Tools for LHC. MadGraph/MadEvent. Ian-Woo Kim, Ji-Hun Kim. Seoul National University. SNU, Mar 31, 2007

Transcription

1 Tools for LHC MadGraph/MadEvent Ian-Woo Kim, Ji-Hun Kim Seoul National University SNU, Mar 31, 2007 Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

2 Introduction We are facing with the exciting era with a great machine! Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

3 Building under ground. 27 km, pp collider s = 14TeV 4 Detectors : ATLAS, CMS, LHCb, ALICE L = fb 1 /yr Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

4 We want to see a new physics from a hard scattering. But the real life is not so simple. Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

5 What is really happening is... We have to simulate it. Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

6 Understanding the detector structure: Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

7 ATLAS ( A Toroidal LHC AppratuS ) CMS (The Compact Muon Solenoid ) Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

8 Particle signatures left in the detector components Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

9 Finally, we identify the following objects. Photons : detected as energy in the ECAL, with no high PT track and little energy in the HCAL Electrons : detected as energy in the ECAL, with high P T track and little energy in the HCAL Muons :little energy in the calorimeters, with a high PT track, travel to the muon detector system. Taus : Hadronic decay to 1 charged π ± or 1 charged π ± and 2 π 0 1-prong tau single charged track, leaves energy in HCAL, very narrow cone. (2 π + and 1 π ) or (1 π + and 2 π ) 3-prong tau 3 tracks, a very narrow jet with invariant mass 2 GeV. Jets next page. Missing Transverse Energy : Summing all the transverse energy deposited in calorimeters and the transverse momenta of all muons Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

10 Jets: Groups of particles (tracks and energy bumps in calorimeters) that fit inside a cone in φ and η space. (Cone algorithm needed. ) jets closely related to kinematics of partons in hard process. Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

11 b-tagging Particles of a life-time τ s, such as B 0,± may travel a distinguishable distance cτ 100µm. displaced secondary vertex and nonzero impact parameter. Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

12 Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

13 MadGraph/MadEvent/PYTHIA/PGS MadGraph : Feynman diagram generator MadEvent : Event generator for hard process ( parton level PYTHIA : Hadronization event generator ( it has more functionalities) PGS : Pretty Good (Detector) simulator A new model can be easily implemented in MadGraph : MSSM, 2HDM, etc unified framework for various models. parameter input must be set by another program. For SUSY, for example, SoftSUSY, SUSY-HIT ( SDECAY,HDECAY) Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

14 My system Intel core 2-duo (Merom) T GHz Memory 2G Scientific Linux v4.4 SUSY spectrum and Decay rate calculator : SUSY-HIT MadGraph/MadEvent/PYTHIA/PGS Analysis tool : ROOT lhco-to-root file converter: ExRootAnalysis ( provide HEP definition for ROOT) LHC Inverse analysis tool : MARMOSET Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

15 Web interface of MadGraph/MadEvent It has a web interface at Need an id/password. It has a summary webpage for each process. MadEvent is provided as a source code which can be compiled in user s computer. To run MadEvent+PYTHIA+PGS on the website (cluster), we must have more previlaged id/password. impossible to use it. But it gives us a simple analysis tool. Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

16 Installation Install Scientific Linux v4.4 : Install ROOT : download v5.14, compile or directly install binaries. Make sure you set environment variables correctly in.bashrc or.profile Install MadGraph/MadEvent/PYTHIA/PGS From MadGraph webpage, download MadGraph V4, PYTHIA and PGS package. PYTHIA and PGS are optimized for MadGraph/MadEvent. Note that all the packages must be installed in the directory MG_ME_v Install ExRootAnalysis : download from MadGraph webpage. ExRootLHCOlympicsConverter will convert.lhco file to.root file. (.lhco = LHC Olympics format ) Install SUSY-HIT : They can be installed seperately. The output must be SLHA (SUSY Les Houches Accord) format which will be used for the param_card.dat file for MadGraph. Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

17 Running MadGraph/MadEvent/PYTHIA/PGS You can set your own model in MadGraph. Here I will only focus on SM and MSSM. copy Template with your own directory name( e.g. MyTestDir ) Prepare for proc_card.dat and param_card.dat. For SM, param_card.dat needs not be changed from Template. for MSSM param_card.dat is just SLHA format. Note that SoftSUSY generate only spectrum part of SLHA. We need decay rate input. (Using SUSY-HIT) newprocess : generate Feynman diagrams. build up numerical analysis codes for each process. You can see such processes in index.html generate_events : generate parton-level events. Output files are in the directory Events in.lhe.gz format. If PYTHIA/PGS are installed, then it automatically run them. cards MadGraph library MadEvent.lhe.gz PYTHIA/PGS.lhco Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

18 LHC Olympics format At collider, we can only identify the following elements for a given event. - A high energy jet (b-tagging is possible) - an electron e ± - a muon µ ± - a photon - Missing transverse momentum LHC olympics format contains such identification. # typ eta phi pt jmass ntrk btag had/em dummy dummy # is increasing simply in a given event. Next event starts with 0. Type : 0 = photon 1 = electron 2 = muon 3 = hadronically-decaying tau 4 = jet 6 = missing transverse energy Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

19 LHC Olympics format eta = pseudorapidity, phi = azimuthal angle, pt = transverse momentum jmass = invariant mass ntrk = number of track btag = b-tagging had/em = ratio of hadronic vs EM energy in the calorimeter Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

