P33(1232) resonance contribution to the amplitudes M1+3/2,E1+3/2,S1+3/2 from an analysis of the p(e,ep)π0 data at Q2=2.8, 3.2, and 4(GeV/c)2 within the dispersion relation approach

I. G. Aznauryan and S. G. Stepanyan
Phys. Rev. D 59, 054009 – Published 1 February 1999
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Abstract

Within the fixed-t dispersion relation approach we have analyzed the TJNAF and DESY data on the exclusive p(e,ep)π0 reaction in order to find the P33(1232) resonance contribution to the multipole amplitudes M1+3/2,E1+3/2,S1+3/2. As an input for the resonance and nonresonance contributions to these amplitudes the earlier obtained solutions of the integral equations which follow from dispersion relations are used. The obtained values of the ratio E2/M1 for the γ*NP33(1232) transition are 0.039±0.029,0.121±0.032, 0.04±0.031 for Q2=2.8, 3.2, and 4(GeV/c)2, respectively. The comparison with the data at low Q2 shows that there is no evidence for the presence of the visible perturbative QCD (PQCD) contribution into the transition γNP33(1232) at Q2=34GeV2. The ratio S1+3/2/M1+3/2 for the resonance parts of multipoles is 0.049±0.029, 0.099±0.041, 0.085±0.021 for Q2=2.8, 3.2, and 4(GeV/c)2, respectively. Our results for the transverse form factor GT(Q2) of the γ*NP33(1232) transition are lower than the values obtained from the inclusive data. With increasing Q2, Q4GT(Q2) decreases, so there is no evidence for the presence of the PQCD contribution here too.

  • Received 14 August 1998

DOI:https://doi.org/10.1103/PhysRevD.59.054009

©1999 American Physical Society

Authors & Affiliations

I. G. Aznauryan*

  • Yerevan Physics Institute, Alikhanian Brothers St.2, Yerevan, 375036 Armenia

S. G. Stepanyan

  • Thomas Jefferson National Accelerator Facility, 12000 Jefferson Avenue, Newport News, Virginia 23606
  • Yerevan Physics Institute, Alikhanian Brothers St.2, Yerevan, 375036 Armenia

  • *Email addresses: aznaur@jerewan1.yerphi.am, aznaury@cebaf.gov
  • Email address: stepanyan@jlab.org

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Vol. 59, Iss. 5 — 1 March 1999

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