Production of pions, kaons and protons in pp collisions at $\sqrt{s}= 900~\mathrm{GeV}$ with ALICE at the LHC

TLDR

The ALICE experiment identified charged pions, kaons, and protons using specific energy loss in the silicon tracker and TPC, time‑of‑flight for higher momenta, and kaon decay kink topology, combining these methods to extract transverse‑momentum spectra from 100 MeV/c to 2.5 GeV/c. Measured mid‑rapidity spectra of π±, K±, p, and p̄ at √s = 900 GeV show that QCD‑inspired models poorly describe the data, while total yields and mean pT follow the energy‑dependent trends observed in earlier experiments.

Abstract

The production of $\pi^+$, $\pi^-$, $K^+$, $K^-$, p, and pbar at mid-rapidity has been measured in proton-proton collisions at $\sqrt{s} = 900$ GeV with the ALICE detector. Particle identification is performed using the specific energy loss in the inner tracking silicon detector and the time projection chamber. In addition, time-of-flight information is used to identify hadrons at higher momenta. Finally, the distinctive kink topology of the weak decay of charged kaons is used for an alternative measurement of the kaon transverse momentum ($p_{\rm T}$) spectra. Since these various particle identification tools give the best separation capabilities over different momentum ranges, the results are combined to extract spectra from $p_{\rm T}$ = 100 MeV/$c$ to 2.5 GeV/$c$. The measured spectra are further compared with QCD-inspired models which yield a poor description. The total yields and the mean $p_{\rm T}$ are compared with previous measurements, and the trends as a function of collision energy are discussed.