The ResonanceWidths is the base class. Also used for generic resonaces. More...

#include <ResonanceWidths.h>

Inheritance diagram for ResonanceWidths:

Public Member Functions
virtual	~ResonanceWidths ()
	Destructor.

void	initBasic (int idResIn, bool isGenericIn=false)
	Set up standard properties.

virtual bool	init (Info *infoPtrIn)
	Calculate and store partial and total widths at the nominal mass. More...

int	id () const
	Return identity of particle species.

double	width (int idSgn, double mHatIn, int idInFlavIn=0, bool openOnly=false, bool setBR=false, int idOutFlav1=0, int idOutFlav2=0)
	Calculate the total/open width for given mass, charge and instate. More...

double	widthOpen (int idSgn, double mHatIn, int idIn=0)
	Special case to calculate open final-state width.

double	widthStore (int idSgn, double mHatIn, int idIn=0)
	Special case to store open final-state widths for channel selection.

double	openFrac (int idSgn)
	Return fraction of width open for particle and antiparticle.

double	widthRescaleFactor ()
	Return forced rescaling factor of resonance width.

double	widthChan (double mHatIn, int idOutFlav1, int idOutFlav2)

Protected Member Functions
	ResonanceWidths ()
	Constructor.

virtual void	initConstants ()
	Initialize constants.

virtual bool	initBSM ()

virtual bool	allowCalc ()

virtual void	calcPreFac (bool=false)

virtual void	calcWidth (bool=false)

double	numInt1BW (double mHatIn, double m1, double Gamma1, double mMin1, double m2, int psMode=1)
	Simple routines for matrix-element integration over Breit-Wigners. More...

double	numInt2BW (double mHatIn, double m1, double Gamma1, double mMin1, double m2, double Gamma2, double mMin2, int psMode=1)

Protected Attributes
int	idRes
	Particle properties always present.

int	hasAntiRes

bool	doForceWidth

bool	isGeneric

bool	allowCalcWidth

double	minWidth

double	minThreshold

double	mRes

double	GammaRes

double	m2Res

double	GamMRat

double	openPos

double	openNeg

double	forceFactor

int	iChannel
	Properties for currently studied decay channel(s).

int	onMode

int	meMode

int	mult

int	id1

int	id2

int	id3

int	id1Abs

int	id2Abs

int	id3Abs

int	idInFlav

double	widNow

double	mHat

double	mf1

double	mf2

double	mf3

double	mr1

double	mr2

double	mr3

double	ps

double	kinFac

double	alpEM

double	alpS

double	colQ

double	preFac

weak_ptr< ParticleDataEntry >	particlePtr
	Pointer to properties of the particle species.

Info *	infoPtr
	Pointer to various information on the generation.

Settings *	settingsPtr
	Pointer to the settings database.

ParticleData *	particleDataPtr
	Pointer to the particle data table.

Logger *	loggerPtr
	Pointer to the logger.

CoupSM *	coupSMPtr
	Pointers to Standard Model and SUSY couplings.

CoupSUSY *	coupSUSYPtr

Static Protected Attributes
static const int	NPOINT = 100
	Constants: could only be changed in the code itself. More...

static const double	MASSMIN = 0.1
	The mass of a resonance must not be too small.

static const double	MASSMARGIN = 0.1
	The sum of product masses must not be too close to the resonance mass.

Detailed Description

The ResonanceWidths is the base class. Also used for generic resonaces.

Member Function Documentation

virtual void calcPreFac ( bool = false )

inlineprotectedvirtual

Calculate various common prefactors for the current mass. Optional argument calledFromInit only used for Z0.

virtual void calcWidth ( bool = false )

inlineprotectedvirtual

Calculate width for currently considered channel. Optional argument calledFromInit only used for Z0.

bool init ( Info * infoPtrIn )

virtual

Calculate and store partial and total widths at the nominal mass.

Initialize data members. Calculate and store partial and total widths at the nominal mass.

Save pointers.

Perform any model dependent initialisations (pure dummy in base class).

Minimal decaying-resonance width. Minimal phase space for meMode = 103.

Pointer to particle species.

Generic particles should not have meMode < 100, but allow some exceptions: not used Higgses and not used Technicolor.

Resonance properties: antiparticle, mass, width

A resonance cannot be too light, in particular not = 0.

For very narrow resonances assign fictitious small width.

Secondary decay chains by default all on.

Allow option where on-shell width is forced to current value. Disable for mixes gamma

Check if we are supposed to do the width calculation (can be false e.g. if SLHA decay table should take precedence instead).

Initialize constants used for a resonance.

Calculate various common prefactors for the current mass.

Reset quantities to sum. Declare variables inside loop.

Loop over all decay channels. Basic properties of channel.

Warn if not relevant meMode.

Channels with meMode < 100 must be implemented in derived classes.

