Particle physics

New-Gauge-Boson Processes in Pythia8175

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-production of new Z’^0 and W’^+- gauge bosons, e.g. within the context of a new U(1) or SU(2) gauge group, and also a (rather speculative) horizontal gauge boson R^0.

-gamma^*/Z^0/Z’^0 interference structure for couplings to fermion pairs.

The R^0 boson (particle code 41) represents one possible scenario for a horizontal gauge boson, i.e. a gauge boson that couples between the generations, inducing processes like s dbar -> R^0 -> mu^- e^+.

“NewGaugeBoson:ffbar2R0 = on”

The cross section for this process is 2.955e-11 mb.

pythia8->ReadString(“41:onMode = off”);          //cancel all decays channels
pythia8->ReadString(“41:onIfAny =3 -5 “);          // R0->s + bbar

TLorentzVector s, bbar, R;

R=s + bbar

Double_t invariant mass = R.M();

cout << ” Invariant mass of s-bbar pair is ” << invariant mass << endl;

In this mode , I determined invariant mass of s-bbar pair and I obtained 589.419 Gev, which is exactly mass of the R^0 boson.

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Invariant mass for b-bpair

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I find the Higgs mass in this mode

Source code for this is :

void masa_invarianta(Int_t nev  = 10000, Int_t ndeb = 1) {
// Load libraries
gSystem->Load(“$PYTHIA8/lib/libpythia8”);
gSystem->Load(“libEG”);
gSystem->Load(“libEGPythia8”);

TFile* file = TFile::Open(“masa_invarianta.root”, “RECREATE”);
if (!file || !file->IsOpen()) {
Error(“makeEventSample”, “Couldn;t open file %s”, FILENAME);
return 1;
}
// Histograms
TH1F* masaH = new TH1F(“masaH”,”masa invarianta a perechii de cuarci bottom-antibottom” , 50 , 124.96 , 125.03);
// Array of particles
TClonesArray* particles = new TClonesArray(“TParticle”, 10000);
// Create pythia8 object
TPythia8* pythia8 = new TPythia8();

// Configure
pythia8->ReadString(“HiggsSM:gg2H=on”);      //gluon fusion
pythia8->ReadString(“PartonLevel:MPI=off”);    //no multiple particle interactions
pythia8->ReadString(“HadronLevel:Hadronize=off”);    //no hadronization
pythia8->ReadString(“PartonLevel:ISR=off”);         // no initial-state showers
pythia8->ReadString(“PartonLevel:FSR=off”);          // no final-state showers
//pythia8->ReadString(“25:m0 = 123.5”);
pythia8->ReadString(“25:mHatMin =110”);      //masa minima
pythia8->ReadString(“25:mHatMax = 140”);     //masa maxima
pythia8->ReadString(“25:onMode =off”);          //cancel all decays channels
pythia8->ReadString(“25:OnIfMatch = 5 -5″);    //H->b+bbar

// Initialize
pythia8->Initialize(2212, 2212, 14000);     //pp collider(14Tev in CMS)

// Event loop
for (Int_t iev = 0; iev < nev; iev++) {
pythia8->GenerateEvent();
//if (iev < ndeb) pythia8->EventListing();
pythia8->ImportParticles(particles,”All”);
Int_t np = particles->GetEntriesFast();
TLorentzVector b, bbar, higgs;

// Particle loop
for (Int_t ip = 0; ip < np; ip++) {

TParticle* part = (TParticle*) particles->At(ip);
Int_t idp = part->GetPdgCode();         //pdg number
Int_t pstat = part->GetStatusCode();    // particle status

//select only b and bbar quarks, in final state(pstat>0)

if (idp==5 && pstat>0){
//cout<<“id b = “<<idp<<endl;
Double_t px1 = part->Px();
Double_t py1 = part->Py();
Double_t pz1 = part->Pz();
Double_t e1 = part->Energy();
b.SetPxPyPzE(px1,py1,pz1,e1);
cout<<“b -> PX,PY,PZ,EN = “<<px1<<“, “<<py1<<“, “<<pz1<<“, “<<e1<<endl;
} // end if idp==5

if (idp==-5 && pstat>0){
//cout<<“id bbar = “<<idp<<endl;
Double_t px2 = part->Px();
Double_t py2 = part->Py();
Double_t pz2 = part->Pz();
Double_t e2 = part->Energy();
bbar.SetPxPyPzE(px2,py2,pz2,e2);
cout<<“bbar -> PX,PY,PZ,EN = “<<px2<<“, “<<py2<<“, “<<pz2<<“, “<<e2<<endl;
} //endif idp=-5
}// end particleloop

// mag2 = v*v= t*t-x*x-y*y-z*z
TLorentzVector sum ;
sum = b + bbar;
//Double_t px = sum.Px();
//cout << ” px = ” << px << endl;
Double_t hpx = px1+px2;
Double_t hpy = py1+py2;
Double_t hpz = pz1+pz2;
Double_t hen = e1+e2;
higgs.SetPxPyPzE(hpx,hpy,hpz,hen);

cout<<“Higgs -> PX,PY,PZ,EN = “<<higgs.Px()<<“, “<<higgs.Py()<<“, “<<higgs.Pz() <<“, “<<higgs.Energy()<<“, Higgs Mass = “<<higgs.Mag()<<endl;
} // end event loop

file->Write();
file->Close();

return;
}

Higgs boson is produced via gluon fusion with next cross section:

g g -> H (SM)                         1.245e-07         //gluon fussion

Image

Invariant mass for b-bbar pair (Actualy Higgs mass is 125 Gev)

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