The cross section of the process e+ e- ---> eta gamma has been measured in the 600-1380 MeV c.m. energy range with the CMD-2 detector. The following branching ratios have been determined: B(rho ---> eta gamma) = (3.28 +- 0.37 +- 0.23) 10^{-4}, B(omega ---> eta gamma) = (5.10 +- 0.72 +- 0.34) 10^{-4}, B(phi --> eta gamma) = (1.287 +- 0.013 +- 0.063) 10^{-2}. Evidence for the rho'(1450) ---> eta gamma decay has been obtained for the first time.
The measured Born cross section for the ETA GAMMA final state.
The processes e+ e- --> eta gamma, e+ e- --> pi0 gamma --> 3 gamma have been studied in the c.m. energy range 600--1380 MeV with the CMD-2 detector. The following branching ratios have been determined: Br(rho --> eta gamma) = (3.21 +- 1.39 +- 0.20)x 10^{-4}; Br(omega --> eta gamma) = (4.44 + 2.29 -1.83 +- 0.28)x 10^{-4}; Br(phi --> eta gamma) = (1.373 +- 0.014 +- 0.085)x 10^{-2}; Br(rho --> pi0 gamma) = (6.21 +1.28 - 1.18 +- 0.39)x 10^{-4}; Br(omega --> pi0 gamma) = (9.06 +- 0.20 +- 0.57)x 10^{-2}; Br(phi --> pi0 gamma) = (1.258 +- 0.037 +- 0.077)x 10^{-3};
Born cross section for the process E+ E- --> ETA GAMMA.
Born cross section for the process E+ E- --> PI0 GAMMA.
The cross section of the process e+ e- --> omega pi0 --> pi0 pi0 gamma has been measured in the c.m. energy range 920-1380 MeV with the CMD-2 detector. Its energy dependence is well described by the interference of the rho(770) and rho'(1450) mesons decaying to omega pi0. Upper limits for the cross sections of the direct processes e+ e- --> pi0 pi0 gamma, eta pi0 gamma have been set.
Measurement of the Born cross section and the 'Bare' cross section of the process E+ E- --> OMEGA < PI0 GAMMA > PI0.
Upper limits for the non OMEGA PI0 cross section.
Upper limits of the ETA PI0 GAMMA cross section.
Resonance production in the γγ reactionse+e−→e+e+e−π0π0 ande+e−π0η has been studied with the JADE detector at PETRA. The decay widths into γγ of thef2(1270),a0(980) anda2(1320) were measured to be\(\Gamma _{\gamma \gamma } (f_2 (1270)) = 3.19 \pm 0.09_{ - 0.38}^{ + 0.22} \) Kev,Γλλ(a0(980))=0.28±0.04±0.10 KeV/BR(a0(980)→π0η) andΓλλ(a2(1320))=1.01±0.14±0.22KeV. For thef0(975) andf4(2050) upper limits of the widths were obtained,Γλλ(f0(975))<0.6 KeV, andΓλλ(f4(2050))<1.1 KeV, both at the 95% C.L. Assuming that the spin 0 background under thef2(1270) is small, thef2(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→π0π0 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.
Data read from graph.. Event distributions uncorrected for angular acceptance and the efficiency with energy of the detector RE = GAMMA GAMMA --> PI0 PI0.
Data read from graph.
Data read from graph.. Event distributions uncorrected for angular acceptance and the efficiency with energy of the detector RE = GAMMA GAMMA --> PI0 PI0.