Nuclear Theory·nucl-th

Monday·May 25, 2015

5 papers—2 primary·3 cross-listed

01
[Submitted on 22 May 2015]
Effects of hadronic rescattering on multistrange hadrons in high-energy nuclear collisions
Shiori Takeuchi🇯🇵 · Koichi Murase🇯🇵 · Tetsufumi Hirano🇯🇵 · Pasi Huovinen🇩🇪 · Yasushi Nara🇯🇵
We study the effects of hadronic rescattering on hadron distributions in high-energy nuclear collisions by using an integrated dynamical approach. This approach is based on a hybrid model combining (3+1)-dimensional ideal hydrodynamics for the quark gluon plasma (QGP), and a transport model for the hadron resonance gas. Since the hadron distributions are the result of the entire expansion history of the system, understanding the QGP properties requires investigating how rescattering during the hadronic stage affects the final distributions of hadrons. We include multistrange hadrons in our study, and quantify the effects of hadronic rescattering on their mean transverse momenta and elliptic flow. We find that multistrange hadrons scatter less during the hadronic stage than nonstrange particles, and thus their distributions reflect the properties of the system in an earlier stage than the distributions of nonstrange particles.
Comments:
14 pages, 9 figures, v2: published version, title is changed
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1505.05961 [pdf]
PRC(2015)·67 citations
02
[Submitted on 22 May 2015]
Dilepton production and reaction dynamics in heavy-ion collisions at SIS energies from coarse-grained transport simulations
Stephan Endres🇩🇪 · Hendrik van Hees🇩🇪 · Janus Weil🇩🇪 · Marcus Bleicher🇩🇪
Dilepton invariant-mass spectra for heavy-ion collisions at SIS 18 and BEVALAC energies are calculated using a coarse-grained time evolution from the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model. The coarse-graining of the microscopic simulations enables to calculate thermal dilepton emission rates by application of in-medium spectral functions from equilibrium quantum-field theoretical calculations. The results show that extremely high baryon chemical potentials dominate the evolution of the created hot and dense fireball. Consequently, a significant modification of the $ρ$ spectral shape becomes visible in the dilepton invariant-mass spectrum, resulting in an enhancement in the low-mass region $M_{ee} = 200$ to 600 MeV/ $c^{2}$ . This enhancement, mainly caused by baryonic effects on the $ρ$ spectral shape, can fully describe the experimentally observed excess above the hadronic cocktail contributions in Ar+KCl ( $E_{lab} = 1.76$ $A$ GeV) reactions as measured by the HADES collaboration and also gives a good explanation of the older DLS Ca+Ca ( $E_{lab} = 1.04$ $A$ GeV) data. For the larger Au+Au ( $E_{lab} = 1.23$ $A$ GeV) system, we predict an even stronger excess from our calculations. A systematic comparison of the results for different system sizes from C+C to Au+Au shows that the thermal dilepton yield increases stronger ( $\propto A^{4/3}$ ) than the hadronic background contributions, which scale with $A$ , due to its sensitivity on the time evolution of the reaction. We stress that the findings of the present work are consistent with our previous coarse-graining results for the NA60 measurements at top SPS energy. We argue that it is possible to describe the dilepton results from SIS 18 up to SPS energies by considering the modifications of the $ρ$ spectral function inside a hot and dense medium within the same model.
Comments:
15 pages, 9 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1505.06131 [pdf]
PRC(2015)·78 citations
03
[Submitted on 21 May 2015] (cross-list from hep-ph)
Distinguishing cusp effects and near-threshold-pole effects
Zhi-Yong Zhou🇨🇳 · Zhiguang Xiao🇨🇳
