Sigma terms from an SU(3) chiral extrapolation

Abstract

We report a new analysis of lattice simulation results for octet baryon masses in 2+1-flavor QCD, with an emphasis on a precise determination of the strangeness nucleon sigma term. A controlled chiral extrapolation of a recent PACS-CS Collaboration data set yields baryon masses which exhibit remarkable agreement both with experimental values at the physical point and with the results of independent lattice QCD simulations at unphysical meson masses. Using the Feynman-Hellmann relation, we evaluate sigma commutators for all octet baryons. The small statistical uncertainty, and considerably smaller model-dependence, allows a signifcantly more precise determination of the pion-nucleon sigma commutator and the strangeness sigma term than hitherto possible, namely σπN=45 \pm 6 MeV and σs = 21 \pm 6 MeV at the physical point.

Figures (4)

• Figure 1: Fit to the PACS-CS baryon octet data. Error bands shown are purely statistical, and incorporate correlated uncertainties between all fit parameters. Note that the data shown has been corrected for finite volume and the simulation strange quark mass, which was somewhat larger than the physical value. The green stars show experimental values.
• Figure 2: Dimensionless baryon sigma terms, evaluated using a dipole regulator, based on fits to the NPLQCD results at the lightest 5 (all), 4, and 3 pseudoscalar mass points.
• Figure 3: Prediction of UKQCD-QCDSF lattice data, based on our fit to the PACS-CS octet baryon mass simulation. Red (square) and green (diamond) points correspond to $24^3$ and $32^3$ lattice volumes respectively. Error bands shown are purely statistical, and incorporate correlated uncertainties between all fit parameters.
• Figure 4: Locations of lattice QCD simulations by the PACS-CS Collaboration (blue circles), and UKQCD-QCDSF Collaboration (red and green squares and diamonds) in the $m_l-m_s$ plane. The star denotes the physical point. Figure \ref{['fig:zan']} shows the fit to the PACS-CS data only, evaluated at the UKQCD-QCDSF simulation quark masses.