Nuclear Theory·nucl-th

Tuesday·February 20, 2018

7 papers—3 primary·4 cross-listed

01
[Submitted on 16 Feb 2018]
Decay Modes of the Hoyle State in $^{12} C$
H. Zheng · A. Bonasera · M. Huang · S. Zhang
Recent experimental results give an upper limit less than 0.043\% (95\% C.L.) to the direct decay of the Hoyle state into 3 $α$ respect to the sequential decay into $^{8}$ {Be}+ $α$ . We performed one and two-dimensional tunneling calculations to estimate such a ratio and found it to be more than one order of magnitude smaller than experiment depending on the range of the nuclear force. This is within high statistics experimental capabilities. Our results can also be tested by measuring the decay modes of high excitation energy states of $^{12}$ C where the ratio of direct to sequential decay might reach 10\% at $E^{*}$ ( $^{12}$ C)=10.3 MeV. The link between a Bose Einstein Condensate (BEC) and the direct decay of the Hoyle state is also addressed. We discuss a hypothetical `Efimov state' at $E^{*}$ ( $^{12}$ C)=7.458 MeV, which would mainly {\it sequentially} decay with 3 $α$ of {\it equal energies}: a counterintuitive result of tunneling. Such a state, if it would exist, is at least 8 orders of magnitude less probable than the Hoyle's, thus below the sensitivity of recent and past experiments.
Comments:
6 pages, 2 figures, accepted by Phys. Lett. B
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1802.06078 [pdf]
PLB(2018)·25 citations
02
[Submitted on 18 Feb 2018]
Octupole deformation in neutron-rich actinides and superheavy nuclei and the role of nodal structure of single-particle wavefunctions in extremely deformed structures of light nuclei
A. V. Afanasjev · H.Abusara · S.E.Agbemava
Octupole deformed shapes in neutron-rich actinides and superheavy nuclei as well as extremely deformed shapes of the N~Z light nuclei have been investigated within the framework of covariant density functional theory. We confirmed the presence of new region of octupole deformation in neutron-rich actinides with the center around Z~96, N~196 but our calculations do not predict octupole deformation in the ground states of superheavy Z~108 nuclei. As exemplified by the study of 36Ar, the nodal structure of the wavefunction of occupied single-particle orbitals in extremely deformed structures allows to understand the formation of the alpha-clusters in very light nuclei, the suppression of the alpha-clusterization with the increase of mass number, the formation of ellipsoidal mean-field type structures and nuclear molecules.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1802.06461 [pdf]
Phys.Scripta(2018)·13 citations
03
[Submitted on 19 Feb 2018]
Exactly Solvable Pairing Models
J. P. Draayer · V. G. Gueorguiev · K. D. Sviratcheva · C. Bahri · Feng Pan · A. I. Georgieva
Some results for two distinct but complementary exactly solvable algebraic models for pairing in atomic nuclei are presented: 1) binding energy predictions for isotopic chains of nuclei based on an extended pairing model that includes multi-pair excitations; and 2) fine structure effects among excited $0^{+}$ states in $N \approx Z$ nuclei that track with the proton-neutron ( $p n$ ) and like-particle isovector pairing interactions as realized within an algebraic $s p (4)$ shell model. The results show that these models can be used to reproduce significant ranges of known experimental data, and in so doing, confirm their power to predict pairing-dominated phenomena in domains where data is unavailable.
Comments:
12 pages, 3 figures, Proceedings of the 8th International Spring Seminar on Nuclear Physics in Paestum, Italy, 23 - 27 May 2004. Published by World Scientific as Key Topics in Nuclear Structure. March 2005, pp 483-494, Edited by Aldo Covello
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1802.06508 [pdf]
0 citations
04
[Submitted on 16 Feb 2018] (cross-list from hep-ph)
Rho-meson properties in medium
J. P. B. C. de Melo🇧🇷 · K. Tsushima (Laboratório de Física Teórica e Computacional, LFTC, UCS)🇧🇷
Properties of $ρ$ -meson in symmetric nuclear matter are investigated in a light-front constituent quark model (LFCQM), using the in-medium inputs calculated by the quark-meson coupling (QMC) model. The LFCQM used in this study was already applied for the studies of the electromagnetic properties of $ρ$ -meson in vacuum, namely, the charge~ $G_{0}$ , magnetic~ $G_{1}$ , and quadrupole~ $G_{2}$ form factors, electromagnetic charge radius, and electromagnetic decay constant. We predict that the electromagnetic decay constant, charge radius, and quadrupole moment are enhanced as increasing the nuclear matter density, while the magnetic moment is slightly quenched. Furthermore, we predict that the value $Q_{zero}^{2}$ , which crosses zero of the charge form factor, $G_{0} (Q_{zero}^{2}) = 0$ ( $Q^{2} = - q^{2} > 0$ with $q$ being the four-momentum transfer), decreases as increasing the nuclear matter density.
