Nuclear Theory·nucl-th

Monday·September 12, 2016

14 papers—7 primary·7 cross-listed

01
[Submitted on 8 Sept 2016]
Natural constraints on the gluon-quark vertex
Daniele Binosi🇮🇹 · Lei Chang🇨🇳 · Joannis Papavassiliou🇪🇸 · Si-Xue Qin🇺🇸 · Craig D. Roberts🇺🇸
In principle, the strong-interaction sector of the Standard Model is characterised by a unique renormalisation-group-invariant (RGI) running interaction and a unique form for the dressed--gluon-quark vertex, $Γ_{μ}$ ; but, whilst much has been learnt about the former, the latter is still obscure. In order to improve this situation, we use a RGI running-interaction that reconciles both top-down and bottom-up analyses of the gauge sector in quantum chromodynamics (QCD) to compute dressed-quark gap equation solutions with 1,660,000 distinct Ansaetze for $Γ_{μ}$ . Each one of the solutions is then tested for compatibility with three physical criteria and, remarkably, we find that merely 0.55% of the solutions survive the test. Plainly, therefore, even a small selection of observables places extremely tight bounds on the domain of realistic vertex Ansaetze. This analysis and its results should prove useful in constraining insightful contemporary studies of QCD and hadronic phenomena.
Comments:
6 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1609.02568 [pdf]
PRD(2017)·120 citations
02
[Submitted on 8 Sept 2016]
Collectivity and electromagnetic radiation in small systems
Chun Shen🇨🇦 · Jean-François Paquet🇺🇸 · Gabriel S. Denicol🇧🇷 · Sangyong Jeon🇨🇦 · Charles Gale🇨🇦
Collective behaviour has been observed in hadronic measurements of high multiplicity proton+lead collisions at the Large Hadron Collider (LHC), as well as in (proton, deuteron, helium-3)+gold collisions at the Relativistic Heavy-Ion Collider (RHIC). To better understand the evolution dynamics and the properties of the matter created in these small systems, a systematic study of the soft hadronic observables together with electromagnetic radiation from these collisions is performed, using a hydrodynamic framework. Quantitative agreement is found between theoretical calculations and existing experimental hadronic observables. The validity of the fluid dynamical description is estimated by calculating Knudsen and inverse Reynolds numbers. Sizeable thermal yields are predicted for low $p_{T}$ photons. Further predictions of higher order charged hadron anisotropic flow coefficients and of thermal photon enhancement are proposed.
Comments:
21 pages, 23 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1609.02590 [pdf]
PRC(2017)·155 citations
03
[Submitted on 9 Sept 2016]
Investigating the correlations of flow harmonics in 2.76A TeV Pb--Pb collisions
Xiangrong Zhu🇨🇳 · You Zhou🇩🇰 · Haojie Xu🇨🇳 · Huichao Song🇨🇳
This proceeding briefly summarizes our recent investigations on the correlations of flow harmonics in 2.76A TeV Pb--Pb collisions with viscous hydrodynamics {\tt VISH2+1}. We calculated both the symmetric cumulants $S C^{v} (m, n)$ and the normalized symmetric cumulants $N S C^{v} (m, n)$ , and found $v_{2}$ and $v_{4}$ , $v_{2}$ and $v_{5}$ , $v_{3}$ and $v_{5}$ are correlated, $v_{2}$ and $v_{3}$ , $v_{3}$ and $v_{4}$ are anti-correlated. We also found $N S C^{v} (3, 2)$ are insensitive to the QGP viscosity, which are mainly determined by the initial conditions.
Comments:
SQM2016 proceeding, 4pages, 2 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1609.02628 [pdf]
J.Phys.Conf.Ser.(2017)·0 citations
04
[Submitted on 9 Sept 2016]
Brueckner-Hartree-Fock and its renormalized calculations for finite nuclei
B. S. Hu · F. R. Xu · Y. Z. Ma · Q. Wu · Z. H. Sun
We have performed self-consistent Brueckner-Hartree-Fock (BHF) and its renormalized theory to the structure calculations of finite nuclei. The $G$ -matrix is calculated within the BHF basis, and the exact Pauli exclusion operator is determined by the BHF spectrum. Self-consistent occupation probabilities are included in the renormalized Brueckner-Hartree-Fock (RBHF). Various systematics and convergences are studies. Good results are obtained for the ground-state energy and radius. RBHF can give a more reasonable single-particle spectrum and radius. We present a first benchmark calculation with other {\it ab initio} methods using the same effective Hamiltonian. We find that the BHF and RBHF results are in good agreement with other $ab$ $initio$ methods.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1609.02675 [pdf]
