Centrality Dependence of the Charged-Particle Multiplicity Density at Midrapidity in Pb-Pb Collisions at √sNN= = 5.02 TeV

İngilizce (OpenAlex)

The pseudorapidity density of charged particles, $d{N}_{\mathrm{ch}}/d\ensuremath{\eta}$, at midrapidity in Pb-Pb collisions has been measured at a center-of-mass energy per nucleon pair of $\sqrt{{s}_{NN}}=5.02\text{ }\text{ }\mathrm{TeV}$. For the 5% most central collisions, we measure a value of $1943\ifmmode\pm\else\textpm\fi{}54$. The rise in $d{N}_{\mathrm{ch}}/d\ensuremath{\eta}$ as a function of $\sqrt{{s}_{NN}}$ is steeper than that observed in proton-proton collisions and follows the trend established by measurements at lower energy. The increase of $d{N}_{\mathrm{ch}}/d\ensuremath{\eta}$ as a function of the average number of participant nucleons, $⟨{N}_{\text{part}}⟩$, calculated in a Glauber model, is compared with the previous measurement at $\sqrt{{s}_{NN}}=2.76\text{ }\text{ }\mathrm{TeV}$. A constant factor of about 1.2 describes the increase in $d{N}_{\mathrm{ch}}/d\ensuremath{\eta}$ from $\sqrt{{s}_{NN}}=2.76$ to 5.02 TeV for all centrality classes, within the measured range of 0%--80% centrality. The results are also compared to models based on different mechanisms for particle production in nuclear collisions.