Polarization measurement of ${\mathrm{\Lambda }}_c^{+}$ and $\bar{\mathrm{\Lambda }}{}_c^{-}$ baryons in $p$Ne collisions at $\sqrt{s_{NN}}=68.6$ GeV

The first measurement of the polarization of charm baryons by the LHCb experiment recorded in fixed-target mode is presented. The polarization of ${\mathrm{\Lambda }}_c$ baryons is studied in collisions of protons, at an energy of 2.51 TeV, incident on a gaseous target of neon, at a nucleon-nucleon center-of-mass energy of $68.6$ GeV. The world’s first measurement of separate-charge polarizations for ${\mathrm{\Lambda }}_c^{+}$ and $\bar{\mathrm{\Lambda }}{}_c^{-}$ baryons is performed, determining $$P_{{\mathrm{\Lambda }}_c^{+}}=(24\pm 9\pm 2)\mathrm{\%},$$ $$P_{\bar{\mathrm{\Lambda }}{}_c^{-}}=(-8\pm 12\pm 3)\mathrm{\%},$$ where the first uncertainty is statistical and the second systematic. The polarization is also measured in intervals of baryon transverse momentum and the Feynman-$x$ variable.