Upsilon Production as a Probe for Early State Dynamics in High Energy Nuclear Collisions at RHIC

TL;DR

This paper investigates Upsilon production in high energy nuclear collisions at RHIC, highlighting how different states reveal early stage dynamics and the importance of measuring excited states for understanding the initial conditions.

Contribution

It introduces the role of excited Upsilon states as probes for early state dynamics and emphasizes the need for their measurement to extract initial collision information.

Findings

Ground state Upsilon(1s) spectra are influenced by the Cronin effect.

Excited $b\bar b$ states are affected by cold and hot nuclear matter effects.

Measurement of excited states is crucial for understanding early collision stages.

Abstract

Upsilon production in heavy ion collisions at RHIC energy is investigated. While the transverse momentum spectra of the ground state Upsilon(1s) are controlled by the initial state Cronin effect, the excited $b\bar b$ states are characterized by the competition between the cold and hot nuclear matter effects and sensitive to the dissociation temperatures determined by the heavy quark potential. We emphasize that it is necessary to measure the excited heavy quark states in order to extract the early stage information in high energy nuclear collisions at RHIC.