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mom_resol_tracker.C
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mom_resol_tracker.C
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// Momentum resolution for charged particles
// Shyam Kumar
#include<TMath.h>
#include <TString.h>
void MultipleScattering(Double_t mp, Double_t momI, Double_t &theta, Double_t effradlen);
// masses in MeV
Double_t mel = 0.51099891; // Mass of electron and positron
Double_t mmu = 105.6583715; // Mass of muons
Double_t mpi = 139.57018; // mass of charged pions
Double_t mk = 493.667; // mass of charged kaons
Double_t mp = 938.272046; // mass of protons and antiprotons
Double_t speed= 3.0e8; //speed of light
Int_t charge=1;
Double_t min_effradlen=0.013; // All Silicon Tracker
Double_t N = 9; // 3 Vtx + 2Barrel + 4Micromegas
Double_t resolution_silicon = 10*1.0e-6/sqrt(12); // pixel resolution in meter
Double_t resolution_micromegas = 150*1.0e-6; // pixel resolution in meter micormegas
Double_t resolution = (5.0*resolution_silicon+4.0*resolution_micromegas)/9.0; // pixel resolution in meter micormegas
Double_t min_length = 0.7747; // Radius of outer Barrel layer-first layer
Double_t magfield = 3.0; // Mag field Eic 3.0 T
Double_t eta = 0.5;
void mom_resol_tracker()
{
gStyle->SetTitleSize(0.04,"");
gStyle->SetTitleSize(0.04,"X");
gStyle->SetTitleSize(0.04,"Y");
gStyle->SetTitleOffset(1.05,"Y");
TCanvas *c1 = new TCanvas("c1", "c1",0,52,1400,1000);
c1->SetGridy();
c1->SetMargin(0.12, 0.01 ,0.10,0.07);
std::vector<Double_t> x,y,c,d,e,f;
std::vector<Double_t> mre,mrmu,mrpi,mrk,mrp;
//--------Muon Bethe Bloch---------------------
for (Int_t pt=350; pt<=10000.;pt=pt+100)
{
x.push_back(pt*0.001);
Double_t p = pt*TMath::CosH(eta);
Double_t theta = 2.0*TMath::ATan(TMath::Exp(-1.0*eta));
Double_t sin_theta = fabs(TMath::Sin(theta));
Double_t length = fabs(min_length/sin_theta);
Double_t effradlen = fabs(min_effradlen/sin_theta);
//----Energy of incident particles----------
Double_t ms_el=0.,ms_mu=0., ms_pi=0., ms_k=0. , ms_p=0. ;
MultipleScattering(mel,p,ms_el,effradlen);
MultipleScattering(mmu,p,ms_mu,effradlen);
MultipleScattering(mpi,p,ms_pi,effradlen);
MultipleScattering(mk,p,ms_k,effradlen);
MultipleScattering(mp,p,ms_p,effradlen);
// Length can be parameterize as a function of eta or theta
// Momentum (pT) measurement error due to multiple scattering
Double_t MSpi=100.*(ms_pi*pt*0.001)*TMath::Sqrt(720/(N+4))/(0.3*magfield*length*N);
// pT resolution due to curvature measurement B = 3.0T
Double_t pi_pT_resol = 100.*pt*0.001*resolution*TMath::Sqrt(720/(N+4))/(0.3*magfield*length*length);
d.push_back(MSpi);
mrpi.push_back(pi_pT_resol);
}
//----------Pion----------------------------------
const Int_t n=x.size();
Double_t a[n], b[n], g[n],h[n];
for(Int_t i=0;i<n;i++)
{
a[i]=x[i];
b[i]=d[i];
g[i] = mrpi[i];
h[i] = TMath::Sqrt(b[i]*b[i]+g[i]*g[i]);
}
TGraph *gr1 = new TGraph(n,a,b);
gr1->SetLineColor(2);
gr1->GetYaxis()->SetRangeUser(0.0, 2.0);
gr1->SetLineWidth(1);
gr1->SetMarkerColor(2);
gr1->SetMarkerStyle(6);
gr1->SetTitle(Form("Transverse Momentum Resolution for #eta = %1.1f",eta));
gr1->GetXaxis()->SetTitle("p_{T} (GeV/c)");
gr1->GetXaxis()->CenterTitle(true);
gr1->GetYaxis()->SetTitle("#frac{#sigma_{p_{T}}}{p_{T}}"); // #sigma_{x} (cm)
gr1->GetYaxis()->CenterTitle(true);
gr1->Draw("ACP");
TGraph *gr2 = new TGraph(n,a,g);
gr2->SetLineWidth(1);
gr2->SetMarkerColor(kMagenta);
gr2->SetLineColor(kMagenta);
gr2->SetMarkerStyle(6);
gr2->Draw("same");
TGraph *gr1sumpi = new TGraph(n,a,h);
gr1sumpi->SetLineWidth(1);
gr1sumpi->SetMarkerColor(kBlack);
gr1sumpi->SetLineColor(kBlack);
gr1sumpi->SetMarkerStyle(6);
gr1sumpi-> SetLineStyle(9);
gr1sumpi->Draw("same");
//--------------Legend Draw----------------------
TLegend *leg_hist = new TLegend(0.65,0.7,0.99,0.93);
leg_hist->SetHeader("Particle in Silicon Tracker");
leg_hist->SetTextFont(42);
leg_hist->SetTextSize(0.04);
leg_hist->AddEntry(gr1,"p_{T} Resol. ( M.S.)","l");
leg_hist->AddEntry(gr2,"p_{T} Resol. (Sagitta)","l");
leg_hist->AddEntry(gr1sumpi,"Sum p_{T} Resol. (Pion)","l");
leg_hist->Draw();
// c1->SaveAs("Mom_resol.Pdf");
}
// This will return theta in radian
void MultipleScattering(Double_t mp, Double_t momI, Double_t &theta, Double_t effradlen){
Double_t En = TMath::Sqrt(mp*mp+momI*momI);
Double_t beta = momI/En;
theta=((13.6*charge)/(beta*momI))*(TMath::Sqrt(effradlen))*(1+0.038*TMath::Log(effradlen)); //*(1+0.038*TMath::Log(effradlen))
}