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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:

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DOI (Published version): 10.1016/0920-5632(95)00051-A

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 09205632 1994 https://cronfa.swan.ac.uk/Record/cronfa31910 No Tags, Be the first to tag this record!
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 Faculty of Science and Engineering 2-3 101 105