First observation of $B_s^0\to J/ψη$ and $B_s^0\to J/ψη'$

Abstract

We report first observations of $B_s^0\to J/ψη$ and $B_s^0\to J/ψη'$. The results are obtained from 121.4 fb^{-1} of data collected at the $Υ(5S)$ resonance with the Belle detector at the KEKB $e^+e^-$ collider. We obtain the branching fractions Br(B_s^0\to J/ψη)= [5.10\pm 0.50(stat.)\pm 0.25(syst.)^{+1.14}_{-0.79}(N_{B_s^(*)\bar B_s^(*))] \times 10^{-4}, and Br(B_s^0\to J/ψη')=[3.71\pm 0.61(stat.)\pm 0.18(syst.)^{+0.83}_{-0.57}(N_{B_s^(*)\bar B_s^(*))] \times 10^{-4}. The ratio of the two branching fractions is measured to be $\frac{Br(B_s\to J/ψη')}{Br(B_s\to J/ψη)} = 0.73\pm 0.14(stat.)\pm 0.02(syst.)$.

5 pages, 3 figures, 2 tables