“School of Particles And Accelerator”

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Paper   IPM / Particles And Accelerator / 8943
School of Particles and Accelerator
  Title:   Meson clouds and dressed constituent quarks in the complete RG-improvement approach
1.  K. Keshavarzian
2.  Abolfazl Mirjalili
3.  Mohammad Mehdi Yazdanpanah
  Status:   Published
  Journal: Int. J. Mod. Phys. A
  No.:  31
  Vol.:  23
  Year:  2008
  Pages:   5037-5058
  Supported by:  IPM
Sea quark densities in the nucleon, based on the constituent quark model are analyzed. To model the asymmetry of these densities the meson cloud or alternatively chiral quark model (�QM) is used. Valence quark densities of the meson which are required to extract the sea quark densities in the constituent quarks are obtained using the phenomenological valon model. In addition to the standard pertutrbative QCD approach which uses the MS scheme with a physical choice of renormalization scale , the calculations are also performed using the Complete RG-Improvement (CORGI) approach. To avoid a physically unacceptable Q2 behavior of the sea densities inside the constituent quarks, we assume that the free parameter which exists in the vertex function of the boson-quark splitting function, is Q2-dependent. Using the unsymmetrized sea densities of the nucleon which result from convoluting the constituent density in a nucleon with the quark density in the constituent quark, the Gottfried Sum Rule (GSR) is calculated using the standard perturbative and CORGI approaches. The CORGI result is closer to the reported experimental value for the GSR. The extracted sea and valence quark density in a nucleon, using �QM and also the CORGI approach, have been compared with available experimental data and what was obtained, based on �QM in the standard approach. This comparison confirms the anticipated better agreement of the CORGI approach with the data.

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