Evidence for D0−¯¯¯D0 Mixing

Abstract

We present evidence for D 0 − ¯¯¯ D 0 mixing in D 0 → K + π − decays from 384 fb − 1 of e + e − colliding-beam data recorded near √ s = 10.6 GeV with the BABAR detector at the PEP-II storage rings at the Stanford Linear Accelerator Center. We find the mixing parameters x ' 2 = [ − 0.22 ± 0.30 ( stat ) ± 0.21 ( syst ) ] × 10 − 3 and y ′ = [ 9.7 ± 4.4 ( stat ) ± 3.1 ( syst ) ] × 10 − 3 and a correlation between them of − 0.95 . This result is inconsistent with the no-mixing hypothesis with a significance of 3.9 standard deviations. We measure R D , the ratio of doubly Cabibbo-suppressed to Cabibbo-favored decay rates, to be [ 0.303 ± 0.016 ( stat ) ± 0.010 ( syst ) ] % . We find no evidence for C P violation.