PROGRAM SUMMARY
Title of program:
CASCADE 1.00/01
Catalogue identifier:
ADPK
Ref. in CPC:
143(2002)100
Distribution format: tar gzip file
Number of lines in distributed program, including test data, etc:
276142
Keywords:
Quantum chromodynamics, Small x, kt-factorization, CCFM,
Parton showers, Leptoproduction, Photoproduction, pp- and
ppbar-scattering, Heavy quark production, Elementary
particle physics, Event simulation.
Programming language used: Fortran
Computer:
SGI ,
HP-UX ,
SUN ,
PC .
CPC Program Library subprograms used:
Cat. Id. Title Ref. in CPC ADNN PYTHIA V6.154 135(2001)238 ADBJ BASES/SPRING V5.1 88(1995)309
Nature of physical 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.
Method of solution:
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.
Restrictions:
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).
Typical running time:
~0.03 sec/event on Pentium II (266 MHz), depends on the problem studied.
Unusual features:
None.