--- /dev/null
+///////////////////////////////////////////////////////////////////////////////
+// //
+// Time Projection Chamber version 3 -- detailed TPC and slow simulation //
+// //
+//Begin_Html
+/*
+<img src="picts/AliTPCv3Class.gif">
+*/
+//End_Html
+// //
+// //
+///////////////////////////////////////////////////////////////////////////////
+
+#include <stdlib.h>
+#include <TMath.h>
+
+#include "AliTPCv3.h"
+#include "AliRun.h"
+#include "AliConst.h"
+
+ClassImp(AliTPCv3)
+
+//_____________________________________________________________________________
+AliTPCv3::AliTPCv3(const char *name, const char *title) :
+ AliTPC(name, title)
+{
+ //
+ // Standard constructor for Time Projection Chamber version 2
+ //
+
+ SetBufferSize(128000);
+}
+
+//_____________________________________________________________________________
+void AliTPCv3::CreateGeometry()
+{
+ //
+ // Create the geometry of Time Projection Chamber version 3
+ //
+ //Begin_Html
+ /*
+ <img src="picts/AliTPCv3.gif">
+ */
+ //End_Html
+ //Begin_Html
+ /*
+ <img src="picts/AliTPCv3Tree.gif">
+ */
+ //End_Html
+
+ Int_t *idtmed = fIdtmed->GetArray()-399;
+
+ Float_t tana, rlsl, wlsl, rssl, rlsu, wssl, wlsu,
+ rssu, wssu, alpha, x, y, sec_thick;
+
+ Float_t x1, z0, z1, x2, theta1, theta2, theta3, dm[21];
+ Int_t il, iu;
+ Float_t z_side;
+ Int_t idrotm[100];
+
+ Float_t x0l, x0u;
+ Int_t idr;
+ //Float_t thl, thu;
+ Float_t opl, opu, phi1, phi2, phi3;
+
+ // ----------------------------------------------------
+ // FIELD CAGE WITH ENDCAPS - CARBON FIBER
+ // THIS IS ALSO A TPC MOTHER VOLUME
+ // ----------------------------------------------------
+ dm[0] = 76.;
+ dm[1] = 278.;
+ dm[2] = 275.;
+
+ gMC->Gsvolu("TPC ", "TUBE", idtmed[407], dm, 3);
+ // -------------------------------------------------------
+ // drift gas Ne/CO2 (90/10 volume) - sensitive
+ // field cage thickness = 0.52% X0
+ // ----------------------------------------------------
+ dm[0] = 76.+0.09776;
+ dm[1] = 257.;
+ dm[2] = 250.;
+
+ gMC->Gsvolu("TGAS", "TUBE", idtmed[403], dm, 3);
+ // ------------------------------------------------------
+ // "side" gas volume (the same as drift gas)
+ // here the readout chambers are positioned
+ // ------------------------------------------------------
+ dm[2] = 0.5*(275.-250.);
+ z_side = dm[2];
+
+ gMC->Gsvolu("TPSG", "TUBE", idtmed[401], dm, 3);
+ // ------------------------------------------------------
+ // HV midplane - 20 microns of mylar
+ // -----------------------------------------------------
+ dm[2] = .001;
+
+ gMC->Gsvolu("TPHV", "TUBE", idtmed[405], dm, 3);
+
+ // ====================================================
