Partial wave analysis of J/ψ → γηη′

Based on a sample of (10.09 +/- 0.04 )x10(9) J /psi events collected with the BESIII detector operating at the BEPCII storage ring, a partial wave analysis of the decay J/psi -> gamma eta eta ' is performed. An isoscalar state with exotic quantum numbers J(P) (C)=1(-+), denoted as eta(1)(1855 ), has been observed for the first time with statistical significance larger than 19 sigma . Its mass and width are measured to be (1855 +/- 9(-1)(+6)) MeV /c(2) and (188 +/- 18(-8)(+3)) MeV , respectively. The first uncertainties are statistical and the second are systematic. The product branching fraction B (J /psi -> gamma eta(1)(1855 ))B (eta(1)(1855 )->eta eta ') is measured to be (2.70 +/- 0.41(-0.35)(+0.16))x10(-6) . In addition, an upper limit on the ratio of branching fractions B (f(0)(1710 )->eta eta ')/B (f(0)(1710 )->pi pi) is determined to be 1.61 x10(-3) at 90% confidence level, which lends support to the hypothesis that the f(0)(1710 ) has a large glueball component.

Automated summary

Based on a sample of J/psi events collected with the BESIII detector, a partial wave analysis of the decay J/psi -> gamma eta eta ' is performed. A new state with exotic quantum numbers J(P)(C)=1(-+), denoted as eta(1)(1855), is observed for the first time. The study also measures the product branching fraction and establishes an upper limit on the ratio of branching fractions for the decay of f(0)(1710).