Abstract
We use new high statistics data from CLAS and COMPASS on the nucleon's spin structure function at low Bjorken x and low virtuality, Q^2 < 0.5 GeV^2, together with earlier measurements from the SLAC E-143, HERMES and GDH experiments to estimate the effective intercept(s) for spin dependent Regge theory. We find alpha_{a_1} = 0.31 \pm 0.04 for the intercept describing the high-energy behaviour of spin dependent photoabsorption together with a new estimate for the high-energy part of the Gerasimov-Drell-Hearn sum-rule, -15 \pm 2 mu b from photon-proton centre-of-mass energy greater than 2.5 GeV. Our value of alpha_[a_1} suggests QCD physics beyond a simple straight-line a_1 trajectory.
Highlights
The high-energy behavior of the spin dependent part of the photon-proton total cross section is important for determining the Gerasimov-Drell-Hearn sum rule for polarized photoabsorption with real photons [1,2], as well as studies of the transition from polarized photoproduction to deep inelastic scattering [3]
The large s dependence of hadronic total cross sections is usually described in terms of Regge exchanges [9,10], e.g., summing the exchanges of hadrons with given quantum numbers that occur along Regge trajectories with slope related to the confinement potential
It is very interesting that the intercept in Eq (11) is close to the value found in deep inelastic scattering, viz., αa1 (Q2) = 0.22 ± 0.07 at Q2 = 3 GeV2 in Eq (4)
Summary
The high-energy behavior of the spin dependent part of the photon-proton total cross section is important for determining the Gerasimov-Drell-Hearn sum rule for polarized photoabsorption with real photons [1,2], as well as studies of the transition from polarized photoproduction to deep inelastic scattering [3]. We investigate this behavior using the new high statistics measurements from CLAS at Jefferson Laboratory [4]. Regge phenomenology has had considerable success in describing unpolarized high-energy scattering processes [11]
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