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Observation of a Λ b 0 − Λ ¯ b 0 production asymmetry in proton-proton collisions at s = 7 and 8 TeV

Published version
Peer-reviewed

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Authors

Aaij, R. 
Abdelmotteleb, A. S. W. 
Abellán Beteta, C. 
Ackernley, T. 
Adeva, B. 

Abstract

Abstract: This article presents differential measurements of the asymmetry between Λb0 and Λ¯b0 baryon production rates in proton-proton collisions at centre-of-mass energies of s = 7 and 8 TeV collected with the LHCb experiment, corresponding to an integrated luminosity of 3 fb−1. The Λb0 baryons are reconstructed through the inclusive semileptonic decay Λb0 → Λc+μ−ν¯μX. The production asymmetry is measured both in intervals of rapidity in the range 2.15 < y < 4.10 and transverse momentum in 2 < pT< 27 GeV/c. The results are found to be incompatible with symmetric production with a significance of 5.8 standard deviations for both s = 7 and 8 TeV data, assuming no CP violation in the decay. There is evidence for a trend as a function of rapidity with a significance of 4 standard deviations. Comparisons to predictions from hadronisation models in Pythia and heavy-quark recombination are provided. This result constitutes the first observation of a particle-antiparticle asymmetry in b-hadron production at LHC energies.

Description

Keywords

Regular Article - Experimental Physics, Hadron-Hadron scattering (experiments), Heavy quark production, proton-proton scattering, Hard scattering, B physics

Journal Title

Journal of High Energy Physics

Conference Name

Journal ISSN

1029-8479

Volume Title

2021

Publisher

Springer Berlin Heidelberg