20 # typ eta phi pt jmas ntrk btag had/em dum1 dum Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

21 ExRootAnalysis ExRootAnalysis for interpreting.lhco format. run ExRootLHCOlympicsConverter, then obtain.root format file..root is a snapshot of ROOT object instances. an object LHCO which is an instance of TTree class. To browse LHCO in ROOT, gsystem->load("lib/libexrootanalysis.so"); TFile::Open("pgs_events.root"); LHCO->StartViewer(); Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

22 ExRootAnalysis LHCO contains several branches: Event, Photon, Electron, Muon, Tau, Jet, MissingET They are TRootEvent, TRootPhoton, TRootElectron, TRootMuon, TRootTau, TRootJet, TRootMissingET class objects, respectively. Each object has data defined in ExRootAnalysis/doc/RootTreeDescription.html Using TTreeViewer, one can easily draw a histogram by drag and dropping. Use Draw with fields, cut and option, you can simply make a histogram as you want. We made a simple script drawing histogram w.r.t. the invariant mass of several objects. The script in ROOT is written in C++. It can be run on the command line, or as a batch procedure. For detail of analysis, refer to ROOT User s guide. Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

23 Input files for MadGraph Now, we know how to deal with output fils, let s understand the input files for MadGraph. Every input file in Cards. proc_card.dat specify the model and process we analyze. To change models, just change the line in # Begin MODEL # This is TAG. Do not modify this line sm # End MODEL # This is TAG. Do not modify this line change sm to mssm, then we can analyze MSSM. Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

24 To specify processes, modify this # Begin PROCESS # This is TAG. Do not modify this line # First Process QCD=99 # Max QCD couplings QED=2 # Max QED couplings end_coup # End the couplings input QCD=99 QED=2 end_coup # Second Process # Max QCD couplings # Max QED couplings # End the couplings input # Third Process QCD=99 # Max QCD couplings end_coup # End the couplings input done # this tells MG there are no more procs # End PROCESS # This is TAG. Do not modify this line Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

25 For model description, we can refer to MG_ME_V4.1.19/Models/(model name) particles.dat contains the particle information. For SM, particle names are d, d d-quark u, u u-quark s, s s-quark c, c c-quark b, b b-quark t, t t-quark e-, e+ electron ve, ve e-neutrino mu-,mu+ muon vm, vm µ-neutrino ta-,ta+ tau vt, vt τ-neutrino g gluon z Z-boson a photon W-,W+ W-boson h higgs interaction.dat contains the interactions. Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

26 Let us build our new model. Consider 4th generation lepton e whose charge is the same as the electron and vector-like. Assume it has a flavor-changing neutral current coupled to the electron mediated by Z boson. First, the template directory usrmod must be copied with an appropriate name, say Myeprime. Change particle.dat. Add new particle content. #MODEL EXTENSION ep- ep+ F S EPMASS EPWID S ep # END Change interactions.dat. Add new interactions. # USRVertex ep- ep- a GAL QED ep- ep- z GEPEPZ QED ep- e- z GEPEZ QED e- ep- z GEPEZ QED Set new parameter variables in VariableName.dat. Run ConversionScript.pl. This generates couplings.f Enter the expression for couplings in terms of parameters. Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

27 Now, decide what processes will be event-generated. proc_card.dat sets the model and the processes. initial > intermediate > final Here, we want to generate new physics signal only. # Begin PROCESS # This is TAG. Do not modify this line #e-e+ > ep- ep+ > e-e+e-e+ # First Process u u~ > ep+ > z e+ QCD=99 # Max QCD couplings QED=9 # Max QED couplings end_coup # End the couplings input u u~ > ep- > z e+ QCD=99 # Max QCD couplings QED=9 # Max QED couplings end_coup # End the couplings input u u~ > ep- ep+ > z z e+ QCD=99 # Max QCD couplings QED=9 # Max QED couplings end_coup # End the couplings input done # this tells MG there are no more procs # End PROCESS # This is TAG. Do not modify this line #********************************************************************* # Model information * #********************************************************************* # Begin MODEL # This is TAG. Do not modify this line myeprime # End MODEL # This is TAG. Do not modify this line Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

28 Run newprocess. Then, new param_card.dat is generated. Enter proper parameter values in param_card.dat. Run generate_events. Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

29 param_card.dat : Les Houches Accord format. This must contain mass spectrum and decay rates. For MSSM, we already have MadGraph model definition in Models/mssm. param_card.dat is of SUSY Les Houches Accord format. We can obtain such parameters from GUT scale SUSY breaking model definition using SUSY-HIT ( SUspect-SdecaY-Hdecay-InTerface ) SUSY-HIT has inputs from susyhit.in and suspect2.in It generates SLHA format file susyhit_slha.out It can directly be renamed to param_card.dat MadGraph has another input cards for Pythia and PGS. Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

30 After newprocess, MadGraph generates the info webpage. index.html For collective particle like protons and jets, in and out particle is one of the components, so a process is divided into several subprocesses. MadGraph generates a MadEvent code madevent.tar.gz After running generate_events, at the homepage, we can access data : Parton-level( LHE format ), Hadron-level(Pythia, STDHEP format), Recognized Objects( LHCO format ). Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30

31 ENJOY YOUR MONTE CARLO SIMULATION! Ian-Woo Kim (SNU) Tools for LHC SNU 03/ / 30