[u/mrichter/AliRoot.git] / HBTAN / AliHBTCrab.cxx

#include "AliHBTCrab.h"
//______________________________________________________________________
/////////////////////////////////////////////////////////////////////////
//                                                                     //
// AliRoot wrapper to CRAB                                             //
// taken from http://www.nscl.msu.edu/~pratt/freecodes/crab/home.html  //
// written by Scott Pratt                                              //
//                                                                     //
/////////////////////////////////////////////////////////////////////////
 
#include "AliHBTPair.h"

#include <TMath.h>
#include <TPDGCode.h>

#include "volya_complex.h"

//#include <complex>
//using namespace std;
AliHBTCrab* AliHBTCrab::fgCrab = 0x0;

const Double_t AliHBTCrab::fgkWcons = 1./0.1973;
const Double_t AliHBTCrab::fgkROOT2=1.41421356237309504880;
const double_complex AliHBTCrab::ci(0.0,1.0);

/************************************************************/

AliHBTCrab* AliHBTCrab::Instance()
{
// returns instance of class
 if (fgCrab == 0x0)
  {
    fgCrab = new AliHBTCrab();
  }
 return fgCrab;
}
//===================================================================
void AliHBTCrab::Set()
{
 //sets this as weighitng class
 Info("Set","Setting CRAB as Weighing Class");
 
 if ( fgWeights == 0x0 )  
  {
    fgWeights = AliHBTCrab::Instance();
    return;
  }  
 if ( fgWeights == AliHBTCrab::Instance() ) return;
 delete fgWeights;
 fgWeights = AliHBTCrab::Instance();
}
//===================================================================

AliHBTCrab::AliHBTCrab():
fBreitWigner(kFALSE),
fReducedMom(kTRUE),
fMaxMomentum(100.0)
{
  //ctor
}
//===================================================================
void AliHBTCrab::Init(Int_t pid1,Int_t pid2)
{
  MASS1 = TDatabasePDG::Instance()->GetParticle(pid1)->Mass();
  MASS2 = TDatabasePDG::Instance()->GetParticle(pid2)->Mass();
  INTERACTION_WSYM = 1.0;
  INTERACTION_WANTI = 0.0;
  INTERACTION_WNOSYM = 0.0;
  INTERACTION_DELK  = 1.0;
  INTERACTION_NKMAX = 100;
     
  fPid1 = pid1;   
  fPid2 = pid2;
  
}

Bool_t AliHBTCrab::SetConfig(const AliHBTPair* pair)
{
  Int_t pdg1 = pair->Particle1()->GetPdgCode();
  Int_t pdg2 = pair->Particle2()->GetPdgCode();
  
  if ( ( pdg1 == fPid1) && ( pdg2  == fPid2) ) return kFALSE;
  else Init (pdg1,pdg2);
  
  return kTRUE;
}
//===================================================================

Double_t AliHBTCrab::GetWeight(const AliHBTPair* partpair)
{
  Double_t qred, r, qdotr, mom;
  Int_t test;
  
  SetConfig(partpair);
  
  get_com_quantities(partpair, &qred, &r, &qdotr, &mom, &test);
  if(test==0) 
   {
     Info("GetWeight","Test is 0");
   }
  Double_t corr = corrcalc(qred,qdotr,r);
  
  return corr;
}
//===================================================================

void AliHBTCrab::get_com_quantities(const AliHBTPair* pair, 
       double *qred,double *r,double *qdotr,double *mom, int *test)
 {
//************************************
//  ALICE //

 double p1[4]; 
 double p2[4]; 
 double r1[4]; 
 double r2[4]; 
 
 static const Double_t cmtofm = 1.e13;
// static const Double_t cmtoOneOverGeV = cmtofm*fgkWcons;
 
