Speaker
Description
In relativistic heavy-ion collisions a hot and dense thermalized matter of deconfined partons, the Quark-Gluon Plasma (QGP), is created. Its global properties can be characterized by the measurements of particles in the low transverse momentum (or “soft”) regime, which represents over 95% of created particles. Many soft observables in proton-proton ($pp$) collisions at the highest LHC energies exhibit similar behavior as in heavy-ion collisions. Such observables can be interpreted as signals of QGP in $pp$ collisions. We will review some of them in this talk.
The recent experimental results on Bose-Einstein correlations (BEC) of like-sign charged pions yield some new interesting results. Both ATLAS and CMS collaborations measured the source radius $R_{HBT}$ and particle correlation strength $\lambda$ as a function of charged particle multiplicity $N_{ch}$ (up to $300$). Discovered source size saturation at high multiplicities $N_{ch}>100$ along with low values of $\lambda$ are not typical for heavy-ion collisions. Thereby these results call into question the formation of QGP in $pp$ experiments.
In this talk we will discuss a simple analytic model of an ideal gas of identical bosons that can quantitatively reproduce HBT data. We claim that the peculiarities of discussed experimental results might be observed from a completely thermal system if one considers subensembles of fixed but high enough multiplicities with noticeable Bose condensation. In the proposed model increase in particle multiplicity, enhances the ground-state contribution to particle momentum spectra and leads to the suppression of the Bose-Einstein momentum correlations.
