MScThesis-MCpythiaDijet

MC event generation for dijet and trijet event topologies produced at the LHC

dijet01.cc

• C++ macro used to generate dijet events with the LO MC event generator PYTHIA
• the main function takes two arguments (via user input): a random number seed and the number of events to generate; in order to run N events with RndmNSeed j, for instance, one could type

make dijet01

./dijet01 j N > dijet01_j

in which case the PYTHIA readout (run statistics, etc.) will be saved to a file called "dijet01_j" (otherwise it will be printed in the terminal)

• the running order of the strong coupling constant is set to 1
• by default, PYTHIA SlowJet algorithm is set to anti-kT algorithm with pTmin = 50 GeV
• kinematic phase space cuts: PhaseSpace:mHatMin = 2400, PhaseSpace:pTHatMin = 380
• kinematic selection cut on leading (subleading) jet is 440 (50) GeV
• angular selection cuts are |y^*|<1.7, |yB|<1.1
• the following jet parameters are stored: invariant mass, pT, y, y^*, yB, chi, phi (only used for sanity checks)
• events are grouped into seven mass intervals according to the dijet invariant mass (range is from 2.5 TeV < m < 5.4 TeV + m > 5.4 TeV)
• additional run statistics are printed; it is possible to check what fraction of events passes certain selection cuts, ends up in a particular mass interval, etc.
• histograms are output in the form of .txt files (two columns: 1) x value and 2) number of entries)

trijet01R10m3.cc

• works analogous to dijet01.cc, with an additional associated jet (ardQCD:all = off,HardQCD:3parton = on)
• additional kinematic phase space cut for the subsubleading jet: PhaseSpace:pTHat5Min = 114

Plotting macros; included in all of these is the option to correct the LO dijet topology up to NLO using k-factors derived from NLOJET++; they are extracted from the file "kfacOriginal.root"

diOkinVar.py

• allows to plot histograms of kinematic dijet variables for different running orders of the strong coupling constant using the .txt files produced with "dijet01.cc"

ditrikinVar.py

• allows to compare the kinematic variables of dijet and trijet events in a single histogram

chiHistRatioRvsW.py

• used to compared normalised angular distributions of the form 1/N dN/dchi vs. chi for weighted and unweighted trijet topologies together with the LO and NLO corrected dijet results

chiHistRatioWvsW.py

• allows to plot normalised angular distributions of the form 1/N dN/dchi vs. chi for two or more weighted trijet topologies generated with different minimum angular separation thresholds together with the LO and NLO corrected dijet results