Measurement of the CP-violation Parameter sin2${\varphi }_1$ with a New Tagging Method at the ${\rm Y}(5S)$ Resonance

Abstract

We report a measurement of the CP-violation parameter sin2${\varphi }_1$ at the ${\rm Y}(5S)$ resonance using a new tagging method, called "$B$-$\pi$ tagging." In ${\rm Y}(5S)$ decays containing a neutral $B$ meson, a charged $B$, and a charged pion, the neutral $B$ is reconstructed in the $J/\psi K_S^0$ CP-eigenstate decay channel. The initial flavor of the neutral $B$ meson at the moment of the ${\rm Y}(5S)$ decay is opposite to that of the charged $B$ and may thus be inferred from the charge of the pion without reconstructing the charged $B$. From the asymmetry between $B$-${\pi }^{+}$ and $B$-${\pi }^{-}$ tagged $J/\psi K_S^0$ yields, we determine sin2${\varphi }_1$ = 0.57 $\pm$ 0.58(stat) $\pm$ 0.06(syst). The results are based on 121 fb${}^{-1}$ of data recorded by the Belle detector at the KEKB $e^{+}{e}^{-}$ collider.

6 pages, 3 figures (submitted to PRL)

References in corpus (4)

• Observation of Time-Dependent CP Violation in B0 -> eta' K0 Decays and Improved Measurements of CP Asymmetries in B0 -> phiK0, KsKsKs and B0 -> J/psi K0 Decays
• Measurement of Y(5S) decays to B^0 and B^+ mesons
• Study of direct CP violation in $B^{\pm }\to J/\psi K^{\pm }({\pi }^{\pm })$ decays
• Search for CP violating charge asymmetry in B^+ -> J/psi K^+ decays

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