Nuclear Physics Seminar: Rutik Manikandhan
Non-Monotonic Transverse-Momentum Correlations in Au+Au Collisions at High Baryon Density
Event Details
- Time: 1:00pm - 2:00pm
Location: 4138 PRB
Abstract
Characterizing the QCD phase diagram at finite baryon density is a central goal of high-energy nuclear physics. Two-particle transverse-momentum correlations offer sensitivity to the system's bulk dynamics, thermalization, and possible critical fluctuations, and are constructed to suppress the leading effects of volume fluctuations.
I present STAR measurements of the relative dynamical correlation C_pT in Au+Au collisions at √s_NN = 3.0–7.7 GeV from the fixed-target and collider programs, recently published in Physical Review Letters, combined with BES-I data to cover 3–200 GeV in a single consistent analysis. The correlations follow the approximate N_part^(−1/2) scaling expected from independent particle-emitting sources over most of this range, and we identify a breakdown of that scaling at √s_NN = 3.0 GeV, where the system is dominated by hadronic interactions throughout its evolution. In central collisions we observe a non-monotonic energy dependence with a significance of approximately 5σ relative to a monotonic reference — the first such observation as a function of collision energy. AMPT and Boltzmann–Langevin calculations do not reproduce this structure. I will discuss the analysis methods behind these results, including the scaling baseline and the significance procedure, and the non-critical mechanisms that must be controlled before a critical interpretation can be sustained.
I will then turn to ongoing phenomenological work connecting C_pT directly to the QCD equation of state, using a thermodynamic linear-response relation in which the speed of sound links event-by-event multiplicity fluctuations to mean-p_T fluctuations. This offers a route to constraining c_s² at finite μ_B from correlation measurements, with lattice input, and a natural extension of these observables to smaller collision systems.
