Daniel Jenkins

We determine the light baryon spectrum on ensembles generated by the Coordinated Lattice Simulations (CLS) effort, employingN_f= 2 + 1 flavours of non-perturbatively improved Wilson fermions. The hadron masses are interpolated and extrapolated within the quark mass plane, utilizing three distinct trajectories, two of which intersect close to the physical quark mass point and the third one approaching the SU(3) chiral limit. The results are extrapolated to the continuum limit, utilizing six different lattice spacings ranging froma≈ 0.10 fm down to below 0.04 fm. The light pion mass varies fromM_π≈ 429 MeV down to 127 MeV. In general, the spatial extent is kept larger than four times the inverse pion mass and larger than 2.3 fm, with additional small and large volume ensembles to investigate finite size effects. We determine the Wilson flow scales $$ \sqrt{t_{0,\textrm{ph}}}={0.1449}_{(9)}^{(7)}\textrm{fm} $$t0,ph=0.144997fm [1] and $$ {t}_0^{\ast}\approx {t}_{0,\textrm{ph}} $$t0∗≈t0,ph [2] from the octet cascade (Ξ baryon). Determining the light baryon spectrum in the continuum limit, we find the nucleon mass $$ {m}_N={941.7}_{(7.6)}^{(6.5)} $$mN=941.77.66.5 MeV and the other stable baryon masses to agree with their experimental values within sub-percent level uncertainties. Moreover, we determine SU(3) and SU(2) chiral perturbation theory low energy constants, including the octet and the Ω baryon sigma termsσ_πN= 43.9(4.7) MeV, $$ {\sigma}_{\pi \Lambda}={28.2}_{(5.4)}^{(4.3)} $$σπΛ=28.25.44.3 MeV, $$ {\sigma}_{\pi \Sigma}={25.9}_{(6.1)}^{(3.8)} $$σπΣ=25.96.13.8 MeV, $$ {\sigma}_{\pi \Xi}={11.2}_{(6.4)}^{(4.5)} $$σπΞ=11.26.44.5 and $$ {\sigma}_{\pi \Omega}={6.9}_{(4.3)}^{(5.3)} $$σπΩ=6.94.35.3 MeV, as well as various parameters, renormalization factors and improvement coefficients that are relevant for simulations with our lattice action.

We determine the light baryon spectrum on ensembles generated by the Coordinated Lattice Simulations (CLS) effort, employing $N_f=2+1$ flavours of non-perturbatively improved Wilson fermions. The hadron masses are interpolated and extrapolated within the quark mass plane, utilizing three distinct trajectories, two of which intersect close to the physical quark mass point and the third one approaching the SU(3) chiral limit. The results are extrapolated to the continuum limit, utilizing six different lattice spacings ranging from $a\approx 0.10\,$fm down to below $0.04\,$fm. The light pion mass varies from $M_{\pi}\approx 429\,$MeV down to $127\,$MeV. In general, the spatial extent is kept larger than four times the inverse pion mass and larger than $2.3\,$fm, with additional small and large volume ensembles to investigate finite size effects. We determine the Wilson flow scales $\sqrt{t_{0,{\rm ph}}}=0.1449^{(7)}_{(9)}\,$fm and $t_0^*\approx t_{0,{\rm ph}}$ from the octet cascade ($\Xi$ baryon). Determining the light baryon spectrum in the continuum limit, we find the nucleon mass $m_N=941.7^{(6.5)}_{(7.6)}\,$MeV and the other stable baryon masses to agree with their experimental values within sub-percent level uncertainties. Moreover, we determine SU(3) and SU(2) chiral perturbation theory low energy constants, including the octet and the $\Omega$ baryon sigma~terms $\sigma_{\pi N}=43.9(4.7)\,$MeV, $\sigma_{\pi\Lambda}=28.2^{(4.3)}_{(5.4)}\,$MeV, $\sigma_{\pi\Sigma}=25.9^{(3.8)}_{(6.1)}\,$MeV, $\sigma_{\pi\Xi}=11.2^{(4.5)}_{(6.4)}\,$MeV and $\sigma_{\pi\Omega}=6.9^{(5.3)}_{(4.3)}\,$MeV, as well as various parameters, renormalization factors and improvement coefficients that are relevant for simulations with our lattice action.

A lot of progress has been made in the direct determination of nucleon sigma terms. Using similar methods, we consider the sigma terms of the other octet baryons as well. These are determined on CLS gauge field ensembles employing the Lüscher-Weisz gluon action and the Sheikholeslami-Wohlert fermion action with $N_\mathrm{f} = 2 + 1$. The ensembles have pion masses ranging from ${410}\,\mathrm{MeV}$ down to the physical value and lattice spacings covering a range between ${0.098}\,\mathrm{fm}$ and ${0.039}\,\mathrm{fm}$. We present some preliminary results for the pion and strange sigma terms and compare to indirect determinations. To do so, we discuss multi-state fits to tackle the well-known problem of excited state contamination comparing the ratio and summation methods also including priors.

A lot of progress has been made in the direct determination of nucleon sigma terms. Using similar methods, we consider the sigma terms of the other octet baryons as well. These are determined on CLS gauge field ensembles employing the Lüscher-Weisz gluon action and the Sheikholeslami-Wohlert fermion action with $N_\mathrm{f} = 2 + 1$. The ensembles have pion masses ranging from ${410}\,\mathrm{MeV}$ down to the physical value and lattice spacings covering a range between ${0.098}\,\mathrm{fm}$ and ${0.039}\,\mathrm{fm}$. We present some preliminary results for the pion and strange sigma terms and compare to indirect determinations. To do so, we discuss multi-state fits to tackle the well-known problem of excited state contamination comparing the ratio and summation methods also including priors.