PYTHIA  8.303
Public Member Functions | Public Attributes | Static Public Attributes | List of all members
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)
 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.


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