Speakers
Description
The NA61/SHINE experiment at the CERN SPS is a multipurpose fixed-target spectrometer for charged and neutral hadron measurements. Its research program includes strong interactions studies focusing on the exploration of the QCD phase diagram and understanding the phase structures of strongly interacting matter, including the hypothesized QCD critical point. To achieve these goals, the experiment conducted beam momentum (from 13A to 150A/158A GeV/c, corresponding to $\sqrt{s_{NN}} = 5 - 17$ GeV) and system size (p+p, p+Pb, Be+Be, Ar+Sc, Xe+La, Pb+Pb) scans, allowing coverage of a significant part of the QCD phase diagram.
In the vicinity of the QCD critical point, a heavy-ion collision system is expected to undergo a 2nd order phase transition; in such a state, non-monotonic fluctuations of various observables are expected as we vary the system freeze-out conditions; furthermore, the correlation functions of final state particles in momentum space assume a scale-invariant, power-law form that can be probed through intermittency analysis in transverse momentum space. In this contribution, we present recent measurements of multiplicity and net-electric charge fluctuations of higher order moments at NA61/SHINE as a function of system size (p+p, Ar+Sc) and collision energy. The results are compared across different energies, as well as against model predictions. We also present recent measurements of femtoscopic correlations, revealing that the shape of the particle-emitting source is not Gaussian. The measurements are based on alpha-stable symmetric L\'evy sources, and we discuss the average pair transverse mass, collision energy, and system size dependence of the source parameters. Finally, we summarize the current status of proton and $h^-$ intermittency analyses in the collision energy range $\sqrt{s_{NN}} = 5 - 17$ GeV, for a variety of nucleus-nucleus collisions (Ar+Sc, Xe+La, Pb+Pb). Attention is brought to the importance of baseline effects in factorial moment intermittency analysis, taken into account in NA61/SHINE studies but not so in analyses from other experiments. We also report on the development of novel methods aimed at solving the long-standing problem of bin-by-bin correlations in experimental intermittency analysis, and for a more accurate handling of systematics and uncertainties.
| Is the talk given on behalf of the Collaboration? | no |
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| Topic area | Critical Point |