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Branching fraction measurement of the Λ → pμ- ν[bar]μ decay

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A measurement of the branching fraction for the decay $$ \Lambda \to p{\mu}^{-}{\overline{\nu}}_{\mu } $$is presented using pp collision data collected by the LHCb experiment at a centre-of-mass energy of 13 TeV. The analysis is based on data recorded between 2016 and 2018, corresponding to an integ...

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Main Authors: Aaij, Roel (Author) , Bachmann, Sebastian (Author) , Carus, Leon (Author) , Caspary, Rowina (Author) , Celani, Sara (Author) , Cocha Toapaxi, Carlos (Author) , Dittmann, Lucas (Author) , Glaser, Fabian (Author) , Han, Xiaoxue (Author) , Hansmann-Menzemer, Stephanie (Author) , Herrero Gascón, Paula (Author) , Langenbruch, Christoph (Author) , Leverington, Blake (Author) , Marks, Jörg (Author) , Morgenthaler, Maurice Pierre (Author) , Ruiz Diaz, Miguel (Author) , Schiller, Manuel (Author) , Tat, Martin Duy (Author) , Tuci, Giulia (Author) , Uecker, Lennart Henning (Author) , Uwer, Ulrich (Author) , Wang, Chishuai (Author) , Wolf, Tom (Author) , Zhao, Ya (Author) , Zhelezov, Alexey (Author)
Corporate Author: LHCb Collaboration (Author)
Format: Article (Journal)
Language:English
Published: 14 April 2026
In: Journal of high energy physics
Year: 2026, Issue: 4, Pages: 1-27
ISSN:1029-8479
DOI:10.1007/JHEP04(2026)096
Online Access:Verlag, kostenfrei, Volltext: https://doi.org/10.1007/JHEP04(2026)096
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Author Notes:the LHCb collaboration*
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Summary:A measurement of the branching fraction for the decay $$ \Lambda \to p{\mu}^{-}{\overline{\nu}}_{\mu } $$is presented using pp collision data collected by the LHCb experiment at a centre-of-mass energy of 13 TeV. The analysis is based on data recorded between 2016 and 2018, corresponding to an integrated luminosity of 5.4 fb−1. The result is obtained using Λ → pμ− decays as a normalisation channel. The measured branching fraction is $$ \mathcal{B}\left(\Lambda \to p{\mu}^{-}{\overline{\nu}}_{\mu}\right)=\left(1.462\pm 0.016\pm 0.100\pm 0.011\right)\times {10}^{-4} $$, where the uncertainties are statistical, systematic, and due to the limited knowledge of the normalisation mode branching fraction, respectively. This result improves the precision of the branching fraction measurement by a factor of two compared to the previous best measurement and sets a more stringent bound on lepton flavour universality in s → u quark transitions. It is consistent with previous measurements, and the extracted lepton flavour universality test observable, $$ {R}^{\mu e}=\frac{\Gamma \left(\Lambda \to p{\mu}^{-}{\overline{\nu}}_{\mu}\right)}{\Gamma \left(\Lambda \to p{e}^{-}{\overline{\nu}}_e\right)}=0.175\pm 0.012 $$, agrees with the Standard Model prediction.
Item Description:Veröffentlicht: 14. April 2026
*The LHCb collaboration: R. Aaij, S. Bachmann, L. Carus, R. Caspary, S. Celani, C. Cocha Toapaxi, L. Dittmann, F.C. Glaser, X. Han, S. Hansmann-Menzemer, P. Herrero Gascon, C. Langenbruch, B. Leverington, J. Marks, M.P. Morgenthaler, M. Ruiz Diaz, M. Schiller, M.D. Tat, G. Tuci, L.H. Uecker, U. Uwer, C. Wang, T. Wolf, Y. Zhao, A. Zhelezov [und sehr viele weitere Personen]
Gesehen am 19.08.2026
Im Titel ist das Minuszeichen hochgestellt und das zweite [mu] tiefgestellt
Im Titel steht das v mit einem Oberstrich
Physical Description:Online Resource
ISSN:1029-8479
DOI:10.1007/JHEP04(2026)096

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