Total Cross Sections
The SigmaTotal
class returns the total, elastic, diffractive
and nondiffractive cross sections in hadronic collisions, and also the
slopes of the d(sigma)/dt distributions. The parametrizations
used are from [Sch97] which borrows some of the total cross
sections from [Don92].
The allowed combinations of incoming particles are p + p,
pbar + p, pi+ + p, pi- + p,
pi0/rho0 + p, phi + p, J/psi + p,
rho + rho, rho + phi, rho + J/psi,
phi + phi, phi + J/psi, J/psi + J/psi.
The strong emphasis on vector mesons is related to the description
of gamma + p and gamma + gamma interactions in a
Vector Dominance Model framework (which will not be available for some
time to come, so this is a bit of overkill).
Variables
If the internally implemented cross section parametrizations are not
satisfactory, it is possible to override the cross section values
(but currently not the t slopes), with
flag name="SigmaTotal:setOwn" default="no"
Allow a user to set own cross sections by hand; yes/no = true/false.
When SigmaTotal:setOwn = yes
, the user is expected to set
values for the corresponding cross sections:
parameter name="SigmaTotal:sigmaTot" default="80." min="0."
Total cross section in mb.
parameter name="SigmaTotal:sigmaEl" default="20." min="0."
Elastic cross section in mb.
parameter name="SigmaTotal:sigmaXB" default="8." min="0."
Single Diffractive cross section A + B -> X + B in mb.
parameter name="SigmaTotal:sigmaAX" default="8." min="0."
Single Diffractive cross section A + B -> A + X in mb.
parameter name="SigmaTotal:sigmaXX" default="4." min="0."
Double Diffractive cross section A + B -> X_1 + X_2 in mb.
Note that the total cross section subtracted by the elastic and various
diffractive ones gives the inelastic nondiffractive cross section,
which therefore is not set separately. If this cross section evaluates
to be negative the internal parametrizations are used instead of the
ones here. However, since the nondiffractive inelastic cross section
is what makes up the minimum-bias event class, and plays a major role
in the description of multiple interactions, it is important that a
consistent set is used.