Measuring quark polarizations at ATLAS and CMS

Being able to measure the polarization of quarks produced in various processesat the LHC would be of fundamental significance. Measuring the polarizations ofquarks produced in new physics processes, once discovered, can provide crucialinformation about the new physics Lagrangian. In a series of recent papers, wehave investigated how quark polarization measurements can be done in practice.The polarizations of heavy quarks (b and c) are expected to be largely preservedin the lightest baryons they hadronize into, the Λ b and Λ c , respectively.Furthermore, it is known experimentally that s-quark polarization is preservedas well, in Λ baryons. We study how ATLAS and CMS can measure polarizations ofb, c and s quarks using certain decays of these baryons. We propose to use theStandard Model t ¯ t and W c samples to calibrate these measurements. Weestimate that the Run 2 dataset will suffice for measuring the quarkpolarizations in these Standard Model samples with precisions of order 10%. Wealso propose various additional measurements for the near and far future thatwould help characterize the polarization transfer from the quarks to thebaryons.