+ // lower and upper readout chambers
+ // ====================================================
+ // sectros opening angles in degrees
+ // ---------------------------------------------------
+ opl = 30.;
+ opu = 15.;
+ //thl = TMath::Tan(opl * .5 * kDegrad);
+ //thu = TMath::Tan(opu * .5 * kDegrad);
+ // ---------------------------------------------------
+ // S and L-sectors radii
+ // ---------------------------------------------------
+ rssl = 88.;
+ rssu = 136.;
+ rlsl = 142.;
+ rlsu = 250.;
+ // --------------------------------------------------
+ // Sectors widths
+ // --------------------------------------------------
+ wssl = 46.5;
+ wssu = 72.2;
+ wlsl = 37.;
+ wlsu = 65.4;
+ // ---------------------------------------------------
+ // Sector thickness 25% of X0 (Al)
+ // ---------------------------------------------------
+ sec_thick = 2.225;
+ // ---------------------------------------------------
+ // S-sectors readout chambers (lower sectors)
+ // ---------------------------------------------------
+ dm[0] = wssl * .5;
+ dm[1] = wssu * .5;
+ dm[2] = sec_thick * .5;
+ dm[3] = (rssu - rssl) * .5;
+
+ x0l = rssl + dm[3];
+
+ gMC->Gsvolu("TRCS", "TRD1", idtmed[399], dm, 4);
+ // ---------------------------------------------------
+ // L-sectors readout chambers (upper sectors)
+ // ---------------------------------------------------
+ dm[0] = wlsl * .5;
+ dm[1] = wlsu * .5;
+ dm[2] = sec_thick * .5;
+ dm[3] = (rlsu - rlsl) * .5;
+
+ x0u = rlsl + dm[3];
+
+ gMC->Gsvolu("TRCL", "TRD1", idtmed[399], dm, 4);
+ // ----------------------------------------------------
+ // positioning of the S-sector readout chambers
+ // rotation matices 1-12
+ // ----------------------------------------------------
+ z1 = -z_side + sec_thick * .5;
+
+ for (il = 1; il <= 12; ++il) {
+ phi1 = (il - 1) * opl + 270.;
+ if (phi1 > 360.) {
+ phi1 += -360.;
+ }
+ theta1 = 90.;
+ phi2 = 90.;
+ theta2 = 180.;
+ phi3 = (il - 1) * opl;
+ theta3 = 90.;
+
+ idr = il;
+
+ alpha = (il - 1) * opl * kDegrad;
+ x = x0l * TMath::Cos(alpha);
+ y = x0l * TMath::Sin(alpha);
+
+ AliMatrix(idrotm[idr], theta1, phi1, theta2, phi2, theta3, phi3);
+ gMC->Gspos("TRCS", il, "TPSG", x, y, z1, idrotm[idr], "ONLY");
+ }
+ // ----------------------------------------------------
+ // positioning of the L-sector readout chambers
+ // rotation matices 13-36
+ // ----------------------------------------------------
+ for (iu = 1; iu <= 24; ++iu) {
+ phi1 = (iu - 1) * opu + 270.;
+ if (phi1 > 360.) {
+ phi1 += -360.;
+ }
+ theta1 = 90.;
+ phi2 = 90.;
+ theta2 = 180.;
+ phi3 = (iu - 1) * opu;
+ theta3 = 90.;
+
+ idr = iu + 12;
+ AliMatrix(idrotm[idr], theta1, phi1, theta2, phi2, theta3, phi3);
