Results are reported on the reaction p p → π + π + π − π − π 0 at six lab momenta spanning the region from 0.686 to 1.098 GeV/ c . The cross section for this process drops from 20.3 ± 1.2 mb at 0.686 GeV/ c to 13 1.0 mb at 1.098 GeV/ c . Resonance production is determined by means of a model which includes Bose symmetrization, Breit-Wigner amplitudes and Bose-Einstein correlations for the like-charged pion pairs in the nonresonant part of the amplitude. The likelihood fit to the resonance channels yields about 0.8% ηππ , 12% ϱ ± πππ , 2% f πππ , 8% ω ππ , 22% ϱ ± ϱ 0 π , 13% ωϱ 0 and 9% ω f with errors on the order of a few percent. Several percent A 1 ± ππ and X(1440) π were also needed to obtain good fits. The ϱ 0 πππ and ϱ 0 ϱ 0 π channels as well as A 2 ππ and A 1 0 ππ are consistent with zero. Reasonable fits to the mass distributions are obtained. Production angular distributions are found to be essentially uniform. The angular correlations between pion pairs are approximately fit by the simple model of resonance production with Bose symmetrization.
Axis error includes +- 0.0/0.0 contribution.
Axis error includes +- 0.0/0.0 contribution.
Exclusive rho^+ rho^- production in two-photon collisions involving a single highly-virtual photon is studied with data collected at LEP at centre-of-mass energies 89 GeV < \sqrt{s} < 209 GeV with a total integrated luminosity of 854.7 pb^-1. The cross section of the process gamma gamma^* -> rho^+ rho^- is determined as a function of the photon virtuality, Q^2, and the two-photon centre-of-mass energy, W_gg, in the kinematic region: 1.2 GeV^2 < Q^2 < 30 GeV^2 and 1.1 GeV < W_gg < 3 GeV. The \rho^+\rho^- production cross section is found to be of the same magnitude as the cross section of the process gamma gamma^* -> rho^0 rho^0, measured in the same kinematic region by L3, and to have similar W_gg and Q^2 dependences.
Cross sections for the reaction E+ E- --> E+ E- RHO+ RHO-. The differentialcross sections are corrected to the centre of each bin.
Cross sections for the two photon production of RHO+ RHO-.
Differential cross section for the process E+ E- --> E+ E- (RHO+ PI- PI0 + RHO+ RHO- PI0 PI0) corrected to bin centre.
The reaction e^+e^- -> e^+e^- proton antiproton is studied with the L3 detector at LEP. The analysis is based on data collected at e^+e^- center-of-mass energies from 183 GeV to 209 GeV, corresponding to an integrated luminosity of 667 pb^-1. The gamma gamma -> proton antiproton differential cross section is measured in the range of the two-photon center-of-mass energy from 2.1 GeV to 4.5 GeV. The results are compared to the predictions of the three-quark and quark-diquark models.
Total cross section for P PBAR production at a mean centre-of-mass energy of 197 GeV.
The cross section as a function of W for ABS(COS(THETA)) < 0.6.
The differential cross section as a function of COS(THETA*) for three W ranges.
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