Valence quark polarization in the nucleon and the deuteron data

Abstract

Within the framework of the so-called valon model, We argue that a substantial part of the nucleon spin, about 40%, is carried by the polarized valence quarks. The remaining is the result of cancelations between gluon polarization and the orbital angular momentum, where the gluon polarization is the dominant one. It is shown that the sea quark contributions to the spin of any hadron is simply marginal and consistent with zero. Our findings point to a substantially smaller value for a 8 than inferred from hyperon -β 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 g p,n,d 1 are reproduced. *

Gluon Spin Contribution to The Nucleon Spin

“…The growth of δg(x, Q 2 ) in part is compensated by a negative and large orbital angular momentum, L q,g . Although, we have not calcu- lated L q and L g individually, but the overall L q,g is given in [7].…”

“…This representation is also used to calculate the polarized structure of nucleon. The details can be found in [6]and [7]. We have worked in MS scheme with Λ QCD = 0.22 GeV and Q 2 0 = 0.283 GeV 2 .…”

“…We also note that the growth rate of δG is especially fast at low Q 2 . In order to satisfy the sum rule in Equation (1) it requires that the orbital angular momentum component to be negative and decreasing as Q 2 increases [7]. .…”

Gluon Contribution To The Nucleon Spin

“…We take the view that when a nucleon is probed with high Q 2 it is the internal structure of the valon that is resolved. The parton content of a valon is calculated in the next-to-leading order in QCD for the unpolarized [2,3] and the polarized [4,5] cases. The polarized structure function of the nucleon is obtained by the convolution of the valon structure with the valon distribution in the hosting nucleon:…”

Transversity distribution functions in the valon model

“…The valon model is a phenomenological model originally proposed by R. C. Hwa, [11] in early 80's. It was improved later by Hwa [12] and Others [13,14,15] and extended to the polarized cases [16,17,18]. In this model a hadron is viewed as three (two) constituent quark-like objects, called valons.…”