2. Analysis of Signal Events

In this part we are going to reconstruct the signal channel pbar p -> J/psi pi+ pi- for which we just created some simulated events. The basis for the analysis is the macro tut_ana.C in the tutorial directory tutorials/rho, so all code snippets listed on this page can be found in the macro. To run it and inspect the resulting histograms simply type

> root -l
root [0] .x tut_ana.C
root [1] TBrowser t

The various aspects of analysis and the corresponding source code used in the macro are explained in detail in the following sections.

Topics:

• 2.1. Data Access
• 2.2. Particle Identification
  • 2.2.1. Set Mass Hypothesis only
  • 2.2.2. Various PID Criteria
  • 2.2.3. PID Algorithms
  • 2.2.4. Stand-alone PID Selector
• 2.3. Combinatorics
• 2.4. Monte Carlo Truth Match
  • 2.4.1. Accessing the MC truth
  • 2.4.2. Full MC truth tree match
  • 2.4.3. MC Truth List
• 2.5. Fitting
  • 2.5.1. Vertex Constraint
  • 2.5.2. Energy-Momentum-Constraint
  • 2.5.3. Mass constraint
  • 2.5.3. Decay Tree Fitter