Abstract
We present first evidence that the cosine of the CP-violating weak phase 2β is positive, and hence exclude trigonometric multifold solutions of the Cabibbo-Kobayashi-Maskawa (CKM) Unitarity Triangle using a time-dependent Dalitz plot analysis of B^{0}→D^{(*)}h^{0} with D→K_{S}^{0}π^{+}π^{-} decays, where h^{0}∈{π^{0},η,ω} denotes a light unflavored and neutral hadron. The measurement is performed combining the final data sets of the BABAR and Belle experiments collected at the ϒ(4S) resonance at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain (471±3)×10^{6}BB[over ¯] pairs recorded by the BABAR detector and (772±11)×10^{6}BB[over ¯] pairs recorded by the Belle detector. The results of the measurement are 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 β of the CKM Unitarity Triangle is β=[22.5±4.4(stat)±1.2(syst)±0.6(model)]°. The measurement assumes no direct CP violation in B^{0}→D^{(*)}h^{0} decays. The quoted model uncertainties are due to the composition of the D^{0}→K_{S}^{0}π^{+}π^{-} decay amplitude model, which is newly established by performing a Dalitz plot amplitude analysis using a high-statistics e^{+}e^{-}→cc[over ¯] data sample. CP violation is observed in B^{0}→D^{(*)}h^{0} decays at the level of 5.1 standard deviations. The significance for cos2β>0 is 3.7 standard deviations. The trigonometric multifold solution π/2-β=(68.1±0.7)° is excluded at the level of 7.3 standard deviations. The measurement resolves an ambiguity in the determination of the apex of the CKM Unitarity Triangle.
Highlights
Key Laboratory of Nuclear Physics and Ion-Beam Application (MOE) and Institute of Modern Physics, Fudan University, INFN Sezione di Ferrara, I-44122 Ferrara, Italy
We present first evidence that the cosine of the CP-violating weak phase 2β is positive, and exclude trigonometric multifold solutions of the Cabibbo-Kobayashi-Maskawa (CKM) Unitarity Triangle using a time-dependent Dalitz plot analysis of B0 → DðÞ h0 with D → K 0S π þ π − decays, where h0 ∈ fπ 0 ; η; ωg denotes a light unflavored and neutral hadron
Dalitz plot amplitude model or other experimental knowledge of the relative strong phase in the three-body D meson decay is required. Previous measurements of these decays performed separately by BABAR and Belle were not sufficiently sensitive to establish CP violation [16,17,18], obtaining results far outside of the physical region of the parameter space [16], and using different Dalitz plot amplitude models [16,17], which complicates the combination of individual results
Summary
Dalitz plot amplitude model or other experimental knowledge of the relative strong phase in the three-body D meson decay is required Previous measurements of these decays performed separately by BABAR and Belle were not sufficiently sensitive to establish CP violation [16,17,18], obtaining results far outside of the physical region of the parameter space [16], and using different Dalitz plot amplitude models [16,17], which complicates the combination of individual results. Υð5SÞ resonances with the Belle detector [21] at the asymmetric-energy eþ e− collider KEKB [22] This gives a large sample of D mesons enabling precise measurement of the decay amplitudes, so there is no benefit to be gained from including the equivalent BABAR data. K 0 ð1430Þ, which are floated to improve the fit quality
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