PRC(2017)·9 citations
05
[Submitted on 9 Sept 2016]
Hyperon star in a modified quark meson coupling model
R.N. Mishra🇮🇳 · H.S. Sahoo🇮🇳 · P.K. Panda🇮🇳 · N. Barik🇮🇳 · T. Frederico🇧🇷
We determine the equation of state (EOS) of nuclear matter with the inclusion of hyperons in a self-consistent manner by using a Modified Quark Meson Coupling Model (MQMC) where the confining interaction for quarks inside a baryon is represented by a phenomenological average potential in an equally mixed scalar-vector harmonic form. The hadron-hadron interaction in nuclear matter is then realized by introducing additional quark couplings to $σ$ , $ω$ , and $ρ$ mesons through mean-field approximations. The effect of a nonlinear $ω$ - $ρ$ term on the equation of state is studied. The hyperon couplings are fixed from the optical potential values and the mass-radius curve is determined satisfying the maximum mass constraint of $2$ ~M $_{⊙}$ for neutron stars, as determined in recent measurements of the pulsar PSR J0348+0432. We also observe that there is no significant advantage of introducing the nonlinear $ω$ - $ρ$ term in the context of obtaining the star mass constraint in the present set of parametrizations.
Comments:
10 pages, Accepted in Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1609.02708 [pdf]
PRC(2016)·27 citations
06
[Submitted on 9 Sept 2016]
Isomerism in the "south-east" of $^{132}$ Sn and a predicted neutron-decaying isomer in $^{129}$ Pd
Cenxi Yuan · Zhong Liu · Furong Xu · P. M. Walker · Zs. Podolyak · C. Xu · Z.Z. Ren · B. Ding · M.L. Liu · X.Y. Liu · H.S. Xu · X.H. Zhou · Y.H. Zhang · W. Zuo
Excited states in neutron-rich nuclei located south-east of $^{132}$ Sn are investigated by shell-model calculations. A new shell-model Hamiltonian is constructed for the present study. The proton-proton and neutron-neutron interactions of the Hamiltonian are obtained through the existing CD-Bonn $G$ matrix results, while the proton-neutron interaction across two major shells is derived from the monopole based universal interaction plus the M3Y spin-orbit force. The present Hamiltonian can reproduce well the experimental data available in this region, including one-neutron separation energies, level energies and the experimental $B (E 2)$ values of isomers in $^{134, 136, 138}$ Sn, $^{130}$ Cd, and $^{128}$ Pd. New isomers are predicted in this region, $e . g .$ in $^{135}$ Sn, $^{131}$ Cd, $^{129}$ Pd, $^{132, 134}$ In and $^{130}$ Ag, in which almost no excited states are known experimentally yet. In the odd-odd $^{132, 134}$ In and $^{130}$ Ag, the predicted very long $E 2$ life-times of the low-lying $5^{-}$ states are discussed, demanding more information on the related proton-neutron interaction. The low-lying states of $^{132}$ In are discussed in connection with the recently observed $γ$ rays. The predicted $19/ 2^{-}$ isomer in $^{129}$ Pd could decay by both electromagnetic transitions and neutron emission with comparable partial life-times, making it a good candidate for neutron radioactivity, a decay mode which is yet to be discovered.
Comments:
Accepted for publication in Physics Letters B
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1609.02766 [pdf]
PLB(2016)·39 citations
07
[Submitted on 9 Sept 2016]
Do nuclear collisions create a locally equilibrated quark-gluon plasma?
Paul Romatschke🇺🇸
Experimental results on azimuthal correlations in high energy nuclear collisions (nucleus-nucleus, proton-nucleus and proton-proton) seem to be well described by viscous hydrodynamics. It is often argued that this agreement implies either local thermal equilibrium or at least local isotropy. In this note, I present arguments why this is not the case. Neither local near-equilibrium nor near-isotropy are required in order for hydrodynamics to offer a successful and accurate description of experimental results. However, I predict the breakdown of hydrodynamics at momenta of order seven times the temperature, corresponding to a smallest possible QCD liquid drop size of 0.15 fm.
Comments:
14 pages, 6 figures; v2: references added, major changes in section VI, qualitative conclusions unchanged; v3: minor typos fixed, matches published version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1609.02820 [pdf]
EPJC(2017)·138 citations
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

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