The normalised decay rate of B+ -> J/Psi(-> mu+mu-)K+ is measured as a function of the lepton helicity angle using a data sample corresponding to an integrated luminosity of 1.1 fb-1 collected during October 2024 with the upgraded (Upgrade I) LHCb detector. This angular distribution can be parameterised by two coefficients, the forward-backward asymmetry, AFB, and the flatness parameter, FH, whose values are constrained by conservation of angular momentum. These coefficients are measured both integrated and differentially across various kinematic and detector-response variables, and the results are found to be in good agreement with expectations. These measurements show that the detector response of the LHCb Upgrade I experiment is understood to the precision required to reliably extract the angular coefficients associated with rare b ->smu+mu- and b → dmu+mu- transitions, which are particularly sensitive to physics beyond the Standard Model.

Differential decay rate of B+-> J/Psi K+ with the LHCb Upgrade I experiment

Celestino I.
Membro del Collaboration Group
;
Cordova G.
Membro del Collaboration Group
;
Kleijne N.
Membro del Collaboration Group
;
Morello M. J.
Membro del Collaboration Group
;
Passaro D.
Membro del Collaboration Group
;
Pica L.
Membro del Collaboration Group
;
Riccardi D.
Membro del Collaboration Group
;
Xu A.
Membro del Collaboration Group
;
2026

Abstract

The normalised decay rate of B+ -> J/Psi(-> mu+mu-)K+ is measured as a function of the lepton helicity angle using a data sample corresponding to an integrated luminosity of 1.1 fb-1 collected during October 2024 with the upgraded (Upgrade I) LHCb detector. This angular distribution can be parameterised by two coefficients, the forward-backward asymmetry, AFB, and the flatness parameter, FH, whose values are constrained by conservation of angular momentum. These coefficients are measured both integrated and differentially across various kinematic and detector-response variables, and the results are found to be in good agreement with expectations. These measurements show that the detector response of the LHCb Upgrade I experiment is understood to the precision required to reliably extract the angular coefficients associated with rare b ->smu+mu- and b → dmu+mu- transitions, which are particularly sensitive to physics beyond the Standard Model.
2026
Settore FIS/01 - Fisica Sperimentale
Settore PHYS-01/A - Fisica sperimentale delle interazioni fondamentali e applicazioni
B Physics; Flavour Physics; Hadron-Hadron Scattering; Rare Decay
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11384/167784
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