The normalised decay rate of B+ → J/ψ(→ μ+μ−)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 → sμ+μ− and b → dμ+μ− transitions, which are particularly sensitive to physics beyond the Standard Model. [The LHCb collaboratio]

Differential decay rate of B+ → J/ψK+ with the LHCb Upgrade I experiment / R. Aaij, A.S.W.A.. - In: JOURNAL OF HIGH ENERGY PHYSICS. - ISSN 1029-8479. - 2026:4(2026 Apr 22), pp. 170.1-170.30. [10.1007/jhep04(2026)170]

Differential decay rate of B+ → J/ψK+ with the LHCb Upgrade I experiment

S. Cesare;C. Mancuso;D. Marangotto;N. Neri;G. Tonani;T. Tork;Z. Wang;
2026

Abstract

The normalised decay rate of B+ → J/ψ(→ μ+μ−)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 → sμ+μ− and b → dμ+μ− transitions, which are particularly sensitive to physics beyond the Standard Model. [The LHCb collaboratio]
B Physics; Flavour Physics; Hadron-Hadron Scattering; Rare Decay;
Settore PHYS-01/A - Fisica sperimentale delle interazioni fondamentali e applicazioni
   European Particle physics Latin American NETwork
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22-apr-2026
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/1250739
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