Observation of a Lambda(0)(b) - (Lambda)over-bar(b)(0) production asymmetry in proton-proton collisions at root s=7 and 8 TeV

LHCb collaboration, Sascha Stahl*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


This article presents differential measurements of the asymmetry between Lambda(0)(b) and (Lambda) over bar (0)(b) baryon production rates in proton-proton collisions at centre-of-mass energies of root s = 7 and 8 TeV collected with the LHCb experiment, corresponding to an integrated luminosity of 3 fb(-1). The Lambda(0)(b) baryons are reconstructed through the inclusive semileptonic decay Lambda(0)(b) -> Lambda(+)(c) mu(-)(nu) over bar X-mu. The production asymmetry is measured both in intervals of rapidity in the range 2:15 < y < 4:10 and transverse momentum in 2 < p T < 27 GeV/c. The results are found to be incompatible with symmetric production with a significance of 5.8 standard deviations for both root 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.
Original languageEnglish
Article number060
Number of pages38
JournalJournal of High Energy Physics
Issue number10
Publication statusPublished - 7 Oct 2021


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

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