6533b836fe1ef96bd12a12d0

RESEARCH PRODUCT

Polarization effects in the cascade decayΛb→Λ(→pπ−)+J/ψ(→ℓ+ℓ−)in the covariant confined quark model

subject

description

We calculate the invariant and helicity amplitudes for the nonleptonic decay ${\ensuremath{\Lambda}}_{b}\ensuremath{\rightarrow}\ensuremath{\Lambda}+J/\ensuremath{\psi}$, $\ensuremath{\psi}(2S)$ in the covariant confined quark model. We discuss joint angular decay distributions in the cascade decay ${\ensuremath{\Lambda}}_{b}\ensuremath{\rightarrow}\ensuremath{\Lambda}(\ensuremath{\rightarrow}p{\ensuremath{\pi}}^{\ensuremath{-}})+J/\ensuremath{\psi}$, $\ensuremath{\psi}(2S)(\ensuremath{\rightarrow}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}})$ and calculate some of the asymmetry parameters that characterize the joint angular decay distribution. We confirm expectations from the naive quark model that the transitions into the ${\ensuremath{\lambda}}_{\ensuremath{\Lambda}}=1/2$ helicity states of the daughter baryon $\ensuremath{\Lambda}$ are strongly suppressed leading to a near maximal negative polarization of the $\ensuremath{\Lambda}$. For the same reason the azimuthal correlation between the two decay planes spanned by ($p{\ensuremath{\pi}}^{\ensuremath{-}}$) and (${\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$) is negligibly small. We provide form factor results for the whole accessible ${q}^{2}$ range. Our results are close to lattice results at minimum recoil and light-cone sum rule results at maximum recoil. A new feature of our analysis is that we include lepton mass effects in the calculation, which allows us to also describe the cascade decay ${\ensuremath{\Lambda}}_{b}\ensuremath{\rightarrow}\ensuremath{\Lambda}(\ensuremath{\rightarrow}p{\ensuremath{\pi}}^{\ensuremath{-}})+\ensuremath{\psi}(2S)(\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}})$.