A Combined Study of the Pion's Static Properties and form Factors

Autor(es)

El-Bennich, B. ^{[1, 2]} ; de Melo, J. P. B. C. ^[2] ; Frederico, T.

Afiliação do(s) autor(es)

^[1] Univ Estadual Paulista, Inst Fis Teor, BR-01140070 Sao Paulo - Brazil

^[2] Univ Cruzeiro Sul, Lab Fis Teor & Computac, BR-01506000 Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: FEW-BODY SYSTEMS; v. 54, n. 11, p. 1851-1863, NOV 2013.
• Citações Web of Science: 20

Resumo

We study consistently the pion's static observables and the elastic and gamma{*} gamma -> pi (0) transition form factors within a light-front model. Consistency requires that all calculations are performed within a given model with the same and single adjusted length or mass-scale parameter of the associated pion bound-state wave function. Our results agree well with all extent data including recent Belle data on the gamma{*} gamma -> pi (0) form factor at large q (2), yet the BaBar data on this transition form factor resists a sensible comparison. We relax the initial constraint on the bound-state wave function and show the BaBar data can partially be accommodated. This, however, comes at the cost of a hard elastic form factor not in agreement with experiment. Moreover, the pion charge radius is about 40 % smaller than its experimentally determined value. It is argued that a decreasing charge radius produces an ever harder form factor with a bound-state amplitude difficultly reconcilable with soft QCD. We also discuss why vector dominance type models for the photon-quark vertex, based on analyticity and crossing symmetry, are unlikely to reproduce the litigious transition form factor data. (AU)

• Processo FAPESP: 09/51296-1 - Efeitos hadrônicos na física dos quarks pesados
• Beneficiário: Bruno Omar El Bennich
• Modalidade de apoio: Auxílio à Pesquisa - Jovens Pesquisadores
• Processo FAPESP: 09/53351-0 - Particulas elementares e fisica computacional.
• Beneficiário: Joao Pacheco Bicudo Cabral de Mello
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 10/05772-3 - Efeitos hadrônicos na física dos quarks pesados
• Beneficiário: Bruno Omar El Bennich
• Modalidade de apoio: Bolsas no Brasil - Jovens Pesquisadores
• Processo FAPESP: 09/00069-5 - Aspectos de poucos corpos na física de muitos corpos
• Beneficiário: Tobias Frederico
• Modalidade de apoio: Auxílio à Pesquisa - Temático