E decays to ηππ in pp annihilation at rest

We have observed the ηπ+π− and ηπ0π0 decay modes of the E meson in pp annihilation at rest into π+π−π0π0η. The mass and width of the E meson are 1409 ± 3 and 86 ± 10 MeV. The production and decay branching ratio is B(pp → Eππ)B(E → ηππ) = (3.3 ± 1.0) × 10−3. With a spin-parity analysis we determine that JP = 0−. The observation of the ηπ0π0 decay mode establishes that E is isoscalar (C = +1). We find that E decays to η(ππ)s (where (ππ)s is an S-wave dipion) and πa0(980)(→ πη) with a relative branching ratio of (78 ± 16) %. Using the KKπ production and decay branching ratio measured earlier we determine that B[E → KKπ]B[E → ηππ] = 0.61 ± 0.19. A comparison with observations in radiative JΨ decays suggests that E and ιη(1416) are identical.