\(\kt\)-factorised \(\ggww\)

The two-photon production of gauge boson pairs process, i.e. \(pp \rightarrow p^{(\ast)}(\ggww)p^{(\ast)}\), is only defined using the \(\kt\)-factorisation approach.

A full review of this process may be found in [LuszczakSchaferS18].

Process-specific options

method

This integer allows to switch between the two matrix element definitions:

• 0: on-shell amplitude [DDS95],

• 1: off-shell amplitude [NNPU06a, NNPU06b].

mode

This enumeration allows to specify the kinematic regime to generate and the size of the phase space to perform the integration. It can take the following values:

• ProcessMode.ElasticElastic := 1: elastic emission of photons from the incoming protons (default value if unspecified),

• ProcessMode.ElasticInelastic := 2 / ProcessMode.InelasticElastic := 3: elastic scattering of one photon and an inelastic/semi-exclusive emission of the other photon, resulting in the excitation/fragmentation of the outgoing proton state,

• ProcessMode.InelasticInelastic := 4: both protons fragmented in the final state.

polarisationStates

This enumeration lets you switch between all combinations of polarisation states to be included in the matrix element. It can take the following values:

• 0: all contributions,

• 1: longitudinal-longitudinal,

• 2: longitudinal-transverse,

• 3: transverse-longitudinal,

• 4: transverse-transverse.

Full object reference

class PPtoWW : public FactorisedProcess

Compute the matrix element for a CE \(\gamma\gamma\rightarrow W^+W^-\) process using \(k_{\rm T}\)-factorization approach.

Note

The full theoretical description of this process definition may be found in [20].

Private Types

enum class Polarisation

Values:

enumerator full

enumerator LL

enumerator LT

enumerator TL

enumerator TT

Private Functions

inline virtual void prepareFactorisedPhaseSpace() override

Prepare central part of the Jacobian after kinematics is set.

inline virtual double computeFactorisedMatrixElement() override

Factorised matrix element (event weight)

inline double onShellME() const

inline double offShellME() const

Private Members

const double mW_

const double mW2_

const int method_

const NachtmannAmplitudes ampl_

const PolarisationState pol_