Nuclear Theory·nucl-th

Thursday·December 22, 2016

12 papers—3 primary·9 cross-listed

01
Pre-equilibrium effects in charge-asymmetric low-energy reactions
H. Zheng · S. Burrello · M. Colonna · V. Baran
We study the pre-equilibrium dipole response in the charge-asymmetric reaction $^{132}$ Sn+ $^{58}$ Ni at $E_{l ab} = 10$ MeV/A, within a semi-classical transport model employing effective interactions for the nuclear mean-field. In particular, we adopt the recently introduced SAMi-J Skyrme interactions, whose parameters are specifically tuned to improve the description of spin-isospin properties of nuclei. Within the same framework, we also discuss pre-equilibrium nucleon emission. Our results show that both mechanisms, i.e., pre-equilibrium dipole oscillations and nucleon emission, are sensitive to the symmetry energy below the saturation density $ρ_{0}$ (in the range $0.6 ρ_{0} - ρ_{0}$ ), to the effective mass and to the nucleon-nucleon cross section. Finally, a covariant analysis is applied to study the correlations between the model parameters and observables of experimental interest.
nucl-thPLB(2017)·15 citations
02
Comparison of equation of state models with different cluster dissolution mechanisms
Helena Pais🇵🇹 · Stefan Typel🇩🇪
The appearance of nuclear clusters in stellar matter at densities below nuclear saturation is an important feature in the modeling of the equation of state for astrophysical applications. There are different theoretical concepts to describe the dissolution of nuclei with increasing density and temperature. In this contribution, the predictions of two approaches are compared: the medium dependent change of the nuclear masses in a generalized relativistic density functional approach and the excluded-volume mechanism in a statistical model. Both approaches use the same description for the interaction between the nucleons. The composition of neutron star matter, in particular the occurrence of light and heavy nuclei, and its thermodynamic properties are studied.
nucl-thastro-ph.SR9 citations
03
Compact bifluid hybrid stars: Hadronic Matter mixed with self-interacting fermionic Asymmetric Dark Matter
Somnath Mukhopadhyay🇮🇳 · Debasis Atta🇮🇳 · Kouser Imam🇮🇳 · D. N. Basu🇮🇳 · C. Samanta🇺🇸
The masses and radii of non-rotating and rotating configurations of pure hadronic stars mixed with self-interacting fermionic Asymmetric Dark Matter are calculated within the two-fluid formalism of stellar structure equations in general relativity. The Equation of State (EoS) of nuclear matter is obtained from the density dependent M3Y effective nucleon-nucleon interaction. We consider dark matter particle mass of 1 GeV. The EoS of self-interacting dark matter is taken from two-body repulsive interactions of the scale of strong interactions. We explore the conditions of equal and different rotational frequencies of nuclear matter and dark matter and find that the maximum mass of differentially rotating stars with self-interacting dark matter to be $\sim 1.94 M_{⊙}$ with radius $\sim 10.4$ kms.
nucl-thEPJC(2017)·52 citations
04
Pseudomagnetic helicons
E. V. Gorbar🇺🇦 · V. A. Miransky🇨🇦 · I. A. Shovkovy🇺🇸 · P. O. Sukhachov🇨🇦
The existence of pseudomagnetic helicons is predicted for strained Dirac and Weyl materials. The corresponding collective modes are reminiscent of the usual helicons in metals in strong magnetic fields but can exist even without a magnetic field due to a strain-induced background pseudomagnetic field. The properties of both pseudomagnetic and magnetic helicons are investigated in Weyl matter using the formalism of the consistent chiral kinetic theory. It is argued that the helicon dispersion relations are affected by the electric and chiral chemical potentials, the chiral shift, and the energy separation between the Weyl nodes. The effects of multiple pairs of Weyl nodes are also discussed. A simple setup for experimental detection of pseudomagnetic helicons is proposed.
↳ cond-mat.mes-hallhep-thnucl-thPRB(2017)·23 citations
05
Determination of plasma screening effects for thermonuclear reactions in laser-generated plasmas
Yuanbin Wu · Adriana Pálffy
