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Herwig::MEPP2VVPowheg Class Reference

Here is the documentation of the MEPP2VVPowheg class. More...

#include <MEPP2VVPowheg.h>

Inheritance diagram for Herwig::MEPP2VVPowheg:

List of all members.

Public Member Functions

 MEPP2VVPowheg ()
 The default constructor.
virtual bool generateKinematics (const double *r)
 Generate internal degrees of freedom given nDim() uniform random numbers in the interval $ ]0,1[ $.
virtual int nDim () const
 The number of internal degrees of freedom used in the matrix element.
virtual double me2 () const
 The matrix element for the kinematical configuration previously provided by the last call to setKinematics(), suitably scaled by sHat() to give a dimension-less number.
virtual Energy2 scale () const
 Return the scale associated with the last set phase space point.
bool sanityCheck () const
 This member check the collinear limits of the real emission matrix elements are equal to the appropriate combinations of Born ME's multiplied by the splitting functions.
Complex CKM (int ix, int iy) const
 Return the CKM matrix elements.
void getKinematics (double xt, double y, double theta2)
 Function to set the born variables.
double NLOweight () const
 Calculate the correction weight with which leading-order configurations are re-weighted.
double Lhat_ab (tcPDPtr a, tcPDPtr b, realVVKinematics Kinematics) const
 Calculate the ratio of the NLO luminosity to the LO luminosity function for the $q\bar{q}$ initiated channel.
double Vtilde_universal (realVVKinematics S) const
 Calculate the universal soft-virtual contribution to the NLO weight.
double Ctilde_Ltilde_qq_on_x (tcPDPtr a, tcPDPtr b, realVVKinematics C) const
 Function for calculation of the $q\bar{q}$ initiated real contribution.
double Ctilde_Ltilde_gq_on_x (tcPDPtr a, tcPDPtr b, realVVKinematics C) const
 Function for calculation of the $gq$ initiated real contribution.
double Rtilde_Ltilde_qqb_on_x (tcPDPtr a, tcPDPtr b) const
 Function for calculation of the $q\bar{q}$ initiated real contribution.
double Rtilde_Ltilde_qg_on_x (tcPDPtr a, tcPDPtr b) const
 Function for calculation of the $qg$ initiated real contribution.
double Rtilde_Ltilde_gqb_on_x (tcPDPtr a, tcPDPtr b) const
 Function for calculation of the $gqb$ initiated real contribution.
double M_V_regular (realVVKinematics S) const
 The regular part of the virtual correction matrix element(s).
Energy2 t_u_M_R_qqb (realVVKinematics R) const
 The matrix element q + qb -> n + g times tk*uk.
Energy2 t_u_M_R_qg (realVVKinematics R) const
 The matrix element q + g -> n + q times tk*uk.
Energy2 t_u_M_R_gqb (realVVKinematics R) const
 The matrix element g + qb -> n + q times tk*uk.
Energy2 t_u_M_R_qqb_hel_amp (realVVKinematics R) const
 The matrix element q + qb -> n + g times (tk*uk)^2 - using helicity amplitudes.
Energy2 t_u_M_R_qg_hel_amp (realVVKinematics R) const
 The matrix element q + g -> n + q times (tk*uk)^2 - using helicity amplitudes.
Energy2 t_u_M_R_gqb_hel_amp (realVVKinematics R) const
 The matrix element g + qb -> n + qb times (tk*uk)^2 - using helicity amplitudes.
double lo_me () const
 The leading order matrix element - using helicity amplitudes.
double M_Born_WZ (bornVVKinematics B) const
 The Born matrix element as given in Equation 3.1 - 3.3 in NPB 383 (1992) *** modulo a factor 1/(2s) ***, which is a flux factor that those authors absorb in the matrix element.
double M_Born_ZZ (bornVVKinematics B) const
 The Born matrix element as given in Equation 2.18 - 2.19 in NPB 357 (1991) *** modulo a factor 1/(2s) ***, which is a flux factor that those authors absorb in the matrix element.
double M_V_regular_ZZ (realVVKinematics S) const
 M_V_regular_ZZ is the regular part of the one-loop ZZ matrix element exactly as defined in Eqs.
Energy2 t_u_M_R_qqb_ZZ (realVVKinematics R) const
 t_u_M_R_qqb_ZZ is the q + qb -> n + g times tk*uk real emission matrix element as defined in Eq.
double M_Born_WW (bornVVKinematics B) const
 The Born matrix element as given in Equation 3.2 - 3.8 in NPB 410 (1993) *** modulo a factor 1/(2s) ***, which is a flux factor that those authors absorb in the matrix element.
double M_V_regular_WW (realVVKinematics S) const
 M_V_regular_WW is the regular part of the one-loop WW matrix element exactly as defined in Eqs.
Energy2 t_u_M_R_qqb_WW (realVVKinematics R) const
 t_u_M_R_qqb_WW is the q + qb -> n + g times tk*uk real emission matrix element as defined in Eq.
Energy2 mu_F2 () const
 Return the factorion scale squared.
Energy2 mu_UV2 () const
 Return the renormalisation scale squared.
Member functions for the generation of hard QCD radiation
virtual POWHEGType hasPOWHEGCorrection ()
 Has a POWHEG style correction.
virtual HardTreePtr generateHardest (ShowerTreePtr)
 Apply the POWHEG style correction.
Functions used by the persistent I/O system.
void persistentOutput (PersistentOStream &os) const
 Function used to write out object persistently.
void persistentInput (PersistentIStream &is, int version)
 Function used to read in object persistently.

