Can transverse mass scaling shed light on the event-activity dependence of γ-meson production at the LHC

Iakov Aizenberg, Zvi Citron, Alexander Milov

Research output: Contribution to journalArticlepeer-review


Measurements by the CMS experiment [S. Chatrchyan (CMS Collaboration), J. High Energy Phys. 04 (2014) 103JHEPFG1029-847910.1007/JHEP04(2014)103; A. M. Sirunyan (CMS Collaboration), J. High Energy Phys. 11 (2020) 001JHEPFG1029-847910.1007/JHEP11(2020)001] reveal a deficit of charged particle tracks in events with higher γ(nS) states. This observation is suggested to be a manifestation of the excited bottomonia suppression in pp interactions. Transverse mass (mT) scaling can be implied to check this assumption in an independent way. The scaling has been observed for a wide range of particle species in proton-proton collisions at various energies from the SPS to RHIC and the LHC. The observed scaling is known to be different for baryons and mesons, and this work presents a comprehensive study of the mT-scaling of mesons at LHC energies with a focus on heavier mesons. The study demonstrates patterns in the scaling properties of mesons, which are related to the particle quark content. In particular, light species and ground-state quarkonia obey the same scaling, whereas open-flavor particles deviate from it because their spectra are significantly harder. The magnitude of deviation depends on the flavor of the heaviest quark in the meson. By extending the mT-scaling assumption to the excited bottomonia states, it is observed that the measured cross sections of γ(2S) and γ(3S) are reduced by factors of 1.6 and 2.4 compared to the expectation from the scaling. This observation is consistent with recently observed differences between the event-activity dependence of different γ(nS) meson states.

Original languageAmerican English
Article number014012
Number of pages7
JournalPhysical review D
Issue number1
StatePublished - 1 Jan 2023

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics


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