Recent Results from Proton Intermittency Analysis in Nucleus--Nucleus Collisions from NA61 at CERN SPS

The search for experimental signatures of the critical point (CP) of strongly interacting matter is one of the main objectives of the NA61/SHINE experiment at CERN SPS. In the course of the experiment, an energy (beam momentum 13A–150A GeV/c) and system size (p+p, p+Pb, Be+Be, Ar+Sc, Xe+La) scan is performed. Local proton density fluctuations in transverse momentum space represent an order parameter of the chiral phase transition and are expected to scale according to a universal power-law in the vicinity of the CP; we probe their behaviour through an intermittency analysis of the proton second scaled factorial moments (SSFMs) in transverse momentum space. Previous such analyses revealed power-law behaviour in NA49 “Si”+Si collisions at 158A GeV/c; no intermittency was observed in NA49 “C”+C and Pb+Pb collisions at the same energy, and in NA61/SHINE Be+Be collisions at 150A GeV/c. Results suggest a baryochemical potential for the critical point in the vicinity of 250 MeV. In the present work, we extend the analysis to the NA61/SHINE Ar+Sc system at 150A GeV/c. We employ statistical techniques to subtract non-critical background and estimate statistical and systematic uncertainties. Finally, we use Monte Carlo simulations to estimate the likelihood of a spurious signal.