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  • Letter
  • Open Access

Interpreting LHCb’s Λb→Λcτν¯ measurement and puzzles in semileptonic Λb decays

Florian U. Bernlochner1, Zoltan Ligeti2,3, Michele Papucci4, and Dean J. Robinson2,3

  • 1Physikalisches Institut der Rheinischen Friedrich-Wilhelms-Universität Bonn, 53115 Bonn, Germany
  • 2Ernest Orlando Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720, USA
  • 3Berkeley Center for Theoretical Physics, Department of Physics, University of California, Berkeley, California 94720, USA
  • 4Burke Institute for Theoretical Physics, California Institute of Technology, Pasadena, California 91125, USA

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Phys. Rev. D 107, L011502 – Published 11 January, 2023

DOI: https://doi.org/10.1103/PhysRevD.107.L011502

Abstract

Normalizing the recent LHCb measurement of Λb→Λcτν¯ to the standard model (SM) prediction for the Λb→Λcμν¯ rate, instead of a LEP measurement, provides a more consistent comparison with the SM prediction for the lepton flavor universality ratio R(Λc). This modestly increases R(Λc) compared to the quoted LHCb result, such that it no longer hints at a suppression compared to the SM, which would be hard to accommodate in new physics scenarios that enhance R(D(*)). We point out that the fraction of excited states in inclusive semileptonic Λb decay may be significantly greater than the corresponding fraction in B decays. Possible implications are speculated upon.

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Phys. Rev. D 107, L011502– Published 11 January, 2023
  • Received 7 July 2022
  • Accepted 21 December 2022
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