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Kinematics

The Kinematics function allows to display and change a general scheme of the phase space parameterization. A kinematics scheme in CompHEP  is defined by a set of subsequent 1 -> 2 decays of the incoming state into the outgoing particle sets.

After activation of this menu function the current decay scheme will be displayed and a dialogue message will propose the user to accept it or put in another one.

During the input CompHEP  consequently asks the user to define a first outgoing cluster of virtual decay. The user input must be a sequence of particle (momentum) numbers without any separating symbols. It is assumed that particles are numerated in the same order as they are written down in the (sub)process name.

An example of kinematics definition for 2 -> 4 process is given by the following lines:
12  -> 3,456
456 -> 56,3
56   -> 5,6
Here the user input is indicated in bold characters.

In the framework of such a decay scheme the multi-particle phase space is parameterized by masses of sub-clusters and by two-dimensional spherical angles of 1 -> 2 decays [Byckling&Kajantie,Ilyin-1996]. A choice of kinematics influences on the phase space mapping and by this way it influences on convergence of Monte Carlo integration. See Section .