Search for day-night and semiannual variations in the solar neutrino flux observed in the Kamiokande-II detector

Searches for possible day-night and semiannual variations of the ${}_{}{}^8{}_{}{}^{}\mathrm{B}$ solar neutrino flux are reported based on 1040 days of Kamiokande-II data. Within statistical error, no such short-time variations were observed. The limit on the day-night difference sets a constraint on neutrino-oscillation parameters. A region defined by ${\sin }^2$2θ>0.02 and 2×${10}^{\mathrm{-}6}$≲Δ${\mathit{m}}^2$≲${10}^{\mathrm{-}5}$ ${\mathrm{eV}}^2$ is excluded at 90% C.L. without any assumption on the absolute value of the expected solar neutrino flux.