EvtdFunction.cc

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//--------------------------------------------------------------------------
//
// Environment:
//      This software is part of the EvtGen package developed jointly
//      for the BaBar and CLEO collaborations.  If you use all or part
//      of it, please give an appropriate acknowledgement.
//
// Copyright Information: See EvtGen/COPYRIGHT
//      Copyright (C) 1998      Caltech, UCSB
//
// Module: EvtKine.cc
//
// Description: Evaluates the Wigner d-Functions.
//
// Modification history:
//
//    RYD            March 14, 1999         Module created
//
//------------------------------------------------------------------------
//
#include "EvtdFunction.hh"
#include "EvtPatches.hh"
#include "EvtdFunctionSingle.hh"
#include <assert.h>
#include <iostream>
#include <math.h>
#include <stdlib.h>
 
double EvtdFunction::d( int j, int m1, int m2, double theta ) {
 
  int m1p = m1;
  int m2p = m2;
 
  int signp = 1;
  // make |m2p|>|m1p|
  if ( abs( m2p ) < abs( m1p ) )
  {
    int tmp = m1p;
    m1p     = m2p;
    m2p     = tmp;
    if ( ( m1p - m2p ) % 4 != 0 ) signp = -signp;
  }
 
  // make m2p non-negative
  if ( m2p < 0 )
  {
    m1p = -m1p;
    m2p = -m2p;
    if ( ( m1p - m2p ) % 4 != 0 ) signp = -signp;
  }
 
  EvtdFunctionSingle df;
 
  df.init( j, m1p, m2p );
 
  double d = df.d( j, m1p, m2p, theta ) * signp;
 
  return d;
}