P{sub 33}(1232) resonance contribution to the amplitudes M{sub 1+}{sup 3/2},E{sub 1+}{sup 3/2},S{sub 1+}{sup 3/2} from an analysis of the p(e,e{sup {prime}}p){pi}{sup 0} data at Q{sup 2}=2.8, 3.2, and 4;(GeV/c){sup 2} within the dispersion relation approach
- Yerevan Physics Institute, Alikhanian Brothers St.2, Yerevan, 375036 (Armenia)
- Thomas Jefferson National Accelerator Facility, 12000 Jefferson Avenue, Newport News, Virginia 23606 (United States)
Within the fixed-t dispersion relation approach we have analyzed the TJNAF and DESY data on the exclusive p(e,e{sup {prime}}p){pi}{sup 0} reaction in order to find the P{sub 33}(1232) resonance contribution to the multipole amplitudes M{sub 1+}{sup 3/2},E{sub 1+}{sup 3/2},S{sub 1+}{sup 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 {gamma}{sup {asterisk}}N{r_arrow}P{sub 33}(1232) transition are 0.039{plus_minus}0.029,0.121{plus_minus}0.032, 0.04{plus_minus}0.031 for Q{sup 2}=2.8, 3.2, and 4(GeV/c){sup 2}, respectively. The comparison with the data at low Q{sup 2} shows that there is no evidence for the presence of the visible perturbative QCD (PQCD) contribution into the transition {gamma}N{r_arrow}P{sub 33}(1232) at Q{sup 2}=3{endash}4GeV{sup 2}. The ratio S{sub 1+}{sup 3/2}/M{sub 1+}{sup 3/2} for the resonance parts of multipoles is {minus}0.049{plus_minus}0.029, {minus}0.099{plus_minus}0.041, {minus}0.085{plus_minus}0.021 for Q{sup 2}=2.8, 3.2, and 4(GeV/c){sup 2}, respectively. Our results for the transverse form factor G{sub T}(Q{sup 2}) of the {gamma}{sup {asterisk}}N{r_arrow}P{sub 33}(1232) transition are lower than the values obtained from the inclusive data. With increasing Q{sup 2}, Q{sup 4}G{sub T}(Q{sup 2}) decreases, so there is no evidence for the presence of the PQCD contribution here too. {copyright} {ital 1999} {ital The American Physical Society}
- OSTI ID:
- 328567
- Journal Information:
- Physical Review, D, Journal Name: Physical Review, D Journal Issue: 5 Vol. 59; ISSN PRVDAQ; ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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