Eur. Phys. J. C (2013) 73: 2614
https://doi.org/10.1140/epjc/s10052-013-2614-4

Regular Article - Experimental Physics

Measurement of the η–η′ mixing angle in π ⁻ and K ⁻ beams with the GAMS-4π Spectrometer

Institute for High Energy Physics, Nauka Sq. 1, Protvino, Russia

^* e-mail: Vladimir.Samoylenko@ihep.ru

Received: 13 March 2013
Revised: 25 July 2013
Published online: 24 October 2013

Abstract

The η–η′ mixing angle has been measured with the GAMS-4π spectrometer in a high statistics experiment. η′ and η mesons were generated with charge–exchange reactions in 32.5 GeV/c π ⁻ and K ⁻ beams. Using both π ⁻ and K ⁻ beams allows the study of the |η _q 〉 and |η _s 〉 components of the meson wave function. The cross section ratio at t′=0 (GeV/c)² in the π ⁻ beam is R _π (η′/η)=0.54±0.04, and the mixing angle ϕ _P =(36.3±1.0)^∘. For the K ⁻ beam the ratio is R _K (η′/η)=1.27±0.15. It was found that the gluonium content in η′ is sin² ϕ _G =0.17±0.07.