Final-final electroweak resonance antenna. More...

#include <VinciaEW.h>

Inheritance diagram for EWAntennaFFres:

Public Member Functions
bool	init (Event &event, int iMotIn, int iRecIn, int iSysIn, vector< EWBranching > &branchings, Settings *settingsPtr) override
	Overridden virtual functions. More...

bool	isResonanceDecay () override

double	generateTrial (double q2Start, double q2End, double alphaIn) override
	Generate a trial. More...

bool	acceptTrial (Event &event) override
	Accept a trial. More...

void	updateEvent (Event &event) override
	Update an event. More...

bool	genForceDecay (Event &event)
	Generate the kinematics and channel for decays below matching scale. More...

Public Member Functions inherited from EWAntenna
	EWAntenna ()
	Constructor and destructor.

void	print ()
	Print, must be implemented by base classes.

void	initPtr (Info infoPtrIn, VinciaCommon vinComPtrIn, AlphaEM alphaPtrIn, AmpCalculator ampCalcPtrIn)
	Initialize pointers.

void	setVerbose (int verboseIn)
	Set verbosity level.

virtual void	updatePartonSystems (Event &event)
	Base class for an electroweak antenna. More...

int	getIndexMot ()
	Return index.

int	getIndexRec ()

bool	isSplitToFermions ()
	Check if splitting to fermions, inital, or resoance.

virtual bool	isInitial ()

bool	selectChannel (int idx, const double &cSum, const map< double, int > &cSumSoFar, int &idi, int &idj, double &mi2, double &mj2)
	Select a channel.

Additional Inherited Members
Protected Attributes inherited from EWAntenna
int	iMot
	Indices, PID, and polarization of I, K in Pythia event record.

int	iRec

int	idMot

int	idRec

int	polMot

Vec4	pMot
	Momenta of antenna constituents.

Vec4	pRec

double	sAnt
	Masses and invariants of antenna constituents.

double	mMot

double	mMot2

double	mRec

double	mRec2

double	alpha
	Overestimate of QED coupling.

int	iSys
	Parton system this antenna is part of.

vector< EWBranching >	brVec
	EW branchings.

bool	hasTrial
	Trial variables.

double	q2Trial

double	sijTrial

double	sjkTrial

int	poliTrial

int	poljTrial

vector< Vec4 >	pNew
	Outgoing momenta after branching.

double	c0Sum
	Info on coefficents.

double	c1Sum

double	c2Sum

double	c3Sum

map< double, int >	c0SumSoFar

map< double, int >	c1SumSoFar

map< double, int >	c2SumSoFar

map< double, int >	c3SumSoFar

double	q2Match
	Matching scale.

int	jNew
	Information for partonSystems.

unordered_map< int, int >	iReplace

double	shat

EWBranching *	brTrial {}
	Pointers.

Info *	infoPtr {}

Rndm *	rndmPtr {}

Logger *	loggerPtr {}

PartonSystems *	partonSystemsPtr {}

VinciaCommon *	vinComPtr {}

AlphaEM *	alphaPtr {}

AmpCalculator *	ampCalcPtr {}

bool	doBosonInterference
	Settings.

int	verbose
	Verbosity.

Detailed Description

Final-final electroweak resonance antenna.

Member Function Documentation

bool acceptTrial ( Event & event )

overridevirtual

Accept a trial.

Check if this is a resonance decay.

Force the decay. Always return true afterwards.

If it is a shower branching, we need to veto.

Shower suppression for matching to the Breit-Wigner distribution.

On-shell masses, off-shellness, and suppression factor.

Veto to add the suppression factor.

If passed, do regular shower veto.

Reimplemented from EWAntennaFF.

double generateTrial	(	double	q2Start,
		double	q2End,
		double	alphaIn
	)

overridevirtual

Generate a trial.

Reset the current trial.

If the offshellness is above the current shower scale, decay immediately.

If this is a resonance decay without recoiler or if ewMatchMode == 1, decay immediately.

Set the lower bound to q2Dec. Note that for ewMode == 4, q2Dec == 0.

If applying the suppression factor, add a cutoff.

Sample a trial scale.

Check if the trial scale is above the cutoff.

Set q2Trial equal to the resonance offshelless.

Reimplemented from EWAntennaFF.

bool genForceDecay ( Event & event )

Generate the kinematics and channel for decays below matching scale.

Check if allowed to decay (according to Pythia decay table).

Resonance mass to be used in decay, total and partial width.

Fetch daughter ids.

Check if Pythia thinks this channel should be switched off.

EW shower only does 1->2 decays so ignore any others.

Found mode. Check if it is on.

Add partial width.

Add to cumulative.

Check if there is at least a single decay channel.

Select a channel with relative prob of its partial width. Subject to which modes are switched on in Pythia.

Store selection.

Next step is to sample angles for the decay in the CM frame. The azimuthal angle is uniformly distributed.

The polar angle is distributed according to the final-state spin-summed amplitudes. It is not uniform due to the polarization of the resonance. The distribution always looks like r0 + r1 * c + r2 * c^2, where c = cosTheta. First determine these coefficients for this decay.

Top decay - amplitudes are identical for t and tbar.

Higgs decay - no polarization, so uniform distribution.

Vector boson decay.

Get fermion couplings.

Positive transverse polarization.

Negative transverse polarization.

Longitudinal polarization.

Without too much loss of efficiency, we can overestimate the distribution with a constant function. We find the maximum by considering the function at c=1,0,-1.

Rejection sampling loop.

Fetch the momenta for this decay channel.

Now select a spin channel - use the polarise function.

Special case for top decays. Redistribute the W mass using the Breit-Wigner.

Keep trying until inside phase space.

Redo the kinematics.

Apply bosonic interference weight.

bool init	(	Event &	event,
		int	iMotIn,
		int	iRecIn,
		int	iSysIn,
		vector< EWBranching > &	branchings,
		Settings *	settingsPtr
	)

overridevirtual

Overridden virtual functions.

Final-final electroweak resonance antenna.

Initialize.

Call the FF antenna init function.

Resonance-related settings.

Check if this resonance has a recoiler.

Compute offshellness = minimum decay scale. (In principle, choice = 0 should be hardcoded = width, but not sure that makes sense here so defaulting to scale of order width in that case.)

Minimum offshellness is NANO to avoid numerical issues. Multiply by 0.999 to make sure Pythia decays get to go first.

Reimplemented from EWAntennaFF.

void updateEvent ( Event & event )

overridevirtual

Update an event.

Clear information for replacing later in partonSystems.

Fetch ids, masses, trial vectors.

If this is not a 1->2 decay, we need a temporary entry for resonance just prior to decay with recoiled momentum and with special status code(57).

Update the mother particle.

Update the recoiler if this was not a 1->2 branching.

Save information for parton systems.

Add daughters.

If new particles are qqbar pair, we need new color indices.

Otherwise carry I color indices to i.

Update the resonance.

Save information for parton systems.

Reimplemented from EWAntennaFF.

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

include/Pythia8/VinciaEW.h
src/VinciaEW.cc

Public Member Functions

Additional Inherited Members

Detailed Description

Member Function Documentation