nucl-th digest · Dec 11, 2014

Signatures of collective behavior in small systems

We perform 3+1D viscous hydrodynamics calculations of proton-nucleus (pA) and nucleus-nucleus (AA) collisions. Our goal is to understand the apparent collective behavior recently observed in pA collisions and to verify whether the highest multiplicity collision systems can be accurately described as a relativistic fluid. We compare our calculations of flow variables to existing measurements, and demonstrate that hydrodynamics correctly captures the measured trends. We show that our predictions for the pair correlation observable

r_{n}

are validated by recent experimental pA measurements, and that our results are sensitive to the granularity of the initial state. We also compare our results with measurements done for nucleus-nucleus collisions.

Comments:: Talk presented by IK at Quark Matter 2014
Subjects:: Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:: 1412.3147 [pdf]

NPA(2014)·15 citations

[Submitted on 10 Dec 2014]

Photoproduction of the $f_{2} (1270)$ resonance

Ju-Jun Xie🇨🇳 · E. Oset🇨🇳

We have performed a calculation of the $γ p \to π^{+} π^{-} p$ reaction, where the two pions have been separated in $D$ -wave producing the $f_{2} (1270)$ resonance. We use elements of the local hidden gauge approach that provides the interaction of vector mesons in which the $f_{2} (1270)$ resonance appears as a $ρ$ - $ρ$ molecular state in $L = 0$ and spin 2. The vector meson dominance, incorporated in the local hidden gauge approach converts a photon into a $ρ^{0}$ meson and the other meson connects the photon with the proton. The picture is simple and has no free parameters, since the parameters of the theory have been constrained in the previous study of the vector-vector states. In a second step we introduce new elements, not present in the local hidden gauge approach, adapting the $ρ$ propagator to Regge phenomenology and introducing the $ρN N$ tensor coupling. We find that both the differential cross section as well as the $t$ dependence of the cross section are in good agreement with the experimental results and provide support for the molecular picture of the $f_{2} (1270)$ in the first baryonic reaction where it has been tested.

Comments:: Published version. Eur. Phys. J. A 51, 111 (2015)
Subjects:: Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:: 1412.3234 [pdf]

EPJA(2015)·18 citations

Thursday·December 11, 2014

Signatures of collective behavior in small systems

Photoproduction of the $f_{2} (1270)$ resonance

Affiliations

Signatures of collective behavior in small systems

Photoproduction of the f2​(1270) resonance

Affiliations

Photoproduction of the $f_{2} (1270)$ resonance