Doubleπ0Photoproduction on the Proton at GRAAL

Abstract

The double pi(0) photoproduction off the proton has been measured in the beam energy range of 0.65-1.5 GeV. The total and differential cross sections and the Sigma beam asymmetry were extracted. The total cross section measured for the first time in the third resonance region of the nucleon shows a prominent peak. The interpretation of these results by two independent theoretical models infers mostly the selective excitation of P11- and D13-nucleon resonances.

Experimental study of theγp→π0π0preaction with the Crystal Ball/TAPS detector system at the Mainz Microtron

“…1, we include only the most recent results obtained with three different experimental setups: DAPHNE [8], TAPS [12], and Crystal Ball/TAPS [40]. The other measurements were performed at ELSA [11,12] and by GRAAL [6]. The results obtained in this work are in good agreement with all previous measurements within the given statistical and systematic uncertainties.…”

“…This model describes roughly the experimental distributions in the energy region close to D 13 (1520). At the energies below E γ = 900 MeV, the shape of the measured cos distributions shows good agreement with formula (6). However, at the energies below D 13 (1520), where the model of Ref.…”

“…The results obtained in this work are compared to the existing data from GRAAL [6], CB-ELSA [11,12], DAPHNE [8], TAPS [12], and Crystal Ball/TAPS [40]. Only statistical uncertainties are shown for all data.…”

“…During the last two decades, an extensive study of doublepion photoproduction for E γ < 1 GeV has been undertaken [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The theoretical interpretation of the data in various isospin channels was carried out using different phenomenological analyses [15][16][17][18][19][20].…”

Experimental study of the γp→π0ηp reaction with the A2 setup at the Mainz Microtron

“…[7][8][9][10][11][12][13][14][15][16]). In comparison to the widely studied γN → 2π 0 N reaction, the γN → π 0 ηN reaction provides a more selective identification of contributing resonances and their decay modes.…”