f_1(1285) Formation in Two-Photon Collisions at LEP

TL;DR

This study observes the f_1(1285) meson in two-photon collisions at LEP, measuring its production characteristics, gamma-gamma coupling, and decay branching ratios to enhance understanding of its structure and formation mechanisms.

Contribution

The paper reports the first measurement of the f_1(1285) meson production in two-photon collisions at LEP, including its gamma-gamma coupling and decay branching fractions.

Findings

f_1(1285) observed in two-photon collisions

Gamma-gamma coupling parameter measured as 3.5 +/- 0.6 +/- 0.5 keV

Branching ratio of decay modes determined

Abstract

The eta pi^+ pi^- final state in two-photon collisions is studied with the L3 detector at LEP, at centre-of-mass energies from 183 to 209 GeV with an integrated luminosity of 664.6/pb. The f_1(1285) meson is observed and the Q^2 dependence of its production is compared to different form factor models. The gamma-gamma coupling parameter is found to be 3.5 +/- 0.6(stat.) +/- 0.5(sys.) keV. The branching fraction (f_1(1285) -> a_0 pi) / (f_1(1285) -> eta pi pi) is also measured.