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, σcc¯. 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 σcc¯ in an explicitly covariant manner. We find a close correlation between a possible nonperturbative component of the charm structure function, F2,ICcc¯, and σcc¯. Independent of the prescription for the covariant relativistic quark-nucleon vertex, we determine σcc¯ under several different scenarios for the magnitude of intrinsic charm in DIS, namely ‹x›c+c¯=0.1%, 0.35%, and 1%, obtaining for these σcc¯=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 σcc¯ such that new information from either DIS or improved determinations of σcc¯ could significantly impact constraints to the charm sector of the proton wave function.