Measurement of η'(958) formation in two-photon collisions at LEP1

Abstract

The formation of the η' in the reaction e⁺e ⁻→ e⁺e ⁻η'→e⁺e ⁻π ⁺π^-γ has been measured by the L3 detector at a centre-of-mass energy of 91GeV. The radiative width of the η' has been found to be Γ_γγ = 4.17±0.10(stat.)±0.27(sys.) keV. The Q² dependence of the η' formation cross section has been measured for Q² ≤ 10 GeV² and the η' electromagnetic transition form factor has been determined. The form factor can be parametrised by a pole form with Λ = 0.900±0.046(stat.)±0.022(sys.) GeV. It is also consistent with recent non-perturbative QCD calculations.