New results on spectra and fluctuations from NA61/SHINE

Abstract

The NA61/SHINE experiment aims to discover the critical point of strongly interacting matter and study the properties of the onset of deconfinement. For this purpose we perform a twodimensional scan of the (T − µ B ) phase diagram by varying the energy (5.1 < √ s NN < 16.8/17.3 GeV) and the system size (p+p, p+Pb, Be+Be, Ar+Sc, Xe+La, Pb+Pb) of the collisions. In this article the NA61/SHINE results on particle spectra as well as fluctuations and correlations in p+p, Be+Be, Ar+Sc, and Pb+Pb collisions are presented. In particular, the latest results on charged kaons spectra, charged pions ratios (electromagnetic effects), proton intermittency, and anisotropic flow are discussed. Finally, the motivation, NA61/SHINE plans, and the first measurements of open charm production in heavy ion collisions at the Super Proton Synchrotron energies are shown.

Cumulative $${\pi}$$-Mesons in $${}^{{12}}{C}{+}{}^{{9}}$$Be-Interactions at 3.2 GeV/Nucleon

“…The experimental data show a rise of the π − /π + ratio with the decrease of the π meson momentum in a good agreement with the prediction of the BC model and to a lesser extent with the INCL model prediction. This increase can be associated with the so-called "spectator" effect, for the first time observed in the experiments at the LBL in Berkeley [30,31] in the fragmentation of light ions at 0 • at energies of several hundred MeV/nucleon and later seen in the NA49 and NA61/SHINE experiments at the SPS CERN in peripheral collisions of lead ions at 150 GeV/nucleon and small (≤100 MeV/c) π meson transverse momenta (for a review of these data, see [32]). A theoretical explanation of this effect was given in [33] back in 1982, but the processes, associated with this Coulomb effect in interactions of relativistic heavy ions, are widely discussed at the present time (see, e.g., [34]).…”

Rapidity distributions of pions in p+p and Pb+Pb collisions at CERN SPS energies

“…Refs. [10,11] for experimental documentation of the phenomenon). The latter is enhancement of the strange over non-strange particles production in heavy ion collisions (see e.g.…”

“…For Pb + Pb collisions at √ s NN = 17.3 GeV the NA49 Collaboration estimated K ≈ 0.78 [10]. Assuming that the ratio of average energy of one kaon over that of one pion remains constant between p + p and Pb + Pb collisions and knowing the enhancement about 2 times of K/π ratios in Pb + Pb compared to p + p reactions [11], we get the R Pb + Pb The above value should be compared with the factor 0.812 in Fig. 4, giving roughly 4 % agreement.…”

Theory Summary

“…The point at which the two straight lines intersect is approximately the point at which baryons dominate the energy density of strongly interacting matter. We were also presented with data from NA61 by Grabieskow [4] that showed in the region of this transition that various ratios of particle abundances show distinctive changes in their dependence on collision energy, and that there are intriguing structures associated with intermittancy. The first is associated with the so-called Horn originally observed by Gazdzicki [5].…”

“…They used a sigma model to simulate the approach to criticality. The approach to masslessness of the sigma field in such a theory generates scale invariant correlation functions that might be responsible for the observed effect in NA61 [4]. The effect is localized in energy, A, and collision centrality since one has to be very near to critical point to get a sizable signal.…”