The spin-dependent structure function

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The spin-dependent structure function g1 is given by the following equation,


Bjorken sum rule

The Bjorken sum rule is written as follows using the axial and vector coupling constants GA and Gv,


Ellis-Jaffe sum rule

Accoring to the Ellis and Jaffe, another sum rule is deriven from the quark light-cone algebra with the assumption that strange sea quarks do not contribute to the asymmetry,


Recent measurements and analyses of the Deep Inelastic Scattering of polarized muons or electrons from the polarized nucleons by the EMC [1], SLAC [2] and SMC [3] groups have shown the deviations from the Ellis-Jaffe sum rule of the experiment data. This means that the spin of the nucleon (= 1/2) cannot be reproduced from the sum of the spin of quarks in nucleon: this is called spin crisis .

(Click here to get some plots for g1 integrations from SLAC E143.)

To solve Spin Crisis

The possible explanation for the spin crisis is thought to be due to the contributions to the nucelon spin from

PHENIX/Spin collabration is planning to carry out several experiments with polarized proton-proton collider at the enegy of = 50-500 GeV at RHIC to extract the helicity distributions of quarks and anti-quarks in nucleon and to investigate gluon polarization, via

Return to the PHNEX/Spin collaboration page

12 January 1995 T.Ichihara (