Using a sample of $1.06 \times 10^{ 8}$ $\psi(2S)$ events collected with the BESIII detector at BEPCII, the decay $\psi(2S) \to p \bar{ p}\eta$ is studied. A partial wave analysis determines that the intermediate state N(1535) with a mass of $1524\pm5^{ +10}_{ -4}$ MeV/$c^2$ and a width of $130^{ +27+57}_{ -24-10}$ MeV/$c^2$ is dominant in the decay; the product branching fraction is determined to be $B(\psi(2S) \to N(1535)\bar{ p})\times B(N(1535)\to p\eta)+c.c. = (5.2\pm0.3^{ +3.2}_{ -1.2})\times 10^{ -5}$. Furthermore, the branching fraction of $\psi(2S) \to \eta p \bar{ p}$ is measured to be $(6.4\pm0.2\pm0.6)\times 10^{ -5}$.
Categories: hep-ex