Charged-particle pseudorapidity density at mid-rapidity in p–Pb collisions at $$\pmb {\sqrt{s_{\scriptscriptstyle {\mathrm{NN}}}}}$$ = 8.16 TeV
The pseudorapidity density of charged particles, dNch/dη, in p–Pb collisions has been measured at a centre-of-mass energy per nucleon–nucleon pair of $$\sqrt{s_{NN}}$$ = 8.16 TeV at mid-pseudorapidity for non-single-diffractive events. The results cover 3.6 units of pseudorapidity, |η|<1.8. The dNch/dη value is 19.1±0.7 at |η|<0.5. This quantity divided by $$\langle$$Npart$$\rangle$$ / 2 is 4.73±0.20, where $$\langle$$Npart$$\rangle$$is the average number of participating nucleons, is 9.5% higher than the corresponding value for p–Pb collisions at $$\sqrt{s_{NN}}$$ = 5.02 TeV. Measurements are compared with models based on different mechanisms for particle production. All models agree within uncertainties with data in the Pb-going side, while HIJING overestimates, showing a symmetric behaviour, and EPOS underestimates the p-going side of the dNch/dη distribution. Saturation-based models reproduce the distributions well for η>-1.3. The dNch/dη is also measured for different centrality estimators, based both on the charged-particle multiplicity and on the energy deposited in the Zero-Degree Calorimeters. A study of the implications of the large multiplicity fluctuations due to the small number of participants for systems like p–Pb in the centrality calculation for multiplicity-based estimators is discussed, demonstrating the advantages of determining the centrality with energy deposited near beam rapidity.
- Research Organization:
- Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Nuclear Physics (NP)
- Contributing Organization:
- ALICE Collaboration
- Grant/Contract Number:
- AC02-05CH11231; AC05-00OR22725
- OSTI ID:
- 1546662
- Alternate ID(s):
- OSTI ID: 1564134
- Journal Information:
- European Physical Journal. C, Particles and Fields, Vol. 79, Issue 4; ISSN 1434-6044
- Publisher:
- SpringerCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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