Nuclear Theory·nucl-th

Friday·April 21, 2017

12 papers—6 primary·6 cross-listed

01
Evidence for chiral symmetry restoration in heavy-ion collisions
Pierre Moreau🇩🇪 · Alessia Palmese🇩🇪 · Wolfgang Cassing🇩🇪 · Eduard Seifert🇩🇪 · Thorsten Steinert🇩🇪 · Elena Bratkovskaya🇩🇪
We study the effect of the chiral symmetry restoration (CSR) on heavy-ion collisions observables in the energy range $s_{N N}$ = 3-20 GeV within the Parton-Hadron-String Dynamics (PHSD) transport approach. The PHSD includes the deconfinement phase transition as well as essential aspects of CSR in the dense and hot hadronic medium, which are incorporated in the Schwinger mechanism for particle production. Our systematic studies show that chiral symmetry restoration plays a crucial role in the description of heavy-ion collisions at $s_{N N}$ = 3-20 GeV, realizing an increase of the hadronic particle production in the strangeness sector with respect to the non-strange one. Our results provide a microscopic explanation for the "horn" structure in the excitation function of the $K^{+} / π^{+}$ ratio: the CSR in the hadronic phase produces the steep increase of this particle ratio up to $s_{N N} \approx$ 7 GeV, while the drop at higher energies is associated to the appearance of a deconfined partonic medium. Furthermore, the appearance/disappearance of the "horn" structure is investigated as a function of the system size. We additionally present an analysis of strangeness production in the ( $T, μ_{B}$ )-plane (as extracted from the PHSD for central Au+Au collisions) and discuss the perspectives to identify a possible critical point in the phase diagram.
nucl-thNPA(2017)·6 citations
02
Existence problem of proton semi-bubble structure in the $2_{1}^{+}$ state of $^{34}$ Si
Feng Wu · C.L. Bai · J.M. Yao · H.Q. Zhang · X.Z. Zhang
The fully self-consistent Hartree-Fock (HF) plus random phase approximation (RPA) based on Skyrme-type interaction is used to study the existence problem of proton semi-bubble structure in the $2_{1}^{+}$ state of $^{34}$ Si. The experimental excitation energy and the B(E2) strength of the $2_{1}^{+}$ state in $^{34}$ Si can be reproduced quite well. The tensor effect is also studied. It is shown that the tensor interaction has a notable impact on the excitation energy of the $2_{1}^{+}$ state and a small effect on the B(E2) value. Besides, its effect on the density distributions in the ground and $2_{1}^{+}$ state of $^{34}$ Si is negligible. Our present results with T36 and T44 show that the $2_{1}^{+}$ state of $^{34}$ Si is mainly caused by proton transiton from $π 1 d_{5/2}$ orbit to $π 2 s_{1/2}$ orbit, and the existence of a proton semi-bubble structure in this state is very unlikely.
nucl-thEPJA(2017)·1 citation
03
Nuclear final-state interactions in deep inelastic scattering off the lightest nuclei
W. Cosyn🇧🇪 · M. Sargsian🇺🇸
We review recent progress in studies of nuclear final-state interactions in deep inelastic scattering (DIS) off the lightest nuclei tagged by a recoil nucleon. These processes hold a lot of potential for resolving the outstanding issues related to the dynamics of hadronization in QCD. Within the minimal Fock component framework, valid at large Bjorken $x$ , the main features of the theoretical approach based on the virtual nucleon approximation are elaborated. In this approach, the strong final-state interaction of the DIS products with the nuclear fragments is described by an effective eikonal amplitude, whose parameters can be extracted from the analysis of semi-inclusive DIS off the deuteron target. The extraction of the $Q^{2}$ and $W$ mass dependences of these parameters gives a new observable in studying the QCD structure of DIS final states. Another important feature of tagged DIS off the lightest nuclei is the possibility of performing pole extrapolation with a high degree of accuracy. Such extrapolation allows an extraction of the neutron structure function in a model independent way due to suppression of the final-state interaction in the on-shell limit of the struck nucleon propagator. We review the first application of the pole extrapolation to recent experimental data. Finally, we outline the extension of the framework to inclusive DIS, including a polarized deuteron target as well as its application to the tagged DIS reactions for future experiments at fixed target and collider energies.
