Kinematics types

The reactions are classified into 8 different types, depending on the data present in the library. These are called kinematics types, because the classification is related to the kinematics of the reactions. Cross sections are given in all cases. The different kinematics types are as follows, along with a description of the additional data provided.

Kinematics type 0:

Only cross sections are given.

Kinematics type 1:

This kind of data describes 2-body interactions in center-of-mass coordinates. The library provides angular distributions ( $\tt I\_number$ = 1 data) and energy deposition to the secondary particle ( $\tt I\_number$ = 10 data). Energy distributions for the secondary particle are not given, because they are easily derived. In fact, the mcfgen code identifies this kinematics type by a lack of energy distribution data ( $\tt I\_number$ = 4). In addition, if the residual nucleus is light enough to be viewed as a particle (an alpha-particle or lighter), energy deposition to it is provided.

Kinematics type 2:

Usually, this kinematics type refers to reactions with more than two final particles, but it also applies to capture reactions (y_i,$\gamma$). With one exception, energy distributions ( $\tt I\_number$ = 4 data) are given only for the first secondary particle. The exception is that (y_i, pn'$\gamma$) reactions with excited residual are classified as kinematics type 4, irrespective of what energy distributions are given. Angular distributions may also be included. The angular data is independent of the energy distributions, and it is given in the laboratory system.

Kinematics type 3:

This kinematics type applies to the case when joint distributions in angle and secondary energy (both $\tt I\_number$ = 1 and $\tt I\_number$ = 3 data) are given.

Kinematics type 4:

For this kinematics type we start with a 2-body reaction in center-of-mass coordinates, but one of the products is an unstable intermediate nucleus which decays with type-2 kinematics. Most of these reactions are identified by the presence in the library of energy distribution data ( $\tt I\_number$ = 4) for a secondary particle which is not the first. The exception to this rule is that (y_i, pn'$\gamma$) reactions with an excited residual are automatically given kinematics type 4.

Kinematics type 5:

This is a very special case which is currently used only for the reaction d (n, n')np. We start with a 2-body reaction in center-of-mass coordinates, with sufficient energy to break up the deuteron. The neutron and proton resulting from the break-up of the deuteron simply go off independently at the velocity of the unstable recoil deuteron.

Kinematics type 6:

In this special case the data consists of form factors for coherent (Rayleigh) scattering of a photon ( $\tt I\_number$ = 941).

Kinematics type 7:

In this special case the data consists of form factors for incoherent (Compton) scattering of a photon ( $\tt I\_number$ = 942).

The subroutine models in mcfgen determines the kinematics type, based on the information given above.