Bayesian analysis of light-front models and the nucleon's charmed sigma term

We present the results of a recent analysis to study the nucleon's charm sigma term, sigma(c (c) over bar). We construct a minimal model in terms of light- front variables and constrain the range of possibilities using extant knowledge from deeply inelastic scattering (DIS) and Bayesian parameter estimation, ultimately computing sigma(c (c) over bar) in an explicitly covariant manner. We find a close correlation between a possible nonperturbative component of the charm structure function, F-2,IC(c (c) over bar), and sigma(c (c) over bar). Independent of the prescription for the covariant relativistic quark-nucleon vertex, we determine sigma(c (c) over bar) under several different scenarios for the magnitude of intrinsic charm in DIS, namely < x >(c+(c) over bar) = 0.1%, 0.35%, and 1%, obtaining for these sigma(c (c) over bar) = 4 +/- 4, 12 +/- 13, and 32 +/- 34 MeV, respectively. These results imply the existence of a reciprocity between the intrinsic charm parton distribution function and sigma(c (c) over bar) such that new information from either DIS or improved determinations of sigma(c (c) over bar) could significantly impact constraints to the charm sector of the proton wave function.