main14
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// main14.cc is a part of the PYTHIA event generator.
// Copyright (C) 2024 Torbjorn Sjostrand.
// PYTHIA is licenced under the GNU GPL v2 or later, see COPYING for details.
// Please respect the MCnet Guidelines, see GUIDELINES for details.
// Keywords:
// Pythia 6
// Process cross sections
// Comparison with some PYTHIA 6.413 cross sections process by process.
// Several processes have been left out to keep reasonable execution time.
// Some processes are not handled absolutely identically, so minor
// systematic differences may occur in addition to the statistical ones.
// (For some MSSM Higgs processes 6.413 has been modified to use
// running quark masses in loops, like 8.1, to allow proper comparison.)
// Subruns 0 - 5 : QCD jets
// 6 - 10 : prompt photons.
// 11 - 12 : t-channel gamma/Z/W exchange.
// 13 - 23 : gamma*/Z^0/W^+-, singly, in pairs or with parton
// 24 - 25 : onia.
// 26 - 30 : top.
// 31 - 40 : Standard Model Higgs.
// 41 - 45 : MSSM Higgses (trivial couplings).
// 46 - 47 : Z' and W'
// 48 - 51 : Left-right-symmetric scenario.
// 52 - 52 : Leptoquark.
// 53 - 55 : Excited fermions (compositeness).
// 56 - 56 : excited Graviton (RS extra dimensions).
#include "Pythia8/Pythia.h"
using namespace Pythia8;
int main() {
// First and last process to test: can run from 0 through 40.
int iFirst = 0;
int iLast = 56;
// Statistics. Pythia6 run was with 10000, so no point to use more.
int nEvent = 10000;
// Normally one subprocess word per subrun, but exceptions exist.
int nSub[100];
for (int i = 0; i < 100; ++i) nSub[i] = 1;
nSub[1] = 3;
nSub[5] = 3;
// Starting positions in subprocess words list, recursively defined.
int iBeg[101] = { 0 };
for (int i = 0; i < 100; ++i) iBeg[i + 1] = iBeg[i] + nSub[i];
// List of subprocess words.
string processes[61] = { "HardQCD:gg2gg", "HardQCD:gg2qqbar",
"HardQCD:gg2ccbar", "HardQCD:gg2bbbar","HardQCD:qg2qg" ,
"HardQCD:qq2qq", "HardQCD:qqbar2gg", "HardQCD:qqbar2qqbarNew",
"HardQCD:qqbar2ccbar", "HardQCD:qqbar2bbbar", "PromptPhoton:qg2qgamma",
"PromptPhoton:qqbar2ggamma", "PromptPhoton:gg2ggamma",
"PromptPhoton:ffbar2gammagamma", "PromptPhoton:gg2gammagamma",
"WeakBosonExchange:ff2ff(t:gmZ)", "WeakBosonExchange:ff2ff(t:W)",
"WeakSingleBoson:ffbar2gmZ", "WeakSingleBoson:ffbar2W",
"WeakDoubleBoson:ffbar2gmZgmZ", "WeakDoubleBoson:ffbar2ZW",
"WeakDoubleBoson:ffbar2WW", "WeakBosonAndParton:qqbar2gmZg",
"WeakBosonAndParton:qg2gmZq", "WeakBosonAndParton:ffbar2gmZgm",
"WeakBosonAndParton:qqbar2Wg", "WeakBosonAndParton:qg2Wq",
"WeakBosonAndParton:ffbar2Wgm", "Charmonium:all", "Bottomonium:all",
"Top:gg2ttbar", "Top:qqbar2ttbar", "Top:qq2tq(t:W)",
"Top:ffbar2ttbar(s:gmZ)", "Top:ffbar2tqbar(s:W)",
"HiggsSM:ffbar2H", "HiggsSM:gg2H", "HiggsSM:ffbar2HZ",
"HiggsSM:ffbar2HW", "HiggsSM:ff2Hff(t:ZZ)", "HiggsSM:ff2Hff(t:WW)",
"HiggsSM:qg2Hq", "HiggsSM:gg2Hg(l:t)", "HiggsSM:qg2Hq(l:t)",
"HiggsSM:qqbar2Hg(l:t)", "HiggsBSM:allH1", "HiggsBSM:allH2",
"HiggsBSM:allA3", "HiggsBSM:allH+-", "HiggsBSM:allHpair",
"NewGaugeBoson:ffbar2gmZZprime", "NewGaugeBoson:ffbar2Wprime",
"LeftRightSymmmetry:ffbar2ZR", "LeftRightSymmmetry:ffbar2WR",
"LeftRightSymmmetry:ffbar2HLHL", "LeftRightSymmmetry:ffbar2HRHR",
"LeptoQuark:all", "ExcitedFermion:dg2dStar",
"ExcitedFermion:qq2dStarq", "ExcitedFermion:qqbar2eStare",
"ExtraDimensionsG*:all" };
// List of cross sections from Pythia6.
