Electroexcitation of the Roper resonance for 1.7<Q{sup 2}<4.5 GeV{sup 2} in e-vectorp{yields}en{pi}{sup +}

Journal Article · Wed Oct 15 00:00:00 EDT 2008 · Physical Review. C, Nuclear Physics

DOI:https://doi.org/10.1103/PHYSREVC.78.045209· OSTI ID:21192347

Aznauryan, I G ^[1]; Burkert, V D; Avakian, H; Carman, D S; Cords, D; Degtyarenko, P V; Deur, A; Elouadrhiri, L; Guo, L; Gyurjyan, V; Heddle, D; Ito, M M; Mecking, B A; Mestayer, M D; Niczyporuk, B B; Sharabian, Y G; Smith, E S; Stepanyan, S; Weygand, D P; Wolin, E ^[1]

---

1. Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States)

The helicity amplitudes of the electroexcitation of the Roper resonance are extracted for 1.7<Q{sup 2}<4.5 GeV{sup 2} from recent high precision JLab-CLAS cross section and longitudinally polarized beam asymmetry data for {pi}{sup +} electroproduction on protons at W=1.15-1.69 GeV. The analysis is made using two approaches, dispersion relations and a unitary isobar model, which give consistent Q{sup 2} behavior of the helicity amplitudes for the {gamma}*p{yields}N(1440)P{sub 11} transition. It is found that the transverse helicity amplitude A{sub 1/2}, which is large and negative at Q{sup 2}=0, becomes large and positive at Q{sup 2}{approx_equal}2 GeV{sup 2}, and then drops slowly with Q{sup 2}. The longitudinal helicity amplitude S{sub 1/2}, which was previously found from CLAS e-vectorp{yields}ep{pi}{sup 0},en{pi}{sup +} data to be large and positive at Q{sup 2}=0.4,0.65 GeV{sup 2}, drops with Q{sup 2}. Available model predictions for {gamma}*p{yields}N(1440)P{sub 11} allow us to conclude that these results provide strong evidence in favor of N(1440)P{sub 11} as a first radial excitation of the 3q ground state. The results of the present paper also confirm the conclusion of our previous analysis for Q{sup 2}<1 GeV{sup 2} that the presentation of N(1440)P{sub 11} as a q{sup 3}G hybrid state is ruled out.

• OSTI ID: 21192347
• Journal Information: Physical Review. C, Nuclear Physics, Vol. 78, Issue 4; Other Information: DOI: 10.1103/PhysRevC.78.045209; (c) 2008 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2813
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ACCURACY
AMPLITUDES
ASYMMETRY
CEBAF ACCELERATOR
CROSS SECTIONS
DISPERSION RELATIONS
ELECTRON-PROTON INTERACTIONS
ELECTROPRODUCTION
EXCITATION
FORECASTING
GEV RANGE 01-10
GROUND STATES
HELICITY
HYBRIDIZATION
ISOBAR MODEL
N-1440 BARYONS
PIONS PLUS
POLARIZED BEAMS
PROTONS