EW AND SYMMETRY BREAKING
BEYOND THE SM
HEAVY FLAVOUR PHYSICS
NEUTRINO AND NON ACCEL PHYSICS
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PERT AND NON-PERT QCD EW AND SYMMETRY BREAKING BEYOND THE SM HEAVY FLAVOUR PHYSICS NEUTRINO AND NON ACCEL PHYSICS |
Parton distributions of the proton are central to understanding all high energy hard scattering processes initiated by protons. The `MRS(T)' series of partons are used throughout the world, and are always among the most highly cited academic papers in Particle Physics. The distributions are obtained from global analyses of deep inelastic and related hard scattering data. The global fits are regularly updated and incorporate the latest data, as well as new theoretical developments. The latest MRST parton sets can be found here, whilst the effect of next-to-next leading order (NNLO) contributions is discussed in this paper. The latter shows the hierarchy of parton distributions obtained at LO, NLO, and NNLO, and more important, the stability of the resulting predictions for physical observables. The longitudinal structure function FL and the cross sections for W and Z hadroproduction are used as examples. The latter predictions are shown in the figure where a comparison is made with recent measurements at the TEVATRON.
The distributions, fa(x,kt2,µ2), unintegrated over the proton transverse momentum, kt, are also needed to describe less inclusive observables. They satisfy evolution equations which depend on two hard scales; kt and the scale µ of the probe. It has been demonstrated [1,2] how these distributions may be obtained from a single scale evolution equation. In particular the unitegrated gluon distribution has been determined from knowledge of the integrated gluon, itself obtained from a unified scheme which embodies both BFKL (log(1/x)) and DGLAP (log(µ2)) evolution. See also the section on low x dynamics.
There are also processes, such as diffractive hard scattering, that depend on skewed parton distributions. It has been shown how these distributions can be determined from the conventional partons found in the global analyses. See also low x dynamics and diffractive processes.
Words by Alan Martin.