 AliHBTParticle *part1 = pair->Particle1();
 AliHBTParticle *part2 = pair->Particle2();

 p1[0] = part1->Energy()*1000.0;
 p1[1] = part1->Px()*1000.0;
 p1[2] = part1->Py()*1000.0;
 p1[3] = part1->Pz()*1000.0;
 
 p2[0] = part2->Energy()*1000.0;
 p2[1] = part2->Px()*1000.0;
 p2[2] = part2->Py()*1000.0;
 p2[3] = part2->Pz()*1000.0;

 r1[0] = part1->T();
 r1[1] = part1->Vx()*cmtofm;
 r1[2] = part1->Vy()*cmtofm;
 r1[3] = part1->Vz()*cmtofm;

 r2[0] = part2->T();
 r2[1] = part2->Vx()*cmtofm;
 r2[2] = part2->Vy()*cmtofm;
 r2[3] = part2->Vz()*cmtofm;

//  END OF ALICE STUFF

// This code is written by Scott Pratt
// taken from http://www.nscl.msu.edu/~pratt/freecodes/crab/home.html
  int alpha;
  double kdotr;
  double momtest;
  if (fReducedMom)
   {
     momtest=4.0*fMaxMomentum*fMaxMomentum;
   }  
  else
   {
     momtest=fMaxMomentum*fMaxMomentum;
   }  
   
  double ptot2,pdotr,pp,rr;
  
  if ( part1->GetPdgCode() == part2->GetPdgCode() )
   {
    *test=1;
    *mom=-(p2[0]-p1[0])*(p2[0]-p1[0]);
    for(alpha=1;alpha<4;alpha++){
      *mom=*mom+(p2[alpha]-p1[alpha])*(p2[alpha]-p1[alpha]);
    }
   //#if ! defined MIXED_PAIRS_FOR_DENOM
   //  if(*mom>momtest){
   //    *test=0;
   //    return;
   //  }
   //#endif
    pp=(p1[0]+p2[0]);
    rr=(r2[0]-r1[0]);
    pdotr=pp*rr;
    kdotr=(p2[0]-p1[0])*rr;
    ptot2=pp*pp;
    *r=-rr*rr;
    for(alpha=1;alpha<4;alpha++){
      pp=(p1[alpha]+p2[alpha]);
      rr=(r2[alpha]-r1[alpha]);
      pdotr=pdotr-pp*rr;
      kdotr=kdotr-(p2[alpha]-p1[alpha])*rr;
      ptot2=ptot2-pp*pp;
      *r=*r+rr*rr;
    }
    *mom=sqrt(*mom);
    *qred=0.5**mom;

    if (fReducedMom)
     {
      *mom=*qred;
     } 

    *qdotr=0.5*kdotr;
    *r=sqrt(*r+pdotr*pdotr/ptot2);
   }  
  else //identical
  {
  //  const double  kdotp=MASS2*MASS2-MASS1*MASS1;
   const double  kdotp = part2->GetMass()*part2->GetMass()- part1->GetMass()*part1->GetMass();
   *test=1;
   *mom=-(p2[0]-p1[0])*(p2[0]-p1[0]);
   ptot2=(p1[0]+p2[0])*(p1[0]+p2[0]);
   for(alpha=1;alpha<4;alpha++){
     *mom=*mom+(p2[alpha]-p1[alpha])*(p2[alpha]-p1[alpha]);
     ptot2=ptot2-(p1[alpha]+p2[alpha])*(p1[alpha]+p2[alpha]);
   }
   *mom=*mom+kdotp*kdotp/ptot2;
  //#if ! defined MIXED_PAIRS_FOR_DENOM
  //  if(*mom>momtest){
  //    *test=0;
  //    return;
  //  }
  //#endif
   pp=(p1[0]+p2[0]);
   rr=(r2[0]-r1[0]);
   pdotr=pp*rr;
   kdotr=(p2[0]-p1[0])*rr;
   *r=-rr*rr;
   for(alpha=1;alpha<4;alpha++){
     pp=(p1[alpha]+p2[alpha]);
     rr=(r2[alpha]-r1[alpha]);
     pdotr=pdotr-pp*rr;
     kdotr=kdotr-(p2[alpha]-p1[alpha])*rr;
     *r=*r+rr*rr;
   }
   kdotr=(-kdotr+kdotp*pdotr/ptot2);
   *mom=sqrt(*mom);
   *qred=0.5**mom;