Static Public Member Functions

static void Init ()
 The standard Init function used to initialize the interfaces.

Public Attributes

double M_V_regular_
 Member variable to store the regular part of the virtual correction matrix element(s).
Energy2 t_u_M_R_qqb_
 Member variable to store the matrix element q + qb -> n + g times tk*uk.
Energy2 t_u_M_R_qg_
 Member variable to store the matrix element q + g -> n + q times tk*uk.
Energy2 t_u_M_R_gqb_
 Member variable to store the matrix element g + qb -> n + q times tk*uk.
Energy2 t_u_M_R_qqb_hel_amp_
 Member variable to store the matrix element q + qb -> n + g times (tk*uk)^2 - using helicity amplitudes.
Energy2 t_u_M_R_qg_hel_amp_
 Member variable to store the matrix element q + g -> n + q times (tk*uk)^2 - using helicity amplitudes.
Energy2 t_u_M_R_gqb_hel_amp_
 Member variable to store the matrix element g + qb -> n + qb times (tk*uk)^2 - using helicity amplitudes.
double M_Born_
 Member variable to store the Born matrix element as given in Equation 3.1 - 3.3 in NPB 383 (1992) *** modulo a factor 1/(2s) ***, which is a flux factor that those authors absorb in the matrix element.

Protected Member Functions

double getResult (int emis_type, realVVKinematics R, Energy pT)
 Returns the matrix element for a given type of process, rapidity of the jet $y_j$ and transverse momentum $p_T$.
bool getEvent (vector< Lorentz5Momentum > &pnew, unsigned int &emissiontype)
 generates the hardest emission (yj,p)
void setTheScales (Energy pT)
 sets the QCD, EW and PDF scales
Energy2 t_u_M_R_qqb_hel_amp (realVVKinematics R, bool getMatrix) const
 The matrix element q + qb -> n + g times tk*uk.
Energy2 t_u_M_R_qg_hel_amp (realVVKinematics R, bool getMatrix) const
 The matrix element q + g -> n + q times tk*uk.
Energy2 t_u_M_R_gqb_hel_amp (realVVKinematics R, bool getMatrix) const
 The matrix element g + qb -> n + q times tk*uk.
double lo_me (bool getMatrix) const
 The matrix element for the kinematical configuration previously provided by the last call to setKinematics(), suitably scaled by sHat() to give a dimension-less number.
void recalculateVertex ()
 Recalculate hard vertex to include spin correlations for radiative events.
bool isotropicDecayer ()
 Member which selects a two body decay mode for each vector boson and distributes decay products isotropically.
Energy2 triangleFn (Energy2, Energy2, Energy2)
 The triangle function lambda(x,y,z)=sqrt(x^2+y^2+z^2-2*x*y-2*y*z-2*x*z)
Standard Interfaced functions.
virtual void doinit ()
 Initialize this object after the setup phase before saving an EventGenerator to disk.
Clone Methods.
virtual IBPtr clone () const
 Make a simple clone of this object.
virtual IBPtr fullclone () const
 Make a clone of this object, possibly modifying the cloned object to make it sane.

Private Member Functions

MEPP2VVPowhegoperator= (const MEPP2VVPowheg &)
 The assignment operator is private and must never be called.

