New measurements of the $\eta$ and $K^0$ masses

Abstract

New measurements of the $\eta$ and $K^0$ masses have been performed using decays to 3${\pi }^0$ with the NA48 detector at the CERN SPS. Using symmetric decays to reduce systematic effects, the results $M(\eta )=547.843\pm 0.051$ MeV/c${}^2$ and $M(K^0)=497.625\pm 0.031$ MeV/c${}^2$ were obtained.

17 pages, 4 figures to be published in Physics Letters B