pt and y-parameterisations for PMD physics simulation.

THIS VERSION IS JUST A TEMPLATE THE PT AND Y DISTRIBUTIONS HAVE TO BE CORRECTED !!!!.

diff --git a/EVGEN/AliGenPMDlib.cxx b/EVGEN/AliGenPMDlib.cxx
new file mode 100644 (file)
index 0000000..fcf3242
--- /dev/null
+++ b/EVGEN/AliGenPMDlib.cxx
@@ -0,0 +1,204 @@
+/**************************************************************************
+ * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
+ *                                                                        *
+ * Author: The ALICE Off-line Project.                                    *
+ * Contributors are mentioned in the code where appropriate.              *
+ *                                                                        *
+ * Permission to use, copy, modify and distribute this software and its   *
+ * documentation strictly for non-commercial purposes is hereby granted   *
+ * without fee, provided that the above copyright notice appears in all   *
+ * copies and that both the copyright notice and this permission notice   *
+ * appear in the supporting documentation. The authors make no claims     *
+ * about the suitability of this software for any purpose. It is          *
+ * provided "as is" without express or implied warranty.                  *
+ **************************************************************************/
+
+/*
+$Log$
+*/
+
+#include "AliGenPMDlib.h"
+#include "AliMC.h"
+#include "AliPDG.h"
+
+ClassImp(AliGenPMDlib)
+//
+//  Neutral Pions
+
+Double_t AliGenPMDlib::PtPi0(Double_t *px, Double_t *dummy)
+{
+//
+//     PT-PARAMETERIZATION CDF, PRL 61(88) 1819
+//     POWER LAW FOR PT > 500 MEV
+//     MT SCALING BELOW (T=160 MEV)
+//
+  const Double_t kp0 = 1.3;
+  const Double_t kxn = 8.28;
+  const Double_t kxlim=0.5;
+  const Double_t kt=0.160;
+  const Double_t kxmpi=0.139;
+  const Double_t kb=1.;
+  Double_t y, y1, xmpi2, ynorm, a;
+  Double_t x=*px;
+  //
+  y1=TMath::Power(kp0/(kp0+kxlim),kxn);
+  xmpi2=kxmpi*kxmpi;
+  ynorm=kb*(TMath::Exp(-sqrt(kxlim*kxlim+xmpi2)/kt));
+  a=ynorm/y1;
+  if (x > kxlim)
+    y=a*TMath::Power(kp0/(kp0+x),kxn);
+  else
+    y=kb*TMath::Exp(-sqrt(x*x+xmpi2)/kt);
+  return y*x;
+}
+
+//
+// y-distribution
+//
+Double_t AliGenPMDlib::YPi0( Double_t *py, Double_t *dummy)
+{
+  //
+  // y parametrisation for pi0
+  //
+    const Double_t ka1    = 4913.;
+    const Double_t ka2    = 1819.;
+    const Double_t keta1  = 0.22;
+    const Double_t keta2  = 3.66;
+    const Double_t kdeta1 = 1.47;
+    const Double_t kdeta2 = 1.51;
+    Double_t y=TMath::Abs(*py);
+    //
+    Double_t ex1 = (y-keta1)*(y-keta1)/(2*kdeta1*kdeta1);
+    Double_t ex2 = (y-keta2)*(y-keta2)/(2*kdeta2*kdeta2);
+    return ka1*TMath::Exp(-ex1)+ka2*TMath::Exp(-ex2);
+}
+
+//                 particle composition
+//
+Int_t AliGenPMDlib::IpPi0()
+{
+// Pi0
+    return kPi0;
+}
+
+//____________________________________________________________
+//
+// Mt-scaling
+
+Double_t AliGenPMDlib::PtScal(Double_t pt, Int_t np)
+{
+  //    SCALING EN MASSE PAR RAPPORT A PTPI
+  //    MASS PI,K,ETA,RHO,OMEGA,ETA',PHI
+  const Double_t khm[10] = {.13957,.493,.5488,.769,.7826,.958,1.02,0,0,0};
+  //     VALUE MESON/PI AT 5 GEV
+  const Double_t kfmax[10]={1.,0.3,0.55,1.0,1.0,1.0,1.0,0,0,0};
+  np--;
+  Double_t f5=TMath::Power(((sqrt(100.018215)+2.)/(sqrt(100.+khm[np]*khm[np])+2.0)),12.3);
+  Double_t fmax2=f5/kfmax[np];
+  // PIONS
+  Double_t ptpion=100.*PtPi0(&pt, (Double_t*) 0);
+  Double_t fmtscal=TMath::Power(((sqrt(pt*pt+0.018215)+2.)/
+                                (sqrt(pt*pt+khm[np]*khm[np])+2.0)),12.3)/ fmax2;
+  return fmtscal*ptpion;
+}
+//
+// kaon
+//
+//                pt-distribution
+//____________________________________________________________
+
+Double_t AliGenPMDlib::PtEta( Double_t *px, Double_t *dummy)
+{
+// Kaon pT
+  return PtScal(*px,3);
+}
+
+// y-distribution
+//____________________________________________________________
+Double_t AliGenPMDlib::YEta( Double_t *py, Double_t *dummy)
+{
+    //
+    // y parametrisation for etas
+    //
+    const Double_t ka1    = 4913.;
+    const Double_t ka2    = 1819.;
+    const Double_t keta1  = 0.22;
+    const Double_t keta2  = 3.66;
+    const Double_t kdeta1 = 1.47;
+    const Double_t kdeta2 = 1.51;
+    Double_t y=TMath::Abs(*py);
+    //
+    Double_t ex1 = (y-keta1)*(y-keta1)/(2*kdeta1*kdeta1);
+    Double_t ex2 = (y-keta2)*(y-keta2)/(2*kdeta2*kdeta2);
+    return ka1*TMath::Exp(-ex1)+ka2*TMath::Exp(-ex2);
+}
+
+//                 particle composition
+//
+Int_t AliGenPMDlib::IpEta()
+{
+    return 221;
+}
+
+
+typedef Double_t (*GenFunc) (Double_t*,  Double_t*);
+GenFunc AliGenPMDlib::GetPt(Param_t param,  const char* tname)
+{
+// Return pointer to pT parameterisation
+    GenFunc func=NULL;
+    switch (param) 
+    {
+    case Pion:
+       func=PtPi0;
+       break;
+    case Eta:
+       func=PtEta;
+       break;
+    default:
+        func=0;
+        printf("<AliGenPMDlib::GetPt> unknown parametrisation\n");
+    }
+    return func;
+}
+
+GenFunc AliGenPMDlib::GetY(Param_t param, const char* tname)
+{
+// Return pointer to y- parameterisation
+    GenFunc func=NULL;
+    switch (param) 
+    {
+    case Pion:
+       func=YPi0;
+       break;
+    case Eta:
+       func=YEta;
+       break;
+    default:
+        func=0;
+        printf("<AliGenPMDlib::GetY> unknown parametrisation\n");
+    }
+    return func;
+
+}
+typedef Int_t (*GenFuncIp) ();
+GenFuncIp AliGenPMDlib::GetIp(Param_t param,  const char* tname)
+{
+// Return pointer to particle type parameterisation
+    GenFuncIp func=NULL;
+    switch (param) 
+    {
+    case Pion:
+       func=IpPi0;
+       break;
+    case Eta:
+       func=IpEta;
+       break;
+    default:
+        printf("<AliGenPMDlib::GetIp> unknown parametrisation\n");
+    }
+    return func;
+}
+
+
+
+

