| CMS Physics Analysis Summaries | |
| Report number | CMS-PAS-HIN-25-008 |
| Title | Measurement of the charged particle nuclear modification factor in oxygen-oxygen collisions with CMS |
| Corporate author(s) | CMS Collaboration |
| Collaboration | CMS Collaboration |
| Subject category | Nuclear Physics - Experiment |
| Accelerator/Facility, Experiment | CERN LHC ; CMS |
| Abstract | A hot medium, known as the quark-gluon plasma (QGP), is created in collisions of relativistic heavy nuclei such as lead or gold. Highly energetic quarks and gluons, collectively referred to as partons, lose energy as they travel through the QGP leading to suppressed production of particles with transverse momenta ($p_{\mathrm{T}}$) of roughly 10--100 GeV. This suppression is typically quantified with the nuclear modification factor ($R_{\text{AA}}$). Questions regarding what minimum system size is required to see parton energy loss effects remain, as no such suppression has been seen in smaller proton-lead collisions. Experiments involving light nuclei examine a domain that lies between these two extreme cases. Using $6.1~\text{nb}^{-1}$ of oxygen-oxygen (OO) collisions and $1.02~\text{pb}^{-1}$ of proton-proton data collected at a nucleon-nucleon center-of-mass energy of $\sqrt{\smash[b]{s_{_{\mathrm{NN}}}}}=5.36$ TeV by the CMS experiment at the CERN LHC, charged particle invariant cross sections and the OO charged particle $R_{\text{AA}}$ are measured as a function of particle $p_{\mathrm{T}}$ for the first time. The $R_{\text{AA}}$ is notably suppressed, with a local minimum of $0.69\pm0.04$ at $p_{\mathrm{T}}=6$ GeV, but increases to a value of $0.97\pm0.06$ at $p_{\mathrm{T}}=100$ GeV. To evaluate if parton energy loss effects may be present in OO collisions, the data are compared to previous measurements of other collision systems and a variety of theoretical models. |
| Related | superseded by: CERN-EP-2025-226 |
|
Email contact: cms-pag-conveners-heavyions@cern.ch | |
Record created 2025-09-08, last modified 2025-10-11