get_amplitude_rcl¶

get_amplitude_rcl
(npr, order, colour, hel, pow=None, gs=None)¶ Extracts a specific contribution to the amplitude of the process with process number
npr
, according to the values ofpow
,order
,colour
andhel
. Parameters
npr (int) – process number
order (str) –
looporder of the contribution
order = ‘LO’: tree squared amplitude
order = ‘NLO’: loop squared amplitude
order = ‘NLOD4’: loop squared amplitude, bare loop contribution
order = ‘NLOCT’: loop squared amplitude, counterterms contribution
order = ‘NLOR2’: loop squared amplitude, rational terms contribution
colour (int[l]) – colour structure which is a vector of type integer and length l, where each position in the vector corresponds to one of the l external particles of process
npr
(ordered as in the process definition). For colourless particles, incoming quarks and outgoing antiquarks, the corresponding entry in colour must be 0. For all other particles (gluons, outgoing quarks and incoming antiquarks), the entries must be, without repetition, the positions of the gluons, incoming quarks and outgoing antiquarks in the process definition.hel (int[l]) –
helicity (array) with entries:
lefthanded fermions/antifermions: 1
righthanded fermions/antifermions: +1
logitudinal vector bosons: 0
transverse vector bosons: 1, +1
scalar particles: 0
pow/gs (int[]) – array with values representing the powers in fundamental couplings in the order as dictated by the model file, e.g. [2, 3] \(\equiv g_\mathrm{s}^2 e^3\), or, if supported by the model, the power in terms of \(g_\mathrm{s}\) only (power in \(e\) is determined automatically from the underlying process)
 Returns
(Ar, Ai)
 Return type
(float, float)