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

Abbas, E. and Abelev, B. and Adam, J. and Adamová, D. and Adare, A. M. and Aggarwal, M. M. and Aglieri, Rinella G. and Agnello, M. and Agócs, András and Agostinelli, A. and Ahammed, Z. and Ahmad, N. and Ahmad, Masoodi A. and Ahmed, I. and Ahn, S. A. and Ahn, S. U. and Aimo, I. and Ajaz, M. and Akindinov, A. and Aleksandrov, D. and Alessandro, B. and Alici, A. and Alkin, A. and Almaráz, Aviña E. and Alme, J. and Alt, T. and Altini, V. and Altinpinar, S. and Altsybeev, I. and Andrei, C. and Barnaföldi, Gergely Gábor and Bencédi, Gyula and Berényi, Dániel and Boldizsár, László and Dénes, Ervin and Hamar, Gergő and Lévai, Péter and Molnár, Levente and Pochybova, Sona (2013) Mid-rapidity anti-baryon to baryon ratios in pp collisions at √s = 0.9, 2.76 and 7 TeV measured by ALICE. EUROPEAN PHYSICAL JOURNAL C, 73 (7). ISSN 1434-6044

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Abstract

The ratios of yields of anti-baryons to baryons probes the mechanisms of baryon-number transport. Results for p/p, Λ/Λ, Ξ+/Ξ− and Ω+/Ω− in pp collisions at √s = 0.9, 2.76 and 7 TeV, 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 genera- tors, such as PYTHIA and HIJING/B, that are used to model the particle production in pp collisions. The energy dependence of p/p, Λ/Λ, Ξ+/Ξ− and Ω+/Ω−, reaching values compatible with unity for √s = 7 TeV, complement the earlier p/p measurement of ALICE. These dependencies can be described by exchanges with the Regge-trajectory intercept of αJ ≈ 0.5, which are suppressed with increasing rapidity interval ∆y. Any significant contribution of an exchange not suppressed at large ∆y (reached at LHC energies) is disfavoured.

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