Higher twists in spin structure functions from a 'constituent quark' point of view
We discuss the implications of a ''constituent quark'' structure of the nucleon for the leading (1/Q{sup 2-}) power corrections to the spin structure functions. Our basic assumption is the presence of quark-gluon correlations in the nucleon wave function, whose size, {rho} {approx} 0.3 fm, is small compared to the nucleon radius, R (two-scale picture). We argue that in this picture the isovector twist-4 matrix element in the proton has a sizable negative value, M{sub N}{sup 2}|f{sub 2}{sup u-d}| {approx} {rho}{sup -2}, while the twist-3 matrix elements are small, M{sub N}{sup 2}d{sub 2} {approx} R{sup -2}. These findings are in agreement with the result of a QCD fit to g{sub 1} world data, including recent neutron data from HERMES and Jefferson Lab Hall A, which gives M{sub N}{sup 2}f{sub 2}{sup u-d} = -0.28 {+-} 0.08 GeV{sup 2}.
- Research Organization:
- Thomas Jefferson National Accelerator Facility, Newport News, VA (US)
- Sponsoring Organization:
- USDOE Office of Energy Research (ER) (US)
- DOE Contract Number:
- AC05-84ER40150
- OSTI ID:
- 833532
- Report Number(s):
- JLAB-THY-04-32; DOE/ER/40150-2920
- Country of Publication:
- United States
- Language:
- English
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