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Observation of a Λb0 − Λ¯b0 production asymmetry in proton-proton collisions at √s = 7 and 8 TeV

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Aaij, R 
Abdelmotteleb, ASW 
Abellán Beteta, C 
Ackernley, T 
Adeva, B 


This article presents differential measurements of the asymmetry between Λb0 and Λb0 baryon production rates in proton-proton collisions at centre-of-mass energies of s=7 and 8TeV collected with the LHCb experiment, corresponding to an integrated luminosity of 3fb−1. The Λb0 baryons are reconstructed through the inclusive semileptonic decay Λb0→Λc+μνμX. The production asymmetry is measured both in intervals of rapidity in the range 2.15<y<4.10 and transverse momentum in 2<pT<27GeV/c. The results are found to be incompatible with symmetric production with a significance of 5.8 standard deviations for both s=7 and 8TeV 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.



Hadron-Hadron scattering (experiments), Heavy quark production, proton-proton scattering, Hard scattering, B physics

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Journal of High Energy Physics

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Springer Berlin Heidelberg