , provides a new candidate for an exotic degree of freedom in the nuclear equation of state at high matter densities. In this paper a first calculation of the role of the $d^{*} (2380)$ in neutron stars is performed, based on a relativistic mean field description of the nucleonic degrees of freedom supplemented by a free boson gas of $d^{*} (2380)$ . The calculations indicate that the $d^{*} (2380)$ would appear at densities around three times normal nuclear matter saturation density, influencing the upper mass limit for a stable neutron star and the neutron and proton fractions. New possibilities for neutron star cooling mechanisms arising from the $d^{*} (2380)$ are also predicted.
Comments:
Included comparisons with LIGO data. Included the Delta contributions
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
1706.09701 [pdf]
PLB(2018)·38 citations
05
[Submitted on 28 Jun 2017] (cross-list from cond-mat.quant-gas)
The Efimov effect for heteronuclear three-body systems at positive scattering length and finite temperature
Samuel B. Emmons · Daekyoung Kang · Bijaya Acharya · Lucas Platter
We study the recombination process of three atoms scattering into an atom and diatomic molecule in heteronuclear mixtures of ultracold atomic gases with large and positive interspecies scattering length at finite temperature. We calculate the temperature dependence of the three-body recombination rates by extracting universal scaling functions that parametrize the energy dependence of the scattering matrix. We compare our results to experimental data for the 40K-87Rb mixture and make a prediction for 6Li-87Rb. We find that contributions from higher partial wave channels significantly impact the total rate and, in systems with particularly large mass imbalance, can even obliterate the recombination minima associated with the Efimov effect.
Comments:
19 pages, 5 figures
Subjects:
Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th)
arXiv:
1706.09458 [pdf]
PRA(2017)·3 citations
06
[Submitted on 29 Jun 2017] (cross-list from hep-ph)
Top-quark pair production cross sections at NNLO+NNLL in pPb collisions at $s_{N N}$ = 8.16 TeV
David d'Enterria🇨🇭
Total and fiducial top pair ( $t t ˉ$ ) production cross sections in proton-lead (pPb) collisions at $s_{N N}$ = 8.16 TeV are computed at next-to-next-to-leading-order (NNLO) accuracy including next-to-next-to-leading-log (NNLL) gluon resummation, using the CT14 and CT10 proton parton distribution functions (PDF), and the EPPS16 and EPS09 nuclear PDF parametrizations for the lead ion. The total cross sections amount to $σ (pP b \to t t ˉ + X) = 59.0 \pm 5.3$ (CT14+EPPS16) $_{- 2.1}^{+ 1.6}$ (scale) nb, and $57.5 \pm_{- 3.3}^{+ 4.3}$ (CT10+EPS09) $_{- 2.0}^{+ 1.5}$ (scale) nb, with small modifications with respect to the result computed using the free proton PDF alone. The normalized ratio of pPb to pp cross sections (nuclear modification factor) is $R_{pP b} = 1.04_{\pm 0.03 (E P S 09)}^{\pm 0.07 (E P P S 16)}$ . In the lepton+jets decay mode, $t t ˉ \to b b ˉ W (ℓ ν) W (q q ˉ^{'})$ , one expects $\sim$ 600 $t t ˉ$ events in the 180 nb $^{- 1}$ integrated luminosity collected in pPb collisions at the LHC so far, after typical acceptance and efficiency losses. Differential cross sections at NLO accuracy are presented as a function of transverse momentum and rapidity of the top quarks, and of their decay b-jets and isolated leptons.
Comments:
Typos corrected, refs. added. 5 pages, 2 figures. Contribution to "Theoretical predictions for p+Pb collisions at 8.16 TeV" (arXiv:1707.09973, Nucl. Phys. A, to appear)
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1706.09521 [pdf]
NPA(2019)·4 citations
07
[Submitted on 29 Jun 2017] (cross-list from hep-ph)
Mass spectra of meson molecular states for heavy and light sectors
S. Rahmani🇮🇷 · H. Hassanabadi🇮🇷
We obtain mass spectra of the light and heavy meson-antimeson (molecular states) sectors by using a nonrelativistic potential model with Coulomb and one pion exchange potential terms for meson-meson interaction. The digamma decay widths are also obtained for the light sector. We compare our results with available experimental and theoretical data.