+
+ alpha = (iu - 1) * opu * kDegrad;
+ x = x0u * TMath::Cos(alpha);
+ y = x0u * TMath::Sin(alpha);
+
+ gMC->Gspos("TRCL", iu, "TPSG", x, y, z1, idrotm[idr], "ONLY");
+ }
+ // --------------------------------------------------------
+ // Spoke wheel structures
+ // --------------------------------------------------------
+ gMC->Gsvolu("TSWS", "TUBE", idtmed[399], dm, 0);
+
+ z0 = -z_side + 2.;
+
+ dm[0] = 82.;
+ dm[1] = 86.;
+ dm[2] = 1.;
+
+ gMC->Gsposp("TSWS", 1, "TPSG", 0, 0, z0, 0, "ONLY", dm, 3);
+
+ dm[0] = 253.;
+ dm[1] = 257.;
+
+ gMC->Gsposp("TSWS", 2, "TPSG", 0, 0, z0, 0, "ONLY", dm, 3);
+
+ dm[0] = 140.9;
+ dm[1] = 141.9;
+
+ gMC->Gsposp("TSWS", 3, "TPSG", 0, 0, z0, 0, "ONLY", dm, 3);
+
+ // -------------------------------------------------------
+ // this volumes are to avoid overlaping
+ // -------------------------------------------------------
+ z0 = 253.;
+
+ dm[0] = 76.;
+ dm[1] = 76.+0.09776;
+
+ gMC->Gsposp("TSWS", 4, "TPC ", 0, 0, z0, 0, "ONLY", dm, 3);
+ gMC->Gsposp("TSWS", 5, "TPC ", 0, 0, -z0,0, "ONLY", dm, 3);
+
+ z0 += 21.;
+
+ gMC->Gsposp("TSWS", 6, "TPC ", 0, 0, z0, 0, "ONLY", dm, 3);
+ gMC->Gsposp("TSWS", 7, "TPC ", 0, 0, -z0, 0, "ONLY", dm, 3);
+
+ dm[0] = 257.;
+ dm[1] = 257.+0.09776;
+ dm[2] = 11.5;
+
+ z0 = 263.5;
+
+ gMC->Gsposp("TSWS", 8, "TPC ", 0, 0, z0, 0, "ONLY", dm, 3);
+ gMC->Gsposp("TSWS", 9, "TPC ", 0, 0, -z0, 0, "ONLY", dm, 3);
+ // ==========================================================
+ // wheels
+ // ==========================================================
+ // ----------------------------------------------------------
+ // Large wheel -> positioned in the TPC
+ // ----------------------------------------------------------
+ dm[0] = 257.+0.09776;
+ dm[1] = 278.;
+ dm[2] = 11.5;
+ gMC->Gsvolu("TPW1", "TUBE", idtmed[399], dm, 3);
+
+ dm[0] = 259.;
+ dm[1] = 278.;
+ dm[2] = 9.5;
+
+ gMC->Gsvolu("TPW2", "TUBE", idtmed[498], dm, 3);
+
+ gMC->Gspos("TPW2", 1, "TPW1", 0, 0, 0, 0, "ONLY");
+
+ gMC->Gspos("TPW1", 1, "TPC ", 0, 0, z0, 0, "ONLY");
+ gMC->Gspos("TPW1", 2, "TPC ", 0, 0, -z0, 0, "ONLY");
+ // -----------------------------------------------------------
+ // Small wheel -> positioned in the TPSG
+ // -----------------------------------------------------------
+ dm[0] = 76.+0.09776;
+ dm[1] = 82.;
+ dm[2] = 11.5;
+
+ gMC->Gsvolu("TPW3", "TUBE", idtmed[399], dm, 3);
+
+ dm[0] = 76.+0.09776;
+ dm[1] = 80.;
+ dm[2] = 9.5;
+
+ gMC->Gsvolu("TPW4", "TUBE", idtmed[401], dm, 3);
+
+ gMC->Gspos("TPW4", 1, "TPW3", 0, 0, 0, 0, "ONLY");
+
+ z0 = 1.;
+
+ gMC->Gspos("TPW3", 1, "TPSG", 0, 0, z0, 0, "ONLY");
+ // ---------------------------------------------------------
