Measuring the Higgs branching fraction into two photons at future linear e(+)e(-) colliders

We examine the prospects for a measurement of the branching fraction of the gamma gamma decay mode of a Standard Model-like Higgs boson with a mass of 120 GeV/c(2) at the future TESLA linear e(+)e(-) collider, assuming an int egrated luminosity of 1 ab(-1) and centre-of-mass energies of 350 GeV and 5 00 GeV. A relative uncertainty un BF(H --> gamma gamma) of 16% can be achie ved in unpolarised e(+)e(-) collisions at roots = 500 GeV, while for roots = 350 GeV tile expected precision is slightly poorer. With appropriate init ial state polarisations the uncertainty carl be improved to 10%. If this me asurement is combined with a measurement of the total Higgs width. a precis ion of 10% on th Higgs boson partial width for the gamma gamma decay mode a ppears feasible.