De-Confinement in small systems: Clustering of color sources in high multiplicity $\bar{p}$p collisions at $\sqrt{s}$= 1.8 TeV

Abstract

It is shown that de-confinement can be achieved in high multiplicity non jet $\bar{p}$p collisions at $\sqrt{s}$= 1.8 TeV Fermi National Accelerator Laboratory(FNAL- E735) experiment. Previously the evidence for de-confinement was the demonstrated by the constant freeze out energy density in high multiplicity events. In this paper we use the same data but analyze the transverse momentum spectrum in the framework of the clustering of color sources. The charged particle pseudorapidities densities in the range 7.0 $\leq \langle dN_{c}/d\eta \rangle \leq$26.0 are considered. Results are presented for both thermodynamic and transport properties. The initial temperature and energy density are obtained and compared with the Lattice Quantum Chromo Dynamics(LQCD) simulations. The energy density ($\varepsilon/T^{4}$) $\sim$ 11.5 for $ \langle dN_{c}/d\eta \rangle \sim $ 25.0 is close to the value for 0-10\% central events in Au+Au collisions at $\sqrt{s_{NN}}$= 200 GeV. The shear viscosity to entropy density ratio($\eta/s$) is $\sim$ 0.2 at the transition temperature. The result for the trace anomaly $\Delta$ is in excellent agreement with LQCD simulations. These results confirm our earlier observation that the de-confined state of matter was created in high multiplicity events in $\bar{p}$p collisions at $\sqrt{s}$=1.8 TeV.