ρ resonance from the I=1 \pi\pi potential in lattice QCD
The first principle calculation of hadron-hadron interaction is an important step toward the understanding of nuclear physics from QCD. The HAL QCD method is largely contributing to this purpose by making it possible to calculate nuclear potentials in lattice QCD. In this talk, we present results of \pi\pi potentials extracted in 2+1 flavor lattice QCD at m_\pi =410 MeV, using all-to-all propagators with LapH smearing. We first investigate the sink operator dependence of the I=2 \pi\pi potential. While the potential from the smeared sink operators drastically changes its shape from the conventional one with the local sink operator, physical observables such as the scattering phase shift are unchanged as long as the next-to-leading order term is included in the smeared potential. We then extract the I=1 \pi\pi potential with the smeared sink operator, whose scattering phase shift reproduces \rho resonance. We also discuss the \rho pole of the S-matrix in the complex energy plane.
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Hadron Spectroscopy and Interactions