The reaction e+e- -> e+e- pi0 pi0 has been analyzed using 97 pb-1 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 gamma gamma -> pi0 pi0 for pi0 pi0 mvariant masses ranging from threshold to about 2 GeV. We measure an approximately flat cross section of about 10 nb for W=m(pi0 pi0)<0.8 GeV, which is below 0.6 GeV, in good agreement with a theoretical prediction based on an unitarized Born-term model. At higher invariant masses we observe formation of the f2(1270) resonance and a hint of the f0(975). We deduce the following two-photon widths: Gamma(gamma gamma)(f2(1270))=3.19±0.16±0.280.29 keV and Gamma(gamma gamma)(f0(975))<0.53 keV at 90% C.L. The decay-angular distributions show the pi0 pi0 system to be dominantly spin 0 for W<0.7 GeV and spin 2, helicity 2 in the f2(1270) region, with helicity 0 contributing at most 22% (90% C.L.).
Measurement of pi0 pi0 production in two-photon collisions / H., Marsiske; D., Antreasyan; H. W., Bartels; D., Besset; Bieler, C. h.; J. K., Bienlein; Bizzeti, Andrea; E. D., Bloom. - In: PHYSICAL REVIEW D. - ISSN 0556-2821. - STAMPA. - 41:(1990), pp. 3324-3335. [10.1103/PhysRevD.41.3324]
Measurement of pi0 pi0 production in two-photon collisions
BIZZETI, Andrea;
1990
Abstract
The reaction e+e- -> e+e- pi0 pi0 has been analyzed using 97 pb-1 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 gamma gamma -> pi0 pi0 for pi0 pi0 mvariant masses ranging from threshold to about 2 GeV. We measure an approximately flat cross section of about 10 nb for W=m(pi0 pi0)<0.8 GeV, which is below 0.6 GeV, in good agreement with a theoretical prediction based on an unitarized Born-term model. At higher invariant masses we observe formation of the f2(1270) resonance and a hint of the f0(975). We deduce the following two-photon widths: Gamma(gamma gamma)(f2(1270))=3.19±0.16±0.280.29 keV and Gamma(gamma gamma)(f0(975))<0.53 keV at 90% C.L. The decay-angular distributions show the pi0 pi0 system to be dominantly spin 0 for W<0.7 GeV and spin 2, helicity 2 in the f2(1270) region, with helicity 0 contributing at most 22% (90% C.L.).
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