nucl-thhep-phnucl-exIJMPE(2017)·18 citations
04
On the possibility of revealing the transition of a baryon pair state to a six-quark confinement state
V.I. Komarov🇷🇺
Proton-proton collisions are considered to find favourable conditions for searching for the transition of a baryon pair state to a hexa-quark confinement state $(3 q) + (3 q) \to (6 q)_{cnf}$ . It is admitted that central $pp$ collisions in a definite range of the initial energy can lead to creation of an intermediate compound system where the hexa-quark dibaryon can be formed. Criteria for selection of central collision events and for manifestation of the quark-structure dibaryon production are proposed.
nucl-thnucl-exPhys.Part.Nucl.Lett.(2018)·5 citations
05
A derivation of the entropy-based relativistic smoothed particle hydrodynamics by variational principle
Philipe Mota · Weixian Chen · Wei-Liang Qian
In this work, a second order smoothed particle hydrodynamics is derived for the study of relativistic heavy ion collisions. The hydrodynamical equation of motion is formulated in terms of the variational principle. In order to describe the fluid of high energy density but of low baryon density, the entropy is taken as the base quantity for the interpolation. The smoothed particle hydrodynamics algorithm employed in this study is of the second order, which guarantees better particle consistency. Furthermore, it is shown that the variational principle preserves the translational invariance of the system, and therefore improves the accuracy of the method. A brief discussion on the potential implications of the model in heavy ion physics is also presented.
nucl-thCommun.Theor.Phys.(2017)·3 citations
06
Final state interactions and the extraction of neutron single spin asymmetries from SIDIS by a transversely polarized $^{3}$ He target
A. Del Dotto🇮🇹 · L.P. Kaptari🇷🇺 · E. Pace🇮🇹 · G. Salmè🇮🇹 · S. Scopetta🇮🇹
The semi-inclusive deep inelastic electron scattering off transversely polarized $^{3}$ He, i.e. the process, $e +^{3} He \to e^{'} + h + X$ , with $h$ a detected fast hadron, is studied beyond the plane wave impulse approximation. To this end, a distorted spin-dependent spectral function of a nucleon inside an A=3 nucleus is actually evaluated through a generalized eikonal approximation, in order to take into account the final state interactions between the hadronizing system and the (A-1) nucleon spectator one. Our realistic description of both nuclear target and final state is a substantial step forward for achieving a reliable extraction of the Sivers and Collins single spin asymmetries of the free neutron. To illustrate how and to what extent the model dependence due to the treatment of the nuclear effects is under control, we apply our approach to the extraction procedure of the neutron single spin asymmetries from those measured for $^{3}$ He for values of the kinematical variables relevant both for forthcoming experiments at Jefferson Lab and, with an exploratory purpose, for the future Electron Ion Collider.
nucl-thhep-phPRC(2017)·8 citations

Affiliations

first authorsco-authorsvia INSPIRE

Evidence for chiral symmetry restoration in heavy-ion collisions

Existence problem of proton semi-bubble structure in the 21+​ state of 34Si

Nuclear final-state interactions in deep inelastic scattering off the lightest nuclei

On the possibility of revealing the transition of a baryon pair state to a six-quark confinement state

A derivation of the entropy-based relativistic smoothed particle hydrodynamics by variational principle

Final state interactions and the extraction of neutron single spin asymmetries from SIDIS by a transversely polarized 3He target

Affiliations

Existence problem of proton semi-bubble structure in the $2_{1}^{+}$ state of $^{34}$ Si

Final state interactions and the extraction of neutron single spin asymmetries from SIDIS by a transversely polarized $^{3}$ He target