Angular analysis of the B+ → π+μ+μ− decay

A bstract This paper presents the first measurement of the forward-backward asymmetry, A FB , and the flat term, F H , that parameterise the angular distribution of the B + → π + μ + μ − decay. The proton-proton collision dataset used in the analysis corresponds to an integrated luminosity of 9 fb − 1 , collected with the LHCb experiment between 2011 and 2018. The analysis is performed in two intervals of dimuon mass squared, one above and one below the region containing the J/ψ and ψ (2 S ) narrow charmonium resonances. The Standard Model predictions lie within the obtained 68% confidence level interval in the high-mass and within the 99% interval in the low-mass region.