are taken into account in an explicit form. The inclusion of 
pairs leads automatically to an excess of 
over 
quarks in the proton, in ageement with experimental data.]]>
. La inclusión de los pares lleva inmediatamente a un exceso de cuarks sobre en el protón, de acuerdo con los datos experimentales.]]>
R. Bijkerª and E. Santopintob
ª Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Apartado Postal 70–543 México, D.F 04510, México e–mail: bijker@nucleares.unam.mx
b I.N.F.N. and Dipartimento di Fisica, via Dodecaneso 33, Genova, I–16146, Italy, e–mail: santopinto@ge.infn.it
Recibido el 31 de marzo de 2008
Aceptado el 31 de mayo de 2008
]]> Abstract
The flavor asymmetry of the nucleon sea is discussed in an unquenched quark model for baryons in which the effects of quark–antiquark pairs 
are taken into account in an explicit form. The inclusion of 
pairs leads automatically to an excess of 
over 
quarks in the proton, in ageement with experimental data.
Keywords: Protons and neutrons; quark models; flavor symmetries; Gottfried sum rule.
Resumen
Se discute la asimetría de sabor del nucleón en una extensión del modelo de cuarks en que se toman en cuenta de manera explícita los efectos de creación de pares cuark–anticuark 
. La inclusión de los pares lleva inmediatamente a un exceso de cuarks sobre en el protón, de acuerdo con los datos experimentales.
Descriptores: Protones y neutrones, modelos de cuarks, simetría de sabor, regla de suma de Gottfried.
PACS: 14.20.Dh; 12.39.–x; 11.30.Hv; 11.55.Hx
]]> DESCARGAR ARTÍCULO EN FORMATO PDF
Acknowledgments
This work was supported in part by PAPIIT–UNAM, México (grant IN113808) and in part by I.N.F.N., Italy.
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