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HEJ 2.1.4
High energy resummation for hadron colliders
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HEJ::MatrixElement Class Reference

Class to calculate the squares of matrix elements. More...

#include <MatrixElement.hh>

Public Member Functions

 MatrixElement (std::function< double(double)> alpha_s, MatrixElementConfig conf)
 MatrixElement Constructor. More...
 
Weights operator() (Event const &event) const
 squares of regulated HEJ matrix elements More...
 
Weights tree (Event const &event) const
 Squares of HEJ tree-level matrix elements. More...
 
std::vector< Weightsvirtual_corrections (Event const &event) const
 Virtual corrections to matrix element squares. More...
 
Weights tree_param (Event const &event) const
 Scale-dependent part of tree-level matrix element squares. More...
 
std::vector< double > tree_kin (Event const &event) const
 Kinematic part of tree-level matrix element squares. More...
 

Detailed Description

Class to calculate the squares of matrix elements.

Constructor & Destructor Documentation

◆ MatrixElement()

HEJ::MatrixElement::MatrixElement ( std::function< double(double)>  alpha_s,
MatrixElementConfig  conf 
)

MatrixElement Constructor.

Parameters
alpha_sFunction taking the renormalisation scale and returning the strong coupling constant
confGeneral matrix element settings

Member Function Documentation

◆ operator()()

Weights HEJ::MatrixElement::operator() ( Event const &  event) const

squares of regulated HEJ matrix elements

Parameters
eventThe event for which to calculate matrix elements
Returns
The squares of HEJ matrix elements including virtual corrections

This function returns one value for the central parameter choice and one additional value for each entry in Event::variations(). See eq. (22) in [1] for the definition of the squared matrix element.

◆ tree()

Weights HEJ::MatrixElement::tree ( Event const &  event) const

Squares of HEJ tree-level matrix elements.

Parameters
eventThe event for which to calculate matrix elements
Returns
The squares of HEJ matrix elements without virtual corrections

cf. eq. (22) in [1]

◆ tree_kin()

std::vector< double > HEJ::MatrixElement::tree_kin ( Event const &  event) const

Kinematic part of tree-level matrix element squares.

Parameters
eventThe event for which to calculate matrix elements
Returns
The kinematic part of the squares of the tree-level matrix elements

The tree-level matrix elements factorises into a renormalisation-scale dependent part, given by the strong coupling to some power, and a scale-independent remainder. This function only returns the latter part.

If there is more than one entry in the returned vector, each entry corresponds to the contribution from the interference of two channels. The order of these entries matches the one returned by the virtual_corrections member function, but is otherwise unspecified.

See also
tree, tree_param

◆ tree_param()

Weights HEJ::MatrixElement::tree_param ( Event const &  event) const

Scale-dependent part of tree-level matrix element squares.

Parameters
eventThe event for which to calculate matrix elements
Returns
The scale-dependent part of the squares of the tree-level matrix elements

The tree-level matrix elements factorises into a renormalisation-scale dependent part, given by the strong coupling to some power, and a scale-independent remainder. This function only returns the former parts for the central scale choice and all Event::variations().

See also
tree, tree_kin

◆ virtual_corrections()

std::vector< Weights > HEJ::MatrixElement::virtual_corrections ( Event const &  event) const

Virtual corrections to matrix element squares.

Parameters
eventThe event for which to calculate matrix elements
Returns
The virtual corrections to the squares of the matrix elements

The all order virtual corrections to LL in the MRK limit is given by replacing 1/t in the scattering amplitude according to the lipatov ansatz.

If there is more than one entry in the returned vector, each entry corresponds to the contribution from the interference of two channels. The order of these entries matches the one returned by the tree_kin member function, but is otherwise unspecified.

cf. second-to-last line of eq. (22) in [1] note that indices are off by one, i.e. out[0].p corresponds to p_1


The documentation for this class was generated from the following file: