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Articles Particle Physics Positivity Constraints on Quark and Gluon Distributions in QCD (1978)
Positivity Constraints on Quark and Gluon Distributions in QCD (1978) |
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(1) The formulae are known in full only to leading order in 
(
is the number of quark flavours) and in 
. Experiment indicates that 
.
(2) It is easy to construct cross sections involving hypothetical but conceivable currents which are proportional to the quark and antiquark distributions of each flavour, and to the glue distribution. These quantities, and the corresponding local operator matrix elements, cannot therefore be negative.
