Nuclear Theory·nucl-th

Monday·June 26, 2017

10 papers—4 primary·6 cross-listed

01
[Submitted on 22 Jun 2017]
Spin-flip doublets of $^{9}$ Be spectrum within a cluster model
I. Filikhin🇺🇸 · V. M. Suslov🇺🇸 · B. Vlahovic🇺🇸
The structure of the $^{9}$ Be low-lying spectrum is studied within the cluster model $α + α + n$ . In the model the total orbital momentum is fixed for each energy level. Thus each level is determined as a member of the spin-flip doublet corresponding to the total orbital momentum ( $L^{π} = 0^{+}, 2^{+}, 4^{+}, 1^{-}, 2^{-}, 3^{-}, 4^{-}$ ) of the system. The Ali-Bodmer potential (model E) is applied for the $α α$ interaction. We employ a local $α n$ potential which was constructed to reproduce the $α - n$ scattering data. The Pauli blocking is simulated by the repulsive core of the $s$ -wave components of these potentials. Configuration space Faddeev equations are used to calculate the energy of the bound state ( $E_{c a l .}$ =-1.493 MeV v.s. $E_{e x p .}$ =-1.5735 MeV) and resonances. A variant of the method of analytical continuation in the coupling constant is applied to calculate the energies of low-lying levels. Available $^{9}$ Be spectral data are satisfactorily reproduced by the proposed model.
Comments:
17 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1706.07481 [pdf]
FIZIKA B (Zagreb) 20 (2011) 3, 189-202·0 citations
02
[Submitted on 22 Jun 2017]
Estimation of M1 scissors mode strength for deformed nuclei in the medium to heavy mass region by statistical Hauser-Feshbach model calculations
M. R. Mumpower · T. Kawano · J. L. Ullmann · M. Krtička · T. M. Sprouse
Radiative neutron capture is an important nuclear reaction whose accurate description is needed for many applications ranging from nuclear technology to nuclear astrophysics. The description of such a process relies on the Hauser-Feshbach theory which requires the nuclear optical potential, level density and $γ$ -strength function as model inputs. It has recently been suggested that the M1 scissors mode may explain discrepancies between theoretical calculations and evaluated data. We explore statistical model calculations with the strength of the M1 scissors mode estimated to be dependent on the nuclear deformation of the compound system. We show that the form of the M1 scissors mode improves the theoretical description of evaluated data and the match to experiment in both the fission product and actinide regions. Since the scissors mode occurs in the range of a few keV $\sim$ a few MeV, it may also impact the neutron capture cross sections of neutron-rich nuclei that participate in the rapid neutron capture process of nucleosynthesis. We comment on the possible impact to nucleosynthesis by evaluating neutron capture rates for neutron-rich nuclei with the M1 scissors mode active.
Comments:
11 pages, 9 figures
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR)
arXiv:
1706.07504 [pdf]
PRC(2017)·54 citations
03
[Submitted on 23 Jun 2017]
Solving the $q^$ puzzle with $x$ and scale dependence
Amit Kumar🇺🇸 · Evan Bianchi🇺🇸 · Jacob Elledge🇺🇸 · Abhijit Majumder🇺🇸 · Guang-You Qin🇺🇸 · Chun Shen🇺🇸
We present here a possible resolution of the jet quenching parameter $q^$ puzzle by exploring the momentum fraction $x$ and scale $Q^{2}$ dependence of $q^$ , in addition to temperature dependence. We explore the momentum broadening of the jet due to Glauber gluon exchange with the quark-gluon plasma (QGP). This has led us to define the momentum fraction $x$ for the partons in the QGP. We also show here, for the first time, possible forms of the parton distribution function (PDF) of the QGP. The QGP-PDF as input in $q^$ has been used to fit the PHENIX and CMS data simultaneously. We observe that the scale evolution of the QGP-PDF and the energy of the jet are the missing ingredients responsible for the enhancement of $q^$ at the same temperature in RHIC collisions compared to LHC collisions.
Comments:
4 pages, 8 figures, talk at conference Quark-Matter 2017
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1706.07547 [pdf]
NPA(2017)·12 citations
04
[Submitted on 23 Jun 2017]
Quantum Monte Carlo calculations of light nuclei with local chiral two- and three-nucleon interactions
