${\mathrm{\Lambda }}_{\mathrm{c}}^{+}$ polarimetry using the dominant hadronic mode

The polarimeter vector field for multibody decays of a spin-half baryon is introduced as a generalisation of the baryon asymmetry parameters. Using a recent amplitude analysis of the ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}\to p{K}^{-}{\pi }^{+}$ decay performed at the LHCb experiment, we compute the distribution of the kinematic-dependent polarimeter vector for this process in the space of Mandelstam variables to express the polarised decay rate in a model-agnostic form. The obtained representation can facilitate polarisation measurements of the ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}$ baryon and eases inclusion of the ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}\to p{K}^{-}{\pi }^{+}$ decay mode in hadronic amplitude analyses.