Nuclear Theory·nucl-th

Monday·March 13, 2017

10 papers—6 primary·4 cross-listed

01
Applicability of the Wong formula for fusion cross sections from light to heavy systems
N. W. Lwin · N. N. Htike · K. Hagino
We discuss the applicability of the Wong formula for fusion cross sections in a single-channel problem. To this end, we carry out a systematic study and compare the approximate fusion cross sections with the exact results in a wide mass region of reaction systems. We show that the deviation of the approximate results from the exact cross sections is large for light systems, even though the Wong formula provides a reasonable approximation for heavy systems. We also discuss the energy dependence of the deviation, and show that for a given projectile nucleus the critical energy, at which the deviation exceeds 5\% of the exact cross sections, increases as a function of the mass number of the target nucleus.
nucl-thnucl-exPRC(2017)·6 citations
02
Limiting symmetry energy elements from empirical evidence
B. K. Agrawal · S. K. Samaddar · J. N. De · C. Mondal · Subhranil De
In the framework of an equation of state (EoS) constructed from a momentum and density-dependent finite-range two-body effective interaction, the quantitative magnitudes of the different symmetry elements of infinite nuclear matter are explored. The parameters of this interaction are determined from well-accepted characteristic constants associated with homogeneous nuclear matter. The symmetry energy coefficient $a_{2}$ , its density slope $L_{0}$ , the symmetry incompressibility $K_{δ}$ as well as the density dependent incompressibility $K (ρ)$ evaluated with this EoS are seen to be in good harmony with those obtained from other diverse perspectives. The higher order symmetry energy coefficients $a_{4}, a_{6}$ etc are seen to be not very significant in the domain of densities relevant to finite nuclei, but gradually build up at supra-normal densities. The analysis carried with a Skyrme-inspired energy density functional obtained with the same input values for the empirical bulk data associated with nuclear matter yields nearly the same results.
nucl-thIJMPE(2017)·11 citations
03
In-medium viscous coefficients of a hot hadronic gas mixture
Utsab Gangopadhyaya🇮🇳 · Snigdha Ghosh🇮🇳 · Sukanya Mitra🇮🇳 · Sourav Sarkar🇮🇳
We estimate the shear and the bulk viscous coefficients for a hot hadronic gas mixture constituting of pions and nucleons. The viscosities are evaluated in the relativistic kinetic theory approach by solving the transport equation in the relaxation time approximation for binary collisions ( $π π$ , $π N$ and $N N$ ). Instead of vacuum cross-sections usually used in the literature we employ in-medium scattering amplitudes in the estimation of the relaxation times. The modified cross-sections for $π π$ and $π N$ scattering are obtained using one-loop modified thermal propagators for $ρ$ , $σ$ and $Δ$ in the scattering amplitudes which are calculated using effective interactions. The resulting suppression of the cross sections at finite temperature and baryon density is observed to significantly affect the $T$ and $μ_{N}$ dependence of the viscosities of the system.
nucl-thhep-phPRC(2016)·15 citations
04
Study of the nucleon radiative captures 8Li(n,gamma)9Li, 9Be(p,gamma)10B, 10Be(n,gamma)11Be, 10B(p,gamma)11C, and 16O(p,gamma)17F at thermal and astrophysical energies
Sergey Dubovichenko · Albert Dzhazairov-Kakhramanov
We have studied the neutron-capture reactions 8Li(n,gamma)9Li and its role in the primordial nucleosynthesis. The n + 8Li --> 9Li + gamma reaction has a significant astrophysical interest because it includes one of the variants of chain of primordial nucleosynthesis processes of the Universe and thermonuclear reactions in type II supernova.
nucl-thIJMPE(2017)·16 citations
05
Global $Λ$ Polarization in high energy collisions
Yilong Xie🇳🇴 · Dujuan Wang🇨🇳 · László P. Csernai🇳🇴
With a Yang-Mills flux-tube initial state and a high resolution (3+1)D Particle-in-Cell Relativistic (PICR) hydrodynamics simulation, we calculate the $Λ$ polarization for different energies. The origination of polarization in high energy collisions is discussed, and we find linear impact parameter dependence of the global $Λ$ polarization. Furthermore, the global $Λ$ polarization in our model decreases very fast in the low energy domain, and the decline curve fits well the recent results of Beam Energy Scan (BES) program launched by the STAR collaboration at the Relativistic Heavy Ion Collider (RHIC). The time evolution of polarization is also discussed.
nucl-thPRC(2017)·186 citations
06
How Well Do We Know The Supernova Equation of State?
Matthias Hempel🇨🇭 · Micaela Oertel🇫🇷 · Stefan Typel🇩🇪 · Thomas Klähn🇵🇱
We give an overview about equations of state (EOS) which are currently available for simulations of core-collapse supernovae and neutron star mergers. A few selected important aspects of the EOS, such as the symmetry energy, the maximum mass of neutron stars, and cluster formation, are confronted with constraints from experiments and astrophysical observations. There are just very few models which are compatible even with this very restricted set of constraints. These remaining models illustrate the uncertainty of the uniform nuclear matter EOS at high densities. In addition, at finite temperatures the medium modifications of nuclear clusters represent a conceptual challenge. In conclusion, there has been significant development in the recent years, but there is still need for further improved general purpose EOS tables.
