Topological susceptibility in 2+1 flavors lattice QCD with domain-wall fermions

We measure the topological charge and its fluctuation for the gauge configurations generated by the RBC and UKQCD Collaborations using 2+1 flavors of domain-wall fermions on the 163×32 lattice (L≃2 fm) with length 16 in the fifth dimension at the inverse lattice spacing a−1≃1.62 GeV. From the spectral flow of the Hermitian operator Hw(2+γ5Hw)−1, we obtain the topological charge Qt of each gauge configuration in the three ensembles with light sea quark masses mqa=0.01, 0.02, and 0.03, and with the strange quark mass fixed at msa=0.04. From our result of Qt, we compute the topological susceptibility χt=〈Qt2〉/Ω, where Ω is the volume of the lattice. In the small mq regime, our result of χt agrees with the chiral effective theory. Using the formula χt=Σ/(mu−1+md−1+ms−1) by Leutwyler-Smilga, we obtain the chiral condensate ΣMS¯(2GeV)=[259(6)(9)MeV]3.