PYTHIA  8.303
Public Member Functions | List of all members
Sphericity Class Reference

#include <Analysis.h>

Public Member Functions

 Sphericity (double powerIn=2., int selectIn=2)
bool analyze (const Event &event)
 Analyze event. More...
double sphericity () const
 Return info on results of analysis.
double aplanarity () const
double eigenValue (int i) const
Vec4 eventAxis (int i) const
void list () const
 Provide a listing of the info. More...
int nError () const
 Tell how many events could not be analyzed.

Detailed Description

Sphericity class. This class performs (optionally modified) sphericity analysis on an event.

Member Function Documentation

bool analyze ( const Event event)

Analyze event.

Initial values, tensor and counters zero.

Loop over desired particles in the event.

Calculate matrix to be diagonalized. Special cases for speed.

Very low multiplicities (0 or 1) not considered.

Normalize tensor to trace = 1.

Find eigenvalues to matrix (third degree equation).

Begin find first and last eigenvector.

If all particles are back-to-back then simpleminded third axis.

Set up matrix to diagonalize.

Find largest = pivotal element in matrix.

Subtract one row from the other two; find new largest element.

Construct eigenvector. Normalize to unit length; sign irrelevant.

Store eigenvectors.

Middle eigenvector is orthogonal to the other two; sign irrelevant.


void list ( ) const

Provide a listing of the info.


The three eigenvalues and eigenvectors.

Listing finished.

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