   if (fReducedMom)
    {
     *mom=*qred;
    } 

   *qdotr=0.5*kdotr;
   *r=sqrt(*r+pdotr*pdotr/ptot2);
  }//not identical  

  return;
}


//===================================================================

double  AliHBTCrab::corrcalc(double trueqred,double trueqdotr,double truer)
{
//#define REDUCED_MOM
// This code is written by Scott Pratt
// taken from http://www.nscl.msu.edu/~pratt/freecodes/crab/home.html
  double eta,arg,corr0;
//  double xx,xxprime,xxjj,p1,zk;
//  int jj,kk,ipart,ipartcount,ispin;
  int kk;
  double wsym_leftover,wanti_leftover,wnosym_leftover;
  double qred,qdotr,r;
//  const double rmass=MASS1*MASS2/(MASS1+MASS2);
  double_complex cphi1,cphi2,cphis,cphia;

  arg=trueqdotr/197.323-2.0*TMath::Pi()*TMath::Floor(trueqdotr/(197.323*2.0*TMath::Pi()));
  cphi1=exp(ci*arg);
  cphis=fgkROOT2*real(cphi1);
  cphia=ci*fgkROOT2*imag(cphi1);
  corr0=real(INTERACTION_WSYM*cphis*conj(cphis)
	     +INTERACTION_WANTI*cphia*conj(cphia)
	     +INTERACTION_WNOSYM*cphi1*conj(cphi1));
  goto OUTSIDE_INTERACTION_RANGE;

#ifdef REDUCED_MOM
  kk=(int)TMath::Floor(trueqred/INTERACTION_DELK);
  qred=(0.5+kk)*INTERACTION_DELK;
#else
  kk=(int)TMath::Floor(2.0*trueqred/INTERACTION_DELK);
  qred=(0.5+kk)*INTERACTION_DELK/2.0;
#endif
  qdotr=trueqdotr*qred/trueqred;
  if(kk>=INTERACTION_NKMAX){
    corr0=1.0;
    goto OUTSIDE_INTERACTION_RANGE;
  }
  r=truer;

  eta=0.0;
  arg=qdotr/197.323-2.0*TMath::Pi()*TMath::Floor(qdotr/(197.323*2.0*TMath::Pi()));
  cphi1=exp(ci*arg);
  cphi2=conj(cphi1);

  cphis=(cphi1+cphi2)/fgkROOT2;
  cphia=(cphi1-cphi2)/fgkROOT2;
  corr0=0.0;
  /* If there are corrections for strong interactions, add the
     change for each partial wave.  If npartial = 0 then there
     are no strong int. corrections. */
  wsym_leftover=INTERACTION_WSYM;
  wanti_leftover=INTERACTION_WANTI;
  wnosym_leftover=INTERACTION_WNOSYM;

  corr0=corr0+real(wsym_leftover*cphis*conj(cphis)
		   +wanti_leftover*cphia*conj(cphia)
		   +wnosym_leftover*cphi1*conj(cphi1));
OUTSIDE_INTERACTION_RANGE:

