9th International Workshop on Multiple Partonic Interactions at the LHC

System size dependence of particle production in pp, p-Pb and Pb-Pb collisions at 5.02 TeV

12 Dec 2017, 12:15

15m

Conference Hall (Hotel Peterhoff, Shimla, India)

WG6: Interactions with Nuclei

Speaker

Dr Ajay Kumar Dash (National Institute of Science Education and Research, Jatni)

Description

The ALICE collaboration has measured the production of light-flavour hadrons in pp, p--Pb and Pb--Pb collisions at$\sqrt{s{}_{\mathrm{N}\mathrm{N}}}=$ 5.02 TeV over a wide range of transverse momentum ($p_{\mathrm{T}}$). The results on $\pi$, K, p,K${}^{\ast 0}$ and $\varphi$ $p_{\mathrm{T}}$ spectra, ratios of the $p_{\mathrm{T}}$-integrated yields and mean transverse momentum will be presented for the three colliding systems at the same energy ($\sqrt{s_{\mathrm{N}\mathrm{N}}}$ = 5.02 TeV), and compared as a function of average charged particle multiplicity measured at mid-rapidity. It will be shown that the production of these particles follows a continuous trend as a function of multiplicity across the three systems. Identified particle ratios provide information on the composition and the thermal properties of the medium. The measurement of short-lived hadronic resonance production and their ratio to stable hadron species, such as $\varphi /$K and K${}^{\ast 0}/$K, is used to infer information on the hadronic phase.

Parton energy loss is investigated by determining the nuclear modification factor ($R{}_{\mathrm{AA}}$). The production of light-flavour hadrons in the most central Pb--Pb collisions relative to pp collisions is found to be strongly suppressed at high $p{}_{\mathrm{T}}$ ($>$ 8 GeV/$c$), whereas in p--Pb collisions the nuclear modification factors are consistent with unity. This indicates that the strong suppression of high-$p{}_{\mathrm{T}}$ hadrons measured in central Pb--Pb collisions is not due to an initial state effect but instead to the energy loss of partons traversing a hot and dense QCD medium. A similar suppression is observed for all the measured light-flavour hadrons at $p{}_{\mathrm{T}}$ $>$ 8 GeV/$c$. This suggests that the partonic energy loss in the medium for light quark flavors ($u,d,s$) is independent of flavour.

Presentation materials

3.pdf