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[OK] Event Filter in FastSim [message #16706] Sat, 24 May 2014 13:00 Go to previous message
Klaus Götzen is currently offline  Klaus Götzen
Messages: 293
Registered: June 2006
Location: GSI
first-grade participant
From: *
Hi all,

since the more general event filter apparently cannot be enabled so simple, I introduced a rather simple event filter in PndFastSim itself (in trunk and scrut14). It is not intensively tested so far, but you might give it a try (and help validating it).

It offers simple multiplicity cuts (trk+, trk-, gamma, pi0, eta, Ks - see below in the code) and a single invariant mass filter. Concerning particle species, no filtering has been implemented on pdg codes intentionally to not spoil PID performance in the later analysis. The filtering happens on the PndStack before smearing, mergeing or rejecting particles.

You could copy the code snippet below to your simfast_opt.C somewhere before fRun->AddTask to use it. I'd suggest to first use it for signal events (which should survive!), and then do a rough comparison for background with and without filtering to check whether everything is fine.


//set event filters
bool useFilter=true;
if (useFilter)
      // Filters are:
      // -----------
      // Multiplicity filter: fastSim->SetMultFilter(type, min, max); 
      // requires min <= mult <= max
      // available types are:
      //  "+"   : positive charged particles
      //  "-"   : negative charged particles
      //  "gam" : gammas
      //  "pi0" : pi0 candidates ( -> 2 gammas); mass window 0.135 +- 0.03 GeV
      //  "eta" : eta candidates ( -> 2 gammas); mass window 0.547 +- 0.04 GeV 
      //  "ks"  : K_S candidates ( -> pi+ pi-);  mass window 0.497 +- 0.04 GeV
      fastSim->SetMultFilter("+",   2,1000);  // at least 2 trk+
      fastSim->SetMultFilter("-",   2,1000);  // at least 2 trk-
      fastSim->SetMultFilter("gam", 0,   4);  // at most 4 gammas

      // Invariant Mass filter: fastSim->SetInvMassFilter(comb, m_min, m_max, mult);
      // requires at least mult combined candidates with m_min < m < m_max
      // comb is a TString describing the combinatoric
      // - particle codes are: e+ e- mu+ mu- pi+ pi- k+ k- p+ p- gam pi0 ks eta
      // - codes must be separated exactly with a single blank; no extra blank somewhere else!
      // - for charged final states only the mass is set; no pdg code selection is done! 
      // - optional a 'cc' added at the end also takes into account charge conjugation;
      //   not to be used with symmetric channels like pi+ pi- pi0, K+ K-, etc.!!
      // Examples: 
      // - ("k+ k-", 0.98, 1.1, 2)       : forms K+ K- candidate and requires >=2 in the given window
      // - ("ks k+ pi- cc", 2.8, 3.2,1 ) : forms ks k+ pi- / ks k- pi+ cands and req. at least one in window
      fastSim->SetInvMassFilter("e+ e-",2.8,3.3,1);  // look for J/psi -> e+ e- candidate

[Updated on: Fri, 12 September 2014 10:38] by Moderator

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