English

Interpreting LHCb's $\Lambda_b\to \Lambda_c\tau\bar\nu$ measurement and puzzles in semileptonic $\Lambda_b$ decays

High Energy Physics - Phenomenology 2023-01-25 v1

Abstract

Normalizing the recent LHCb measurement of ΛbΛcτνˉ\Lambda_b \to \Lambda_c \tau \bar\nu to the standard model (SM) prediction for the ΛbΛcμνˉ\Lambda_b \to \Lambda_c \mu \bar\nu rate, instead of a LEP measurement, provides a more consistent comparison with the SM prediction for the lepton flavor universality ratio R(Λc)R(\Lambda_c). This modestly increases R(Λc)R(\Lambda_c) 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())R(D^{(*)}). We point out that the fraction of excited states in inclusive semileptonic Λb\Lambda_b decay may be significantly greater than the corresponding fraction in BB decays. Possible implications are speculated upon.

Keywords

Cite

@article{arxiv.2206.11282,
  title  = {Interpreting LHCb's $\Lambda_b\to \Lambda_c\tau\bar\nu$ measurement and puzzles in semileptonic $\Lambda_b$ decays},
  author = {Florian U. Bernlochner and Zoltan Ligeti and Michele Papucci and Dean J. Robinson},
  journal= {arXiv preprint arXiv:2206.11282},
  year   = {2023}
}

Comments

3 pages

R2 v1 2026-06-24T12:00:39.957Z