Baryon-number-violating nucleon decays were studied by searching for x and γ rays associated with radioactive residual nuclei produced by single- and multinucleon decays in ${}_{}{}^{127}{}_{}{}^{}\mathrm{I}$. Large volume NaI(Tl) detectors were used for the study. New lower limits of τ(n)>4.7×${10}^{24}$ yr and τ(p)>3.0×${10}^{24}$ yr were obtained on the mode-independent mean lives for the neutron and proton decays in ${}_{}{}^{127}{}_{}{}^{}\mathrm{I}$, respectively. Lower limits of τ(nn)>2.1×${10}^{24}$ yr, τ(nnn)>1.8×${10}^{23}$ yr, and τ(nnnn)>1.4×${10}^{23}$ yr were deduced for the first time on the mode-independent mean lives for dineutron, trineutron, and tetraneutron decays in ${}_{}{}^{127}{}_{}{}^{}\mathrm{I}$, respectively.

• Received 20 December 1993

DOI:https://doi.org/10.1103/PhysRevC.49.2407