Can Transverse Mass Scaling Shed Light on the Event-Activity Dependence of $\Upsilon$ Mesons Production at LHC?

TL;DR

This study investigates transverse mass scaling of mesons at LHC energies, revealing patterns related to quark content and showing deviations for excited bottomonia states, which relate to their suppression in high-activity events.

Contribution

It provides a comprehensive analysis of $m_{T}$-scaling for mesons at LHC, highlighting differences based on quark content and extending the scaling to excited bottomonia states.

Findings

Light mesons and ground-state quarkonia obey similar $m_{T}$-scaling.

Open-flavor mesons deviate due to harder spectra.

Measured $ ext{Upsilon}$(2S,3S) cross sections are reduced compared to scaling expectations.

Abstract

Measurements by the CMS experiment [CMS Collaboration, JHEP04 (2014) 103; CMS Collaboration, JHEP11 (2020) 001] reveal a deficit of charged particle tracks in events with higher $\Upsilon$(nS) states. This observation is suggested to be a manifestation of the excited bottomonia suppression in $pp$ interactions. Transverse mass ($m_{\mathrm{T}}$) 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 $m_{\mathrm{T}}$-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 $m_{\mathrm{T}}$-scaling assumption to the excited bottomonia states, it is observed that the measured cross sections of $\Upsilon$(2S) and $\Upsilon$(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 $\Upsilon$(nS) meson states.