Journal Article

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

Olivares, M. E., Vorobyev, V., Chefdeville, M., Alexander, M., Jones, C. R., Durante, P., Malczewski, J. J., Gao, Y., Eschle, J., Brossa Gonzalo, A., Yang, Z., Petric, M., Cardinale, R., Meinert, N., Mead, J. V., Barlow, R. J., Schmelling, M., Vázquez Sierra, C., Cai, H., Bedeschi, F., Swientek, K., Yang, Y., Millard, E., Pugatch, V., Ketel, T., Bobulska, D., Ferro-Luzzi, M., Lefèvre, R., Zhang, S., Solovev, A., Golubkov, D., Passalacqua, B., Terentev, A., Lampis, A., Dalseno, J., Jawahery, A., Lai, A., Schneider, O., Rama, M., Bozzi, C., Carniti, P., Tran, M. T., Fontana, M., Straticiuc, M., Ene, A., Tanner, A. R., Smith, E., Zhou, X., Gibson, V., Mulder, M., Ramos Pernas, M., Jiang, F., Hollitt, S. E., Bezshyiko, Ia, Ribatti, R., Bertella, C., Tuning, N., Zharkova, A., Cobbledick, J. L., Kvaratskheliya, T., Morris, A. B., Carboni, G., Downes, A. G., Zenaiev, O., Puill, V., Didenko, S., Calero Diaz, L., McNulty, R., Baldini, W., Ponce, S., Karacson, M., Nguyen-Mau, C., Marshall, A. M., Bian, L., Decamp, D., Hancock, T. H., Brea Rodriguez, A., Skidmore, N., Chulikov, V., Romanovskiy, V., Malecki, B., Cadeddu, S., Pappagallo, M., Nanut, T., Materok, M

2021

Overview

A bstract This article presents differential measurements of the asymmetry between Λ b 0 and Λ ¯ b 0 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 Λ b 0 baryons are reconstructed through the inclusive semileptonic decay Λ b 0 → Λ c + μ − 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 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.

• Publisher: Springer Berlin Heidelberg,Springer Nature B.V
• Subject: Asymmetry / Baryons / Classical and Quantum Gravitation / CP violation / Decay / Elementary Particles / High energy physics / Large Hadron Collider / Luminosity / Particle collisions / Physics / Physics and Astronomy / Protons / Quantum Field Theories / Quantum Field Theory / Quantum Physics / Regular Article - Experimental Physics / Relativity Theory / Standard deviation / String Theory / Transverse momentum