Abstract
An angular analysis of the decay Bd0 → K∗μ+μ− is presented, based on proton-proton collision data recorded by the ATLAS experiment at the LHC. The study is using 20.3 fb−1 of integrated luminosity collected during 2012 at centre-of-mass energy of sqrt{s}=8 TeV. Measurements of the K* longitudinal polarisation fraction and a set of angular parameters obtained for this decay are presented. The results are compatible with the Standard Model predictions.
Highlights
Background modesThe fit to data includes a combinatorial background component that does not peak in the mKπμμ distribution
An angular analysis of the decay Bd0 → K∗μ+μ− is presented, based on protonproton collision data recorded by the ATLAS experiment at the Large Hadron Collider (LHC)
This paper presents results following the methodology outlined in ref. [3] and the convention adopted by the LHCb Collaboration for the definition of angular observables described in ref
Summary
Three angular variables describing the decay are defined according to convention described by the LHCb Collaboration in ref. [9]: the angle between the K+ and the direction opposite to the Bd0 in the K∗ centre-of-mass frame (θK); the angle between the μ+ and the direction opposite to the Bd0 in the dimuon centre-of-mass frame (θL); and the angle between the two decay planes formed by the Kπ and the dimuon systems in the Bd0 rest frame (φ). FL is the fraction of longitudinally polarised K∗ mesons and the Si are angular coefficients These angular parameters are functions of the real and imaginary parts of the transversity amplitudes of Bd0 decays into K∗μ+μ−. It is possible to reduce the theoretical uncertainty in these predictions by transforming the Si using ratios constructed to cancel form factor uncertainties at leading order The ATLAS experiment at the LHC is a general-purpose detector with a cylindrical geometry and nearly 4π coverage in solid angle [19]. It consists of an inner detector (ID).
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