+ // spokes, inner and outer, also the inner ring
+ // ---------------------------------------------------------
+ dm[0] = 0.5*(135.9-82.1);
+ dm[1] = 3.;
+ dm[2] = 2.;
+
+ x1 = dm[0] + 82.;
+
+ gMC->Gsvolu("TSPI", "BOX ", idtmed[399], dm, 3);
+
+ dm[1] = 2.;
+ dm[2] = 1.;
+
+ gMC->Gsvolu("TSP1", "BOX ", idtmed[498], dm, 3);
+
+ gMC->Gspos("TSP1", 1, "TSPI", 0, 0, 0, 0, "ONLY");
+
+ dm[0] = 0.5*(256.9-142.1);
+ dm[1] = 3.;
+ dm[2] = 2.;
+
+ x2 = dm[0] + 142.;
+
+ gMC->Gsvolu("TSPO", "BOX ", idtmed[399], dm, 3);
+
+ dm[1] = 2.;
+ dm[2] = 1.;
+
+ gMC->Gsvolu("TSP2", "BOX ", idtmed[498], dm, 3);
+
+ gMC->Gspos("TSP2", 1, "TSPO", 0, 0, 0, 0, "ONLY");
+ // --------------------------------------------------------
+ dm[0] = 136.;
+ dm[1] = 142.;
+ dm[2] = 2.;
+
+ gMC->Gsvolu("TSWH", "TUBE", idtmed[399], dm, 3);
+
+ dm[0] = 137.;
+ dm[1] = 141.;
+ dm[2] = 1.;
+
+ gMC->Gsvolu("TSW1", "TUBE", idtmed[498], dm, 3);
+
+ gMC->Gspos("TSW1", 1, "TSWH", 0, 0, 0, 0, "ONLY");
+
+ z0 = z_side - .16168 - 2.;
+ // --------------------------------------------------------
+ gMC->Gspos("TSWH", 1, "TPSG", 0, 0, z0, 0, "ONLY");
+ // -------------------------------------------------------
+ // posiioning of the inner spokes
+ // -------------------------------------------------------
+ for (il = 1; il <= 6; ++il) {
+ phi1 = opl * .5 + (il - 1) * 2. * opl;
+ theta1 = 90.;
+ phi2 = opl * .5 + 90. + (il - 1) * 2. * opl;
+ if (phi2 > 360.) {
+ phi2 += -360.;
+ }
+ theta2 = 90.;
+ phi3 = 0.;
+ theta3 = 0.;
+
+ alpha = phi1 * kDegrad;
+ x = x1 * TMath::Cos(alpha);
+ y = x1 * TMath::Sin(alpha);
+
+ idr = il + 36;
+
+ AliMatrix(idrotm[idr], theta1, phi1, theta2, phi2, theta3, phi3);
+ gMC->Gspos("TSPI", il, "TPSG", x, y, z0, idrotm[idr], "ONLY");
+
+ }
+
+ for (iu = 1; iu <= 12; ++iu) {
+ phi1 = opu * .5 + (iu - 1) * 2. * opu;
+ theta1 = 90.;
+ phi2 = opu * .5 + 90. + (iu - 1) * 2. * opu;
+ if (phi2 > 360.) {
+ phi2 += -360.;
+ }
+ theta2 = 90.;
+ phi3 = 0.;
+ theta3 = 0.;
+
+ alpha = phi1 * kDegrad;
+ x = x2 * TMath::Cos(alpha);
+ y = x2 * TMath::Sin(alpha);
+
+ idr = iu + 42;
+
+ AliMatrix(idrotm[idr], theta1, phi1, theta2, phi2, theta3, phi3);
+ gMC->Gspos("TSPO", iu, "TPSG", x, y, z0, idrotm[idr], "ONLY");
+ }
+ // --------------------------------------------------------
+ // endcap cover (C, 0.86% X0)
+ // --------------------------------------------------------
+ dm[0] = 76.+0.09776;
+ dm[1] = 257.;
+ dm[2] = 0.16168*0.5;
+
+ gMC->Gsvolu("TCOV", "TUBE", idtmed[407], dm, 3);
+
+ z0 = z_side - dm[2];
+
+ gMC->Gspos("TCOV", 1, "TPSG", 0, 0, z0, 0, "ONLY");
+ // --------------------------------------------------------
+ // put the readout chambers into the TPC