#ifdef BREIT_WIGNER
  corr0=corr0+bwcalc(trueqred,truer);
#endif

  return corr0;
}

double_complex AliHBTCrab::cgamma(double_complex c){
  /* This calc.s gamma functions which are in the form gamma(n+i*y)
     where n is an int and y is real. */
// This code is written by Scott Pratt
// taken from http://www.nscl.msu.edu/~pratt/freecodes/crab/home.html
  double_complex cg,cphase;
  int mm,j;
  double x,y,phase,delp,cgmag;
  x=real(c);
  y=imag(c);
  phase=-TMath::E()*y;
  for(j=1;j<=100000;j++){
    delp=(y/(double)j)-atan(y/(double)j);
    phase=phase+delp;
    if(TMath::Abs(delp)<1E-10) goto CGAMMA_ESCAPE;
  }
  printf("oops not accurate enough, increase jmax\n");
CGAMMA_ESCAPE:
  phase=phase-2.0*TMath::Pi()*TMath::Floor(phase/(2.0*TMath::Pi()));
  cphase=exp(ci*phase);
  cgmag=sqrt(TMath::Pi()*y/sinh(TMath::Pi()*y));
  mm=(int)TMath::Floor(x+0.5);
  cg=cgmag*cphase;
  if(mm<1){
    for(j=1;j<=-mm+1;j++){
      cg=cg/(1.0+(double)(-j)+ci*y);
    }
  }
  if(mm>1) {
    for(j=1;j<=mm-1;j++){
      cg=cg*((double)(j)+ci*y);
    }
  }
  return cg;
}
//===================================================================
Commit	Line	Data
dd82cadc	1	#include "AliHBTCrab.h"
	2	//______________________________________________________________________
	3	/////////////////////////////////////////////////////////////////////////
	4	// //
	5	// AliRoot wrapper to CRAB //
	6	// taken from http://www.nscl.msu.edu/~pratt/freecodes/crab/home.html //
	7	// written by Scott Pratt //
	8	// //
	9	/////////////////////////////////////////////////////////////////////////
f93c53d8	10
dd82cadc	11	#include "AliHBTPair.h"
	12
	13	#include <TMath.h>
	14	#include <TPDGCode.h>
	15
	16	#include "volya_complex.h"
	17
	18	//#include <complex>
	19	//using namespace std;
	20	AliHBTCrab* AliHBTCrab::fgCrab = 0x0;
	21
	22	const Double_t AliHBTCrab::fgkWcons = 1./0.1973;
	23	const Double_t AliHBTCrab::fgkROOT2=1.41421356237309504880;
	24	const double_complex AliHBTCrab::ci(0.0,1.0);
	25
	26	/************************************************************/
	27
	28	AliHBTCrab* AliHBTCrab::Instance()
	29	{
	30	// returns instance of class
	31	if (fgCrab == 0x0)
	32	{
	33	fgCrab = new AliHBTCrab();
	34	}
	35	return fgCrab;
	36	}
	37	//===================================================================
	38	void AliHBTCrab::Set()
	39	{
	40	//sets this as weighitng class
	41	Info("Set","Setting CRAB as Weighing Class");
	42
	43	if ( fgWeights == 0x0 )
	44	{
	45	fgWeights = AliHBTCrab::Instance();
	46	return;
	47	}
	48	if ( fgWeights == AliHBTCrab::Instance() ) return;
	49	delete fgWeights;
	50	fgWeights = AliHBTCrab::Instance();
	51	}
	52	//===================================================================
	53
	54	AliHBTCrab::AliHBTCrab():
