Measurement of cos2β in B0→D(∗)h0 with D→K0Sπ+π− decays by a combined time-dependent Dalitz plot analysis of BaBar and Belle data
We report measurements of sin2β and cos2β from a time-dependent Dalitz plot analysis of B0→D(∗)h0 with D→K0Sπ+π−decays, where the light unflavored and neutral hadron h0 is a π0, η, or ω meson. The analysis is performed with a combination of the final data sets of the \babar\ and Belle experiments containing 471×106 and 772×106 BB¯ pairs collected at the Υ(4S)resonance at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. We measure sin2β=0.80±0.14(stat.)±0.06(syst.)±0.03(model) and cos2β=0.91±0.22(stat.)±0.09(syst.)±0.07(model). The result for the direct measurement of the angle is β=(22.5±4.4(stat.)±1.2(syst.)±0.6(model))∘. The last quoted uncertainties are due to the composition of the D0→K0Sπ+π− decay amplitude model, which is newly established by a Dalitz plot amplitude analysis of a high-statistics e+e−→cc¯ data sample as part of this analysis. We find the first evidence for cos2β>0 at the level of 3.7 standard deviations. The measurement excludes the trigonometric multifold solution π/2−β=(68.1±0.7)∘ at the level of 7.3 standard deviations and therefore resolves an ambiguity in the determination of the apex of the CKM Unitarity Triangle. The hypothesis of β=0∘ is ruled out at the level of 5.1 standard deviations, and thus CP violation is observed in B0→D(∗)h0 decays.
Also available at: https://arxiv.org/abs/1804.06153