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

Abstract

We present the results of a recent analysis to study the nucleon's charm sigma term, ${\sigma }_{c\overline{c}}$. 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 ${\sigma }_{c\overline{c}}$ in an explicitly covariant manner. We find a close correlation between a possible nonperturbative component of the charm structure function, $F_{2,\mathrm{IC}}^{c\overline{c}}$, and ${\sigma }_{c\overline{c}}$. Independent of prescription for the covariant relativistic quark-nucleon vertex, we determine ${\sigma }_{c\overline{c}}$ under several different scenarios for the magnitude of intrinsic charm (IC) in DIS, namely $⟨x{⟩}_{c+\overline{c}}=0.1\%$, $0.35\%$, and $1\%$, obtaining for these ${\sigma }_{c\overline{c}}=4\pm 4$, $12\pm 13$, and $32\pm 34$ MeV, respectively. These results imply the existence of a reciprocity between the IC parton distribution function (PDF) and ${\sigma }_{c\overline{c}}$ 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.

14 pages, 6 figures

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