“School of Particles And Accelerator”

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Paper   IPM / Particles And Accelerator / 9569
School of Particles and Accelerator
  Title:   Polarized Parton Distribution, Orbital Angular Momentum, and the Violation of a8
1.  F . Arash
2.  Fatemeh Taghavi-Shahri
  Status:   Published
  Journal: AIP CONF PROC
  Vol.:  1105
  Year:  2009
  Pages:   181-184
  Supported by:  IPM
We use the so-called valon model, to describe the spin structure of the nucleon. We show that about 40 percent of the nucleon spin is carried by the polarized valence quarks. The remaining part comes from the gluon polarization and the orbital angular momentum. It is shown that the sea quark contributions to the spin of any hadron is simply marginal and consistent with zero. We also found that the value of a8 is substantially smaller than the value inferred from hyperon?beta decay, suggesting that full SU(3) symmetric assumption needs to be reconsidered. New and emerging experimental data tend to support this finding. Finally, we show that within the model presented here the experimental data on the polarized structure functions are reproduced.

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