Read out information on channel: primarily use first two.

Order first two in descending order of absolute values.

Allow for third product to be treated in derived classes.

Also order third into descending order of absolute values.

Read out masses. Calculate two-body phase space.

Let derived class calculate width for channel provided.

Channels with meMode >= 100 are calculated based on stored values.

Find secondary open fractions of partial width.

Secondary widths not yet initialized for heavier states, so have to assume unit open fraction there.

Store partial widths and secondary open fractions.

Update sum over all channnels and over open channels only.

If no decay channels are open then set particle stable and done.

Set lifetime for displaced vertex calculations (convert GeV^-1 to mm). SLHA decay table should take precedence; decay length already set and potentially over-written as per users request.

Normalize branching ratios to unity.

Optionally force total width by rescaling of all partial ones.

Else update newly calculated partial width.

Updated width-to-mass ratio. Secondary widths for open.

Clip wings of Higgses.

Done.

virtual bool initBSM ( )

inlineprotectedvirtual

Virtual methods to handle model-specific (non-SM) part of initialization for use by derived classes that implement additional models (eg SUSY).

Reimplemented in SUSYResonanceWidths.

double numInt1BW	(	double	mHatIn,
		double	m1,
		double	Gamma1,
		double	mMin1,
		double	m2,
		int	psMode = `1`
	)

protected

Simple routines for matrix-element integration over Breit-Wigners.

Numerical integration of matrix-element in two-body decay, where one particle is described by a Breit-Wigner mass distribution. Normalization to unit integral if matrix element is unity and there are no phase-space restrictions.

Check that phase space is open for integration.

Precalculate coefficients for Breit-Wigner selection.

Step size in atan-mapped variable.

Variables used in loop over integration points.

Loop with first-particle mass selection.

Evaluate value and add to sum. Different matrix elements.

End of loop over integration points. Overall normalization.

Done.

double numInt2BW	(	double	mHatIn,
		double	m1,
		double	Gamma1,
		double	mMin1,
		double	m2,
		double	Gamma2,
		double	mMin2,
		int	psMode = `1`
	)

protected

Numerical integration of matrix-element in two-body decay, where both particles are described by Breit-Wigner mass distributions. Normalization to unit integral if matrix element is unity and there are no phase-space restrictions.

Check that phase space is open for integration.

Precalculate coefficients for Breit-Wigner selection.

If on-shell decay forbidden then split integration range to ensure that low-mass region is not forgotten.

Step size in atan-mapped variable.

Variables used in loop over integration points.

Outer loop with first-particle mass selection.

Inner loop with second-particle mass selection.

Check that point is inside phase space.

Evaluate value and add to sum. Different matrix elements.

End of second and first loop over integration points.

Done.

double width	(	int	idSgn,
		double	mHatIn,
		int	idInFlavIn = `0`,
		bool	openOnly = `false`,
		bool	setBR = `false`,
		int	idOutFlav1 = `0`,
		int	idOutFlav2 = `0`
	)

Calculate the total/open width for given mass, charge and instate.

Calculate the total width and store phase-space-weighted coupling sums.

Calculate various prefactors for the current mass.

Reset quantities to sum. Declare variables inside loop.

Loop over all decay channels. Basic properties of channel.

Initially assume vanishing branching ratio.

Optionally only consider specific (two-body) decay channel. Currently only used for Higgs -> q qbar, g g or gamma gamma.

Optionally only consider open channels.

Channels with meMode < 100 must be implemented in derived classes.

Read out information on channel: primarily use first two.

Order first two in descending order of absolute values.

Allow for third product to be treated in derived classes.

Also order third into descending order of absolute values.

Read out masses. Calculate two-body phase space.

Let derived class calculate width for channel provided.

Now on to meMode >= 100. First case: no correction at all.

Correction by step at threshold.

Correction by a phase space factor for two-body decays.

Correction by simple threshold factor for multibody decay.

Optionally multiply by secondary widths.

Optionally include factor to force to fixed width.

Optionally multiply by current/nominal resonance mass??

Sum back up.

Optionally store partial widths for later decay channel choice.

Done.

double widthChan	(	double	mHatIn,
		int	idOutFlav1,
		int	idOutFlav2
	)

inline

Special case to calculate one final-state width. Currently only used for Higgs -> qqbar, g g or gamma gamma.

Member Data Documentation

const int NPOINT = 100

staticprotected

Constants: could only be changed in the code itself.

Number of points in integration direction for numInt routines.

The ResonanceWidths class. Base class for the various resonances. Constants: could be changed here if desired, but normally should not. These are of technical nature, as described for each.

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

include/Pythia8/ResonanceWidths.h
src/ResonanceWidths.cc

Public Member Functions

Protected Member Functions

Protected Attributes

Static Protected Attributes

Detailed Description

Member Function Documentation

Member Data Documentation