CLAS Physics Database

E1b(E-91-023)

Spokespersons
V. Burkert, D. Crabb, R. Minehart
Year
2001
Abstract
The spin structure functions g1 for the proton and the deuteron have been measured over a wide kinematic range in x and Q2 using 1.6 and 5.7 GeV longitudinally polarized electrons incident upon polarized NH3 and ND3 targets at Jefferson Lab. Scattered electrons were detected in the CEBAF Large Acceptance Spectrometer, for 0.05 < Q2 < 5 GeV2 and W < 3 GeV. The first moments of g1 for the proton and deuteron are presented – both have a negative slope at low Q2, as predicted by the extended Gerasimov–Drell–Hearn sum rule. The first extraction of the generalized forward spin polarizability of the proton γ0p is also reported. This quantity shows strong Q2 dependence at low Q2. Our analysis of the Q2 evolution of the first moment of g1 shows agreement in leading order with Heavy Baryon Chiral Perturbation Theory. However, a significant discrepancy is observed between the γ0p data and Chiral Perturbation calculations for γ0p, even at the lowest Q2.
Publication
  1. Y. Prok, P. Bosted, V. Burkert, A. Deur, V. Dharmawardane, G. Dodge, K. Griffoen, S. Kuhn, R. Minehart and CLAS Collaboration Moments of the Spin Structure Functions g1p and g1d for 0.05 < Q2 < 3.0 GeV2. // Phys. Lett. B 672, 12 (2009)
Quantities
Γ1ptot Γ1dmeas Γ1dextrp Γ1dtot γ0pmeas γ0pextrp γ0ptot Γ1pmeas Γ1pextrp

Measurements

ID Quantity Beam Target Final state Q2min,
GeV2
Q2max,
GeV2
Wmin,
GeV
Wmax,
GeV
E128M1 Γ1pmeas e p inclusive 0.05 4.2 None None
E128M2 Γ1pextrp e p inclusive 0.05 4.2 None None
E128M3 Γ1ptot e p inclusive 0.05 4.2 None None
E128M4 Γ1dmeas e d inclusive 0.0496 2.92 None None
E128M5 Γ1dextrp e d inclusive 0.0496 2.92 None None
E128M6 Γ1dtot e d inclusive 0.0496 2.92 None None
E128M7 γ0pmeas e p inclusive 0.05 4.2 None None
E128M8 γ0pextrp e p inclusive 0.05 4.2 None None
E128M9 γ0ptot e p inclusive 0.05 4.2 None None