Ivan Pidhurskyi (CERN)

Present and future of the open charm program of the NA61/SHINE experiment

NA61/SHINE is a fixed-target particle physics experiment at CERN SPS. The experiment studies the hadronic final states produced in interactions of various target-projectile systems ranging from p+p and up to Pb+Pb at up to the top SPS energies of 150A GeV/c. One of the primary objectives of the experiment as of today is to perform a direct measurement of the open charm hadrons in the Pb+Pb collisions. Predictions from theoretical models give us estimates on the c-cbar pair yields of around 0.1-1 pair per event (Pb+Pb @ 150A GeV/c). Our previous attempts at direct measurement did not succeed. Thus, during the CERN Long Shutdown 2 the experiment was upgraded and now provides significantly better performance for our new attempt at the open charm measurements. The amount of data collected so far already exceeds the statistics used for the previous attempt by two orders of magnitude. Combining high acceptance of a fixed-target experiment, a large variety of colliding systems, and a unique energy range, the NA61/SHINE experiment provides unique opportunities for studies of the medium of deconfined matter. So far, these qualities of the experiment have been used to perform a 2-dimensional scan for the critical point of strongly interacting matter. After the aforementioned upgrades, the experiment has the potential to also become a work site for the exploration of a deconfined medium via studies of heavy quark correlations. Our latest idea is to quantify the transport properties of the strongly interacting medium via a study of the momentum correlations between the final-state open charm hadrons. Within our setup, the head-on Pb+Pb collisions would rarely produce more than one pair of the c-cbar quarks, allowing one to discard collective effects. The low energy of the collision should also result in c and cbar quarks being created essentially at rest in the center of mass frame, allowing one to avoid trivial inputs to the signal such as back-to-back momentum correlations between the quarks created in a pair.