	55	fBreitWigner(kFALSE),
	56	fReducedMom(kTRUE),
	57	fMaxMomentum(100.0)
	58	{
	59	//ctor
	60	}
	61	//===================================================================
	62	void AliHBTCrab::Init(Int_t pid1,Int_t pid2)
	63	{
	64	MASS1 = TDatabasePDG::Instance()->GetParticle(pid1)->Mass();
	65	MASS2 = TDatabasePDG::Instance()->GetParticle(pid2)->Mass();
	66	INTERACTION_WSYM = 1.0;
	67	INTERACTION_WANTI = 0.0;
	68	INTERACTION_WNOSYM = 0.0;
	69	INTERACTION_DELK = 1.0;
	70	INTERACTION_NKMAX = 100;
	71
	72	fPid1 = pid1;
	73	fPid2 = pid2;
	74
75	}
76
77	Bool_t AliHBTCrab::SetConfig(const AliHBTPair* pair)
78	{
79	Int_t pdg1 = pair->Particle1()->GetPdgCode();
80	Int_t pdg2 = pair->Particle2()->GetPdgCode();
81
82	if ( ( pdg1 == fPid1) && ( pdg2 == fPid2) ) return kFALSE;
83	else Init (pdg1,pdg2);
84
85	return kTRUE;
86	}
87	//===================================================================
88
89	Double_t AliHBTCrab::GetWeight(const AliHBTPair* partpair)
90	{
91	Double_t qred, r, qdotr, mom;
92	Int_t test;
93
94	SetConfig(partpair);
95
96	get_com_quantities(partpair, &qred, &r, &qdotr, &mom, &test);
97	if(test==0)
98	{
99	Info("GetWeight","Test is 0");
100	}
101	Double_t corr = corrcalc(qred,qdotr,r);
102
103	return corr;
104	}
105	//===================================================================
106
107	void AliHBTCrab::get_com_quantities(const AliHBTPair* pair,
108	double qred,double r,double qdotr,double mom, int *test)
109	{
110	//************************************
111	// ALICE //
112
113	double p1[4];
114	double p2[4];
115	double r1[4];
116	double r2[4];
117
118	static const Double_t cmtofm = 1.e13;
f93c53d8	119	// static const Double_t cmtoOneOverGeV = cmtofm*fgkWcons;
dd82cadc	120
	121	AliHBTParticle *part1 = pair->Particle1();
	122	AliHBTParticle *part2 = pair->Particle2();
	123
	124	p1[0] = part1->Energy()*1000.0;
	125	p1[1] = part1->Px()*1000.0;
	126	p1[2] = part1->Py()*1000.0;
	127	p1[3] = part1->Pz()*1000.0;
	128
	129	p2[0] = part2->Energy()*1000.0;
	130	p2[1] = part2->Px()*1000.0;
	131	p2[2] = part2->Py()*1000.0;
	132	p2[3] = part2->Pz()*1000.0;
	133
	134	r1[0] = part1->T();
	135	r1[1] = part1->Vx()*cmtofm;
	136	r1[2] = part1->Vy()*cmtofm;
	137	r1[3] = part1->Vz()*cmtofm;
	138
	139	r2[0] = part2->T();
	140	r2[1] = part2->Vx()*cmtofm;
	141	r2[2] = part2->Vy()*cmtofm;
	142	r2[3] = part2->Vz()*cmtofm;
	143
	144	// END OF ALICE STUFF
	145
	146	// This code is written by Scott Pratt
	147	// taken from http://www.nscl.msu.edu/~pratt/freecodes/crab/home.html
	148	int alpha;
	149	double kdotr;
f93c53d8	150	double momtest;
dd82cadc	151	if (fReducedMom)
dd82cadc	152	{
f93c53d8	153	momtest=4.0fMaxMomentumfMaxMomentum;
dd82cadc	154	}
	155	else
	156	{
f93c53d8	157	momtest=fMaxMomentum*fMaxMomentum;
