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The reaction e+e~e+e m. m has been analyzed using 97 pb ' of data taken with the Crystal Ball detector at the DESY e e+ storage ring DORIS II at beam energies around 5.3 GeV. For the first time we have measured the cross section for yy~m. m. for n m invariant masses ranging from threshold to about 2 GeV. We measure an approximately flat cross section of about 10 nb for 8'=m 0 0 (0.8 GeV, which is below 0.6 GeV, in good agreement with a theoretical prediction 'tr n' based on an unitarized Born-term model. At higher invariant masses we observe formation of the ft(1270) resonance and a hint of the fo(975). We deduce the following two-photon widths: I rr(f, (1270)) =3.19+0. 1620 z, keV and I "(fo( 975)) (0.53 keV at 90% CL. The decayangular distributions show the m~system to be dominantly spin 0 for W &0.7 GeV and spin 2, helicity 2 in the f, (1270) region, with helicity 0 contributing at most 22% (90% C.L.).

In Eqs. (4), (6), and (8)-(11) we have neglected relativistic corrections. For tt=sr/2 the relations (2) and (9) vanish whereas (10) and (11) become identical. There remain therefore six independent relations between the coeKcients b(sr/2)=c(sr/2), d(sr/2), and e(sr/2), i.e. , between five real parameters which determine the transition matrix T(sr/2, «b) except for an absolute phase factor. For angles 0&t7&sr/2, one can obtain eleven relations for nine parameters. The experimental quantities are of course not single-valued functions of these parameters, but the ambiguities may be reduced by comparing solutions for diGerent angles and energies. At lower energies also a phase shift analysis can be helpful. A more complete discussion, especially of the correlation experiments, will be published later.