Nuclear Theory·nucl-th

Monday·September 12, 2016

14 papers—7 primary·7 cross-listed

08
[Submitted on 3 Sept 2016] (cross-list from hep-th)
Advances in solving the two-fermion homogeneous Bethe-Salpeter equation in Minkowski space
W. de Paula🇧🇷 · T. Frederico🇧🇷 · G. Salmè🇮🇹 · M. Viviani🇮🇹
Actual solutions of the Bethe-Salpeter equation for a two-fermion bound system are becoming available directly in Minkowski space, by virtue of a novel technique, based on the so-called Nakanishi integral representation of the Bethe-Salpeter amplitude and improved by expressing the relevant momenta through light-front components, i.e. $k^{\pm} = k^{0} \pm k^{3}$ . We solve a crucial problem that widens the applicability of the method to real situations by providing an analytically exact treatment of the singularities plaguing the two-fermion problem in Minkowski space, irrespective of the complexity of the irreducible Bethe-Salpeter kernel. This paves the way for feasible numerical investigations of relativistic composite systems, with any spin degrees of freedom. We present a thorough comparison with existing numerical results, evaluated in both Minkowski and Euclidean space, fully corroborating our analytical treatment, as well as fresh light-front amplitudes illustrating the potentiality of non perturbative calculations performed directly in Minkowski space.
Comments:
5 pages, 2 figures
Subjects:
High Energy Physics — Theory (hep-th); Strongly Correlated Electrons (cond-mat.str-el); Nuclear Theory (nucl-th)
arXiv:
1609.00868 [pdf]
PRD(2016)·50 citations
09
[Submitted on 8 Sept 2016] (cross-list from hep-ph)
Baryons and Chiral Symmetry
Keh-Fei Liu🇺🇸
The relevance of chiral symmetry in baryons is highlighted in three examples in the nucleon spectroscopy and structure. The first one is the importance of chiral dynamics in understanding the Roper resonance. The second one is the role of chiral symmetry in the lattice calculation of $π N σ$ term and strangeness. The third one is the role of chiral $U (1)$ anomaly in the anomalous Ward identity in evaluating the quark spin and the quark orbital angular momentum. Finally, the chiral effective theory for baryons is discussed.
Comments:
To appear in G.E. Brown Memorial Volume
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1609.02572 [pdf]
IJMPE(2017)·17 citations
10
[Submitted on 8 Sept 2016] (cross-list from hep-ph)
The thermalization of soft modes in non-expanding isotropic quark gluon plasmas
Jean-Paul Blaizot🇫🇷 · Jinfeng Liao🇺🇸 · Yacine Mehtar-Tani🇺🇸
We discuss the role of elastic and inelastic collisions and their interplay in the thermalization of the quark-gluon plasma. We consider a simplified situation of a static plasma, spatially uniform and isotropic in momentum space. We focus on the small momentum region, which equilibrates first, and on a short time scale. We obtain a simple kinetic equation that allows for an analytic description of the most important regimes. The present analysis suggests that the formation of a Bose condensate, expected when only elastic collisions are present, is strongly hindered by the inelastic, radiative, processes.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1609.02580 [pdf]
NPA(2017)·32 citations
11
[Submitted on 8 Sept 2016] (cross-list from hep-ph)
Magnetic catalysis of a finite size pion condensate
Alejandro Ayala🇲🇽 · Pedro Mercado🇲🇽 · C. Villavicencio🇨🇱
We study the Bose-Einstein condensation of a finite size pion gas subject to the influence of a magnetic field. We find the expressions for the critical chemical potential and temperature for the onset of condensation. We show that for values of the external magnetic flux larger than the elemental flux, the critical temperature is larger than the one obtained by considering only finite size effects. We use experimentally reported values of pion source sizes and multiplicities at LHC energies to show that if the magnetic flux, produced initially in peripheral heavy-ion collision, is at least partially preserved up to the hadronic phase, the combined finite size and magnetic field effects give rise to a critical temperature above the kinetic freeze-out temperature. We discuss the implications for the evolution of the pion system created in relativistic heavy-ion collisions.
Comments:
8 pages, 3 figures, minor typos corrected, expanded discussion and one new reference added. Version to appear in Phys. Rev. C
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1609.02595 [pdf]
PRC(2017)·19 citations
12
[Submitted on 8 Sept 2016] (cross-list from nucl-th)
Testing of coalescence mechanism in high energy heavy ion collisions using two-particle correlations with identified particle trigger
Subikash Choudhury🇮🇳 · Debojit Sarkar🇮🇳 · Subhasis Chattopadhyay🇮🇳
