Strong constraints on the <i>b</i> → <i>sγ</i> photon polarisation from <i>B</i><SUP>0</SUP> → <i>K</i><SUP>*0</SUP><i>e</i><SUP>+</SUP><i>e<SUP>-</SUP></i> decays



Aaij, R, Beteta, C Abellan, Adeva, B, Adinolfi, M, Aidala, CA, Ajaltouni, Z, Akar, S, Albicocco, P, Albrecht, J, Alessio, F
et al (show 834 more authors) (2020) Strong constraints on the <i>b</i> → <i>sγ</i> photon polarisation from <i>B</i><SUP>0</SUP> → <i>K</i><SUP>*0</SUP><i>e</i><SUP>+</SUP><i>e<SUP>-</SUP></i> decays. JOURNAL OF HIGH ENERGY PHYSICS, 12 (12). 081-.

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Abstract

An angular analysis of the $B^0 \to K^{*0} e^+ e^-$ decay is performed using a data sample corresponding to an integrated luminosity of $9~{\rm fb}^{-1}$ of $pp$ collisions collected with the LHCb experiment. The analysis is conducted in the very low dielectron mass squared ($q^2$) interval between $0.0008$ and $0.257~{\rm GeV}^2$, where the rate is dominated by the $B^0\to K^{\ast 0}\gamma$ transition with a virtual photon. The fraction of longitudinal polarisation of the $K^{\ast 0}$ meson, $F_{\rm L}$, is measured to be $F_{\rm L} = (4.4 \pm 2.6 \pm 1.4)\%$, where the first uncertainty is statistical and the second systematic. The $A_{\rm T}^{\rm Re}$ observable, which is related to the lepton forward-backward asymmetry, is measured to be $A_{\rm T}^{\rm Re}=-0.06 \pm 0.08 \pm 0.02$. The $A_{\rm T}^{(2)}$ and $A_{\rm T}^{\rm Im}$ transverse asymmetries, which are sensitive to the virtual photon polarisation, are found to be $A_{\rm T}^{(2)} = 0.11 \pm 0.10 \ \pm 0.02$ and $A_{\rm T}^{\rm Im} = 0.02 \pm 0.10 \pm 0.01$. The results are consistent with Standard Model predictions and provide the world's best constraint on the $b\to s\gamma$ photon polarisation.

Item Type: Article
Additional Information: All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2020-020.html (LHCb public pages)
Uncontrolled Keywords: Rare decay, Flavour Changing Neutral Currents, Polarization, B physics, Hadron-Hadron scattering (experiments)
Divisions: Faculty of Science and Engineering > School of Physical Sciences
Depositing User: Symplectic Admin
Date Deposited: 01 Sep 2021 10:36
Last Modified: 14 Mar 2024 23:05
DOI: 10.1007/JHEP12(2020)081
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3134996