Search for the decay of a B0 or B0bar meson to K*0bar K0 or K*0 K0bar

TL;DR

This study searches for rare B0 meson decays into specific kaon states, setting upper limits on their branching fractions and constraining Standard Model predictions related to CP asymmetry.

Contribution

First search for B0 decay to K*0bar K0 or K*0 K0bar with a large dataset, providing upper limits and implications for CP violation.

Findings

Branching fraction upper limit: <1.9 x 10^-6

No significant signal observed

Constraints on Standard Model CP asymmetry deviations

Abstract

We present a search for the decay of a B0 or B0bar meson to a K*0bar K0 or K*0 K0bar final state, using a sample of approximately 232 million BBbar events collected with the BABAR detector at the PEP-II asymmetric energy e+e- collider at SLAC. The measured branching fraction is B(B0 --> K*0bar K0) + B(B0 --> K*0 K0bar) = (0.2+0.9-0.8+0.1-0.3)x 10-6. We obtain the following upper limit for the branching fraction at 90% confidence level: B(B0 --> K*0bar K0) + B(B0 --> K*0 K0bar) <1.9 x 10-6. We use our result to constrain the Standard Model prediction for the deviation of the CP asymmetry in B0 --> phi K0 from sin(2beta).