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Doctoral Thesis
DOI
https://doi.org/10.11606/T.43.2005.tde-22012007-140200
Document
Author
Full name
Rômulo Rodrigues da Silva
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2005
Supervisor
Committee
Nielsen, Marina (President)
Bracco, Mirian Enriqueta
Deppman, Airton
Grassi, Frederique Marie Brigitte Sylvie
Natale, Adriano Antonio
Title in Portuguese
"Constantes de acoplamento a partir das regras de soma da QCD"
Keywords in Portuguese
Pentaquarks
Regras de soma da QCD
Vertice J/Psi DD*
Abstract in Portuguese
Usamos as regras de soma da QCD para obter a massa dos pentaquarks " 'teta' POT.+"(1540) e "'ksi' POT.--" (1862), a largura de decaimento da "'teta' POT.+" e a constante de acoplamento e fator de forma presentes no vertice J/ 'psi' "DD POT.*". No estudo dos pentaquarks, usamos dois tipos de campos interpolantes contendo dois diquarks altamente correlacionados. Obtemos as massas consistentes com os dados experimentais, porém esta regra de soma têm uma grande contribuição do contínuo e a OPE não é muito boa. Obtivemos uma largura de decaimento compatível com os valores experimentais desde que sejam subtraídos diagramas que representam a " 'teta' POT.+" como um estado ligado K - n. No estudo do vértice vertice J/ 'psi' "DD POT.*" calculamos o fator de forma e a constante de acoplamento, considerando três casos: D off-shell, "D POT.*" off-shell e J/ 'psi' off-shell. A constante de acoplamento é a mesma nesses três casos, porém o fator de forma depende da escolha da partícula off-shell, onde para a J/ 'psi' off-shell o fator de forma é bem mais duro que o fator de forma obtido para os outros casos. Também comparamos os nossos resultados com outros métodos: o modelo de quark méson constituintes e o modelo de quarks relativísticos constituintes
Title in English
The coupling constants in QCD sum rules
Keywords in English
J/Psi DD* vertex
Pentaquarks
QCD sum rules
Abstract in English
We use the QCD sum rules to obtain the masses of the pentaquarks _+(1540) and _−−(1862), _+ decay width and the coupling constant and the form factor for the J/ DD* vertex.In the study of the pentaquarks, we use two kinds of interpolating fields, containing two highly correlated diquarks. We get the masses in a good agreement with the experimental value, but this sum rule has a large continuuum contribution and the OPE convergence is not so good. We get the decay width compatible with the experimental value, since we subtract the diagrams that represent _+ as a K − n bound state. In the study of J/ DD* vertex, we calculate the form factor and the coupling constant considering three cases: D off-shell, D* off-shell and J/ off-shell. The coupling constant is the same in those three cases, however the form factor depends on the choice of the particle off-shell, where for the J/ off-shell the form factor is much harder than the form factor obtained for the other cases. We also compare our results with other methods: the constituent quark meson model and the relativistic constituent quark model.
 
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1458141.pdf (654.43 Kbytes)
Publishing Date
2007-02-01
 
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