Electroexcitation of the Roper Resonance at Q2<4.2GeV2

Conference · Mon Oct 01 04:00:00 EDT 2007

OSTI ID:1964102

Aznauryan, Inna ^[1]; Burkert, Volker ^[2]; Mokeev, Victor ^[2]

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1. Yerevan Physics Institute; Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

The helicity amplitudes of the electroexcitation of the Roper resonance on proton are extracted at 1.7 < Q2 < 4.2 GeV 2 from recent high precision CLAS data on the cross sections and longitudinally polarized beam asymmetry for ?+ electroproduction on protons. The phenomenological analysis of the data was made using two approaches: dispersion relations and unitary isobar model. It is found that the transverse helicity amplitude for the ?p ! P+ 11(1440) transition, which is large and negative at Q2 = 0, becomes large and positive at Q2 ' 2 GeV 2, and then decreases smoothly. Longitudinal helicity amplitude, which previously was found from CLAS data as large and positive at Q2 = 0.4, 0.65 GeV 2, with increasing Q2 drops rapidly. These results definitely rule out interpretation of the P11(1440) as a q3G hybrid state, and provide strong evidence in favour of the interpretation of this state as a radial excitation of the nucleon.

• Research Organization: Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP)
• DOE Contract Number: AC05-06OR23177
• OSTI ID: 1964102
• Report Number(s): LAB-PHY-07-959; DOE/OR/23177-5911
• Country of Publication: United States
• Language: English