Evidence for Direct $C P$ Violation in $B^{0} \to K^{+} π^{-}$ Decays

Publisher Website

5 November 2004

journal article
research article
Published by American Physical Society (APS) in Physical Review Letters

Vol. 93 (19) , 191802
https://doi.org/10.1103/physrevlett.93.191802

Abstract

We report evidence for direct

C P

violation in the decay

B^{0} \to K^{+} π^{-}

with

253 {f b}^{- 1}

of data collected with the Belle detector at the KEKB

e^{+} e^{-}

collider. Using

275 \times 10^{6}

B \bar{B}

pairs we observe a

B \to K^{\pm} π^{\mp}

signal with

2140 \pm 53

events. The measured

C P

violating asymmetry is

A_{C P} (K^{+} π^{-}) = - 0.101 \pm 0.025 (s t a t) \pm 0.005 (s y s t)

, corresponding to a significance of

3.9 σ

including systematics. We also search for

C P

violation in the decays

B^{+} \to K^{+} π^{0}

and

B^{+} \to π^{+} π^{0}

. The measured

C P

violating asymmetries are

A_{C P} (K^{+} π^{0}) = 0.04 \pm 0.05 (s t a t) \pm 0.02 (s y s t)

and

A_{C P} (π^{+} π^{0}) = - 0.02 \pm 0.10 (s t a t) \pm 0.01 (s y s t)

, corresponding to the intervals

- 0.05 < A_{C P} (K^{+} π^{0}) < 0.13

and

- 0.18 < A_{C P} (π^{+} π^{0}) < 0.14

at 90% confidence level.

Keywords

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