Possible formation of QGP droplets in high-multiplicity events and measurement of (2S) polarization in proton+proton collisions at ps = 13 TeV with ALICE

Abstract

The main goal of the Large Hadron Collider (LHC) is to understand nature at the fundamental level. Through LHC, one can also study the behaviour of matter at extremely high temperatures and densities. This can be achieved by the collision of ultra-relativistic heavy-ions where quantum chromodynamics (QCD) predicts the formation of a new state of matter called the quark-gluon plasma (QGP). QGP is a thermalized soup of quarks and gluons which is expected to be prevalent in the early stage of the Universe, after a few microseconds of the Big Bang. Historically, the proton+proton (pp) collisions were taken as baseline measurements for QGP production in heavy-ion collisions, as their system size is significantly smaller than that of the heavy-ion collisions. However, recent measurements of strangeness enhancement and ridge-like structure formation in high multiplicity pp events have opened Pandora’s box, which raises the question about the viability of using pp collisions as a baseline for the QGP study. Studying the formation of a QGP-like medium in hadronic collisions will help us better understand the experimental data. Thus, it is crucial to approach this problem in a two-fold manner. Firstly, one needs to study the possibility of QGP droplet formation in ultra-relativistic high multiplicity pp collisions through various theoretical and phenomenological models. Secondly, we should look into the experimental data and study the necessary observables that can point us in a conclusive direction in this context.