Multi-strange baryon production in pp collisions at √s = 7 TeV with ALICE

Submission Date: 
02/04/2012
Article Information
Submission Form
System: 
p-p
Energy: 
7 TeV
Abstract Plain Text: 

A measurement of the multi-strange Xi and Omega baryons and their antiparticles by the ALICE experiment at the CERN Large Hadron Collider (LHC) is presented for inelastic proton-proton collisions at centre of mass energy of 7 TeV. The transverse momentum (pt) distributions were studied at mid-rapidity (|y| < 0.5) in the range of 0.6 < pt < 8.5 GeV/c for Xi− and Xi+ baryons, and in the range of 0.8 < pt < 5 GeV/c for Omega− and Omega+. Baryons and antibaryons were measured as separate particles and we find that the baryon to antibaryon ratio of both particle species is consistent with unity over the entire range of the measurement. The statistical precision of the current LHC data has allowed us to measure a difference between the mean pt of Xi− (Xi+) and Omega− (Omega+). Particle yields, mean pt, and the spectra in the intermediate pt range are not well described by the PYTHIA Perugia 2011 tune Monte Carlo event generator, which has been tuned to reproduce the early LHC data. The discrepancy is largest for Omega-(Omega+). This PYTHIA tune approaches the pt spectra of Xi− and Xi+ baryons below pt < 0.85 GeV/c and describes the Xi− and Xi+ spectra above pt > 6.0 GeV/c. We also illustrate the difference between the experimental data and model by comparing the corresponding ratios of (Omega- + Omega+)/ (Xi− +Xi+) as a function of transverse mass.