J. E. Lynn🇩🇪 · I. Tews🇺🇸 · J. Carlson🇺🇸 · S. Gandolfi🇺🇸 · A. Gezerlis🇨🇦 · K. E. Schmidt🇺🇸 · A. Schwenk🇩🇪
Local chiral effective field theory interactions have recently been developed and used in the context of quantum Monte Carlo few- and many-body methods for nuclear physics. In this work, we go over detailed features of local chiral nucleon-nucleon interactions and examine their effect on properties of the deuteron, paying special attention to the perturbativeness of the expansion. We then turn to three-nucleon interactions, focusing on operator ambiguities and their interplay with regulator effects. We then discuss the nuclear Green's function Monte Carlo method, going over both wave-function correlations and approximations for the two- and three-body propagators. Following this, we present a range of results on light nuclei: Binding energies and distribution functions are contrasted and compared, starting from several different microscopic interactions.
Comments:
21 pages, 14 figures, published version, Editor's Suggestion
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1706.07668 [pdf]
PRC(2017)·99 citations
05
[Submitted on 21 Jun 2017] (cross-list from hep-ph)
A determination of the fragmentation functions of pions, kaons, and protons with faithful uncertainties
Valerio Bertone🇳🇱 · Stefano Carrazza🇨🇭 · Nathan P. Hartland🇳🇱 · Emanuele R. Nocera🇬🇧 · Juan Rojo🇳🇱
We present NNFF1.0, a new determination of the fragmentation functions (FFs) of charged pions, charged kaons, and protons/antiprotons from an analysis of single-inclusive hadron production data in electron-positron annihilation. This determination, performed at leading, next-to-leading, and next-to-next-to-leading order in perturbative QCD, is based on the NNPDF methodology, a fitting framework designed to provide a statistically sound representation of FF uncertainties and to minimise any procedural bias. We discuss novel aspects of the methodology used in this analysis, namely an optimised parametrisation of FFs and a more efficient $χ^{2}$ minimisation strategy, and validate the FF fitting procedure by means of closure tests. We then present the NNFF1.0 sets, and discuss their fit quality, their perturbative convergence, and their stability upon variations of the kinematic cuts and the fitted dataset. We find that the systematic inclusion of higher-order QCD corrections significantly improves the description of the data, especially in the small- $z$ region. We compare the NNFF1.0 sets to other recent sets of FFs, finding in general a reasonable agreement, but also important differences. Together with existing sets of unpolarised and polarised parton distribution functions (PDFs), FFs and PDFs are now available from a common fitting framework for the first time.
Comments:
50 pages, 22 figures, 5 tables
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1706.07049 [pdf]
EPJC(2017)·214 citations
06
[Submitted on 21 Jun 2017] (cross-list from hep-ph)
Effect of collisions on neutrino flavor inhomogeneity in a dense neutrino gas
Vincenzo Cirigliano🇺🇸 · Mark W. Paris🇺🇸 · Shashank Shalgar🇺🇸
We investigate the stability, with respect to spatial inhomogeneity, of a two-dimensional dense neutrino gas. The system exhibits growth of seed inhomogeneity due to nonlinear coherent neutrino self-interactions. In the absence of incoherent collisional effects, we observe a dependence of this instability growth rate on the neutrino mass spectrum: the normal neutrino mass hierarchy exhibits spatial instability over a larger range of neutrino number density compared to that of the inverted case. We further consider the effect of elastic incoherent collisions of the neutrinos with a static background of heavy, nucleon-like scatterers. At small scales, the growth of flavor instability can be suppressed by collisions. At large length scales we find, perhaps surprisingly, that for inverted neutrino mass hierarchy incoherent collisions fail to suppress flavor instabilities, independent of the coupling strength.
Comments:
10 pages, 6 figures Version accepted in PLB. Minor changes. Title changed
Subjects:
High Energy Physics — Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Nuclear Theory (nucl-th)
