Observation of a $$ {\varLambda}_b^0 $$ − $$ {\overline{\varLambda}}_b^0 $$ production asymmetry in proton-proton collisions at $$ \sqrt{s} $$ = 7 and 8 TeV

Journal article

A bstract This article presents differential measurements of the asymmetry between $$ {\varLambda}_b^0 $$ Λb0 and $$ {\overline{\varLambda}}_b^0 $$ Λ¯b0 baryon production rates in proton-proton collisions at centre-of-mass energies of $$ \sqrt{s} $$ s = 7 and 8 TeV collected with the LHCb experiment, corresponding to an integrated luminosity of 3 fb − 1 . The $$ {\varLambda}_b^0 $$ Λb0 baryons are reconstructed through the inclusive semileptonic decay $$ {\varLambda}_b^0 $$ Λb0 → $$ {\varLambda}_c^{+} $$ Λc+ μ − $$ \overline{\nu} $$ ν¯ μ X . 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 $$ \sqrt{s} $$ 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 P ythia and heavy-quark recombination are provided. This result constitutes the first observation of a particle-antiparticle asymmetry in b -hadron production at LHC energies.

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

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Springer
• Journal: Journal of High Energy Physics
• Volume: 2021
• Issue: 10
• Pages: 60
• Article number: 60
• Publication date: 2021-10-07
• DOI: 10.1007/jhep10(2021)060
• EISSN: 1029-8479
• ISSN: 1126-6708
• Language: English
• Keywords: Hadron; Physics; Overline; Asymmetry; Nuclear physics; Production (economics); Luminosity; Rapidity; Particle physics; Astrophysics; Baryon; Proton