Charged Multiplicity for W tau nu candidate events

Distribution for the number of charged tracks with Pt.gt.1 GeV within 10 degrees around the direction of tau candidate

As tau leptons decay predominantly into 1- and 3-prong final states, in ideal case the distribution for the charged track multiplicity for W->tau nu events should have only 1- and 3-prong multiplicity bins populated.
Population of the N=2 bin:
- background events (mostly - QCD jets, misidentified as tau's)
- 3-prong W tau nu events with the 3rd track lost
- 1-prong W tau nu events with tau decaying into the channel with pi0's: if one of the pi0 photons converts into e+e- pair, electron or positron track becomes track #2
```
     In 0-th order N=2 bin measures measures the background: for W - tau nu 
     simulated in the CDF detector ratio of the populations of the 1st 2 bins is

             N(N_tracks=1)/N(N_tracks=2)   ~= 6 
```