Search for B^0 --> a_0^+(980)pi^-

TL;DR

This paper reports a search for the rare decay B^0 --> a_0^+(980)pi^- using data from the BABAR detector, observing a 3.7 sigma excess and estimating the branching fraction with improved background suppression.

Contribution

It introduces enhanced background suppression techniques and optimal signal extraction methods for rare decay searches in B meson decays.

Findings

Observed a 3.7 sigma excess of events.

Measured branching fraction BR(B^0 --> a_0^+ pi^-) ≈ 6.2 x 10^{-6}.

Set an upper limit of 11.5 x 10^{-6} at 90% CL.

Abstract

We present preliminary results of a search for the decay B^0 --> a_0^+(980)pi^- among 22.7 million Upsilon(4S)-->B-anti-B pairs collected by the BABAR detector at PEP-II. Using improved background suppression techniques and optimal signal extraction for rare decay searches, an excess of events over expected background is observed at the level of 3.7 standard deviations. This corresponds to the branching fraction BR(B^0 --> a_0^+ (a_0^+ --> eta pi^+) pi^-) =(6.2_{-2.5}^{+3.0}+/-1.1) x 10^{-6}, where the first error is statistical and the second is systematic. The 90% confidence level upper limit is 11.5 x 10^{-6}.