Comments:
21 pages, 17 figures eps. New calculations and improved substantially. To appear in Phys. Lett. B (2018)
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1802.06096 [pdf]
PLB(2019)·10 citations
05
[Submitted on 16 Feb 2018] (cross-list from hep-ph)
The small-x gluon distribution in centrality biased pA and pp collisions
Adrian Dumitru🇺🇸 · Gary Kapilevich🇺🇸 · Vladimir Skokov🇺🇸
The nuclear modification factor $R_{p A} (p_{T})$ provides information on the small- $x$ gluon distribution of a nucleus at hadron colliders. Several experiments have recently measured the nuclear modification factor not only in minimum bias but also for central $p A$ collisions. In this paper we analyze the bias on the configurations of soft gluon fields introduced by a centrality selection via the number of hard particles. Such bias can be viewed as reweighting of configurations of small- $x$ gluons. We find that the biased nuclear modification factor $Q_{p A} (p_{T})$ for central collisions is above $R_{p A} (p_{T})$ for minimum bias events, and that it may redevelop a "Cronin peak" even at small $x$ . The magnitude of the peak is predicted to increase approximately like $1/ A_{⊥}^{ν}$ , $ν \sim 0.6 \pm 0.1$ , if one is able to select more compact configurations of the projectile proton where its gluons occupy a smaller transverse area $A_{⊥}$ . We predict an enhanced $Q_{pp} (p_{T}) - 1 \sim 1/ (p_{T}^{2})^{ν}$ and a Cronin peak even for central $pp$ collisions.
Comments:
14 pages, 5 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1802.06111 [pdf]
NPA(2018)·11 citations
06
[Submitted on 19 Feb 2018] (cross-list from nucl-ex)
Acoustic scaling of linear and mode-coupled anisotropic flow; implications for precision extraction of the specific shear viscosity
Peifeng Liu🇺🇸 · Roy A. Lacey (SUNY Stony Brook Chemistry Dept & SUNY Stony Brook Physics Dept.)🇺🇸
The $n^{th}$ -order linear flow coefficients $v_{n}^{L} (n = 2, 3, 4, 5)$ , and the corresponding nonlinear mode-coupled ( $mc$ ) coefficients $v_{4, (2, 2)}^{mc}$ , $v_{5, (2, 3)}^{mc}$ , $v_{6, (3, 3)}^{mc}$ and $v_{6, (2, 2, 2)}^{mc}$ , are studied for Pb+Pb collisions at $s_{_{NN}} = 2.76$ TeV. Both sets of coefficients indicate a common acoustic scaling pattern of exponential viscous modulation, with a rate proportional to the square of the harmonic numbers and the mean transverse momenta (respectively), and inversely proportional to the cube root of the charged particle multiplicity ( $(N_{ch})^{1/3}$ ), that characterizes the dimensionless size of the systems produced in the collisions. These patterns and their associated scaling parameters, provide new stringent constraints for eccentricity independent estimates of the specific shear viscosity ( $η / s$ ) and the viscous correction to the thermal distribution function for the matter produced in the collisions. They also give crucial constraints for extraction of the initial-state eccentricity spectrum.
Comments:
5 pages, 4 figs., submitted for publication; Improved description of pT-dependent scaling in this version
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1802.06595 [pdf]
PRC(2018)·31 citations
07
[Submitted on 19 Feb 2018] (cross-list from hep-ph)
New class of compact stars: Pion stars
Bastian B. Brandt🇩🇪 · Gergely Endrodi🇩🇪 · Eduardo S. Fraga🇧🇷 · Mauricio Hippert🇧🇷 · Jurgen Schaffner-Bielich🇩🇪 · Sebastian Schmalzbauer🇩🇪
We investigate the viability of a new type of compact star whose main constituent is a Bose-Einstein condensate of charged pions. Several different setups are considered, where a gas of charged leptons and neutrinos is also present. The pionic equation of state is obtained from lattice QCD simulations in the presence of an isospin chemical potential, and requires no modeling of the nuclear force. The gravitationally bound configurations of these systems are found by solving the Tolman-Oppenheimer-Volkov equations. We discuss weak decays within the pion condensed phase and elaborate on the generation mechanism of such objects.
Comments:
8 pages, 5 figures. v2 includes discussion of weak processes in the condensed phase and effects of neutrinos. v3 fixed typos, minor changes, matches journal version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1802.06685 [pdf]
PRD(2018)·104 citations

Affiliations

first authorsco-authorsvia INSPIRE

Decay Modes of the Hoyle State in 12C

Octupole deformation in neutron-rich actinides and superheavy nuclei and the role of nodal structure of single-particle wavefunctions in extremely deformed structures of light nuclei

Exactly Solvable Pairing Models

Rho-meson properties in medium

The small-x gluon distribution in centrality biased pA and pp collisions

Acoustic scaling of linear and mode-coupled anisotropic flow; implications for precision extraction of the specific shear viscosity

New class of compact stars: Pion stars

Affiliations

Decay Modes of the Hoyle State in $^{12} C$