Search for the decay B0 →k∗0τ+τ- at the Belle experiment

This paper presents a search for the rare flavor-changing neutral current process B0→K∗0τ+τ- using data taken with the Belle detector at the KEKB asymmetric energy e+e- collider. The analysis is based on the entire υ(4S) resonance data sample of 711 fb-1, corresponding to 772×106BB¯ pairs. In our search we fully reconstruct the companion B meson produced in the process e+e-→υ(4S)→BB¯ from its hadronic decay modes, and look for the decay B0→K∗0τ+τ- in the rest of the event. No evidence for a signal is found. We report an upper limit on the branching fraction B(B0→K∗0τ+τ-)<3.1×10-3 at 90% confidence level. This is the first direct limit on B(B0→K∗0τ+τ-).