Observation of $B_s^0\to J\mathrm{/}\psi f_0(980)$ and Evidence for $B_s^0\to J\mathrm{/}\psi f_0(1370)$

We report the first observation of $B_s^0\to J\mathrm{/}\psi f_0(980)$ and first evidence for $B_s^0\to J\mathrm{/}\psi f_0(1370)$, which are CP eigenstate decay modes. These results are obtained from $121.4{\mathrm{f}\mathrm{b}}^{-1}$ of data collected at the $\mathrm{{\rm Y}}(5S)$ resonance with the Belle detector at the KEKB $e^{+}{e}^{-}$ collider. We measure the branching fractions $$\mathcal{B}$(B_s^0\to J/\psi f_0(980);f_0(980)\to\pi^+\pi^-)=(1.16^{+0.31}{-0.19}($\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}\mathrm{.}$)^{+0.15}{-0.17}($\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t}\mathrm{.}$)^{+0.26}{-0.18}(N{B_s^{()}\bar B_s^{()}})) \times 10^{-4}$withasignificanceof$8.4\sigma$,and$$\mathcal{B}$(B_s^0\to J/\psi f_0(1370);f_0(1370)\to\pi^+\pi^-)=(0.34^{+0.11}{-0.14}($\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}\mathrm{.}$)^{+0.03}{-0.02}($\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t}\mathrm{.}$)^{+0.08}{-0.05}(N{B_s^{()}\bar B_s^{()}})) \times 10^{-4}$withasignificanceof$4.2\sigma$. The last error listed is due to uncertainty in the number of produced $B_s^{()}\bar B_s^{()}$ pairs.