+ // --------------------------------------------------------
+ theta1 = 90.;
+ phi1 = 0.;
+ theta2 = 90.;
+ phi2 = 270.;
+ theta3 = 180.;
+ phi3 = 0.;
+
+ AliMatrix(idrotm[55], theta1, phi1, theta2, phi2, theta3, phi3);
+
+ z0 = z_side + 250.;
+
+ gMC->Gspos("TPSG", 1, "TPC ", 0, 0, z0, 0, "ONLY");
+ gMC->Gspos("TPSG", 2, "TPC ", 0, 0, -z0, idrotm[55], "ONLY");
+ // ---------------------------------------------------------
+ // outer gas insulation (CO2)
+ // ---------------------------------------------------------
+ dm[0] = 257.+0.09776;
+ dm[1] = 278.-0.25004;
+ dm[2] = 275.-23.;
+
+ gMC->Gsvolu("TPOI", "TUBE", idtmed[406], dm, 3);
+
+ gMC->Gspos("TPHV", 1, "TGAS", 0, 0, 0, 0, "ONLY");
+ gMC->Gspos("TGAS", 1, "TPC ", 0, 0, 0, 0, "ONLY");
+ gMC->Gspos("TPOI", 1, "TPC ", 0, 0, 0, 0, "ONLY");
+
+ gMC->Gspos("TPC ", 1, "ALIC", 0, 0, 0, 0, "ONLY");
+ // ======================================================
+ // all volumes below are positioned in ALIC
+ // ======================================================
+ // ------------------------------------------------------
+ // the last parts of the smaller wheel (TSWS)
+ // ------------------------------------------------------
+ dm[0] = 74.;
+ dm[1] = 76.;
+ dm[2] = 1.;
+
+ z0 = 253.;
+
+ gMC->Gsposp("TSWS", 10, "TPC ", 0, 0, z0, 0, "ONLY", dm, 3);
+ gMC->Gsposp("TSWS", 11, "TPC ", 0, 0, -z0, 0, "ONLY", dm, 3);
+
+ dm[0] = 70.;
+
+ z0 += 21.;
+
+ gMC->Gsposp("TSWS", 12, "TPC ", 0, 0, z0, 0, "ONLY", dm, 3);
+ gMC->Gsposp("TSWS", 13, "TPC ", 0, 0, -z0, 0, "ONLY", dm, 3);
+ // ----------------------------------------------------
+ // Inner vessel (PCON)
+ // This volume is to be positioned directly in ALIC
+ // ----------------------------------------------------
+ dm[0] = 0.;
+ dm[1] = 360.;
+ dm[2] = 4.;
+
+ dm[3] = -250.;
+ dm[4] = 75.;
+ dm[5] = 76.;
+
+ dm[6] = -64.5;
+ dm[7] = 50.;
+ dm[8] = 76.;
+
+ dm[9] = 64.5;
+ dm[10] = 50.;
+ dm[11] = 76.;
+
+ dm[12] = 250.;
+ dm[13] = 75.;
+ dm[14] = 76.;
+
+ gMC->Gsvolu("TPIV", "PCON", idtmed[407], dm, 15);
+ // --------------------------------------------------------
+ // fill the inner vessel with CO2, (HV kDegrader)
+ // cone parts have different thickness
+ // than the central barrel, according to the TP
+ // --------------------------------------------------------
+ tana = 75./185.5;
+
+ dm[0] = 0.;
+ dm[1] = 360.;
+ dm[2] = 6.;
+
+ dm[3] = -(250.-0.2162);
+ dm[4] = (185.5-0.2126)*tana+0.2126;
+ dm[5] = 76-0.001;
+
+ dm[6] = -64.5;
+ dm[7] = 50.+0.2162;
+ dm[8] = 76-0.001;
+
+ dm[9] = -64.5;
+ dm[10] = 50+0.05076;
+ dm[11] = 76-0.001;
+
+ dm[12] = 64.5;
+ dm[13] = 50+0.05076;
+ dm[14] = 76-0.001;
