Search for proton decay via p → e+π0 and p → μ+π0 with an enlarged fiducial volume in Super-Kamiokande I-IV

We have searched for proton decay via p -> e(+)pi(0) and p -> mu(+)pi(0) modes with the enlarged fiducial volume data of Super-Kamiokande from April 1996 to May 2018, which corresponds to 450 kton . years exposure. We have accumulated about 25% more livetime and enlarged the fiducial volume of the SuperKamiokande detector from 22.5 kton to 27.2 kton for this analysis, so that 144 kton . years of data, including 78 kton . years of additional fiducial volume data, has been newly analyzed. No candidates have been found for p -> e(+)pi(0) and one candidate remains for p -> mu(+)pi(0) in the conventional 22.5 kton fiducial volume and it is consistent with the atmospheric neutrino background prediction. We set lower limits on the partial lifetime for each of these modes: tau/B(p -> e(+)pi(0)) > 2.4 x 10(34) years and tau/B(p -> mu(+)pi(0))> 1.6 x 10(34) years at 90% confidence level.