Measurement of the branching fraction and time-dependent $CP$ asymmetry for ${B}^{0}\to J/\psi {\pi }^{0}$ decays

19 December 2018

Abstract: We measure the branching fraction and time-dependent $CP$-violating asymmetry for ${B}^{0}\to J/\psi {\pi }^{0}$ decays using a data sample of $711\text{}\text{}{\mathrm{fb}}^{-1}$ collected on the $\Upsilon \left(4S\right)$ resonance by the Belle experiment running at the KEKB ${e}^{+}{e}^{-}$ collider. The branching fraction is measured to be $B\left({B}^{0}\to J/\psi {\pi }^{0}\right)=\phantom{\rule{0ex}{0ex}}\left[1.62±0.11\left(\mathrm{stat}\right)±0.06\left(\mathrm{syst}\right)\right]×{10}^{-5}$, which is the most precise measurement to date. The measured $CP$ asymmetry parameters are $S=-0.59±0.19\left(\mathrm{stat}\right)±0.03\left(\mathrm{syst}\right)$ and $A=-0.15±0.14\left(\mathrm{stat}\right)\frac{+0.04}{-0.03}\left(\mathrm{syst}\right)$. The mixing-induced $CP$ asymmetry ($S$) differs from the case of no $CP$ violation by 3.0 standard deviations, and the direct $CP$ asymmetry ($A$) is consistent with zero.

Published in: Physical Review D 98 (2018)