dd82cadc	158	}
	159
	160	double ptot2,pdotr,pp,rr;
	161
	162	if ( part1->GetPdgCode() == part2->GetPdgCode() )
	163	{
	164	*test=1;
	165	mom=-(p2[0]-p1[0])(p2[0]-p1[0]);
	166	for(alpha=1;alpha<4;alpha++){
	167	mom=mom+(p2[alpha]-p1[alpha])*(p2[alpha]-p1[alpha]);
	168	}
	169	//#if ! defined MIXED_PAIRS_FOR_DENOM
	170	// if(*mom>momtest){
	171	// *test=0;
	172	// return;
	173	// }
	174	//#endif
	175	pp=(p1[0]+p2[0]);
	176	rr=(r2[0]-r1[0]);
	177	pdotr=pp*rr;
	178	kdotr=(p2[0]-p1[0])*rr;
	179	ptot2=pp*pp;
	180	r=-rrrr;
	181	for(alpha=1;alpha<4;alpha++){
	182	pp=(p1[alpha]+p2[alpha]);
	183	rr=(r2[alpha]-r1[alpha]);
	184	pdotr=pdotr-pp*rr;
	185	kdotr=kdotr-(p2[alpha]-p1[alpha])*rr;
	186	ptot2=ptot2-pp*pp;
	187	r=r+rr*rr;
	188	}
	189	mom=sqrt(mom);
	190	qred=0.5*mom;
	191
	192	if (fReducedMom)
	193	{
	194	mom=qred;
	195	}
	196
	197	qdotr=0.5kdotr;
	198	r=sqrt(r+pdotr*pdotr/ptot2);
	199	}
	200	else //identical
	201	{
	202	// const double kdotp=MASS2MASS2-MASS1MASS1;
	203	const double kdotp = part2->GetMass()part2->GetMass()- part1->GetMass()part1->GetMass();
	204	*test=1;
	205	mom=-(p2[0]-p1[0])(p2[0]-p1[0]);
	206	ptot2=(p1[0]+p2[0])*(p1[0]+p2[0]);
	207	for(alpha=1;alpha<4;alpha++){
	208	mom=mom+(p2[alpha]-p1[alpha])*(p2[alpha]-p1[alpha]);
	209	ptot2=ptot2-(p1[alpha]+p2[alpha])*(p1[alpha]+p2[alpha]);
	210	}
	211	mom=mom+kdotp*kdotp/ptot2;
	212	//#if ! defined MIXED_PAIRS_FOR_DENOM
	213	// if(*mom>momtest){
	214	// *test=0;
	215	// return;
	216	// }
	217	//#endif
	218	pp=(p1[0]+p2[0]);
	219	rr=(r2[0]-r1[0]);
	220	pdotr=pp*rr;
	221	kdotr=(p2[0]-p1[0])*rr;
222	r=-rrrr;
223	for(alpha=1;alpha<4;alpha++){
224	pp=(p1[alpha]+p2[alpha]);
225	rr=(r2[alpha]-r1[alpha]);
226	pdotr=pdotr-pp*rr;
227	kdotr=kdotr-(p2[alpha]-p1[alpha])*rr;
228	r=r+rr*rr;
229	}
230	kdotr=(-kdotr+kdotp*pdotr/ptot2);
231	mom=sqrt(mom);
232	qred=0.5*mom;
233
234	if (fReducedMom)
235	{
236	mom=qred;
237	}
238
239	qdotr=0.5kdotr;
240	r=sqrt(r+pdotr*pdotr/ptot2);
241	}//not identical
242
243	return;
244	}
245
246
247	//===================================================================
248
249	double AliHBTCrab::corrcalc(double trueqred,double trueqdotr,double truer)
250	{
251	//#define REDUCED_MOM
252	// This code is written by Scott Pratt
253	// taken from http://www.nscl.msu.edu/~pratt/freecodes/crab/home.html
f93c53d8	254	double eta,arg,corr0;
	255	// double xx,xxprime,xxjj,p1,zk;
	256	// int jj,kk,ipart,ipartcount,ispin;
	257	int kk;
	258	double wsym_leftover,wanti_leftover,wnosym_leftover;
dd82cadc	259	double qred,qdotr,r;
f93c53d8	260	// const double rmass=MASS1*MASS2/(MASS1+MASS2);
dd82cadc	261	double_complex cphi1,cphi2,cphis,cphia;
dd82cadc	262
3294e9ff	263	arg=trueqdotr/197.323-2.0TMath::Pi()TMath::Floor(trueqdotr/(197.3232.0TMath::Pi()));
