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Measurement of the branching fraction and $$CP$$ asymmetry in $$B^0 to pi^0pi^0$$ decays, and an improved constraint on $$phi_2$$

$$B^0 to pi^0pi^0$$崩壊の分岐比と$$CP$$非対称性の測定および$$phi_2$$に対する制限の改善

Julius, T.*; 谷田 聖   ; Belle Collaboration*; 他184名*

Julius, T.*; Tanida, Kiyoshi; Belle Collaboration*; 184 of others*

We measure the branching fraction and $$CP$$-violating asymmetry in the decay $$B^0 to pi^0pi^0$$, using a data sample of $$752 times 10^6$$ $$Bbar{B}$$ pairs collected at the $$Upsilon(4S)$$ resonance with the Belle detector at the KEKB $$e^+e^-$$ collider. The obtained branching fraction and direct $$CP$$ asymmetry are $$B(B^0 to pi^0pi^0)=[1.31 pm 0.19 ({rm stat.}) pm 0.18 ({rm syst.})]times10^{-6}$$ and $$A_{CP}= 0.14 pm 0.36 ({rm stat.}) pm 0.12 ({rm syst.})$$, respectively. The signal significance, including the systematic uncertainty, is 6.4 standard deviations. We combine these results with Belle's earlier measurements of $$B^0 to pi^0pi^0$$ and $$B^{pm} to pi^{pm}pi^0$$ to exclude the $$CP$$-violating parameter $$phi_2$$ from the range $$15.5^{circ} < phi_2 < 75^{circ}$$ at 95% confidence.

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パーセンタイル:50.23

分野:Astronomy & Astrophysics

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