The role of the U (1) A anomaly in QCD phenomenology is reviewed, focus-ing on the relation between quark dynamics and gluon topology. Topics covered include a generalisation of the Witten-Veneziano formula for the mass of the η ′ , the determination of pseudoscalar meson decay constants, radiative pseudoscalar decays and the U (1) A Goldberger-Treiman relation. Sum rules are derived for the pr...

The determination of the strange quark contribution to the nucleonic axial and vector weak currents has raised large and continuous interest in theoretical and experimental physics, especially after the measurements of the polarised structure function g 1 of the proton, which indicated a non–zero contribution of the strange quark to the proton spin. In recent years, intermediate energy physics ...

Recent progress in the understanding of the nucleon is presented. The unpolarised structure functions are obtained with unprecedented precision from the combined H1 and ZEUS data and are used to extract proton parton distribution functions via NLO QCD fits. The obtained parametrisation displays an improved precision, in particular at low Bjorken x, and leads to precise predictions of cross sect...

Polarised neutron scattering is the method of choice to study magnetism in condensed matter. neutrons are typically very low flux, and complex experimental configurations further reduce count rate. Neutron polarisation corrections would therefore be needed. Here we analytically derive formulae corrected partial differential cross-sections. The analytical designed for longitudinal analysis, corr...

We study the structure function gT = g1+g2, using the factorisation method. It turns out that gT has a much simpler operator structure as compared to g2, in spite of the fact that, like g2, gT has a twist-three component not suppressed by powers of Q . We demonstrate factorisation of the hadronic tensor into hard and soft parts for the case of gT , even though g2 does not admit of such a demons...

This talk gives a brief discussion of extended fracture functions, which parametrise the non-perturbative physics in the target fragmentation region of semi-inclusive DIS. In the forward limit z → 1, it can be seen that fracture functions can be identified with insertions of composite operators. This enables polarised fracture functions to be used to test a target-independence hypothesis of the...

The Drell-Hearn-Gerasimov sum-rule is really two sum-rules: one for each of the valence and the sea/glue contributions to the nucleon wavefunction. The convergence of these sum-rules follows from the Froissart bound for spin dependent processes in QCD and is necessary for the consistency of the constituent quark model of low energy QCD. Some challenges for future polarised photoproduction exper...

Photoproduction spin sum-rules offer a new window on the spin structure of the nucleon that complements the information we can learn from polarised deep inelastic scattering experiments. We review the theory and present status of the Drell-Hearn-Gerasimov sum-rule in QCD, emphasising the possible relation between the present " discrepancy " in this sum-rule and the nucleon's strangeness magneti...

When the new data on polarised lepton nucleon scattering are compared at the same value of Q 2 and with a common set of assumptions, a consistent picture of the spin content of the nucleon begins to emerge. Higher order effects in 0(α s), higher twist effects, modern data on unpolarised structure functions and an updated value for F/D are all important in analysing the data. The detailed x depe...