The intrinsic strangeness and charm of the nucleon using improved staggered fermions

TL;DR

This paper calculates the intrinsic strangeness and charm content of the nucleon using improved staggered fermions, revealing that all heavy quark flavors contribute similarly to dark matter scattering via Higgs exchange.

Contribution

It introduces a hybrid method combining direct three-point function evaluation and Feynman-Hellman theorem, reducing statistical errors in nucleon intrinsic quark content calculations.

Findings

Intrinsic strangeness and charm of the nucleon are quantified.

The hybrid method yields consistent results with other approaches.

Heavy quark flavors contribute equally to dark matter interactions.

Abstract

We calculate the intrinsic strangeness of the nucleon, <N|ss|N> - <0|ss|0>, using the MILC library of improved staggered gauge configurations using the Asqtad and HISQ actions. Additionally, we present a preliminary calculation of the intrinsic charm of the nucleon using the HISQ action with dynamical charm. The calculation is done with a method which incorporates features of both commonly-used methods, the direct evaluation of the three-point function and the application of the Feynman- Hellman theorem. We present an improvement on this method that further reduces the statistical error, and check the result from this hybrid method against the other two methods and find that they are consistent. The values for <N|ss|N> and <N|cc|N> found here, together with perturbative results for heavy quarks, show that dark matter scattering through Higgs-like exchange receives roughly equal contributions from all heavy quark flavors.