Exploring the strangeness enhancement and collectivity in pp and Pb-Pb collisions at the LHC using event shape engineering

Abstract

Quark-Gluon Plasma (QGP) is a deconfined and thermalised medium of partons (quarks and gluons), which is believed to have formed in ultra-relativistic collisions at the Large Hadron Collider (LHC), CERN and Relativistic Heavy-Ion Collider (RHIC), BNL. QGP is transient in nature, having a lifetime of the order 10−23 seconds, which makes its direct observation nearly impossible. However, there are signatures that signify the formation of the QGP phase in heavy-ion collisions. These signatures include the enhanced production of strange hadrons, collectivity, jet quenching, quarkonia supression, thermal photon and dilepton production, etc. A few of these studies require proton-proton (pp) collisions as the baseline measurements where the formation of a QGP medium is usually not anticipated. However, high multiplicity pp collisions at the LHC show observations of nonzero elliptic flow coefficient, characteristic modifications of baryon to meson ratios, enhanced production of strange and multi-strange hadrons, etc., which are believedto be achievable in ultra-relativistic nuclear collisions. This indicates that a common underlying physics mechanism drives these observations throughout the collision systems. However, other signatures, such as quarkonia suppression, jet quenching, etc., are not observed in small collision systems.