Speakers
Description
I present results for the invariant and helicity amplitudes in the transitions
$\Lambda_b~\to~\Lambda^\ast(J^P)~+~J/\psi$ where
$\Lambda^\ast(J^P)$ are $sud$-resonances with
$J^P=\frac12^{\pm},\frac32^{\pm}$. The calculations are performed in
the framework of our covariant confined quark model.
We find that the values
of the helicity amplitudes for the $\Lambda^\ast(1520,\,\frac32^-)$
and $\Lambda^\ast(1890,\,\frac32^+)$
are suppressed compared with those for the
ground state $\Lambda(1116,\,\frac12^+)$ and $\Lambda^\ast(1405,\,\frac12^-)$.
This analysis is important for the identification of
the charmed pentaquark $P_c^+$ since the cascade decay
$\Lambda_b~\to~\Lambda^\ast(\frac32^\pm)(~\to~pK^-)~+~J/\psi$.
involves the same final states as the decay
$\Lambda_b^0~\to~P_c^+(~\to~p~K^-)~+~J/\psi $.
I also discuss polarization effects in the cascade decay
$\Lambda_b~\to~\Lambda(1116)(\to~p\pi^-)~+~J/\psi(\to~\ell^+\ell^-)$.
This analysis was published in [1].
[1] T.~Gutsche, M.~A.~Ivanov, J.~G.~K\"orner, V.~E.~Lyubovitskij
and P.~Santorelli,
Phys.\ Rev.\ D {\bf 88}, no. 11, 114018 (2013)
