First experimental study of photon polarization in radiative $B^{0}_{s}$ decays

TL;DR

This study presents the first experimental measurement of photon polarization in radiative $B^{0}_{s}$ decays, providing insights into the $b o s \, ext{gamma}$ transition and testing Standard Model predictions.

Contribution

It is the first to measure photon polarization in $B^{0}_{s}$ decays using time-dependent analysis, offering new experimental data on polarization amplitudes.

Findings

Measured ${\\mathcal{A}}^\\Delta$ as -0.98 with uncertainties.

Result consistent with Standard Model within two standard deviations.

Provides the first experimental insight into photon polarization in $B^{0}_{s}$ decays.

Abstract

The polarization of photons produced in radiative $B^{0}_{s}$ decays is studied for the first time. The data are recorded by the LHCb experiment in $pp$ collisions corresponding to an integrated luminosity of 3fb$^{-1}$ at center-of-mass energies of $7$ and $8$TeV. A time-dependent analysis of the $B^{0}_{s} \to \phi \gamma$ decay rate is conducted to determine the parameter ${\mathcal{A}}^\Delta$, which is related to the ratio of right- over left-handed photon polarization amplitudes in $b \to s \gamma$ transitions. A value of ${\mathcal{A}}^\Delta=-0.98^{\,+0.46\,+0.23}_{\,-0.52\,-0.20}$ is measured. This result is consistent with the Standard Model prediction within two standard deviations.