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.| File | Dimensione | Formato | |
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JHEP04(2026)170.pdf
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