NPA Seminar (virtual): Mesut Arslandok, Heidelberg University, “A brief story: From raw data to the recent results on net-baryon number fluctuations in Pb-Pb Collisions with ALICE””

One of the key goals of nuclear collision experiments is to map the phase diagram of strongly interacting matter. Fluctuations of conserved charges, expressed as cumulants of net-particle multiplicity distributions, probe the response of the system to external perturbations. Such measurements are hence particularly interesting for studies of possible critical phenomena and the existence of a critical endpoint in the QCD phase diagram.
At LHC energies there would be, for vanishing light quark masses, a temperature-driven genuine phase transition of second order between the hadron gas and the quark-gluon plasma. For realistic quark masses, however, this transition becomes a smooth cross over. Nevertheless, due to the small masses of current quarks one can still probe critical phenomena at the LHC energies, which can be confronted with the ab-initio Lattice QCD calculations at vanishing baryon chemical potential.
There have been many experimental efforts to measure the higher-order cumulants of event-by-event net-particle distributions reported by ALICE, HADES, NA61 and STAR collaborations. In this talk, I will focus on the recent experimental results on net-baryon number fluctuation measurements in Pb-Pb collisions recorded by the ALICE Collaboration at the CERN LHC. Higher order cumulants are more sensitive to the underlying physics, however they require very high precision measurements. Accordingly, the second part of the talk will be dedicated to the experimental challenges in this endeavor. In particular I will discuss processing and calibration of the data taken by the Time Projection Chamber (TPC), which is the main sub-detector used in this analysis.