In central Au-Au collisions at top RHIC energy, two particle correlation measurements with identified hadron trigger have shown attenuation of near side proton triggered jet-like yield at intermediate transverse momentum ( $p_{T}$ ), 2 $< p_{T} <$ 6 GeV/ $c$ . The attenuation has been attributed to the anomalous baryon enhancement observed in the single inclusive measurements at the same $p_{T}$ range. The enhancement has been found to be in agreement with the models invoking coalescence of quarks as a mechanism of hadronization. Baryon enhancement has also been observed at LHC in the single inclusive spectra. We study the consequence of such an enhancement on two particle correlations at LHC energy within the framework of A Multi Phase Transport (AMPT) model that implements quark coalescence as a mode of hadronization. In this paper we have calculated the proton over pion ratio and the near side per trigger yield associated to pion and proton triggers at intermediate $p_{T}$ from String Melting (SM) version of AMPT. Results obtained are contrasted with the AMPT Default (Def.) which does not include coalescence. Baryon enhancement has been observed in AMPT SM at intermediate $p_{T}$ . Near side jet-like correlated yield associated to baryon (proton) trigger in the momentum region where baryon generation is enhanced is found to be suppressed as compared to the corresponding yields for the meson (pion) trigger in most central Pb-Pb events. No such effect has been found in the Default version of AMPT.
Comments:
6 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1609.02608 [pdf]
PRC(2016)·3 citations
13
[Submitted on 9 Sept 2016] (cross-list from hep-ph)
$K^{*}$ vector meson resonances dynamics in heavy-ion collisions
Andrej Ilner🇩🇪 · Daniel Cabrera🇪🇸 · Christina Markert🇺🇸 · Elena Bratkovskaya🇩🇪
We study the strange vector meson ( $K^{*}, K ˉ^{*}$ ) dynamics in relativistic heavy-ion collisions based on the microscopic Parton-Hadron-String Dynamics (PHSD) transport approach which incorporates partonic and hadronic degrees-of-freedom, a phase transition from hadronic to partonic matter - Quark-Gluon-Plasma (QGP) - and a dynamical hadronization of quarks and antiquarks as well as final hadronic interactions. We investigate the role of in-medium effects on the $K^{*}, K ˉ^{*}$ meson dynamics by employing Breit-Wigner spectral functions for the $K^{*}$ 's with self-energies obtained from a self-consistent coupled-channel G-matrix approach. Furthermore, we confront the PHSD calculations with experimental data for p+p, Cu+Cu and Au+Au collisions at energies up to $s_{N N} = 200$ ~GeV. Our analysis shows that at relativistic energies most of the final $K^{*}$ s (observed experimentally) are produced during the late hadronic phase, dominantly by the $K + π \to K^{*}$ channel, such that the fraction of the $K^{*}$ s from the QGP is small and can hardly be reconstructed from the final observables. The influence of the in-medium effects on the $K^{*}$ dynamics at RHIC energies is rather modest due to their dominant production at low baryon densities (but high meson densities), however, it increases with decreasing beam energy. Moreover, we find that the additional cut on the invariant mass region of the $K^{*}$ further influences the shape and the height of the final spectra. This imposes severe constraints on the interpretation of the experimental results.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1609.02778 [pdf]
PRC(2017)·33 citations
14
[Submitted on 9 Sept 2016] (cross-list from hep-th)
Complex Geometry of Nuclei and Atoms
M.F. Atiyah🇬🇧 · N.S. Manton🇬🇧
We propose a new geometrical model of matter, in which neutral atoms are modelled by compact, complex algebraic surfaces. Proton and neutron numbers are determined by a surface's Chern numbers. Equivalently, they are determined by combinations of the Hodge numbers, or the Betti numbers. Geometrical constraints on algebraic surfaces allow just a finite range of neutron numbers for a given proton number. This range encompasses the known isotopes.
Comments:
18 pages, 4 figures
Subjects:
High Energy Physics — Theory (hep-th); math.AG (math.AG); Nuclear Theory (nucl-th)
arXiv:
1609.02816 [pdf]
Int.J.Mod.Phys.A(2018)·11 citations

Affiliations

first authorsco-authorsvia INSPIRE

Advances in solving the two-fermion homogeneous Bethe-Salpeter equation in Minkowski space

Baryons and Chiral Symmetry

The thermalization of soft modes in non-expanding isotropic quark gluon plasmas

Magnetic catalysis of a finite size pion condensate

Testing of coalescence mechanism in high energy heavy ion collisions using two-particle correlations with identified particle trigger

K∗ vector meson resonances dynamics in heavy-ion collisions

Complex Geometry of Nuclei and Atoms

Affiliations

$K^{*}$ vector meson resonances dynamics in heavy-ion collisions