Nuclear Theory·nucl-th

Wednesday·March 8, 2017

10 papers—3 primary·7 cross-listed

01
Coherent Hypernucleus Production in Antiproton-Nucleus Annihilation Reactions as a Probe for $κ$ meson Exchange
A.B. Larionov🇩🇪 · H. Lenske🇩🇪
The hypernucleus production reaction $p ˉ +^{A} Z \to_{Λ}^{A} (Z - 1) + Λ ˉ$ in the beam momentum range 1.5-20 GeV/c is addressed theoretically as a coherent process. The calculations are based on a covariant $t$ -channel meson exchange model for the elementary $p ˉ p \to Λ ˉ Λ$ annihilation amplitude with parameters fixed by comparison with empirical data. Besides pseudo-scalar $K$ and vector $K^{*}$ mesons we also account for correlated $π K$ contributions, modelled by the scalar $K_{0}^{*} (800)$ or $κ$ meson. Initial and final state nuclear interactions are taken into account in eikonal approximation. The bound baryon wave functions are obtained self-consistently in a covariant mean-field approach. It is shown that the hypernucleus production cross sections populating discrete states are dominated by the vector and scalar interaction channels. The pronounced sensitivity on the scalar $κ$ meson exchange contributions indicates that these reactions are well suited as a probe for correlated $π K$ exchange in the scalar $κ / K_{0}^{*}$ interaction channel.
nucl-th0 citations
02
"Mass Without Mass" and Nuclear Matter
Mannque Rho🇫🇷
This is a brief account of the chief accomplishment of the 5-year activity (2008-2013) in the World Class University III Program at Hanyang University with the theme of exploring "From Dense Matter to Compact Stars." The principal objective was to explore and foresee what could be a break-through research that could be initiated at the RIB machine in project "RAON" at the upcoming ambitious Institute for Basic Science (IBS) in Korea. What came out was a possibility for unraveling the mystery of proton's "mass without mass" via nuclear matter and its impact on RAON-type physics and compact stars.
nucl-thhep-ph1 citation
03
Transverse Momentum Spectra and Nuclear Modification Factor using Boltzmann Transport Equation with Flow in Pb+Pb collisions at $s_{N N}$ = 2.76 TeV
Sushanta Tripathy🇮🇳 · Arvind Khuntia🇮🇳 · Swatantra Kumar Tiwari🇮🇳 · Raghunath Sahoo🇮🇳
In the continuation of our previous work, the transverse momentum ( $p_{T}$ ) spectra and nuclear modification factor ( $R_{AA}$ ) are derived using relaxation time approximation of Boltzmann Transport Equation (BTE). The initial $p_{T}$ -distribution used to describe $p + p$ collisions has been studied with the pQCD inspired power-law distribution, the Hagedorn's empirical formula and with the Tsallis non-extensive statistical distribution. The non-extensive Tsallis distribution is observed to describe the complete range of the transverse momentum spectra. The Boltzmann-Gibbs Blast Wave (BGBW) distribution is used as the equilibrium distribution in the present formalism, to describe the $p_{T}$ -distribution and nuclear modification factor in nucleus-nucleus collisions. The experimental data for Pb+Pb collisions at $s_{N N}$ = 2.76 TeV at the Large Hadron Collider at CERN have been analyzed for pions, kaons, protons, $K^{* 0}$ and $ϕ$ . It is observed that the present formalism while explaining the transverse momentum spectra upto 5 GeV/c, explains the nuclear modification factor very well upto 8 GeV/c in $p_{T}$ for all these particles except for protons. $R_{AA}$ is found to be independent of the degree of non-extensivity, $q_{pp}$ after $p_{T} \sim$ 8 GeV/c.
nucl-thhep-phnucl-exEPJA(2017)·22 citations
04
Possible signatures for tetraquarks from the decays of $a_{0} (980)$ , $a_{0} (1450)$
K. S. Kim🇰🇷 · Hungchong Kim🇰🇷
Based on the recent proposal for the tetraquarks with the mixing scheme, we investigate fall-apart decays of $a_{0} (980), a_{0} (1450)$ into two lowest-lying mesons. This mixing scheme suggests that $a_{0} (980)$ and $a_{0} (1450)$ are the tetraquarks with the mixtures of two spin configurations of diquark and antidiquark. Due to the relative sign differences in the mixtures, the couplings of fall-apart decays into two mesons are strongly enhanced for $a_{0} (980)$ but suppressed for $a_{0} (1450)$ . We report that this expectation is supported by their experimental decays. In particular, the ratios of the associated partial decay widths, which depend on some kinematical factors and the couplings, are found to be around $Γ [a_{0} (980) \to π η] /Γ [a_{0} (1450) \to π η] = 2.51 - 2.54$ , $Γ [a_{0} (980) \to K K ˉ] /Γ [a_{0} (1450) \to K K ˉ] = 0.52 - 0.89$ , which seems to agree with the experimental ratios reasonably well. This agreement can be interpreted as the tetraquark signatures for $a_{0} (980), a_{0} (1450)$ .
↳ hep-phnucl-thEPJC(2017)·18 citations
05
Core structure of two-dimensional Fermi gas vortices in the BEC-BCS crossover region
Lucas Madeira · Stefano Gandolfi · Kevin E. Schmidt
We report $T = 0$ diffusion Monte Carlo results for the ground-state and vortex excitation of unpolarized spin-1/2 fermions in a two-dimensional disk. We investigate how vortex core structure properties behave over the BEC-BCS crossover. We calculate the vortex excitation energy, density profiles, and vortex core properties related to the current. We find a density suppression at the vortex core on the BCS side of the crossover, and a depleted core on the BEC limit. Size-effect dependencies in the disk geometry were carefully studied.
↳ cond-mat.quant-gasnucl-thPRA(2017)·10 citations
06
Combining symmetry collective states with coupled cluster theory: Lessons from the Agassi model Hamiltonian
Matthew R. Hermes · Jorge Dukelsky · Gustavo E. Scuseria