arXiv:
1706.07052 [pdf]
PLB(2017)·21 citations
07
[Submitted on 21 Jun 2017] (cross-list from hep-lat)
The Tetraquark Candidate Zc(3900) from Dynamical Lattice QCD Simulations
Yoichi Ikeda (1 and 2, for HAL QCD Collaboration) · ((1) RCNP, Osaka Univ. and (2) Nishina Center, RIKEN)
The structure of the tetraquark candidate $Z_{c} (3900)$ , which was experimentally reported in $e^{+} e^{-}$ collisions, is studied by the s-wave meson-meson coupled-channel scattering on the lattice. The s-wave interactions among the $π J / ψ$ , $ρ η_{c}$ and $D D ˉ^{*}$ channels are derived from (2+1)-flavor dynamical QCD simulations at $m_{π} = 410$ -- $700$ MeV. It is found that the interactions are dominated by the off-diagonal $π J / ψ$ - $D D ˉ^{*}$ and $ρ η_{c}$ - $D D ˉ^{*}$ couplings. With the interactions obtained, the s-wave two-body amplitudes and the pole position in the $π J / ψ$ - $ρ η_{c}$ - $D D ˉ^{*}$ coupled-channel scattering are calculated. The results show that the $Z_{c} (3900)$ is not a conventional resonance but a threshold cusp. A semiphenomenological analysis with the coupled-channel interaction to the experimentally observed decay mode is also presented to confirm the conclusion.
Comments:
19 pages, 12 figures. arXiv admin note: text overlap with arXiv:1602.03465
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1706.07300 [pdf]
J.Phys.G(2018)·46 citations
08
[Submitted on 22 Jun 2017] (cross-list from hep-ph)
Regge phenomenology in $π^{0}$ and $η$ photoproduction
V. L. Kashevarov🇩🇪 · M. Ostrick🇩🇪 · L. Tiator🇩🇪
The $γ N \to π^{0} N$ and $γ N \to η N$ reactions at photon beam energies above 4 GeV are investigated within Regge models. The models include $t$ -channel exchanges of vector ( $ρ$ and $ω$ ) and axial vector ( $b_{1}$ and $h_{1}$ ) mesons. Moreover, Regge cuts of $ρ P$ , $ρ f_{2}$ , $ω P$ , and $ω f_{2}$ are investigated. A good description of differential cross sections and polarization observables at photon beam energies from 4 to 15 GeV can be achieved.
Comments:
11 pages, 10 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1706.07376 [pdf]
PRC(2017)·27 citations
09
[Submitted on 23 Jun 2017] (cross-list from hep-lat)
Three-particle quantization condition in a finite volume: 1. The role of the three-particle force
H.-W. Hammer🇩🇪 · J.-Y. Pang🇩🇪 · A. Rusetsky🇩🇪
Using non-relativistic effective Lagrangians in the particle-dimer picture, we rederive the expression for the energy shift of a loosely bound three-particle bound state of identical bosons in the unitary limit. The effective field theory formalism allows us to investigate the role of the three-particle force, which has not been taken into account in the earlier treatment of the problem. Moreover, we are able to relax the requirement of the unitary limit of infinite scattering length and demonstrate a smooth transition from the weakly bound three-particle state to a two-particle bound state of a particle and a deeply bound dimer.
Comments:
24 pages, 3 figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1706.07700 [pdf]
JHEP(2017)·186 citations
10
[Submitted on 23 Jun 2017] (cross-list from hep-ph)
Finite size effect of hadronic matter on its transport coefficients
Subhasis Samanta🇮🇳 · Sabyasachi Ghosh🇮🇳 · Bedangadas Mohanty🇮🇳
We have theoretically investigated the finite system size effect of hadronic matter on its transport coefficients like shear viscosity, bulk viscosity, and electrical conductivity. We have used a Hadron Resonance Gas (HRG) model to calculate the thermodynamical quantities like entropy density, speed of sound and also the above transport coefficients. All these quantities are found to be sensitive to finite system size effects of hadronic matter. The effect of finite system size is found to be more when the system is at low temperatures and gets reduced at high temperatures. Owing to the intimate linking between system size and centrality, we have presented the centrality dependence of transport coefficients. We have also explored to link of our results with the macroscopic picture of hydrodynamical evolution.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1706.07709 [pdf]
J.Phys.G(2018)·28 citations

Affiliations

first authorsco-authorsvia INSPIRE