6533b861fe1ef96bd12c56ee

RESEARCH PRODUCT

LHCb pentaquark as aD¯*Σc−D¯*Σc*molecular state

subject

description

We perform a theoretical analysis of the ${\mathrm{\ensuremath{\Lambda}}}_{b}\ensuremath{\rightarrow}J/\ensuremath{\psi}{K}^{\ensuremath{-}}p$ reaction from where a recent LHCb experiment extracts a $\mathrm{\ensuremath{\Lambda}}(1405)$ contribution in the ${K}^{\ensuremath{-}}p$ spectrum close to threshold and two baryon states of hidden charm in the $J/\ensuremath{\psi}p$ spectrum. We recall that baryon states of this type have been theoretically predicted matching the mass, width and ${J}^{P}$ of the experiment; concretely some states built up from the $J/\ensuremath{\psi}N$, ${\overline{D}}^{*}{\mathrm{\ensuremath{\Lambda}}}_{c}$, ${\overline{D}}^{*}{\mathrm{\ensuremath{\Sigma}}}_{c}$, $\overline{D}{\mathrm{\ensuremath{\Sigma}}}_{c}^{*}$ and ${\overline{D}}^{*}{\mathrm{\ensuremath{\Sigma}}}_{c}^{*}$ coupled channels. We assume that the observed narrow state around 4450 MeV has this nature and we are able to describe simultaneously the shapes and relative strength of the the ${K}^{\ensuremath{-}}p$ mass distribution close to threshold and the peak of the $J/\ensuremath{\psi}p$ distribution, with values of the $J/\ensuremath{\psi}p$ coupling to the resonance in line with the theoretical ones. The nontrivial matching of many properties gives support to a ${J}^{P}=3/{2}^{\ensuremath{-}}$ assignment to this state and to its nature as a molecular state mostly made of ${\overline{D}}^{*}{\mathrm{\ensuremath{\Sigma}}}_{c}$ and ${\overline{D}}^{*}{\mathrm{\ensuremath{\Sigma}}}_{c}^{*}$.