Contribution of low-lying vector resonances to polarization observables in \bar B_d^0 -> \bar K*0 e+ e- decay

TL;DR

This paper analyzes how low-lying vector resonances affect polarization observables in the rare decay _d^0  K*^0 e+ e-, providing theoretical predictions relevant for upcoming LHCb measurements.

Contribution

It introduces a detailed calculation of resonance contributions to decay observables, enhancing understanding of their impact on polarization and angular distributions in _d^0 decay.

Findings

Resonances significantly influence polarization fractions.

Resonance effects alter angular distribution coefficients.

Predictions aid future experimental analyses at LHCb.

Abstract

The branching ratio and other observables for the rare flavour-changing neutral current decay \bar B_d^0 -> \bar K*0 (-> K- pi+) e+ e- are studied below the \bar{c} c threshold. The total amplitude for this decay includes the term coming from the standard model effective Hamiltonian and the term generated by the processes \bar B_d^0 -> \bar K*0 (-> K- pi+) V with intermediate low-lying vector resonances V = rho(770), omega(782), phi(1020) decaying into the e+ e- pair. The resonance contribution to the branching ratio, polarization fractions of the K* meson and coefficients in the angular distribution is calculated. The influence of the resonances on the integrated observables in the region of electron-positron invariant mass up to 1 GeV is studied in view of the planned measurements of the photon polarization at the LHCb.