Nuclear Theory·nucl-th

Tuesday·February 27, 2018

8 papers—5 primary·3 cross-listed

01
Backbendings of Superdeformed bands in $^{36, 40}$ Ar
Xu-Hui Xiang · Xiao-Tao He
Experimentally observed superdeformed (SD) rotational bands in $^{36}$ Ar and $^{40}$ Ar are studied by the cranked shell model (CSM) with the paring correlations treated by a particle-number-conserving (PNC) method. This is the first time the PNC-CSM calculations are performed on the light nuclear mass region around $A = 40$ . The experimental kinematic moments of inertia $J^{(1)}$ versus rotational frequency are reproduced well. The backbending of the SD band at frequency around $ℏ ω = 1.5$ MeV in $^{36}$ Ar is attributed to the sharp rise of the simultaneous alignments of the neutron and proton $1 d_{5/2} [202] 5/2$ pairs and $1 f_{7/2} [321] 3/2$ pairs, which is the consequence of the band crossing between the $1 d_{5/2} [202] 5/2$ and $1 f_{7/2} [321] 3/2$ configuration states. The gentle upbending at the low frequency of the SD band in $^{40}$ Ar is mainly effected by the alignments of the neutron $1 f_{7/2} [321] 3/2$ pairs and proton $1 d_{5/2} [202] 5/2$ pairs. The PNC-CSM calculations show that besides the diagonal parts, the off-diagonal parts of the alignments play an important role in the rotational behavior of the SD bands.
nucl-thnucl-exCPC(2018)·6 citations
02
Auxiliary field diffusion Monte Carlo calculations of light and medium-mass nuclei with local chiral interactions
D. Lonardoni · S. Gandolfi · J. E. Lynn · C. Petrie · J. Carlson · K. E. Schmidt · A. Schwenk
Quantum Monte Carlo methods have recently been employed to study properties of nuclei and infinite matter using local chiral effective field theory interactions. In this work, we present a detailed description of the auxiliary field diffusion Monte Carlo algorithm for nuclei in combination with local chiral two- and three-nucleon interactions up to next-to-next-to-leading order. We show results for the binding energy, charge radius, charge form factor, and Coulomb sum rule in nuclei with $3 \leq A \leq 16$ . Particular attention is devoted to the effect of different operator structures in the three-body force for different cutoffs. The outcomes suggest that local chiral interactions fit to few-body observables give a very good description of the ground-state properties of nuclei up to $^{16}$ O, with the exception of one fit for the softer cutoff which predicts overbinding in larger nuclei.
nucl-thPRC(2018)·116 citations
03
$η^{'}$ Production in Nucleus-Nucleus collisions as a probe of chiral dynamics
Giorgio Torrieri🇧🇷
We argue that, because of the peculiar properties of the $η^{'}$ meson, it is a promising probe of "chiral" dynamics. In particular, we show that a rotating gluon-dominated plasma might lead to an enhanced production of $η^{'}$ w.r.t. statistical model expectations. The presence of a strong topological susceptibility might give a similar effect. In both cases, unlike the statistical model,we expect a non-trivial dependence on event geometry, such as initial volume and impact parameter. Hence, an observation of $η^{'} / π^{0}$ ratio depending strongly on impact parameter might be a good indication of chiral effects, either from vorticity or topological phases of QCD
nucl-thhep-phnucl-exPRC(2018)·2 citations
04
Configurational entropy and $ρ$ and $ϕ$ mesons production in QCD
G. Karapetyan🇧🇷
In the present work the electroproduction for diffractive $ρ$ and $ϕ$ mesons by considering AdS/QCD correspondence and Color Glass Condensate (CGC) approximation are studied with respect to the associated dipole cross section, whose parameters are studied and analysed in the framework of the configurational entropy. Our results suggest different quantum states of the nuclear matter, showing that the extremal points of the nuclear configurational entropy is able to reflect a true description of the $ρ$ and $ϕ$ mesons production, using current data concerning light quark masses. During the computations parameters, obtained in fitting procedure, coincide to the experimental within 0.1 %.
nucl-thhep-phPLB(2018)·48 citations
05
R-Matrix parametrization for {\gamma} decays to unbound states
Michael Munch
R-matrix theory was originally developed to describe nuclear reactions. The framework was further extended to describe {\beta} decay to unbound states. However, at the time writing, no clear description of {\gamma} decays to unbound states exist. Such a description will be presented in this note.
nucl-th2 citations
06
Gauge Invariant Noether's Theorem in Yang-Mills Theory
Gouranga C Nayak🇺🇸
The gauge invariant definition of the spin dependent gluon distribution function from first principle is necessary to study the proton spin crisis at high energy colliders. In this paper we derive the gauge invariant Noether's theorem in Yang-Mills theory by using combined Lorentz transformation plus local non-abelian gauge transformation. We find that the definition of the gauge invariant spin (or orbital) angular momentum of the Yang-Mills field does not exist in Yang-Mills theory although the definition of the gauge invariant spin (or orbital) angular momentum of the quark exists. We show that the gauge invariant definition of the spin angular momentum of the Yang-Mills field in the literature is not correct because of the non-vanishing boundary surface term in Yang-Mills theory. We also find that the Belinfante-Rosenfeld tensor in Yang-Mills theory is not required to obtain the symmetric and gauge invariant energy-momentum tensor of the quark and the Yang-Mills field.
↳ hep-phnucl-th12 citations
07
The QCD axion beyond the classical level: A lattice study
Y. Nakamura🇯🇵 · G. Schierholz🇩🇪
The axion is a hypothetical elementary particle postulated by the Peccei-Quinn theory to resolve the strong CP problem in QCD. If axions exist and have low mass, they are a candidate for dark matter as well. So far our knowledge of the properties of the QCD axion rests on semi-classical arguments and effective theory. In this work we perform, for the first time, a fully dynamical investigation of the Peccei-Quinn theory, focussing on the axion mass, by simulating the theory on the lattice. The results of the simulation are found to be in conflict with present axion phenomenology.
↳ hep-lathep-phhep-thnucl-th3 citations
08
Different manifestations of S-matrix poles
D. F. Ramírez Jiménez🇨🇴 · N. G. Kelkar🇨🇴
Making use of the analytical properties of the $S$ -matrix and a theorem of Mittag-Leffler, model independent non-relativistic expressions for cross sections in single channel elastic scattering, scattering phase shifts and survival probabilities of resonances are derived. Provided certain conditions are satisfied by the poles, the residues can also be estimated analytically. Considerations of the low energy behaviour of the $S$ -matrix and cross sections reveal additional conditions on the residues of the poles appearing in the Mittag-Leffler expansions. The exact expressions for the resonant cross section and phase shift are shown to reduce to the commonly used Breit-Wigner formula plus corrections. The latter is shown to approach the exact result with the example of a meson and a baryon resonance. Finally, a comparison of the exact expressions with some realistic examples is presented. The calculations of survival probabilities in particular reveal the reason behind the non-observability of non-exponential decay.
↳ hep-phnucl-thquant-phAnnals Phys.(2018)·9 citations

Affiliations

first authorsco-authorsvia INSPIRE