Double pi(0) Photoproduction on the Proton at GRAAL.

Area of Science:

• Nuclear Physics
• Particle Physics
• Hadron Spectroscopy

Background:

• Understanding nucleon resonances is crucial for comprehending the strong nuclear force.
• The third resonance region of the nucleon is less explored, particularly for double pi(0) photoproduction.

Purpose of the Study:

• To measure double pi(0) photoproduction off the proton in the 0.65-1.5 GeV beam energy range.
• To extract total and differential cross sections and Sigma beam asymmetry.
• To investigate the excitation of nucleon resonances in this energy region.

Main Methods:

• Experimental measurement of double pi(0) photoproduction using a proton target.
• Analysis of beam energy from 0.65-1.5 GeV.
• Extraction of cross sections and beam asymmetry data.

Main Results:

• The total cross section shows a prominent peak, measured for the first time in the third resonance region.
• Differential cross sections and Sigma beam asymmetry were successfully extracted.
• Theoretical models suggest selective excitation of P11 and D13 nucleon resonances.

Conclusions:

• The observed peak in the total cross section provides new insights into nucleon structure.
• The results support the selective excitation of specific nucleon resonances (P11 and D13).
• This study contributes to a better understanding of hadron spectroscopy and the nucleon's excited states.