Search for the Critical Point in QCD Matter

It is conjectured that the quantum chromodynamic (QCD) phase diagram contains two distinct types of phase transitions between the quark-gluon plasma (QGP) and a hadron gas. At low baryon chemical potential ($mu_B approx 0$), the phase transition is believed to be a higher-order crossover. However, at larger $mu_B$, theoretical predictions suggest the transition becomes first-order, implying the existence of a critical point separating these two regions. Non-monotonic fluctuations of conserved quantities as a function of collision energy, such as net-proton number fluctuations, have been proposed as experimental signatures of critical behavior within the vicinity of the QCD critical point. Extensive efforts at the Relativistic Heavy Ion Collider (RHIC), especially through the STAR Beam Energy Scan program are aimed at identifying such signals across a range of collision energies in order to determine the location of the QCD critical point on the phase diagram. Moreover, recent theoretical calculations have placed the QCD critical point within the collision energies studied in the Beam Energy Scan. This talk will review the current status of the QCD critical point search, using high-precision, high-statistics datasets from phase two of the STAR Beam Energy Scan, which spans center-of-mass energies from $sqrt{S_{NN}} = 3$–$27$ GeV ($mu_B approx 200$–$700$ MeV).