+
+ dm[15] = 64.5;
+ dm[16] = 50.+0.2162;
+ dm[17] = 76-0.001;
+
+ dm[18] = (250.-0.2162);
+ dm[19] = (185.5-0.2126)*tana+0.2126;
+ dm[20] = 76-0.001;
+
+ gMC->Gsvolu("TPVD", "PCON", idtmed[406], dm, 21);
+
+ gMC->Gspos("TPVD", 1, "TPIV", 0, 0, 0, 0, "ONLY");
+
+ gMC->Gspos("TPIV", 1, "ALIC", 0, 0, 0, 0, "ONLY");
+ // ---------------------------------------------------
+ // volumes ordering
+ // ---------------------------------------------------
+ gMC->Gsord("TPSG", 6);
+}
+
+
+//_____________________________________________________________________________
+void AliTPCv3::DrawDetector()
+{
+ //
+ // Draw a shaded view of the Time Projection Chamber version 1
+ //
+
+
+ // Set everything unseen
+ gMC->Gsatt("*", "seen", -1);
+ //
+ // Set ALIC mother transparent
+ gMC->Gsatt("ALIC","SEEN",0);
+ //
+ // Set the volumes visible
+ gMC->Gsatt("TPC","SEEN",0);
+ gMC->Gsatt("TGAS","SEEN",0);
+ gMC->Gsatt("TPSG","SEEN",0);
+ gMC->Gsatt("TPHV","SEEN",1);
+ gMC->Gsatt("TRCS","SEEN",1);
+ gMC->Gsatt("TRCL","SEEN",1);
+ gMC->Gsatt("TSWS","SEEN",1);
+ gMC->Gsatt("TPW1","SEEN",1);
+ gMC->Gsatt("TPW2","SEEN",1);
+ gMC->Gsatt("TPW3","SEEN",1);
+ gMC->Gsatt("TPW4","SEEN",1);
+ gMC->Gsatt("TSPI","SEEN",1);
+ gMC->Gsatt("TSP1","SEEN",0);
+ gMC->Gsatt("TSPO","SEEN",1);
+ gMC->Gsatt("TSP2","SEEN",0);
+ gMC->Gsatt("TSWH","SEEN",1);
+ gMC->Gsatt("TSW1","SEEN",1);
+ gMC->Gsatt("TPOI","SEEN",1);
+ gMC->Gsatt("TPIV","SEEN",1);
+ gMC->Gsatt("TPVD","SEEN",1);
+ //
+ gMC->Gdopt("hide", "on");
+ gMC->Gdopt("shad", "on");
+ gMC->Gsatt("*", "fill", 7);
+ gMC->SetClipBox(".");
+ gMC->SetClipBox("*", 0, 1000, -1000, 1000, -1000, 1000);
+ gMC->DefaultRange();
+ gMC->Gdraw("alic", 40, 30, 0, 12, 9.5, .025, .025);
+ gMC->Gdhead(1111, "Time Projection Chamber");
+ gMC->Gdman(18, 4, "MAN");
+ gMC->Gdopt("hide","off");
+}
+
+//_____________________________________________________________________________
+void AliTPCv3::CreateMaterials()
+{
+ //
+ // Define materials for version 2 of the Time Projection Chamber
+ //
+
+
+ //
+ // Increase maximum number of steps
+ gMC->SetMaxNStep(30000);
+ //
+ AliTPC::CreateMaterials();
+}
+
+//_____________________________________________________________________________
+void AliTPCv3::Init()
+{
+ //
+ // Initialises version 3 of the TPC after that it has been built
+ //
+ Int_t *idtmed = fIdtmed->GetArray()-399;
+
+ AliTPC::Init();
+
+ fIdSens1=gMC->VolId("TGAS"); // drift gas as a sensitive volume
+
+ gMC->SetMaxNStep(30000); // max. number of steps increased
+
+ gMC->Gstpar(idtmed[403],"LOSS",5);
+
+ printf("*** TPC version 3 initialized ***\n");
+ printf("Maximum number of steps = %d\n",gMC->GetMaxNStep());
+
+ //
