We present improved measurements of CP-violation parameters in the decays B0→π+π-, B0→K+π-, and B0→π0π0, and of the branching fractions for B0→π0π0 and B0→K0π0. The results are obtained with the full data set collected at the Υ(4S) resonance by the BABAR experiment at the PEP-II asymmetric-energy B factory at the SLAC National Accelerator Laboratory, corresponding to (467±5)×106 BB¯ pairs. We find the CP-violation parameter values and branching fractions: Sπ+π-=-0.68±0.10±0.03, Cπ+π-=-0.25±0.08±0.02, AK-π+=-0.107±0.016-0.004+0.006, Cπ0π0=-0.43±0.26±0.05, B(B0→π0π0)=(1.83±0.21±0.13)×10-6, B(B0→K0π0)=(10.1±0.6±0.4)×10-6, where in each case, the first uncertainties are statistical and the second are systematic. We observe CP violation with a significance of 6.7 standard deviations for B0→π+π- and 6.1 standard deviations for B0→K+π-, including systematic uncertainties. Constraints on the unitarity triangle angle α are determined from the isospin relations among the B→ππ rates and asymmetries. Considering only the solution preferred by the Standard Model, we find α to be in the range [71°,109°] at the 68% confidence level.

Measurement of CP asymmetries and branching fractions in charmless two-body B-meson decays to pions and kaons

LANCERI, LIVIO;VITALE, LORENZO;
2013-01-01

Abstract

We present improved measurements of CP-violation parameters in the decays B0→π+π-, B0→K+π-, and B0→π0π0, and of the branching fractions for B0→π0π0 and B0→K0π0. The results are obtained with the full data set collected at the Υ(4S) resonance by the BABAR experiment at the PEP-II asymmetric-energy B factory at the SLAC National Accelerator Laboratory, corresponding to (467±5)×106 BB¯ pairs. We find the CP-violation parameter values and branching fractions: Sπ+π-=-0.68±0.10±0.03, Cπ+π-=-0.25±0.08±0.02, AK-π+=-0.107±0.016-0.004+0.006, Cπ0π0=-0.43±0.26±0.05, B(B0→π0π0)=(1.83±0.21±0.13)×10-6, B(B0→K0π0)=(10.1±0.6±0.4)×10-6, where in each case, the first uncertainties are statistical and the second are systematic. We observe CP violation with a significance of 6.7 standard deviations for B0→π+π- and 6.1 standard deviations for B0→K+π-, including systematic uncertainties. Constraints on the unitarity triangle angle α are determined from the isospin relations among the B→ππ rates and asymmetries. Considering only the solution preferred by the Standard Model, we find α to be in the range [71°,109°] at the 68% confidence level.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11368/2768526
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