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Titolo:
The E2/M1 and C2/M1 ratios and form factors in N -> Delta transitions
Autore:
Tiator, L; Drechsel, D; Hanstein, O; Kamalov, SS; Yang, SN;
Indirizzi:
Univ Mainz, Inst Kernphys, D-55099 Mainz, Germany Univ Mainz Mainz Germany D-55099 , Inst Kernphys, D-55099 Mainz, Germany Joint Inst Nucl Res Dubna, Dubna 141980, Moscow Region, Russia Joint Inst Nucl Res Dubna Dubna Moscow Region Russia 141980 egion, Russia Natl Taiwan Univ, Dept Phys, Taipei 10617, Taiwan Natl Taiwan Univ Taipei Taiwan 10617 iv, Dept Phys, Taipei 10617, Taiwan
Titolo Testata:
NUCLEAR PHYSICS A
fascicolo: 1-2, volume: 689, anno: 2001,
pagine: 205C - 214C
SICI:
0375-9474(20010618)689:1-2<205C:TEACRA>2.0.ZU;2-S
Fonte:
ISI
Lingua:
ENG
Soggetto:
RELATIVIZED QUARK-MODEL; PION-PHOTOPRODUCTION; DELTA(1232) RESONANCE; MOMENTUM-TRANSFER; ELECTROPRODUCTION; N->DELTA; AMPLITUDES; P((GAMMA)OVER-RIGHT-ARROW,P)PI(0); DEPENDENCE; NUCLEON;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
36
Recensione:
Indirizzi per estratti:
Indirizzo: Tiator, L Univ Mainz, Inst Kernphys, D-55099 Mainz, Germany Univ Mainz Mainz Germany D-55099 nphys, D-55099 Mainz, Germany
Citazione:
L. Tiator et al., "The E2/M1 and C2/M1 ratios and form factors in N -> Delta transitions", NUCL PHYS A, 689(1-2), 2001, pp. 205C-214C

Abstract

A partial wave analysis of pion photoproduction has been obtained in the framework of fixed-t dispersion relations valid from threshold up to 500 MeV. In the resonance region we have precisely determined the electromagnetic properties of the Delta (1232) resonance, in particular the E2/M1 ratio R-EM = (-2.5 +/- 0.1)%. For pion electroproduction recent experimental data from Mainz, Bates and JLab for Q(2) up to 4.0 (GeV/c)(2) have been analyzed with two different models, an isobar model (MAID) and a dynamical model. TheE2/M1 ratios extracted with these two models show, starting from a small and negative value at the real photon point, a clear tendency to cross zero,and become positive with increasing Q(2). This is a possible indication ofa very slow approach toward the pQCD region. The C2/M1 ratio near the photon point is found as R-SM(0) = (-6.5 +/- 0.5)%. At high Q(2) the absolute value of the ratio is strongly increasing, a further indication that pQCD isnot yet reached.

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Documento generato il 05/07/20 alle ore 10:18:54