Updating spin-dependent Regge intercepts

TL;DR

This paper combines recent high-statistics data with previous measurements to refine the effective intercepts in spin-dependent Regge theory, revealing insights into QCD physics beyond simple models.

Contribution

It provides updated estimates of spin-dependent Regge intercepts and the high-energy contribution to the Gerasimov-Drell-Hearn sum-rule, based on new experimental data.

Findings

Alpha_{a_1} = 0.31 1 0.04 for spin-dependent photoabsorption

High-energy Gerasimov-Drell-Hearn sum-rule estimate: -15 1 2 5b

QCD physics beyond a simple straight-line a_1 trajectory

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.