Due to screening effects, nuclear reactions in astrophysical plasmas may behave differently than in the laboratory. The possibility to determine the magnitude of these screening effects in colliding laser-generated plasmas is investigated theoretically, having as a starting point a proposed experimental setup with two laser beams at the Extreme Light Infrastructure facility. A laser pulse interacting with a solid target produces a plasma through the Target Normal Sheath Acceleration scheme, and this rapidly streaming plasma (ion flow) impacts on a secondary plasma created by the interaction of a second laser pulse on a gas jet target. We model this scenario here and calculate the reaction events for the astrophysically relevant reaction $^{13}$ C( $^{4}$ He, $n$ ) $^{16}$ O. We find that it should be experimentally possible to determine the plasma screening enhancement factor for fusion reactions by detecting the difference in reaction events between two scenarios of ion flow interacting with the plasma target and a simple gas target. This provides a way to evaluate nuclear reaction cross-sections in stellar environments and can significantly advance the field of nuclear astrophysics.
↳ physics.plasm-phnucl-thApJ(2017)·10 citations
06
Leading Hadron Production in $d$ +Au and $^{3}$ He+Au collisions in the PHENIX experiment
Takao Sakaguchi (for the PHENIX collaboration)🇺🇸
Neutral pions have been measured in $^{3}$ He+Au collisions at $s_{_{N N}}$ =200 GeV up to 20 GeV/ $c$ in the RHIC Year-2014 run. The nuclear modification factor $R_{AA}$ was measured and compared with that from $d$ +Au collisions. The integrated $R_{AA}$ as a function of $N_{part}$ was calculated for $d$ +Au, $^{3}$ He+Au and Au+Au collisions at $s_{_{N N}}$ =200 GeV, and found to converge for $N_{part} >$ 12, while a clear system ordering $R_{dAu}$ $>$ $R_{HeAu}$ $>$ $R_{AuAu}$ was observed for $N_{part} <$ 12. The fractional momentum loss for the most central $^{3}$ He+Au collisions was also estimated.
↳ nucl-exhep-exnucl-thNucl.Part.Phys.Proc.(2017)·1 citation
07
On the Feynman-Hellmann Theorem in Quantum Field Theory and the Calculation of Matrix Elements
Chris Bouchard🇬🇧 · Chia Cheng Chang🇺🇸 · Thorsten Kurth🇺🇸 · Kostas Orginos🇺🇸 · Andre Walker-Loud🇺🇸
The Feynman-Hellmann theorem can be derived from the long Euclidean-time limit of correlation functions determined with functional derivatives of the partition function. Using this insight, we fully develop an improved method for computing matrix elements of external currents utilizing only two-point correlation functions. Our method applies to matrix elements of any external bilinear current, including nonzero momentum transfer, flavor-changing, and two or more current insertion matrix elements. The ability to identify and control all the systematic uncertainties in the analysis of the correlation functions stems from the unique time dependence of the ground-state matrix elements and the fact that all excited states and contact terms are Euclidean-time dependent. We demonstrate the utility of our method with a calculation of the nucleon axial charge using gradient-flowed domain-wall valence quarks on the $N_{f} = 2 + 1 + 1$ MILC highly improved staggered quark ensemble with lattice spacing and pion mass of approximately 0.15 fm and 310 MeV respectively. We show full control over excited-state systematics with the new method and obtain a value of $g_{A} = 1.213 (26)$ with a quark-mass-dependent renormalization coefficient.
↳ hep-lathep-phnucl-thPRD(2017)·94 citations
08
Anomalous Chiral Transport in Heavy Ion Collisions
Jinfeng Liao🇺🇸
Chiral anomaly is a very fundamental aspect of quantum theories with chiral fermion, from the Standard Model to supersymmetric field theories or even string theories. How such microscopic anomaly manifests itself in a macroscopic many-body system with chiral fermions, is a highly nontrivial question that has recently attracted significant interest. As it turns out, unusual transport currents can be induced by chiral anomaly under suitable conditions in such systems, with the notable example of the Chiral Magnetic Effect (CME) where a vector current (e.g. electric current) is generated along an external magnetic field. The CME has been enthusiastically studied in two very different physical systems: the Dirac and Weyl semimetals in condensed matter physics as well as the quark-gluon plasma in heavy ion collisions. In this contribution, we report the latest theoretical and experimental status for the search of CME in heavy ion collisions.
