Experimental search for a 17-keV neutrino in the internal bremsstrahlung spectrum of {sup 71}Ge

We have performed a search for a 17-keV neutrino in the internal bremsstrahlung spectrum accompanying the electron capture decay of {sup 71}Ge by using an ultra-large-size HpGe detector. Special attention was paid to get the well-producing response function, the accurate peak-detection efficiency, and the appropriate counting condition in which the pileup effect can be almost negligible. All these made it possible to compare the experimental spectrum with the theoretical one without using any shape factor or smooth function. We excluded the possibility of the 17-keV neutrino with mixing fraction of (1.6{plus_minus}0.8)% obtained by {hacek Z}limen {ital et} {ital al}. Our upper limit for the mixing fraction of the 17-keV neutrino was estimated to be 0.6% at 95% confidence level with {ital Q}=232.65{sub {minus}0.24}{sup +0.34} keV.