Private Attributes

double alphaS_
 The value of $\alpha_S$ used for the calculation.
bool realMESpinCorrelations_
 If this boolean is true the n+1 body helicity amplitudes will be used to calculate a hard vertex based on those kinematics for spin correlations in the decays.
double lo_me_
 The colour & spin averaged n-body (leading order) matrix element squared.
realVVKinematics R_
 The resolved 2->3 real emission kinematics.
unsigned int channel_
 This specifies the emitting configuration: 1: q + qbar -> V1 + V2 + g 2: q + g -> V1 + V2 + q 3: g + qbar -> V1 + V2 + qbar.
int fermionNumberOfMother_
 Identifies the space-like mother of the branching as quark (+1) or antiquark (-1):
ShowerAlphaPtr showerAlphaS_
 Pointer to the object calculating the strong coupling.
Energy min_pT_
 The transverse momentum of the jet.
Energy2 QCDScale_
 Scale for alpha_S: pT^2 of the diboson system.
Energy2 PDFScale_
 Scale for real emission PDF:
Energy2 EWScale_
 Scale of electroweak vertices: mVV^2 the invariant mass of the diboson system.
Complex productionMatrix_ [3][3][3][3]
 A matrix to hold the home-grown production matrix element.
double tiny
 Parameters for the NLO weight.
tcBeamPtr hadron_A_
 The BeamParticleData object for the plus and minus direction hadrons.
tcBeamPtr hadron_B_
bornVVKinematics B_
 Born / virtual 2->2 kinematics.
realVVKinematics S_
 Soft limit of the 2->3 real emission kinematics.
realVVKinematics SCp_
 Soft-collinear limit of the 2->3 kinematics (emission in +z direction).
realVVKinematics SCm_
 The collinear limit of the 2->3 kinematics (emission in -z direction).
realVVKinematics Cp_
 The collinear limit of the 2->3 kinematics (emission in +z direction).
realVVKinematics Cm_
 The collinear limit of the 2->3 kinematics (emission in -z direction).
realVVKinematics H_
 The resolved 2->3 real emission kinematics:
tcPDPtr ab_
 The ParticleData object for the plus and minus lo partons.
tcPDPtr bb_
tcPDPtr quark_
 The ParticleData object for the quark and antiquark (which can be in a different order to ab_ and bb_).
tcPDPtr antiquark_
double lo_lumi_
 Values of the PDF's before radiation.
double lo_me2_
 The value of the leading order qqbar->VV matrix element.
double CF_
 The CF_ colour factor.
double TR_
 The TR_ colour factor.
double NC_
 The number of colours.
double gW_
 The weak coupling and the sin (squared) of the Weinberg angle.
double sin2ThetaW_
double guL_
 The up and down, left handed, quark-boson couplings.
double gdL_
double guR_
 The up and down, right handed, quark-boson couplings (for WW & ZZ)
double gdR_
double eZ_
 The TGC coupling.
double eZ2_
 The TGC coupling squared.
double Fij2_
 The CKM factor (Fij^2)
unsigned int contrib_
 Whether to generate the positive, negative or leading order contribution.
unsigned int channels_
 Whether to generate all channels contributions or just qqb or just qg+gqb contributions.
unsigned int nlo_alphaS_opt_
 Whether to use a fixed or a running QCD coupling for the NLO weight.
double fixed_alphaS_
 The value of alphaS to use for the nlo weight if nlo_alphaS_opt_=1.
unsigned int removebr_
 Flag to remove or multiply in MCFM branching fractions for testing.
unsigned int scaleopt_
 Selects a dynamic (sHat) or fixed factorization scale.
Energy mu_F_
 The factorization scale.
Energy mu_UV_
 The renormalization scale.
Energy2 k1r_perp2_lab_
 The pT of V1 in a radiative event in the lab frame (for scale setting only)
Energy2 k2r_perp2_lab_
 The pT of V2 in a radiative event in the lab frame (for scale setting only)
vector< vector< Complex > > ckm_
 The ckm matrix elements (unsquared, to allow interference)
bool helicityConservation_
 Option to impose helicity conservation on the real NLO ME's (greatly improves evaluation time).
ProductionMatrixElement qqb_hel_amps_
 The q + qb -> v1 + v2 + g helicity amplitudes.
ProductionMatrixElement qg_hel_amps_
 The q + g -> v1 + v2 + q helicity amplitudes.
ProductionMatrixElement gqb_hel_amps_
 The g + qb -> v1 + v2 + qb helicity amplitudes.
AbstractFFVVertexPtr FFPvertex_
 The vertices.
AbstractFFVVertexPtr FFWvertex_
 The W fermion-antifermion vertex.
AbstractFFVVertexPtr FFZvertex_
 The Z fermion-antifermionvertex.
AbstractVVVVertexPtr WWWvertex_
 The triple electroweak gauge boson vertex.
AbstractFFVVertexPtr FFGvertex_
 The quark-antiquark gluon vertex.
double power_
 Constants for the sampling.
double preqqbar_
 The prefactor, $c$ for the $q\bar{q}$ channel.
double preqg_
 The prefactor, $c$ for the $qg$ channel.
double pregqbar_
 The prefactor, $c$ for the $g\bar{q}$ channel.
double b0_
 The QCD beta function divided by 4pi, (11-2/3*nf)/4/pi, with nf = 5.
Energy LambdaQCD_
 The fundamental QCD scale in the one-loop alpha_{S} used for the crude (not the very crude) overestimate of the Sudakov exponent.
vector< double > prefactor_
 The prefactors as a vector for easy use.
ShowerProgenitorPtr qProgenitor_
 Properties of the incoming particles.
ShowerProgenitorPtr qbProgenitor_
ShowerParticlePtr showerQuark_
 Pointers to the Shower particle objects for the partons.
ShowerParticlePtr showerAntiquark_
tcBeamPtr qHadron_
 Pointers to the BeamParticleData objects.
tcBeamPtr qbHadron_
PPtr gluon_
 Properties of the boson and jets.
ShowerParticlePtr V1_
ShowerParticlePtr V2_
vector< PPtrchildren_
vector< PPtrphotons_
bool flipped_
 Flag indicating if the q & qbar are flipped or not i.e.
double Yk_
 the rapidity of the jet
Energy pT_
 The transverse momentum of the jet.

