Wed·Aug 20, 2014Wednesday·August 20, 2014

1. 01*

   Systematics of Kinetic Freeze-out Properties in High Energy Collisions from STAR

   Lokesh Kumar (for the STAR Collaboration)🇮🇳

   The main aim of the RHIC Beam Energy Scan (BES) program is to explore the QCD phase diagram which includes search for a possible QCD critical point and the phase boundary between QGP and hadronic phase. We report the collision energy and centrality dependence of kinetic freeze-out properties from the measured mid-rapidity ($|y|<0.1)$ light hadrons (pions, kaons, protons and their anti-particles) for Au+Au collisions at the center-of-mass energy $\sqrt{s_{NN}}=$ 7.7, 11.5, 19.6, 27, and 39 GeV. The STAR detector, with a large uniform acceptance and excellent particle identification is used in the data collection and analysis. The kinetic freeze-out temperature $T_{\mathrm{kin}}$ and average collective velocity $⟨\beta ⟩$ parameters are extracted from blast-wave fits to the identified hadron spectra and systematically compared with the results from other collision energies including those at AGS, SPS and LHC. It is found that all results fall into an anti-correlation band in the 2-dimension ($T_{\mathrm{kin}}$, $⟨\beta ⟩$) distribution: the largest value of collective velocity and lowest temperature is reached in the most central collisions at the highest collision energy. The energy dependence of these freeze-out parameters are discussed.

   nucl-exNPA(2014)·60 citations
2. 02*

   Collective Flow of QCD Matter: a Historical Introduction

   Hans Georg Ritter🇺🇸 · Reinhard Stock🇩🇪

   We present a historical review of the physics observables developed for relativistic nuclear collisions, that describe collective hydrodynamic flow of hadronic or partonic matter, and of the corresponding experimental progress. We begin with the early discovery phase of radial and directed flow at the Bevalac, and continue the review until the recent work at RHIC and LHC, and related theory.

   nucl-exJ.Phys.G(2014)·19 citations
3. 03*

   The $\Lambda \Lambda$ Correlation Function in Au+Au collisions at $\sqrt{s_{NN}}=$ 200 GeV

   STAR Collaboration

   We present $\Lambda \Lambda$ correlation measurements in heavy-ion collisions for Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV using the STAR experiment at the Relativistic Heavy-Ion Collider (RHIC). The Lednický-Lyuboshitz analytical model has been used to fit the data to obtain a source size, a scattering length and an effective range. Implications of the measurement of the $\Lambda \Lambda$ correlation function and interaction parameters for di-hyperon searches are discussed.

   nucl-exPRL(2015)·195 citations
4. 04*

   Building relativistic mean field models for finite nuclei and neutron stars

   Wei-Chia Chen🇺🇸 · J. Piekarewicz🇺🇸

   Background: Theoretical approaches based on density functional theory provide the only tractable method to incorporate the wide range of densities and isospin asymmetries required to describe finite nuclei, infinite nuclear matter, and neutron stars. Purpose: A relativistic energy density functional (EDF) is developed to address the complexity of such diverse nuclear systems. Moreover, a statistical perspective is adopted to describe the information content of various physical observables. Methods: We implement the model optimization by minimizing a suitably constructed chi-square objective function using various properties of finite nuclei and neutron stars. The minimization is then supplemented by a covariance analysis that includes both uncertainty estimates and correlation coefficients. Results: A new model, FSUGold2, is created that can well reproduce the ground-state properties of finite nuclei, their monopole response, and that accounts for the maximum neutron star mass observed up to date. In particular, the model predicts both a stiff symmetry energy and a soft equation of state for symmetric nuclear matter--suggesting a fairly large neutron-skin thickness in Pb208 and a moderate value of the nuclear incompressibility. Conclusions: We conclude that without any meaningful constraint on the isovector sector, relativistic EDFs will continue to predict significantly large neutron skins. However, the calibration scheme adopted here is flexible enough to create models with different assumptions on various observables. Such a scheme--properly supplemented by a covariance analysis--provides a powerful tool to identify the critical measurements required to place meaningful constraints on theoretical models.

   ↳ nucl-thnucl-exPRC(2014)·283 citations
5. 05*

   Odd and Even Partial Waves of $\eta {\pi }^{-}$ and ${\eta }^{\prime }{\pi }^{-}$ in ${\pi }^{-}p\to {\eta }^{(\prime )}{\pi }^{-}p$ at $191\text{GeV}/c$

   C. Adolph · R. Akhunzyanov · M.G. Alexeev · G.D. Alexeev · A. Amoroso · V. Andrieux · V. Anosov · A. Austregesilo · B. Badelek · F. Balestra · J. Barth · G. Baum and 197 other authors

   Exclusive production of $\eta {\pi }^{-}$ and ${\eta }^{\prime }{\pi }^{-}$ has been studied with a $191\text{GeV}/c$ ${\pi }^{-}$ beam impinging on a hydrogen target at COMPASS (CERN). Partial-wave analyses reveal different odd/even angular momentum ($L$) characteristics in the inspected invariant mass range up to $3\text{GeV}/c^2$. A striking similarity between the two systems is observed for the $L=2,4,6$ intensities (scaled by kinematical factors) and the relative phases. The known resonances $a_2(1320)$ and $a_4(2040)$ are in line with this similarity. In contrast, a strong enhancement of ${\eta }^{\prime }{\pi }^{-}$ over $\eta {\pi }^{-}$ is found for the $L=1,3,5$ waves, which carry non-$q\bar{q}$ quantum numbers. The $L=1$ intensity peaks at $1.7\text{GeV}/c^2$ in ${\eta }^{\prime }{\pi }^{-}$ and at $1.4\text{GeV}/c^2$ in $\eta {\pi }^{-}$, the corresponding phase motions with respect to $L=2$ are different.

   ↳ hep-exnucl-exPLB(2015)·120 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.