A 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, ${\sigma }_{c\bar{c}}$. 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 ${\sigma }_{c\bar{c}}$ in an explicitly covariant manner. We find a close correlation between a possible nonperturbative component of the charm structure function, $F_{2,\mathrm{I}\mathrm{C}}^{c\bar{c}}$, and ${\sigma }_{c\bar{c}}$. Independent of prescription for the covariant relativistic quark-nucleon vertex, we determine ${\sigma }_{c\bar{c}}$ under several different scenarios for the magnitude of intrinsic charm (IC) in DIS, namely $\langle x \rangle_{c+\overline{c}} = 0.1%$,$0.35%$,and$1%$,obtainingforthese$\sigma_{c\overline{c}} = 4 \pm 4$,$12 \pm 13$,and$32 \pm 34$ MeV, respectively. These results imply the existence of a reciprocity between the IC parton distribution function (PDF) and ${\sigma }_{c\bar{c}}$ such that new information from either DIS or improved determinations of $\sigma_{c \overline{c}}$ could significantly impact constraints to the charm sector of the proton wave function.