Lepton Flavor Universality in Semileptonic $\Lambda_c^+$ Decays at Belle II

by Lukas Bierwirth (TUM)

Thursday May 15, 2025, 9:30 AM → 10:30 AM Europe/Berlin

E18/ENE Seminar Room 3268 (TUM PH)

In this talk I present a model-independent test of Lepton Flavor Universality (LFU) in the light-lepton sector using semileptonic $\Lambda_c^+$ decays at the Belle II experiment. In the Standard Model (SM) of particle physics, LFU dictates that all leptons interact equally with electroweak gauge bosons. Any deviation from LFU could indicate the presence of new physics beyond the SM. 

The analysis is based on 10 % of the available $e^+e^-$ annihilation dataset recorded at a center-of-mass energy of 10.59 GeV between 2019 and 2022, corresponding to a total integrated luminosity of 362 1/fb.
We measure the branching fraction ratio:

 

ℛ(μ/e) = ℬ($\Lambda_c^+$ → $\Lambda$ μ+ ν) / ℬ($\Lambda_c^+$ → $\Lambda$ e+ ν) = 0.96 ± 0.29(stat) ± 0.04(sys)

which is consistent with the SM prediction of ℛ(μ/e) = 0.968 ± 0.003 and shows no evidence of new physics. The dominant systematic uncertainty arises from lepton identification.