Electroexcitation of the Roper resonance from CLAS data

Conference · Mon Oct 29 04:00:00 EDT 2007

OSTI ID:918575

Aznauryan, Inna; Burkert, Volker

The helicity amplitudes of the electroexcitation of the Roper resonance on proton are extracted at $1.7<4.2~GeV^2$ from recent high precision JLab-CLAS cross sections data and longitudinally polarized beam asymmetry for $$\pi^+$$ electroproduction on protons. The analysis is made using two approaches, dispersion relations and unitary isobar model, which give consistent results. It is found that the transverse helicity amplitude for the $$\gamma^* p\rightarrow P_{11}(1440)$$ transition, which is large and negative at $Q^2=0$, becomes large and positive at $$Q^2\simeq 2~GeV^2$$, and then drops slowly with $Q^2$. Longitudinal helicity amplitude, that was previously found from CLAS data as large and positive at $Q^2=0.4,~0.65~GeV^2$, drops with $Q^2$. These results rule out the presentation of $$P_{11}(1440)$$ as a $q^3G$ hybrid state, and provide strong evidence in favor of this resonance as a first radial excitation of the $3q$ ground state.

• Research Organization: Thomas Jefferson National Accelerator Facility, Newport News, VA
• Sponsoring Organization: USDOE - Office of Science (SC)
• DOE Contract Number: AC05-06OR23177
• OSTI ID: 918575
• Report Number(s): JLAB-PHY-07-743; DOE/OR/23177-0182
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
AMPLITUDES
ASYMMETRY
CROSS SECTIONS
DISPERSION RELATIONS
ELECTROPRODUCTION
EXCITATION
GROUND STATES
HELICITY
ISOBAR MODEL
POLARIZED BEAMS
PROTONS
RESONANCE