StringRegion Class Reference

#include <FragmentationSystems.h>

Public Member Functions
	StringRegion ()
	Constructor.
Vec4	gluonOffset (vector< int > &iSys, Event &event, int iPos, int iNeg)
	Calculate offset of the region from parton list. Special junction case. More...
Vec4	gluonOffsetJRF (vector< int > &iSys, Event &event, int iPos, int iNeg, RotBstMatrix MtoJRF)
	Calculate offset when calculation needed in junction rest frame. More...
bool	massiveOffset (int iPos, int iNeg, int iMax, int id1, int id2, double mc, double mb)
	If massive case, the offset of the initial regions is calculated. More...
void	setUp (Vec4 p1, Vec4 p2, int col1, int col2, bool isMassless=false)
	Set up four-vectors for longitudinal and transverse directions. More...
Vec4	pHad (double xPosIn, double xNegIn, double pxIn, double pyIn) const
	Construct a four-momentum from (x+, x-, px, py).
void	project (Vec4 pIn)
	Project a four-momentum onto (x+, x-, px, py). Read out projection. More...
void	project (double pxIn, double pyIn, double pzIn, double eIn)
double	xPos () const
double	xNeg () const
double	px () const
double	py () const

Public Attributes
bool	isSetUp
	Data members.
bool	isEmpty
Vec4	pPos
Vec4	pNeg
Vec4	eX
Vec4	eY
Vec4	pPosMass
Vec4	pNegMass
Vec4	massOffset
double	w2
double	xPosProj
double	xNegProj
double	pxProj
double	pyProj
int	colPos
int	colNeg

Static Public Attributes
static const double	MJOIN = 0.1
	Constants: could only be changed in the code itself. More...
static const double	TINY = 1e-20
	Avoid division by zero.

Detailed Description

The StringRegion class contains the information related to one string section in the evolution of a multiparton system. Only to be used inside StringFragmentation and MiniStringFragmentation, so no private members.

Member Function Documentation

Vec4 gluonOffset	(	vector< int > &	iSys,
		Event &	event,
		int	iPos,
		int	iNeg
	)

Calculate offset of the region from parton list. Special junction case.

Calculate offset of the region due to presence of gluons from parton list.

Half sum of all intervening gluon momenta.

Vec4 gluonOffsetJRF	(	vector< int > &	iSys,
		Event &	event,
		int	iPos,
		int	iNeg,
		RotBstMatrix	MtoJRF
	)

Calculate offset when calculation needed in junction rest frame.

Half sum of all intervening gluon momenta, boosted to junction rest frame.

bool massiveOffset	(	int	iPos,
		int	iNeg,
		int	iMax,
		int	id1,
		int	id2,
		double	mc,
		double	mb
	)

If massive case, the offset of the initial regions is calculated.

Calculate offset if system contains c or b quarks, where the location of energy-momentum-picture breakup points in the initial regions are shifted with respect to the origin, to be removed for the space-time vertices.

Done if not in either of endpoint regions or no massive endpoint quark.

Calculate the offset of initial-region massive endpoint quark.

void project

(

Vec4

pIn

)

Project a four-momentum onto (x+, x-, px, py). Read out projection.

Project a four-momentum onto (x+, x-, px, py).

Perform projections by four-vector multiplication.

void setUp	(	Vec4	p1,
		Vec4	p2,
		int	col1,
		int	col2,
		bool	isMassless = false
	)

Set up four-vectors for longitudinal and transverse directions.

Store the original four-momenta; needed for the massive-quark case.

Simple case: the two incoming four-vectors guaranteed massless.

Calculate w2, minimum value. Lightcone directions = input.

Else allow possibility of masses for incoming partons (also gluons!).

Generic four-momentum combinations.

If crazy kinematics (should not happen!) modify energies.

If still small invariant mass then empty region (e.g. in gg system).

Find two lightconelike longitudinal four-vector directions.

Find two spacelike transverse four-vector directions. Begin by picking two sensible trial directions.

Then construct orthogonal linear combinations.

Remember colour indices.

Done.

Member Data Documentation

const double MJOIN = 0.1

static

Constants: could only be changed in the code itself.

The StringRegion class.

Currently a number of simplifications, in particular ?? 1) No popcorn baryon production. 2) Simplified treatment of pT in stepping and joining. Constants: could be changed here if desired, but normally should not. These are of technical nature, as described for each. If a string region is smaller thsan this it is assumed empty.

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

• include/Pythia8/FragmentationSystems.h
• src/FragmentationSystems.cc