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Target independence of the ‘proton spin’ effect

G.M. Shore, Graham Shore

Nuclear Physics B - Proceedings Supplements, Volume: "39BC", Issue: 2-3, Pages: 101 - 105

Swansea University Author: Graham Shore

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Abstract

Recent work by the author in collaboration with S. Narison and G. Veneziano on the EMC-SMC-SLAC `proton spin' effect is reviewed. This uses a novel approach to deep inelastic scattering in which the matrix elements arising from the OPE are factorised into composite operator propagators and prop...

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Published in: Nuclear Physics B - Proceedings Supplements
ISSN: 09205632
Published: 1994
Online Access: Check full text

URI: https://cronfa.swan.ac.uk/Record/cronfa31910
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Abstract: Recent work by the author in collaboration with S. Narison and G. Veneziano on the EMC-SMC-SLAC `proton spin' effect is reviewed. This uses a novel approach to deep inelastic scattering in which the matrix elements arising from the OPE are factorised into composite operator propagators and proper vertices. For polarised $\mu p$ scattering, the composite operator propagator is equated to the square root of the first moment of the QCD topological susceptibility, $\sqrt{\chi~\prime(0)}$. We evaluate $\chi~\prime(0)$ using QCD spectral sum rules and find a significant suppression relative to its OZI expectation. This is identified as the source of the violation of the Ellis-Jaffe sum rule for the first moment of the polarised proton structure function $g_1~p$. Our predictions, $\int_0~1 dx g_1~p(x;Q~2=10GeV~2) = 0.143\pm 0.005$ and $\Delta\Sigma =0.353\pm 0.052$, are in excellent agreement with the new SMC data. This supports our earlier conjecture that the suppression in the flavour singlet component of the first moment of $g_1~p$ is a target-independent feature of QCD related to the $U(1)$ anomaly and is not a special property of the proton
College: Faculty of Science and Engineering
Issue: 2-3
Start Page: 101
End Page: 105