Static Private Attributes

static ClassDescription
< MEPP2VVPowheg
initMEPP2VVPowheg
 The static object used to initialize the description of this class.

Detailed Description

Here is the documentation of the MEPP2VVPowheg class.

See also:
The interfaces defined for MEPP2VVPowheg.

Definition at line 25 of file MEPP2VVPowheg.h.


Member Function Documentation

virtual IBPtr Herwig::MEPP2VVPowheg::clone ( ) const [inline, protected, virtual]

Make a simple clone of this object.

Returns:
a pointer to the new object.

Reimplemented from Herwig::MEPP2VV.

Definition at line 348 of file MEPP2VVPowheg.h.

virtual void Herwig::MEPP2VVPowheg::doinit ( ) [protected, virtual]

Initialize this object after the setup phase before saving an EventGenerator to disk.

Exceptions:
InitExceptionif object could not be initialized properly.

Reimplemented from Herwig::MEPP2VV.

virtual IBPtr Herwig::MEPP2VVPowheg::fullclone ( ) const [inline, protected, virtual]

Make a clone of this object, possibly modifying the cloned object to make it sane.

Returns:
a pointer to the new object.

Reimplemented from Herwig::MEPP2VV.

Definition at line 354 of file MEPP2VVPowheg.h.

virtual bool Herwig::MEPP2VVPowheg::generateKinematics ( const double *  r) [virtual]

Generate internal degrees of freedom given nDim() uniform random numbers in the interval $ ]0,1[ $.

To help the phase space generator, the dSigHatDR should be a smooth function of these numbers, although this is not strictly necessary.

Parameters:
ra pointer to the first of nDim() consecutive random numbers.
Returns:
true if the generation succeeded, otherwise false.

Reimplemented from Herwig::HwMEBase.

bool Herwig::MEPP2VVPowheg::getEvent ( vector< Lorentz5Momentum > &  pnew,
unsigned int &  emissiontype 
) [protected]

generates the hardest emission (yj,p)

Parameters:
pnewThe momenta of the new particles
emissiontypeThe type of emission, as for getResult
Returns:
Whether not an emission was generated
double Herwig::MEPP2VVPowheg::getResult ( int  emis_type,
realVVKinematics  R,
Energy  pT 
) [protected]

Returns the matrix element for a given type of process, rapidity of the jet $y_j$ and transverse momentum $p_T$.

Parameters:
emis_typethe type of emission, (0 is $q\bar{q}\to Vg$, 1 is $qg\to Vq$ and 2 is $g\bar{q}\to V\bar{q}$)
pTThe transverse momentum of the jet
RThe object containing the kinematics
static void Herwig::MEPP2VVPowheg::Init ( ) [static]

The standard Init function used to initialize the interfaces.

Called exactly once for each class by the class description system before the main function starts or when this class is dynamically loaded.

Reimplemented from Herwig::MEPP2VV.

double Herwig::MEPP2VVPowheg::lo_me ( bool  getMatrix) const [protected]

The matrix element for the kinematical configuration previously provided by the last call to setKinematics(), suitably scaled by sHat() to give a dimension-less number.

Returns:
the matrix element scaled with sHat() to give a dimensionless number.

The regular part of the virtual correction matrix element(s).

For WZ production this is given by Equation B.2 in NPB 383 (1992) 3-44 *** modulo a factor 1/(2s) ***, which is a flux factor that those authors absorb in the matrix element.