↳ hep-phcond-mat.mes-hallhep-thnucl-ex+1PoS(2016)·0 citations
09
Thermal shifts, fluctuations, and missing states
Enrique Ruiz Arriola🇪🇸 · Wojciech Broniowski🇵🇱 · Eugenio Megias🇩🇪 · Lorenzo L. Salcedo🇪🇸
Thermal shifts and fluctuations at finite temperature below the deconfinement crossover from hadronic matter to the quark-gluon plasma provide a viable way to search for missing states with given quantum numbers in the hadronic spectrum. We analyze three realizations of the hadron resonance gas model in the light quark (uds) sector: the states from the Particle Data Group tables with or without width and from the Relativized Quark Model. We elaborate on the meaning of hadronic completeness and thermodynamical equivalence on the light of lattice QCD trace anomaly, heavy quark entropy shift and baryon,charge and strangeness susceptibilities.
↳ hep-phhep-latnucl-th6 citations
10
Quarkonium suppression in heavy-ion collisions: an open quantum system approach
Nora Brambilla🇩🇪 · Miguel A. Escobedo🇫🇮 · Joan Soto🇪🇸 · Antonio Vairo🇩🇪
We address the evolution of heavy-quarkonium states in an expanding quark-gluon plasma by implementing effective field theory techniques in the framework of open quantum systems. In this setting we compute the nuclear modification factors for quarkonia that are $S$ -wave Coulombic bound states in a strongly-coupled quark-gluon plasma. The calculation is performed at an accuracy that is leading-order in the heavy-quark density expansion and next-to-leading order in the multipole expansion. The quarkonium density-matrix evolution equations can be written in the Lindblad form, and, hence, they account for both dissociation and recombination. Thermal mass shifts, thermal widths and the Lindblad equation itself depend on only two non-perturbative parameters: the heavy-quark momentum diffusion coefficient and its dispersive counterpart. Finally, by numerically solving the Lindblad equation, we provide results for the $Υ (1 S)$ and $Υ (2 S)$ suppression.
↳ hep-phhep-exnucl-thPRD(2017)·212 citations
11
The Skyrme model and chiral perturbation theory
Derek Harland🇬🇧
A lagrangian which describes interactions between a soliton and a background field is derived for sigma models whose target is a symmetric space. The background field modifies the usual moduli space approximation to soliton dynamics in two ways: by introducing a potential energy, and by inducing a Kaluza-Klein metric on the moduli space. In the particular case of the Skyrme model, this lagrangian is quantised and shown to agree with the leading pion-nucleon term in the chiral effective lagrangian, which is widely used in theoretical nuclear physics. Thus chiral perturbation theory could be considered a low energy limit of the Skyrme model.
↳ hep-thnucl-th2 citations
12
Internal conversion from excited electronic states of $^{229} T h$ ions
Pavlo V. Bilous · Georgy A. Kazakov · Iain D. Moore · Thorsten Schumm · Adriana Pálffy
The process of internal conversion from excited electronic states is investigated theoretically for the case of the vacuum-ultraviolet nuclear transition of $^{229} T h$ . Due to the very low transition energy, the $^{229} T h$ nucleus offers the unique possibility to open the otherwise forbidden internal conversion nuclear decay channel for thorium ions via optical laser excitation of the electronic shell. We show that this feature can be exploited to investigate the isomeric state properties via observation of internal conversion from excited electronic configurations of $T h^{+}$ and $T h^{2 +}$ ions. A possible experimental realization of the proposed scenario at the nuclear laser spectroscopy facility IGISOL in Jyväskylä, Finland is discussed.
↳ physics.atom-phnucl-thPRA(2017)·18 citations

Affiliations

first authorsco-authorsvia INSPIRE