The failures of single-reference coupled cluster for strongly correlated many-body systems is flagged at the mean-field level by the spontaneous breaking of one or more physical symmetries of the Hamiltonian. Restoring the symmetry of the mean-field determinant by projection reveals that coupled cluster fails because it factorizes high-order excitation amplitudes incorrectly. However, symmetry-projected mean-field wave functions do not account sufficiently for dynamic (or weak) correlation. Here we pursue a merger of symmetry projection and coupled cluster theory, following previous work along these lines that utilized the simple Lipkin model system as a testbed [J. Chem. Phys. 146, 054110 (2017)]. We generalize the concept of a symmetry-projected mean-field wave function to the concept of a symmetry projected state, in which the factorization of high-order excitation amplitudes in terms of low-order ones is guided by symmetry projection and is not exponential, and combine them with coupled cluster theory in order to model the ground state of the Agassi Hamiltonian. This model has two separate channels of correlation and two separate physical symmetries which are broken under strong correlation. We show how the combination of symmetry collective states and coupled cluster is effective in obtaining correlation energies and order parameters of the Agassi model throughout its phase diagram.
↳ cond-mat.str-elnucl-thPRC(2017)·7 citations
07
QCD mechanisms for accessing the nucleon GPDs with the exclusive pion-induced Drell-Yan process at J-PARC
Kazuhiro Tanaka (Juntendo Univ.)🇯🇵
Generalized parton distributions (GPDs) encoding multidimensional information of hadron partonic structure appear as the building blocks in a factorized description of hard exclusive reactions. The nucleon GPDs have been accessed by deeply virtual Compton scattering and deeply virtual meson production with lepton beam. A complementary probe with hadron beam is the exclusive pion-induced Drell-Yan process. We discuss recent theoretical advances on describing this process in terms of the partonic subprocess convoluted with the nucleon GPDs and the pion distribution amplitudes. Furthermore, we mention the feasibility study for measuring the exclusive pion-induced Drell-Yan process, $π^{-} p \to μ^{+} μ^{-} n$ , via a spectrometer at the High Momentum Beamline being constructed at J-PARC in Japan. We also point out the possible soft partonic mechanisms beyond the QCD factorization framework, which could give important contributions at J-PARC kinematics, and present an estimate of the soft mechanisms making use of dispersion relations and quark-hadron duality. Realization of the measurement of the exclusive pion-induced Drell-Yan process at J-PARC will provide a new test of QCD descriptions of a novel class of hard exclusive reactions. It will also offer the possibility of experimentally accessing nucleon GPDs at large timelike virtuality.
↳ hep-phhep-exnucl-exnucl-th3 citations
08
Correlations and fluctuations of the gauge topology at finite temperatures
Rasmus Larsen🇺🇸 · Edward Shuryak🇺🇸
Instanton-dyons are topological solitons -- solutions of Yang-Mills equations -- which appear at non-trivial expectation value of $A_{0}$ at nonzero temperatures. Using the ensembles of those, generated in our previous work, for 2-color and 2-flavor QCD, below and above the deconfinement-chiral phase transition, we study the correlations between them, as well as fluctuations of several global charges in the sub-volumes of the total volume. The determined correlation lengths are the finite- $T$ extension of hadronic masses, such as that of $η^{'}$ meson.
↳ hep-phhep-latnucl-th2 citations
09
Anomalous Transport and Generalized Axial Charge
Vladimir P. Kirilin🇺🇸 · Andrey V. Sadofyev🇺🇸
In this paper we continue studying the modification of the axial charge in chiral media by macroscopic helicities. Recently it was shown that magnetic reconnections result in a persistent current of zero mode along flux tubes. Here we argue that in general a change in the helical part of the generalized axial charge results in the same phenomenon. Thus one may say that there is a novel realization of chiral effects requiring no initial chiral asymmetry. The transfer of flow helicity to zero modes is analyzed in a toy model based on a vortex reconnection in a chiral superfluid. Then, we discuss the balance between the two competing processes effect of reconnections and the chiral instability on the example of magnetic helicity. We argue that in the general case there is a possibility for the distribution of the axial charge between the magnetic and fermionic forms at the end of the instability.
↳ hep-thhep-phnucl-thPRD(2017)·33 citations
10
Kinetic description of Bose-Einstein condensation with test particle simulations
Kai Zhou🇨🇳 · Zhe Xu🇨🇳 · Pengfei Zhuang🇨🇳 · Carsten Greiner🇩🇪
We present a kinetic description of Bose-Einstein condensation for particle systems being out of thermal equilibrium, which may happen for gluons produced in the early stage of ultra-relativistic heavy-ion collisions. The dynamics of bosons towards equilibrium is described by a Boltzmann equation including Bose factors. To solve the Boltzmann equation with the presence of a Bose-Einstein condensate we make further developments of the kinetic transport model BAMPS (Boltzmann Approach of MultiParton Scatterings). In this work we demonstrate the correct numerical implementations by comparing the final numerical results to the expected solutions at thermal equilibrium for systems with and without the presence of Bose-Einstein condensate. In addition, the onset of the condensation in an over-populated gluon system is studied in more details. We find that both expected power-law scalings denoted by the particle and energy cascade are observed in the calculated gluon distribution function at infrared and intermediate momentum regions, respectively. Also, the time evolution of the hard scale exhibits a power-law scaling in a time window, which indicates that the distribution function is approximately self-similar during that time.
↳ hep-phnucl-thPRD(2017)·14 citations

Affiliations

first authorsco-authorsvia INSPIRE