Wednesday, May 8, 2013

1305.1562 (ALICE Collaboration)

Mid-rapidity anti-baryon to baryon ratios in pp collisions at sqrt(s) =
0.9, 2.76 and 7 TeV measured by ALICE

ALICE Collaboration
The ratios of yields of anti-baryons to baryons probes the mechanisms of baryon-number transport. Results for anti-p/p, anti-\Lambda/\Lambda, anti-\Xi+/\Xi- and anti-\Omega+/\Omega- in pp collisions at sqrt(s) = 0.9, 2.76 and 7TeV, measured with the ALICE detector at the LHC, are reported. Within the experimental uncertainties and ranges covered by our measurement, these ratios are independent of rapidity, transverse momentum and multiplicity for all measured energies. The results are compared to expectations from event generators, such as PYTHIA and HIJING/B, that are used to model the particle production in pp collisions. The energy dependence of anti-p/p, anti-\Lambda/\Lambda, anti-\Xi+/\Xi- and anti-\Omega+/\Omega-, reaching values compatible with unity for sqrt(s) = 7TeV, complement the earlier anti-p/p measurement of ALICE. These dependencies can be described by exchanges with the Regge-trajectory intercept of \alpha_j ~ 0.5, which are suppressed with increasing rapidity interval \Delta y. Any significant contribution of an exchange not suppressed at large \Delta y (reached at LHC energies) is disfavoured.
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