nucl-thastro-ph.HEastro-ph.SRJPS Conf.Proc.(2017)·4 citations
07
A Subleading Operator Basis and Matching for $g g \to H$
Ian Moult🇺🇸 · Iain W. Stewart🇺🇸 · Gherardo Vita🇺🇸
The Soft Collinear Effective Theory (SCET) is a powerful framework for studying factorization of amplitudes and cross sections in QCD. While factorization at leading power has been well studied, much less is known at subleading powers in the $λ ≪ 1$ expansion. In SCET subleading soft and collinear corrections to a hard scattering process are described by power suppressed operators, which must be fixed case by case, and by well established power suppressed Lagrangians, which correct the leading power dynamics of soft and collinear radiation. Here we present a complete basis of power suppressed operators for $g g \to H$ , classifying all operators which contribute to the cross section at $O (λ^{2})$ , and showing how helicity selection rules significantly simplify the construction of the operator basis. We perform matching calculations to determine the tree level Wilson coefficients of our operators. These results are useful for studies of power corrections in both resummed and fixed order perturbation theory, and for understanding the factorization properties of gauge theory amplitudes and cross sections at subleading power. As one example, our basis of operators can be used to analytically compute power corrections for $N$ -jettiness subtractions for $g g$ induced color singlet production at the LHC.
↳ hep-phnucl-thJHEP(2017)·77 citations
08
A Complete Basis of Helicity Operators for Subleading Factorization
Ilya Feige🇺🇸 · Daniel W. Kolodrubetz🇺🇸 · Ian Moult🇺🇸 · Iain W. Stewart🇺🇸
Factorization theorems underly our ability to make predictions for many processes involving the strong interaction. Although typically formulated at leading power, the study of factorization at subleading power is of interest both for improving the precision of calculations, as well as for understanding the all orders structure of QCD. We use the SCET helicity operator formalism to construct a complete power suppressed basis of hard scattering operators for $e^{+} e^{-} \to$ dijets, $e^{-} p \to e^{-}$ jet, and constrained Drell-Yan, including the first two subleading orders in the amplitude level power expansion. We analyze the form of the hard, jet, and soft function contributions to the power suppressed cross section for $e^{+} e^{-} \to$ dijet event shapes, and give results for the lowest order matching to the contributing operators. These results will be useful for studies of power corrections both in fixed order and resummed perturbation theory.
↳ hep-phnucl-thJHEP(2017)·91 citations
09
Pseudomagnetic lens as a valley and chirality splitter in Dirac and Weyl materials
E. V. Gorbar🇺🇦 · V. A. Miransky🇨🇦 · I. A. Shovkovy🇺🇸 · P. O. Sukhachov🇨🇦
It is proposed that strain-induced pseudomagnetic fields in Dirac and Weyl materials could be used as valley and chirality sensitive lenses for beams of Weyl quasiparticles. The study of the (pseudo-)magnetic lenses is performed by using the eikonal approximation for describing the Weyl quasiparticles propagation in magnetic and strain-induced pseudomagnetic fields. Analytical expressions for the locations of the principal foci and the focal lengths are obtained in the paraxial approximation in the models with uniform as well as nonuniform effective magnetic fields inside the lens. The results show that the left- and right-handed quasiparticles can be focused at different spatial locations when both magnetic and pseudomagnetic fields are applied. It is suggested that the use of magnetic and pseudomagnetic lenses could open new ways of producing and manipulating beams of chiral Weyl quasiparticles.
↳ cond-mat.mes-hallhep-phnucl-thPRB(2017)·17 citations
10
Heavy-ion Physics at a Fixed-Target Experiment Using the LHC Proton and Lead Beams (AFTER@LHC): Feasibility Studies for Quarkonium and Drell-Yan Production
B. Trzeciak🇳🇱 · C. Da Silva🇺🇸 · E.G. Ferreiro🇪🇸 · C. Hadjidakis🇫🇷 · D. Kikola🇵🇱 · J.P. Lansberg🇫🇷 · L. Massacrier🇫🇷 · J. Seixas🇵🇹 · A. Uras🇫🇷 · Z. Yang🇨🇳
We outline the case for heavy-ion-physics studies using the multi-TeV lead LHC beams in the fixed-target mode. After a brief contextual reminder, we detail the possible contributions of AFTER@LHC to heavy-ion physics with a specific emphasis on quarkonia. We then present performance simulations for a selection of observables. These show that $Υ (n S)$ , $J / ψ$ and $ψ (2 S)$ production in heavy-ion collisions can be studied in new energy and rapidity domains with the LHCb and ALICE detectors. We also discuss the relevance to analyse the Drell-Yan pair production in asymmetric nucleus-nucleus collisions to study the factorisation of the nuclear modification of partonic densities and of further quarkonia to restore their status of golden probes of the quark-gluon plasma formation.
↳ nucl-exhep-exhep-phnucl-thFew Body Syst.(2017)·19 citations

Affiliations

first authorsco-authorsvia INSPIRE