Speaker
Description
High-$p_{T}$ charged-particle suppression in heavy-ion collisions like PbPb, quantified by the nuclear modification factor $R_{AA}$, is a key signature of parton energy loss in quark-gluon plasma. However, it remains inconclusive in smaller systems like pPb. The first oxygen-oxygen run at the LHC provides a unique opportunity to study this suppression dependence on system size. We present the first measurement of charged-particle differential cross sections and $R_{AA}$ in OO collisions at $\sqrt{s_{NN}} = 5.36~\mathrm{TeV}$ using CMS data. The results are compared with models incorporating parton energy loss. Before attributing the observed suppression to energy loss, it is crucial to consider nuclear parton distribution function (nPDF) effects which can substantially contribute to suppression. Collision systems such as proton-oxygen provide a unique opportunity to test nPDF effects and also provide nPDF constraints for oxygen nuclei. We also present a measurement of charged-particle production in pO collisions at $\sqrt{s_{NN}} = 9.62~\mathrm{TeV}$ using CMS data. To isolate the initial state effects, a ratio of pO spectra is taken to proton–proton (pp) reference at $\sqrt{s_{NN}} = 5.36~\mathrm{TeV}$. The ratio is compared to the state of the art perturbative QCD calculations. The level of agreement between data and theoretical calculations will provide unique oxygen nPDF constraints and establish a quantitative baseline for interpreting particle suppression observed in oxygen–oxygen collisions.
| Is this an experimental talk? | Yes |
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| Is this on behalf of a collaboration? | Yes |
| Which collaboration? | CMS collaboration |
| Are you willing to present as a poster if it is not selected for oral presentation? | No |