Roles of scalar mesons in charmless ${\Lambda }_b$ decays

Abstract

We first study the charmless two-body ${\Lambda }_b$ decays with the scalar mesons as the final states and predict that $\mathcal{B}({\Lambda }_b\to \Lambda f_0(980,1500))=(2.9\pm 0.7,12.4\pm 3.8)\times 10^{-6}$ and $\mathcal{B}({\Lambda }_b\to p{K}_0^{\ast -}(800,1430))=(1.9\pm 0.5,14.1\pm 4.5)\times 10^{-6}$. With the resonant $f_0(980,1500)\to ({\pi }^{+}{\pi }^{-},K^{+}{K}^{-})$ and $K_0^{\ast -}\to {\bar{K}}^0{\pi }^{-}$ decays, we then obtain $\mathcal{B}({\Lambda }_b\to \Lambda ({\pi }^{+}{\pi }^{-},K^{+}{K}^{-}))=(4.2\pm 1.0,3.5\pm 0.7)\times 10^{-6}$ and $\mathcal{B}({\Lambda }_b\to p{\bar{K}}^0{\pi }^{-})=(10.4\pm 2.9)\times 10^{-6}$, in comparison with the data of $(4.6\pm 1.9,15.9\pm 2.6)\times 10^{-6}$ and $(12.6\pm 4.0)\times 10^{-6}$ from LHCb, respectively. Our results for ${\Lambda }_b\to \Lambda {\pi }^{+}{\pi }^{-}$ and ${\Lambda }_b\to p{\bar{K}}^0{\pi }^{-}$ would be regarded as the first evidences of the scalar meson productions in the anti-triplet $b$-baryon decays. The smaller predicted value of $\mathcal{B}({\Lambda }_b\to \Lambda K^{+}{K}^{-})$ indicates the existences of other resonant contributions to the decay, such as ${\Lambda }_b\to K^{-}(N^{\ast +}\to )\Lambda K^{+}$.

Comments: 8 pages, 1 figure, revised version accepted by PRD