arXiv subjects
Publications and source records attributed to J. Edelmann.
We present a detailed analysis of resonance contributions in the context of higher twist effects in the moments of the proton spin structure function g_1. For each of these moments, it is found that there exists a characteristic Q^2 region in which (perturbative) higher twist corrections coexist with (non-perturbative) resonance contribution of comparable magnitude.
We generalize the sum rules for the nucleon electric plus magnetic polarizability $Σ=α+β$ and for the nucleon spin-polarizability $γ$, to virtual photons with $Q^2>0$. The dominant low energy cross sections are represented in our calculation by one-pion-loop graphs of relativistic baryon chiral perturbation theory and the $Δ(1232)$-resonance excitation. For the proton we find good agreement of the calculated $Σ_p(Q^2)$ with empirical values obtained from integrating up electroproduction data for $Q^2<0.4 GeV^2$. The proton spin-polarizability $γ_p(Q^2)$ switches sign around $Q^2= 0.4 GeV^2$ and it joins smoothly the "partonic" curve, extracted from polarized deep-inelastic scattering, around $Q^2=0.7 GeV^2$. For the neutron our predictions of $Σ_n(Q^2)$ and $γ_n(Q^2)$ agree reasonably well at $Q^2=0$ with existing determinations. Upcoming (polarized) electroproduction experiments will be able to test the generalized polarizability sum rules investigated here.
We investigate polarized deuteron structure functions at small values of the Bjorken variable, x < 0.1. In this region contributions from the coherent interaction of diffractively excited hadronic states with both nucleons become important. A proper treatment of this process requires an extension of the Glauber-Gribov multiple scattering theory to include spin degrees of freedom. In the kinematic domain of current fixed target experiments we observe that shadowing effects in g_1d are approximately twice as large as for the unpolarized structure function F_2d. Furthermore at x < 0.1 the tensor structure function b_1 is found to receive significant contributions from coherent double scattering.
We investigate shadowing corrections to the polarized deuteron structure functions g_1^d and b_1. In the kinematic domain of current fixed target experiments we observe that shadowing effects in g_1^d are approximately twice as large as for the unpolarized structure function F_2^d. Furthermore, we find that b_1 is surprisingly large at x < 0.1 and receives dominant contributions from coherent double scattering.