M_V_regular_WW is the regular part of the one-loop WW matrix element exactly as defined in Eqs.

C.1 - C.7 of of NPB 410(1993)280-324 *** modulo a factor 1/(2s) ***, which is a flux factor that those authors absorb in the matrix element.

M_V_regular_ZZ is the regular part of the one-loop ZZ matrix element exactly as defined in Eqs.

B.1 & B.2 of NPB 357(1991)409-438 *** modulo a factor 1/(2s) ***, which is a flux factor that those authors absorb in the matrix element.

virtual double Herwig::MEPP2VVPowheg::me2 ( ) const [virtual]

The matrix element for the kinematical configuration previously provided by the last call to setKinematics(), suitably scaled by sHat() to give a dimension-less number.

Returns:
the matrix element scaled with sHat() to give a dimensionless number.

Reimplemented from Herwig::MEPP2VV.

MEPP2VVPowheg& Herwig::MEPP2VVPowheg::operator= ( const MEPP2VVPowheg ) [private]

The assignment operator is private and must never be called.

In fact, it should not even be implemented.

Function used to read in object persistently.

Parameters:
isthe persistent input stream read from.
versionthe version number of the object when written.

Reimplemented from Herwig::MEPP2VV.

Function used to write out object persistently.

Parameters:
osthe persistent output stream written to.

Reimplemented from Herwig::MEPP2VV.

void Herwig::MEPP2VVPowheg::setTheScales ( Energy  pT) [protected]

sets the QCD, EW and PDF scales

Parameters:
pTThe pT of the current step in the veto algorithm

t_u_M_R_qqb_WW is the q + qb -> n + g times tk*uk real emission matrix element as defined in Eq.

D.1-D.5 of NPB 410(1993)280-324 *** modulo a factor 1/(2s) ***, which is a flux factor that those authors absorb in the matrix element.

t_u_M_R_qqb_ZZ is the q + qb -> n + g times tk*uk real emission matrix element as defined in Eq.

C.1 of NPB 357(1991)409-438 *** modulo a factor 1/(2s) ***, which is a flux factor that those authors absorb in the matrix element.


Member Data Documentation

double Herwig::MEPP2VVPowheg::eZ2_ [mutable, private]

The TGC coupling squared.

This is useful for debugging purposes when one wants to turn of t-channel * TGC interference contributions but leave the pure TGC contributions intact. It is also needed in order to transform WZ matrix elements into WW ones.

Definition at line 487 of file MEPP2VVPowheg.h.

The vertices.

The photon fermion-antifermion vertex

Reimplemented from Herwig::MEPP2VV.

Definition at line 578 of file MEPP2VVPowheg.h.

Flag indicating if the q & qbar are flipped or not i.e.

this is true if q enters from the -z direction in the lab frame.

Definition at line 795 of file MEPP2VVPowheg.h.

Properties of the boson and jets.

Pointers to the Shower particle objects for the partons

Definition at line 785 of file MEPP2VVPowheg.h.

The static object used to initialize the description of this class.

Indicates that this is a concrete class with persistent data.

Definition at line 363 of file MEPP2VVPowheg.h.

The fundamental QCD scale in the one-loop alpha_{S} used for the crude (not the very crude) overestimate of the Sudakov exponent.

The default value is set so such that alphaS(MZ), neglecting all flavour threshold effects i.e. MZ*exp(-1/2/b0_/alphaS(MZ)).

Definition at line 747 of file MEPP2VVPowheg.h.

Member variable to store the regular part of the virtual correction matrix element(s).

For WZ production this is given by Equation B.2 in NPB 383 (1992) 3-44 *** modulo a factor 1/(2s) ***, which is a flux factor that those authors absorb in the matrix element.

Definition at line 199 of file MEPP2VVPowheg.h.

Constants for the sampling.

The distribution is assumed to have the form $\frac{c}{{\rm GeV}}\times\left(\frac{{\rm GeV}}{p_T}\right)^n$ The power, $n$, for the sampling

Definition at line 719 of file MEPP2VVPowheg.h.

ShowerProgenitorPtr Herwig::MEPP2VVPowheg::qProgenitor_ [private]

Properties of the incoming particles.

Pointers to the ShowerProgenitor objects for the partons

Definition at line 762 of file MEPP2VVPowheg.h.

double Herwig::MEPP2VVPowheg::tiny [private]

Parameters for the NLO weight.

Parameter to determine when to use limiting value of real emission matrix elements, to avoid rounding error issues.

Definition at line 382 of file MEPP2VVPowheg.h.


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