# Pseudorapidity density of charged particles in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV

The charged-particle pseudorapidity density measured over 4 units of pseudorapidity in non-single-diffractive (NSD) p-Pb collisions at a centre-of-mass energy per nucleon pair $\sqrt{s_{\rm NN}} = 5.02$ TeV is presented. The average value at midrapidity is measured to be $16.81 \pm 0.71$ (syst.), which corresponds to $2.14 \pm 0.17$ (syst.) per participating nucleon. This is 16% lower than in NSD pp collisions interpolated to the same collision energy, and 84% higher than in d-Au collisions at $\sqrt{s_{\rm NN}} = 0.2$ TeV. The measured pseudorapidity density in p-Pb collisions is compared to model predictions, and provides new constraints on the description of particle production in high-energy nuclear collisions.

Figures

## Figure 1

 Pseudorapidity density of charged particles measured in NSD p-Pb collisions at $\snn=5.02$ TeVcompared to theoretical predictions . The calculations have beenshifted to the laboratory system.

## Figure 2

 Charged-particle pseudorapidity density at midrapidity normalized to the number of participants,calculated with the Glauber model,for p-Pb, p-Au and d-Au collisions as a function of $\snn$, comparedto NSD ,and inelastic pp ($\ppbar$) collisions,as well as central heavy-ion collisions The curves $\propto s_{\rm NN}^{0.11}$ and $s_{\rm NN}^{0.15}$ (from ) are superimposedon the NSD pp ($\ppbar$) and central heavy-ion data, respectively, while$\propto s_{\rm NN}^{0.10}$ (from ) on the inelastic pp ($\ppbar$) data.