dd82cadc	264	cphi1=exp(ci*arg);
	265	cphis=fgkROOT2*real(cphi1);
	266	cphia=cifgkROOT2imag(cphi1);
	267	corr0=real(INTERACTION_WSYMcphisconj(cphis)
	268	+INTERACTION_WANTIcphiaconj(cphia)
	269	+INTERACTION_WNOSYMcphi1conj(cphi1));
	270	goto OUTSIDE_INTERACTION_RANGE;
	271
	272	#ifdef REDUCED_MOM
3294e9ff	273	kk=(int)TMath::Floor(trueqred/INTERACTION_DELK);
dd82cadc	274	qred=(0.5+kk)*INTERACTION_DELK;
dd82cadc	275	#else
3294e9ff	276	kk=(int)TMath::Floor(2.0*trueqred/INTERACTION_DELK);
dd82cadc	277	qred=(0.5+kk)*INTERACTION_DELK/2.0;
	278	#endif
	279	qdotr=trueqdotr*qred/trueqred;
	280	if(kk>=INTERACTION_NKMAX){
	281	corr0=1.0;
	282	goto OUTSIDE_INTERACTION_RANGE;
	283	}
	284	r=truer;
	285
	286	eta=0.0;
3294e9ff	287	arg=qdotr/197.323-2.0TMath::Pi()TMath::Floor(qdotr/(197.3232.0TMath::Pi()));
dd82cadc	288	cphi1=exp(ci*arg);
	289	cphi2=conj(cphi1);
	290
	291	cphis=(cphi1+cphi2)/fgkROOT2;
	292	cphia=(cphi1-cphi2)/fgkROOT2;
	293	corr0=0.0;
	294	/* If there are corrections for strong interactions, add the
	295	change for each partial wave. If npartial = 0 then there
	296	are no strong int. corrections. */
	297	wsym_leftover=INTERACTION_WSYM;
	298	wanti_leftover=INTERACTION_WANTI;
	299	wnosym_leftover=INTERACTION_WNOSYM;
	300
	301	corr0=corr0+real(wsym_leftovercphisconj(cphis)
	302	+wanti_leftovercphiaconj(cphia)
	303	+wnosym_leftovercphi1conj(cphi1));
	304	OUTSIDE_INTERACTION_RANGE:
	305
	306	#ifdef BREIT_WIGNER
	307	corr0=corr0+bwcalc(trueqred,truer);
	308	#endif
	309
	310	return corr0;
	311	}
	312
	313	double_complex AliHBTCrab::cgamma(double_complex c){
	314	/* This calc.s gamma functions which are in the form gamma(n+i*y)
	315	where n is an int and y is real. */
	316	// This code is written by Scott Pratt
	317	// taken from http://www.nscl.msu.edu/~pratt/freecodes/crab/home.html
	318	double_complex cg,cphase;
	319	int mm,j;
	320	double x,y,phase,delp,cgmag;
	321	x=real(c);
	322	y=imag(c);
	323	phase=-TMath::E()*y;
	324	for(j=1;j<=100000;j++){
	325	delp=(y/(double)j)-atan(y/(double)j);
	326	phase=phase+delp;
3294e9ff	327	if(TMath::Abs(delp)<1E-10) goto CGAMMA_ESCAPE;
dd82cadc	328	}
	329	printf("oops not accurate enough, increase jmax\n");
	330	CGAMMA_ESCAPE:
3294e9ff	331	phase=phase-2.0TMath::Pi()TMath::Floor(phase/(2.0*TMath::Pi()));
dd82cadc	332	cphase=exp(ci*phase);
dd82cadc	333	cgmag=sqrt(TMath::Pi()y/sinh(TMath::Pi()y));
3294e9ff	334	mm=(int)TMath::Floor(x+0.5);
dd82cadc	335	cg=cgmag*cphase;
	336	if(mm<1){
	337	for(j=1;j<=-mm+1;j++){
	338	cg=cg/(1.0+(double)(-j)+ci*y);
	339	}
	340	}
	341	if(mm>1) {
	342	for(j=1;j<=mm-1;j++){
	343	cg=cg((double)(j)+ciy);
	344	}
	345	}
	346	return cg;
	347	}
	348	//===================================================================
	349