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< Weights >	virtual_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_s	Function taking the renormalisation scale and returning the strong coupling constant
conf	General matrix element settings

Member Function Documentation

operator()()

Weights HEJ::MatrixElement::operator()

(

Event const &

event

)

const

squares of regulated HEJ matrix elements

Parameters

event

The 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.

Incoming momenta must be lightlike and have vanishing transverse momentum.

tree()

Weights HEJ::MatrixElement::tree

(

Event const &

event

)

const

Squares of HEJ tree-level matrix elements.

Parameters

event

The 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

event

The 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.

Incoming momenta must be lightlike and have vanishing transverse momentum.

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

event

The 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

event

The 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

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

• /home/andersen/HEJProjects/website/build/hej/include/HEJ/MatrixElement.hh