Photoproduction of pi+ pi- meson pairs on the proton

The exclusive reaction gamma p -> pp(+)pi(-) was studied in the photon energy range 3.0-3.8 GeV and the momentum transfer range 0.4 < -t < 1.0 GeV(2). Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. In this kinematic range, the integrated luminosity was about 20 pb(-1). The reaction was isolated by detecting the pi(+) and proton in CLAS, and reconstructing the pi(-) via the missing-mass technique. Moments of the di-pion decay angular distributions were derived from the experimental data. Differential cross sections for the S, P, and D-waves, in the M(pi+pi-) mass range 0.4-1.4 GeV, were derived performing a partial wave expansion of the extracted moments. Beside the dominant contribution of the rho(770) meson in the P-wave, evidence for the f(0)(980) and the f(2)(1270) mesons was found in the S and D-waves, respectively. The differential production cross sections d sigma/dt for individual waves in the mass range of the above-mentioned mesons were extracted. This is the first time the f(0)(980) has been measured in a photoproduction experiment.