We make use of a unitarized coupled-channel model to analyze the mass distribution data of final states in production processes of $X (4260)$ . By analyzing the analytical structures of the decay amplitudes, we find that the line shape of $Z_{c} (3900)$ signal is related to the combined effect of a pair of near-threshold "shadow" poles and the $(D D ˉ^{*})^{\pm}$ thresholds, in which the third-sheet pole might provide a dominant contribution. As all the coupled channels effects are tuning off, the trajectories of these two poles suggest that the $Z_{c} (3900)$ might originate from the attractive interaction of $(D^{*} D ˉ^{*})^{\pm}$ through a long-distance interaction, $e . g .$ $π$ -exchange interaction, as a "deuteron-like" state. There is no nearby pole structure corresponding to the $Z_{c} (4025)$ signal in the $(D^{*} D ˉ^{*})^{\pm}$ mass distribution.
Comments:
10 pages, 3 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1505.05761 [pdf]
PRD(2015)·19 citations
04
[Submitted on 22 May 2015] (cross-list from hep-ph)
Stable Yang-Lee zeros in truncated fugacity series from net-baryon number multiplicity distribution
Kenji Morita🇯🇵 · Atsushi Nakamura🇯🇵
We investigate Yang-Lee zeros of grand partition functions as truncated fugacity polynomials of which coefficients are given by the canonical partition functions $Z (T, V, N)$ up to $N \leq N_{max}$ . Such a partition function can be inevitably obtained from the net-baryon number multiplicity distribution in relativistic heavy ion collisions, where the number of the event beyond $N_{max}$ has insufficient statistics, as well as canonical approaches in lattice QCD. We use a chiral random matrix model as a solvable model for chiral phase transition in QCD and show that the closest edge of the distribution to real chemical potential axis is stable against cutting the tail of the multiplicity distribution. The similar behavior is also found in lattice QCD at finite temperature for Roberge-Weiss transition. In contrast, such a stability is found to be absent in the Skellam distribution which does not have phase transition. We compare the number of $N_{max}$ to obtain the stable Yang-Lee zeros with those of critical higher order cumulants.
Comments:
15 pages, 9 figures. Version to appear in Phys. Rev. D. Comments on lattice results are added. Typos are corrected
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1505.05985 [pdf]
PRD(2015)·5 citations
05
[Submitted on 22 May 2015] (cross-list from hep-ph)
The $K K ˉ π$ decay of the $f_{1} (1285)$ and its nature as a $K^{*} K ˉ - cc$ molecule
F. Aceti🇪🇸 · Ju-Jun Xie🇨🇳 · E. Oset🇨🇳
We investigate the decay of $f_{1} (1285) \to π K K ˉ$ with the assumption that the $f_{1} (1285)$ is dynamically generated from the $K^{*} K ˉ - cc$ interaction. In addition to the tree level diagrams that proceed via $f_{1} (1285) \to K^{*} K ˉ - cc \to π K K ˉ$ , we take into account also the final state interactions of $K K ˉ \to K K ˉ$ and $π K \to π K$ . The partial decay width and mass distributions of $f_{1} (1285) \to π K K ˉ$ are evaluated. We get a value for the partial decay width which, within errors, is in fair agreement with the experimental result. The contribution from the tree level diagrams is dominant, but the final state interactions have effects in the mass distributions. The predicted mass distributions are significantly different from phase space and tied to the $K^{*} K ˉ - cc$ nature of the $f_{1} (1285)$ state.
Comments:
Published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1505.06134 [pdf]
PLB(2015)·34 citations

Affiliations

first authorsco-authorsvia INSPIRE

Effects of hadronic rescattering on multistrange hadrons in high-energy nuclear collisions

Dilepton production and reaction dynamics in heavy-ion collisions at SIS energies from coarse-grained transport simulations

Distinguishing cusp effects and near-threshold-pole effects

Stable Yang-Lee zeros in truncated fugacity series from net-baryon number multiplicity distribution

The KKˉπ decay of the f1​(1285) and its nature as a K∗Kˉ−cc molecule

Affiliations

The $K K ˉ π$ decay of the $f_{1} (1285)$ and its nature as a $K^{*} K ˉ - cc$ molecule