Nucleon-sigma terms at $m_π=222 ~\rm MeV$ with a variational analysis from lattice QCD

Abstract

Nucleon sigma terms are important for the decomposition of the nucleon mass and for searches for new physics beyond the Standard Model involving scalar interactions. A persistent tension between lattice QCD and phenomenological determinations may be due to uncontrolled excited-state contamination in lattice QCD analyses. In previous work at $m_π=429~\rm MeV$, we showed that this contamination is dominated by $Nσ$ states and can be strongly suppressed with a variational analysis using $N$ and $Nσ$ operators. In this talk, we present preliminary results at $m_π=222~\rm MeV$, where the $σ$ becomes unstable and decays into $ππ$. We investigate whether the same small variational basis can remove the expected $Nππ$ contamination through the overlap of the $Nσ$ operator with these states.