The spin-dependent structure function
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The spin-dependent structure function g1 is given by the following
Bjorken sum rule
The Bjorken sum rule is written as follows using the
axial and vector coupling constants GA and Gv,
- J.D.Bjorken, Phys Rev. 148 1467 (1966); Phys. Rev. D1 1376 (1970).
- J.Kodaira et al., Phys. Rev. D20 627 (1979); Nucl. Phys. B165 129 (1980).
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,
- J. Ellis and R.L.Jaffe, Phys. Rev. D9 (1974) 1444; D 10 (1974) 1669(E).
Recent measurements and analyses of the
Deep Inelastic Scattering of polarized
muons or electrons from the polarized nucleons by the EMC ,
SMC  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 .
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
- Spin of the sea quarks,
- Polarization of the gluons,
- Orbital angular momentum (L) of the quarks in nucleon, etc.
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
12 January 1995 T.Ichihara (firstname.lastname@example.org)