Charged particle nuclear modification factor in OO collisions at \sqrt{s_{NN}}= 5.36 TeV with CMS

• In heavy-ion collisions, energetic partons produced in initial hard scatterings may lose energy while traversing through a hot and dense medium known as quark-gluon plasma produced at the collision point. This results in suppression of high $p_{T}$ charged particle yield which is quantified by the nuclear modification factor ($R_{AA}$). While such suppression is well established in large systems like Pb-Pb collisions, it is not conclusively observed in smaller systems such as proton-lead, leaving open the question of the minimum system size required to observe parton energy loss. The first oxygen-oxygen collision run at the LHC provides us a great opportunity to study this suppression dependence on system size. We present the first measurement of charged particle differential cross sections and the nuclear modification factor $R_{AA}$ in oxygen-oxygen (OO) collisions at 5.36 TeV as a function of $p_{T}, using around 5 nb^{-1} of OO and 1.1pb^{-1} of proton-proton data collected by the CMS experiment. We also present a comparison with models incorporating parton energy loss mechanisms.