Publication

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

Aurelio Bay
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, A FB , and the flatness parameter, F H , 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.

Official source

https://infoscience.epfl.ch/entities/publication/c89a1c8d-2ebf-4169-a514-af902e02be4b

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Aurelio Bay
2026

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/c89a1c8d-2ebf-4169-a514-af902e02be4b

About this result

Related concepts (32)

LHCb experiment

The LHCb (Large Hadron Collider beauty) experiment is a particle physics detector experiment collecting data at the Large Hadron Collider at CERN. LHCb is a specialized b-physics experiment, designed primarily to measure the parameters of CP violation in the interactions of b-hadrons (heavy particles containing a bottom quark). Such studies can help to explain the matter-antimatter asymmetry of the Universe. The detector is also able to perform measurements of production cross sections, exotic hadron spectroscopy, charm physics and electroweak physics in the forward region.

Angular momentum operator

In quantum mechanics, the angular momentum operator is one of several related operators analogous to classical angular momentum. The angular momentum operator plays a central role in the theory of atomic and molecular physics and other quantum problems involving rotational symmetry. Such an operator is applied to a mathematical representation of the physical state of a system and yields an angular momentum value if the state has a definite value for it.

Standard Model

The Standard Model of particle physics is the theory describing three of the four known fundamental forces (electromagnetic, weak and strong interactions – excluding gravity) in the universe and classifying all known elementary particles. It was developed in stages throughout the latter half of the 20th century, through the work of many scientists worldwide, with the current formulation being finalized in the mid-1970s upon experimental confirmation of the existence of quarks.

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

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