diff --git a/EVGEN/AliGenPMDlib.h b/EVGEN/AliGenPMDlib.h
new file mode 100644 (file)
index 0000000..d3e6170
--- /dev/null
+++ b/EVGEN/AliGenPMDlib.h
@@ -0,0 +1,36 @@
+#ifndef ALIGENPMDLIB_H
+#define ALIGENPMDLIB_H
+/* Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
+ * See cxx source for full Copyright notice                               */
+
+/* $Id$ */
+
+#include "AliGenLib.h"
+
+class AliGenPMDlib :
+public AliGenLib
+{
+ public:
+// Neutral pions
+    static Double_t PtPi0(Double_t *px, Double_t *dummy);
+    static Double_t PtScal(Double_t pt, Int_t np);
+    static Double_t YPi0( Double_t *py, Double_t *dummy);
+    static Int_t    IpPi0();
+// Etas
+    static Double_t PtEta(Double_t *px, Double_t *dummy);
+    static Double_t YEta( Double_t *py, Double_t *dummy);
+    static Int_t    IpEta();
+//
+    GenFunc   GetPt(Param_t param, const char* tname=0);
+    GenFunc   GetY (Param_t param, const char* tname=0);
+    GenFuncIp GetIp(Param_t param, const char* tname=0);    
+    ClassDef(AliGenPMDlib,1) // Library providing y and pT parameterisations
+};
+#endif
+
+
+
+
+
+
+