RESONANT PRODUCTION OF VECTOR MESONS BY POLARIZED PHOTONS - SPECIAL CONSIDERATIONS ON RHO-N-DECAY MODE OF DELTA-(1950) AND DELTA-(2420)

Schildknecht D, SCHREMPP. B. RESONANT PRODUCTION OF VECTOR MESONS BY POLARIZED PHOTONS - SPECIAL CONSIDERATIONS ON RHO-N-DECAY MODE OF DELTA-(1950) AND DELTA-(2420). NUOVO CIMENTO DELLA SOCIETA ITALIANA DI FISICA A. 1971;5(1):103-137

MEASUREMENT OF RESONANCE PRODUCTIONS IN THE REACTIONS gamma gamma ---> pi0 pi0 AND gamma gamma ---> pi0 eta

Resonance production in the γγ reactionse + e −→e + e + e − π 0 π 0 ande + e − π 0 η has been studied with the JADE detector at PETRA. The decay widths into γγ of thef 2(1270),a 0(980) anda 2(1320) were measured to be Γγγ(f2(1270))=3.19±0.09+0.22−0.38 Kev,Γ λλ(a 0(980))=0.28±0.04±0.10 KeV/BR(a 0(980)→π 0 η) andΓ λλ (a 2(1320))=1.01±0.14±0.22KeV. For thef 0(975) andf 4(2050) upper limits of the widths were obtained,Γ λλ (f 0(975))<0.6 KeV, andΓ λλ(f 4(2050))<1.1 KeV, both at the 95% C.L. Assuming that the spin 0 background under thef 2(1270) is small, thef 2(1270) was found to be produced exclusively in a helicity 2 state. The helicity 0 contribution is <15% at the 95% C.L. The cross section forλλ→π 0 π 0 in the mass range 2.0–3.5 GeV/c2 was measured for the first time. Since the cross section forλλ→π + π − is a factor ∼2 larger, ππ production in this range can be interpreted as taking place via isospin 0 production

TWO PHOTON EXCITATION OF THE TENSOR MESON f0 (1270)

We have measured charged particle pair production in two-photon scattering at the e+e- storage ring PETRA. While the main source of such events is the production of lepton pairs, the presence of an additional process is clearly indicated by the measured invariant mass distribution of the two particles and their angular distributions. We determine that the excess is mainly due to the decay f0(1270)→π+π-. We derive a width Γ(f0→γγ)=3.2±0.2±0.6 keV (statistical and systematic). © 1981 Springer-Verlag