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Strong constraints on the b → sγ photon polarisation from B 0 → K *0 e + e − decays

Published version
Peer-reviewed

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Authors

Aaij, R. 
Abellán Beteta, C. 
Ackernley, T. 
Adeva, B. 
Adinolfi, M. 

Abstract

Abstract: An angular analysis of the B0 → K0e+e− decay is performed using a data sample corresponding to an integrated luminosity of 9 fb−1 of pp collisions collected with the LHCb experiment. The analysis is conducted in the very low dielectron mass squared (q2) interval between 0.0008 and 0.257 GeV2, where the rate is dominated by the B0 → K0γ transition with a virtual photon. The fraction of longitudinal polarisation of the K*0 meson, FL, is measured to be FL = (4.4 ± 2.6 ± 1.4)%, where the first uncertainty is statistical and the second systematic. The ATRe observable, which is related to the lepton forward-backward asymmetry, is measured to be ATRe = −0.06 ± 0.08 ± 0.02. The AT2 and ATIm transverse asymmetries, which are sensitive to the virtual photon polarisation, are found to be AT2 = 0.11 ± 0.10 ± 0.02 and ATIm = 0.02 ± 0.10 ± 0.01. The results are consistent with Standard Model predictions and provide the world’s best constraint on the b → sγ photon polarisation.

Description

Keywords

Regular Article - Experimental Physics, Rare decay, Flavour Changing Neutral Currents, Polarization, B physics, Hadron-Hadron scattering (experiments)

Journal Title

Journal of High Energy Physics

Conference Name

Journal ISSN

1029-8479

Volume Title

2020

Publisher

Springer Berlin Heidelberg