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Measurement of resonance production in the reactionsγγ →π 0 π 0 andγγ →π 0 η

Research output: Contribution to journalJournal article


<mark>Journal publication date</mark>1990
<mark>Journal</mark>Zeitschrift für Physik C Particles and Fields
Number of pages10
<mark>Original language</mark>English


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.