Low Q2 Measurement of g2p and the LT Spin Polarizability

الأصل · EN

JLab has been at the forefront of a program to measure the nucleon spin-dependent structure functions over a wide kinematic range, and data of unprecedented quality has been extracted in all three experimental halls. Moments of these quantities have proven to be powerful tools to test QCD sum rules and provide benchmark tests of Lattice QCD and Chiral Perturbation Theory. Precision measurements of g₁,₂ⁿ and g₁ᵖ have been performed as part of the highly successful `extended GDH program', but data on the g₂ᵖ structure function remain scarce. We discuss here JLab experiment E08-027, which will measure quantity g₂ᵖ in the resonance region at low Q². These data will be used to test the Burkhardt-Cottingham sum rule and to extract the higher moments δLTᵖ(Q²) and d₂ᵖ(Q²). Data in the Q² range 0.02<Q²<0.4 GeV² will provide unambiguous benchmark tests of χPT calculations on the lower end, while probing the transition region at the high Q² end where parton-like behaviour begins to emerge. This data will also have a significant impact on our theoretical understanding of the hyperfine structure of the proton, and reduce the systematic uncertainty of previous experiments which extracted the g₁ᵖ structure from purely longitudinal measurements.