double sigma6[57] = { 4.960e-01, 1.627e-02, 2.790e-01, 2.800e-02,
3.310e-04, 3.653e-04, 1.697e-04, 1.163e-05, 1.065e-07, 8.259e-08,
8.237e-08, 2.544e-05, 5.321e-06, 5.571e-05, 1.621e-04, 9.039e-09,
2.247e-08, 5.893e-08, 3.781e-06, 1.078e-05, 4.551e-08, 1.025e-05,
3.208e-05, 5.435e-08, 1.038e-04, 3.929e-05, 4.155e-07, 6.685e-08,
1.898e-07, 4.240e-10, 7.142e-09, 1.547e-10, 7.064e-09, 1.316e-10,
2.332e-10, 5.105e-10, 1.316e-09, 4.462e-11, 5.557e-09, 1.966e-09,
8.725e-12, 2.450e-08, 5.839e-09, 1.687e-08, 8.950e-11, 4.188e-11,
1.980e-07, 4.551e-07, 6.005e-09, 1.102e-07, 7.784e-11, 3.488e-11,
6.006e-08, 3.235e-06, 1.689e-05, 5.986e-07, 3.241e-10 };
// Generator.
Pythia pythia;
// Standard set of masses for comparison with Fortran code.
pythia.readString("5:m0 = 4.2");
pythia.readString("6:m0 = 175.");
pythia.readString("23:m0 = 91.2");
pythia.readString("24:m0 = 80.");
// Same kinematics cuts as Fortran code.
pythia.readString("PhaseSpace:pTHatMin = 20.");
pythia.readString("6:mMin = 20.");
pythia.readString("23:mMin = 20.");
pythia.readString("24:mMin = 20.");
pythia.readString("25:mMin = 20.");
pythia.readString("32:mMin = 400.");
pythia.readString("34:mMin = 400.");
pythia.readString("42:mMin = 50.");
pythia.readString("5000039:mMin = 50.");
// Also same renormalization and factorization scale.
pythia.readString("SigmaProcess:renormScale2 = 3");
pythia.readString("SigmaProcess:factorScale2 = 3");
// Switch off unnecessary parts.
pythia.readString("PartonLevel:all = off");
pythia.readString("ProcessLevel:resonanceDecays = off");
// No printing of settings, particle data or events.
pythia.readString("Init:showProcesses = off");
pythia.readString("Init:showChangedSettings = off");
pythia.readString("Init:showChangedParticleData = off");
pythia.readString("Next:numberCount = 0");
pythia.readString("Next:numberShowInfo = 0");
pythia.readString("Next:numberShowProcess = 0");
pythia.readString("Next:numberShowEvent = 0");
// Debug: show information on cross section maximum and violation.
//pythia.readString("PhaseSpace:showSearch = on");
//pythia.readString("PhaseSpace:showViolation = on");
// Loop over processes.
for (int iProc = iFirst; iProc <= iLast; ++iProc) {
cout << "\n Begin subrun number " << iProc << " : ";
// Switch off previous process(es) and switch on new one(s).
if (iProc > iFirst) for (int i = iBeg[iProc - 1]; i < iBeg[iProc]; ++i)
pythia.readString( processes[i] + " = off" );
for (int i = iBeg[iProc]; i < iBeg[iProc + 1]; ++i) {
pythia.readString( processes[i] + " = on" );
if (i > iBeg[iProc]) cout << " + ";
cout << processes[i];
}
cout << endl;
// Switch between SM and MSSM Higgs scenario.
if (iProc <= 40) {
pythia.readString("Higgs:useBSM = off");
pythia.readString("25:m0 = 200.");
} else {
pythia.readString("Higgs:useBSM = on");
pythia.readString("25:m0 = 115.");
pythia.readString("35:m0 = 300.");
pythia.readString("36:m0 = 300.");
pythia.readString("37:m0 = 320.");
// With default option Higgs:clipWings = on need to reset mass range.
pythia.readString("25:mMin = 50.");
pythia.readString("25:mMax = 0.");
}
// Initialize for LHC.
pythia.readString("Beams:eCM = 14000.");
pythia.init();
// Debug: show initialized resonance data first time around.
//if (iProc == iFirst) pythia.particleData.listChanged(true);
// Generate events to get cross section statistics.
for (int iEvent = 0; iEvent < nEvent; ++iEvent) pythia.next();
// Show statistics.
//pythia.stat();
double sigma = pythia.info.sigmaGen();
cout << " Cross section is " << scientific << setprecision(3)
<< sigma << " and in Pythia6 was " << sigma6[iProc]
<< ",\n i.e. now is factor >>> " << fixed
<< sigma / sigma6[iProc] << " <<< different" <<endl;
// End of loop over processes.
}
// Done.
return 0;
}