Comments:
Accepted for publishing in Chinese Physics C journal
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1706.09580 [pdf]
CPC(2017)·3 citations
08
[Submitted on 29 Jun 2017] (cross-list from nucl-ex)
Experimental Determination of One- and Two-Neutron Separation Energies for Neutron-Rich Copper Isotopes
Mian YU🇨🇳 · Hui-Ling Wei🇨🇳 · Yi-Dan Song🇨🇳 · Chun-Wang Ma🇨🇳
A method is proposed to determine the one-neutron $S_{n}$ or two-neutron $S_{2 n}$ separation energy of neutron-rich isotopes. Relationships between $S_{n}$ ( $S_{2 n}$ ) and isotopic cross sections have been deduced from an empirical formula, i.e., the cross section of an isotope exponentially depends on the average binding energy per nucleon $B / A$ . The proposed relationships have been verified using the neutron-rich copper isotopes measured in the 64 $A$ MeV $^{86}$ Kr + $^{9}$ Be reaction. $S_{n}$ , $S_{2 n}$ , and $B / A$ for the very neutron-rich $^{77, 78, 79}$ Cu isotopes are determined from the proposed correlations. It is also proposed that the correlations between $S_{n}$ , $S_{2 n}$ and isotopic cross sections can be used to find the location of neutron drip line isotopes.
Comments:
4 pages, 2 figures, 2 tables
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1706.09609 [pdf]
CPC(2017)·8 citations
09
[Submitted on 29 Jun 2017] (cross-list from nucl-ex)
Meson-nucleus potentials and the search for meson-nucleus bound states
V. Metag🇩🇪 · M. Nanova🇩🇪 · E. Ya. Paryev🇷🇺
Recent experiments studying the meson-nucleus interaction to extract meson-nucleus potentials are reviewed. The real part of the potentials quantifies whether the interaction is attractive or repulsive while the imaginary part describes the meson absorption in nuclei. The review is focused on mesons which are sufficiently long-lived to potentially form meson-nucleus quasi-bound states. The presentation is confined to meson production off nuclei in photon-, pion-, proton-, and light-ion induced reactions and heavy-ion collisions at energies near the production threshold. Tools to extract the potential parameters are presented. In most cases, the real part of the potential is determined by comparing measured meson momentum distributions or excitation functions with collision model or transport model calculations. The imaginary part is extracted from transparency ratio measurements. Results on $K^{+}, K^{0}, K^{-}, η, η^{'}, ω$ , and $ϕ$ mesons are presented and compared with theoretical predictions. The interaction of $K^{+}$ and $K^{0}$ mesons with nuclei is found to be weakly repulsive, while the $K^{-}, η, η^{'}, ω$ and $ϕ$ meson-nucleus potentials are attractive, however, with widely different strengths. Because of meson absorption in the nuclear medium the imaginary parts of the meson-nucleus potentials are all negative, again with a large spread. An outlook on planned experiments in the charm sector is given. In view of the determined potential parameters, the criteria and chances for experimentally observing meson-nucleus quasi-bound states are discussed. The most promising candidates appear to be the $η$ and $η^{'}$ mesons.
Comments:
86 pages, 67 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1706.09654 [pdf]
PPNP(2017)·126 citations
10
[Submitted on 29 Jun 2017] (cross-list from hep-ph)
Using hadron-in-jet data in a global analysis of $D^{*}$ fragmentation functions
Daniele P. Anderle🇬🇧 · Tom Kaufmann🇩🇪 · Felix Ringer🇩🇪 · Marco Stratmann🇺🇸 · Ivan Vitev🇺🇸
We present a novel global QCD analysis of charged $D^{*}$ -meson fragmentation functions at next-to-leading order accuracy. This is achieved by making use of the available data for single-inclusive $D^{*}$ -meson production in electron-positron annihilation, hadron-hadron collisions, and, for the first time, in-jet fragmentation in proton-proton scattering. It is shown how to include all relevant processes efficiently and without approximations within the Mellin moment technique, specifically for the in-jet fragmentation cross section. The presented technical framework is generic and can be straightforwardly applied to future analyses of fragmentation functions for other hadron species, as soon as more in-jet fragmentation data become available. We choose to work within the Zero Mass Variable Flavor Number Scheme which is applicable for sufficiently high energies and transverse momenta. The obtained optimum set of parton-to- $D^{*}$ fragmentation functions is accompanied by Hessian uncertainty sets which allow one to propagate hadronization uncertainties to other processes of interest.
Comments:
16 pages, 8 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1706.09857 [pdf]
PRD(2017)·73 citations

Affiliations

first authorsco-authorsvia INSPIRE