set_quarkline_rcl

set_quarkline_rcl(npr, q1, q2)

Enforces a quark-flow between two quarks q1 and q2.

Parameters

• npr (int) – process number

• q1 (int) – 1st quark position

• q2 (int) – 2st quark position

Note

All quark pairs need to be assigned for this function to work as expected.

Examples

In order to select the u and t channel diagrams, define two processes like this:

>>> define_process_rcl(2,'u u -> e+ nu_e mu+ nu_mu d d A','LO')
>>> set_quarkline_rcl(2,1,7)
>>> set_quarkline_rcl(2,2,8)
>>> define_process_rcl(3,'u u -> e+ nu_e mu+ nu_mu d d A','LO')
>>> set_quarkline_rcl(3,2,7)
>>> set_quarkline_rcl(3,1,8)

The matrix elements (2,3) need to be computed separately and added up. This constitutes the VBS approximation where interferences between t and u channels diagrams are neglected.