πNσ term, bar ss in the nucleon, and the scalar form factor: A lattice study

We report on a lattice QCD calculation of the πNσ term, the scalar form factor, and left-angle N|bar ss|N right-angle. The disconnected insertion part of σπN is found to be 1.8±0.1 times larger than the connected insertion contribution. The q2 dependence of σπN(q2) is about the same as GE(q2) of the proton so that σπN(2mπ2)-σπN(0)=6.6±0.6 MeV. The ratio y=left-angle N|bar ss|N right-angle/left-angle N|bar uu+bar dd|N right-angle=0.36±0.03. Both results favor a σπN∼53 MeV, slightly larger than our direct calculation of σπN=49.7±2.6 MeV. We also compute Fs and Ds and find that the agreement with those from the octet baryon mass splittings crucially depends on the inclusion of the large disconnected insertion. Finally, we give our result for the KNσ term. copyright 1996 The American Physical Society