Tensor meson excitation in the reaction γγ→KS0KS0

In the analysis of the reactione+e−→e+e−K S 0 K s 0 clear evidence for exclusive γγ→f 2 ′ resonance production is observed. The productΓ γγ ·B(f 2 ′ →K\(\bar K\)) is measured to be 0.10 −0.03−0.02 +0.04+0.03 keV independent of ana priori assumption on the helicity structure. Our data are consistent with a pure helicity 2 contribution and we derive an upper limit for the ratioΓ γγ (0) /Γ γγ . The absence of events in the mass region around 1.3 GeV clearly proves destructivef2−a2 interference and allows to measure the relative phases betweenf2,a2 andf 2 ′ . Upper limits on the production of the glueball candidate statesf2(1720) andX(2230) as well as theK S 0 K S 0 -continuum are given.