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Manuscript Title: The CCFM Monte Carlo generator CASCADE.
Authors: H. Jung
Program title: CASCADE 1.00/01
Catalogue identifier: ADPK_v1_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 143(2002)100
Programming language: Fortran.
Computer: SGI, HP-UX, SUN, PC.
Keywords: Quantum chromodynamics, Small x, kt-factorization, CCFM, Parton showers, Leptoproduction, Photoproduction, pp- and ppbar-scattering, Heavy quark production, Elementary particle physics, Event simulation.
Classification: 11.2.

Subprograms used:
Cat Id Title Reference
ACTU_v2_0 PYTHIA V6.154 CPC 135(2001)238
AAFW_v2_0 BASES/SPRING V5.1 CPC 88(1995)309

Nature of problem:
High-energy collisions of particles at moderate values of x are well described by resummations of leading logarithms of transverse momenta (alphas ln Q^2)^n, generally referred to as DGLAP physics. At small x leading-logs of longitudinal momenta, (alphas ln x)^n, are expected to become equally if not more important (BFKL). An appropriate description valid for both small and moderate x is given by the CCFM evolution equation, resulting in an unintegrated gluon density A(x,kt,,qbar), which is also a function of the evolution scale qbar.

Solution method:
Since measurements involve complex cuts and multi-particle final states, the ideal form for any theoretical description of the data is a Monte Carlo event-generator which embodies small-x resummations, in analogy with event generators which embody DGLAP resummations. In order to build such an event generator one needs to know the underlying parton branching equation which, when iterated over many branchings, reproduces the correct leading logarithms. Also an efficient way of implementing the branching equation into a Monte Carlo event generator has to be found. The CCFM equation for small x parton evolution can be formulated in a manner suitable for carrying out a backward evolution, which is an almost essential requirement to efficiently generate unweighted Monte Carlo events.

Hard sub-processes like: gamma*g* -> qqbar(QQbar), gamma g* -> J/psi g, g*g* -> qqbar(QQbar) can be simulated in deep inelastic- and Q^2 ~ 0GeV^2 ep scattering, gammap scattering, pp- and ppbar-scattering. Limitations come from the parameterization of unintegrated gluon density: the present version is applicable for HERA and TEVATRON energies, for larger energies new data files are needed (please contact the author).

Unusual features:

Running time:
~0.03 sec/event on Pentium II (266 MHz), depends on the problem studied.