Mass spectrum of spin-1/2 pentaquarks with a $c\bar{c}$ component and their anticipated discovery modes in $b$-baryon decays

Abstract

The LHCb discovery of the two baryonic states $P_c^{+}(4380)$ and $P_c^{+}(4450)$, having $J^P=3/2^{-}$ and $J^P=5/2^{+}$, respectively, in the process $pp\to b\bar{b}\to {\Lambda }_{b}X$, followed by the decay ${\Lambda }_b\to J/\psi p{K}^{-}$, has motivated a number of theoretical models. Interpreting them as compact $\{\bar{c}[cu][ud];L_{\mathcal{P}}=0,1\}$ objects, the mass spectroscopy of the $J^P=3/2^{-}$ and $J^P=5/2^{+}$ pentaquarks was worked out by us for the pentaquarks in the $SU(3{)}_F$ multiplets, using an effective Hamiltonian based on constituent diquarks and quarks. Their possible discovery modes in $b$-baryon decays were also given using the heavy quark spin symmetry. In this paper, we calculate the mass spectrum of the hidden $c\bar{c}$ pentaquarks having $J^P={\frac{1}{2}}^{\pm }$ for the $SU(3{)}_F$ multiplets and their anticipated discovery modes in $b$-baryon decays. Some of the $P_c^{+}(J^P=1/2^{\pm }$) pentaquarks, produced in the ${\Lambda }_b$ decays may have their masses just below the $J/\psi p$ threshold, in which case they should be searched for in the modes $P_c^{+}(J^P=1/2^{\pm })\to {\eta }_{c}p,{\mu }^{+}{\mu }^{-}p,e^{+}{e}^{-}p$.

Comments: 1 figure, 11 tables