+
+}
+
+//_____________________________________________________________________________
+void AliTPCv3::StepManager()
+{
+ //
+ // Called for every step in the Time Projection Chamber
+ //
+
+ //
+ // parameters used for the energy loss calculations
+ //
+ const Float_t prim = 14.35; // number of primary collisions per 1 cm
+ const Float_t poti = 20.77e-9; // first ionization potential for Ne/CO2
+ const Float_t w_ion = 35.97e-9; // energy for the ion-electron pair creation
+
+
+ const Float_t big = 1.e10;
+
+ Int_t id,copy;
+ TLorentzVector pos;
+ Float_t hits[4];
+ Int_t vol[2];
+ TClonesArray &lhits = *fHits;
+
+ vol[1]=0;
+ vol[0]=0;
+
+ //
+
+ gMC->SetMaxStep(big);
+
+ if(!gMC->IsTrackAlive()) return; // particle has disappeared
+
+ Float_t charge = gMC->TrackCharge();
+
+ if(TMath::Abs(charge)<=0.) return; // take only charged particles
+
+
+ id=gMC->CurrentVolID(copy);
+
+ // Check the sensitive volume
+
+ if (id != fIdSens1) return;
+
+ //
+ // charged particle is in the sensitive volume
+ //
+
+ if(gMC->TrackStep() > 0) {
+
+
+ Int_t nel = (Int_t)(((gMC->Edep())-poti)/w_ion) + 1;
+ nel=TMath::Min(nel,300); // 300 electrons corresponds to 10 keV
+
+ gMC->TrackPosition(pos);
+ hits[0]=pos[0];
+ hits[1]=pos[1];
+ hits[2]=pos[2];
+
+ //
+ // check the selected side of the TPC
+ //
+
+ if(fSide && fSide*hits[2]<=0.) return;
+
+ hits[3]=(Float_t)nel;
+
+ // Add this hit
+
+ new(lhits[fNhits++]) AliTPChit(fIshunt,gAlice->CurrentTrack(),vol,hits);
+
+ }
+
+ // Stemax calculation for the next step
+
+ Float_t pp;
+ TLorentzVector mom;
+ gMC->TrackMomentum(mom);
+ Float_t ptot=mom.Rho();
+ Float_t beta_gamma = ptot/gMC->TrackMass();
+
+ if(gMC->TrackPid() <= 3 && ptot > 0.002)
+ {
+ pp = prim*1.58; // electrons above 20 MeV/c are on the plateau!
+ }
+ else
+ {
+ pp=prim*BetheBloch(beta_gamma);
+ if(TMath::Abs(charge) > 1.) pp *= (charge*charge);
+ }
+
+ Float_t random[1];
+ gMC->Rndm(random,1); // good, old GRNDM from Geant3
+
+ Double_t rnd = (Double_t)random[0];
+
+ gMC->SetMaxStep(-TMath::Log(rnd)/pp);
+
+}
+
+//_____________________________________________________________________________
+Float_t AliTPCv3::BetheBloch(Float_t bg)
+{
+ //
+ // Bethe-Bloch energy loss formula
+ //
+ const Double_t p1=0.76176e-1;
+ const Double_t p2=10.632;
+ const Double_t p3=0.13279e-4;
+ const Double_t p4=1.8631;
+ const Double_t p5=1.9479;
+
+ Double_t dbg = (Double_t) bg;
+
+ Double_t beta = dbg/TMath::Sqrt(1.+dbg*dbg);
+
+ Double_t aa = TMath::Power(beta,p4);
+ Double_t bb = TMath::Power(1./dbg,p5);
+
+ bb=TMath::Log(p3+bb);
+
+ return ((Float_t)((p2-aa-bb)*p1/aa));
+}
git://git.uio.no / u / mrichter / AliRoot.git / commitdiff