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Comparison of the Gottfried and Adler sum rules within the large-Nc expansion.

Broadhurst, D. J. and Kataev, A. L. and Maxwell, C. J. (2004) 'Comparison of the Gottfried and Adler sum rules within the large-Nc expansion.', Physics letters B., 590 (1-2). pp. 76-85.


The Adler sum rule for deep inelastic neutrino scattering measures the isospin of the nucleon and is hence exact. By contrast, the corresponding Gottfried sum rule for charged lepton scattering was based merely on a valence picture and is modified both by perturbative and by non-perturbative effects. Noting that the known perturbative corrections to two-loop order are suppressed by a factor 1/Nc2, relative to those for higher moments, we propose that this suppression persists at higher orders and also applies to higher-twist effects. Moreover, we propose that the differences between the corresponding radiative corrections to higher non-singlet moments in charged-lepton and neutrino deep inelastic scattering are suppressed by 1/Nc2, in all orders of perturbation theory. For the first moment, in the Gottfried sum rule, the substantial discrepancy between the measured value and the valence-model expectation may be attributed to an intrinsic isospin asymmetry in the nucleon sea, as is indeed the case in a chiral-soliton model, where the discrepancy persists in the limit Nc→∞.

Item Type:Article
Keywords:Unpolarized structure functions, Gottfried sum rule, Large-Nc limit.
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Record Created:12 May 2008
Last Modified:09 Sep 2011 14:37

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