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Unintegrated parton distributions of pions and nucleons from the CCFM equations in the single-loop approximation

Agnieszka Gawron·Jan Kwiecinski·Wojciech Broniowski
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Abstract

The unintegrated quark and gluon distributions in the pion and nucleon are analysed using the CCFM equations in the single-loop approximation. We utilise the transverse-coordinate (or impact-parameter) representation which diagonalises the equations and study in detail the dependence on the transverse coordinate induced by the CCFM evolution. We find considerable broadening of the transverse-momentum distributions with an increasing magnitude of the hard scale, Q. For instance, at the Bjorken x=0.1 the root mean squared transverse momentum of the gluons is enhanced by about 1 GeV when evolved from the the initial low scale to Q^2=10 GeV^2, and by about 2 GeV when evolved up to Q^2=100 GeV^2. The broadening effect is enhanced with decreasing Bjorken x, and is stronger for the gluons than for the quarks. Analytic solution for the average transverse momentum corresponding to the x-moments of the distributions is obtained. The parton luminosities are also discussed.

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Agnieszka Gawron, Jan Kwiecinski, Wojciech Broniowski. 2003-05-20. Unintegrated parton distributions of pions and nucleons from the CCFM equations in the single-loop approximation. https://doi.org/10.1103/physrevd.68.054001

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