1. 9/27/101 Decay length study

2. 9/27/102 outline Look at the CuCu200GeV ~ 70k events after Zvertex (|zvertex|<15 cm) and  vertex < 80 microns Look at the decay length of D0 candidates (from TCFIT) and its error for different configurations of silicon hits

3. 9/27/103 Decay length “2+2” means the pion daughter track and kaon daughter track have 2 silicon hits

4. 9/27/104 Error of decay length

5. 9/27/105 Significance : decaylength/ error

6. 9/27/106 comments The main result is on slide 4 (error on decay length) : –We see that D0 candidates for which daughters have 4 silicon hits have a much lower error of their decay length. –2+2 : mean of histo is 230 microns and the max of the histo is ~ 175 microns –4+4 : mean of histo is 175 microns and the max of the histo is ~ 115 microns This is the same result as for the single track DCA resolution

7. 9/27/107 cut The idea is to apply a cut on the error of decay length I’ve chosen : error < 200 microns (shown in red) with the error less than 200 microns, we’re cutting half of the entries for candidates which have only 2 silicon hits Whereas we cut ~20% for candidates which have 4 silicon hits To do : it does not seem to have a ‘real’ impact’ on the decay length, I will look at the other variables to see if this cut may be useful.