Nuclear Theory·nucl-th

Thursday·October 19, 2017

5 papers—3 primary·2 cross-listed

01
[Submitted on 18 Oct 2017]
Quasiparticle and $γ$ -band structures in $^{156}$ Dy
S. Jehangir · G.H. Bhat · J.A. Sheikh · S. Frauendorf · S.N.T. Majola · P.A. Ganai · J.F. Sharpey-Schafer
Excited band structures recently observed in $^{156}$ Dy are investigated using the microscopic triaxial projected shell model (TPSM) approach and the quasiparticle random phase approximation (QRPA) based on the rotating mean-field. It is demonstrated that new observed excited bands, tracking the ground-state band, are the $γ$ -bands based on the excited two-quasineutron configurations as conjectured in the experimental work.
Comments:
12 pages, 12 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1710.06621 [pdf]
PRC(2018)·29 citations
02
[Submitted on 18 Oct 2017]
Charged $ρ$ -meson condensation in neutron stars
E.E. Kolomeitsev🇸🇰 · K.A. Maslov🇷🇺 · D.N. Voskresensky🇷🇺
We extend relativistic mean-field models with hadron masses and meson-baryon coupling constants dependent on the scalar field $σ$ , including hyperons and $Δ (1232)$ baryons, to incorporate a possibility of the charged $ρ$ meson condensation in neutron star matter. The influence of the $ρ^{-}$ condensation on the equation of state proves to be strongly model dependent. In our models of one type (KVORcut-based ones) the $ρ^{-}$ condensation arises by a second-order phase transition above a critical density and the maximum value of the neutron star mass diminishes only slightly. The matter composition changes more significantly. In our models of other type (MKVOR*-based ones), if the system is considered at fixed density, the $ρ^{-}$ condensation arises by a second-order phase transition at the baryon density $n = n_{c, ρ}^{(II)}$ and at a slightly higher density $n = n_{c, ρ}^{(I)}$ there occurs a first-order phase transition. In a neutron star matter starting with a density $n < n_{c, ρ}^{(II)}$ there appears a region of a mixed phase, or the system is described by Maxwell construction, that results in a substantial decrease of the value of the maximum neutron star mass. Nevertheless in the models under consideration the observational constraint on the maximum neutron star mass is fulfilled. Besides, in MKVOR*-based models the appearance of the $ρ^{-}$ condensate is accompanied by a strong rearrangement of the matter composition. Dependence of the results on a choice of the $ρ$ meson scaling functions for the effective $ρ$ meson mass and coupling constants is also investigated.
Comments:
33 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
1710.06749 [pdf]
NPA(2018)·21 citations
03
[Submitted on 18 Oct 2017]
TDHF investigations of the U+U quasifission process
A.S. Umar🇺🇸 · C. Simenel🇦🇺
The use of actinide collisions have been suggested as a way to produce neutron rich isotopes of high Z nuclei. The collision dynamics of these reactions can be studied using unrestricted time-dependent Hartree-Fock (TDHF) calculations. Here, we report on the recent studies of quasifission for the $^{238}$ U+ $^{238}$ U system.
Comments:
Presented at the XXXV Mazurian Lakes Conference on Physics, Piaski, Poland, September 3-9, 2017}
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1710.06813 [pdf]
Acta Phys.Polon.B(2018)·4 citations
04
[Submitted on 17 Oct 2017] (cross-list from hep-ph)
Nucleon form factors in dispersively improved Chiral Effective Field Theory II: Electromagnetic form factors
J. M. Alarcón🇺🇸 · C. Weiss🇺🇸
We study the nucleon electromagnetic form factors (EM FFs) using a recently developed method combining Chiral Effective Field Theory ( $χ$ EFT) and dispersion analysis. The spectral functions on the two-pion cut at $t > 4 M_{π}^{2}$ are constructed using the elastic unitarity relation and an $N / D$ representation. $χ$ EFT is used to calculate the real functions $J_{\pm}^{1} (t) = f_{\pm}^{1} (t) / F_{π} (t)$ (ratios of the complex $π π \to N N ˉ$ partial-wave amplitudes and the timelike pion FF), which are free of $π π$ rescattering. Rescattering effects are included through the empirical timelike pion FF $∣ F_{π} (t) ∣^{2}$ . The method allows us to compute the isovector EM spectral functions up to $t \sim 1$ GeV $^{2}$ with controlled accuracy (LO, NLO, and partial N2LO). With the spectral functions we calculate the isovector nucleon EM FFs and their derivatives at $t = 0$ (EM radii, moments) using subtracted dispersion relations. We predict the values of higher FF derivatives with minimal uncertainties and explain their collective behavior. We estimate the individual proton and neutron FFs by adding an empirical parametrization of the isoscalar sector. Excellent agreement with the present low- $Q^{2}$ FF data is achieved up to $\sim$ 0.5 GeV $^{2}$ for $G_{E}$ , and up to $\sim$ 0.2 GeV $^{2}$ for $G_{M}$ . Our results can be used to guide the analysis of low- $Q^{2}$ elastic scattering data and the extraction of the proton charge radius.
Comments:
14 pages, 10 figures, 6 tables
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1710.06430 [pdf]
PRC(2018)·37 citations
05
[Submitted on 17 Oct 2017] (cross-list from hep-lat)
Nucleon axial coupling from Lattice QCD
Chia Cheng Chang🇺🇸 · Amy Nicholson🇺🇸 · Enrico Rinaldi🇺🇸 · Evan Berkowitz🇩🇪 · Nicolas Garron🇬🇧 · David Brantley🇺🇸 · Henry Monge-Camacho🇺🇸 · Chris Monahan🇺🇸 · Chris Bouchard🇺🇸 · M.A. Clark🇺🇸 · Balint Joo🇺🇸 · Thorsten Kurth🇺🇸 and 3 other authors
We present state-of-the-art results from a lattice QCD calculation of the nucleon axial coupling, $g_{A}$ , using Möbius Domain-Wall fermions solved on the dynamical $N_{f} = 2 + 1 + 1$ HISQ ensembles after they are smeared using the gradient-flow algorithm. Relevant three-point correlation functions are calculated using a method inspired by the Feynman-Hellmann theorem, and demonstrate significant improvement in signal for fixed stochastic samples. The calculation is performed at five pion masses of $m_{π} \sim {400, 350, 310, 220, 130}$ ~MeV, three lattice spacings of $a \sim {0.15, 0.12, 0.09}$ ~fm, and we do a dedicated volume study with $m_{π} L \sim {3.22, 4.29, 5.36}$ . Control over all relevant sources of systematic uncertainty are demonstrated and quantified. We achieve a preliminary value of $g_{A} = 1.285 (17)$ , with a relative uncertainty of 1.33\%.
Comments:
18 pages, 8 figures, Lattice 2017 Proceedings
Subjects:
High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1710.06523 [pdf]
EPJ Web Conf.(2018)·15 citations

Affiliations

first authorsco-authorsvia INSPIRE

Quasiparticle and γ-band structures in 156Dy

Charged ρ-meson condensation in neutron stars

TDHF investigations of the U+U quasifission process

Nucleon form factors in dispersively improved Chiral Effective Field Theory II: Electromagnetic form factors

Nucleon axial coupling from Lattice QCD

Affiliations

Quasiparticle and $γ$ -band structures in $^{156}$ Dy

Charged $ρ$ -meson condensation in neutron stars