Line data    Source code

       1             : // StringLength.h is a part of the PYTHIA event generator.
       2             : // Copyright (C) 2015 Torbjorn Sjostrand.
       3             : // PYTHIA is licenced under the GNU GPL version 2, see COPYING for details.
       4             : // Please respect the MCnet Guidelines, see GUIDELINES for details.
       5             : 
       6             : // This file contains the class StringLength.
       7             : // It is used to calculate the lambda measure of strings and junctions.
       8             : 
       9             : #ifndef Pythia8_StringLength_H
      10             : #define Pythia8_StringLength_H
      11             : 
      12             : #include "Pythia8/Event.h"
      13             : #include "Pythia8/Info.h"
      14             : #include "Pythia8/Settings.h"
      15             : #include "Pythia8/StringFragmentation.h"
      16             : 
      17             : namespace Pythia8 {
      18             : 
      19             : //==========================================================================
      20             : 
      21             : // StringLength class. It is used to calculate the lambda measure.
      22             : 
      23           0 : class StringLength {
      24             : 
      25             : public:
      26             : 
      27             :   // Initialize.
      28             :   void init(Info* infoPtrIn, Settings& settings);
      29             : 
      30             :   // Calculate string length of a single particle.
      31             :   // The first vector is the 4 vector of the particle.
      32             :   // The second vector represents (1,0,0,0) in dipole restframe.
      33             :   double getLength(Vec4 p, Vec4 v, bool isJunc = false);
      34             : 
      35             :   // Calculate string length for two indices in the event record.
      36             :   double getStringLength(Event& event, int i, int j);
      37             : 
      38             :   // Calculate string length for two particles given their four-momenta.
      39             :   double getStringLength(Vec4 p1, Vec4 p2);
      40             : 
      41             :   // Calculate the length of a single junction given the 3 entries in event.
      42             :   double getJuncLength(Event& event, int i, int j, int k);
      43             : 
      44             :   // Calculate the length of a single junction given the 3 four-momenta.
      45             :   double getJuncLength(Vec4 p1, Vec4 p2, Vec4 p3);
      46             : 
      47             :   // Calculate the length of a double junction given the 4 entries in event.
      48             :   // The first two are expected to be quarks, the second two to be antiquarks.
      49             :   double getJuncLength(Event& event, int i, int j, int k, int l);
      50             : 
      51             :   // Calculate the length of a double junction given the 4 four-momenta.
      52             :   // The first two are expected to be quarks, the second two to be antiquarks.
      53             :   double getJuncLength(Vec4 p1, Vec4 p2, Vec4 p3, Vec4 p4);
      54             : 
      55             : private:
      56             : 
      57             :   static const double MINDELTAR, TINY;
      58             : 
      59             :   double m0, m0sqr, sqrt2, juncCorr;
      60             :   int lambdaForm;
      61             : 
      62             :   // Pointer to various information on the generation.
      63             :   Info*          infoPtr;
      64             : 
      65             :   // This is only to access the function call junctionRestFrame.
      66             :   StringFragmentation stringFragmentation;
      67             : 
      68             : };
      69             : 
      70             : //==========================================================================
      71             : 
      72             : } // end namespace Pythia8
      73             : 
      74             : #endif // Pythia8_StringLength_H