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Update on D0 reco. using KFParticle

Update on D0 reco. using KFParticle. J. Bouchet (KSU). outline. Update plots shown for the D0 reco : run over 3k events on the thick production Slight changes in the codes : p T of tracks > 0.5 GeV/c (was .3 before) Number of silicon hits = 4 (was 3 before)

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Update on D0 reco. using KFParticle

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  1. Update on D0 reco. using KFParticle J. Bouchet (KSU)

  2. outline • Update plots shown for the D0 reco : run over 3k events on the thick production • Slight changes in the codes : • pT of tracks > 0.5 GeV/c (was .3 before) • Number of silicon hits = 4 (was 3 before) • Cut on |n|<2.5 for the PID (was 3 before)

  3. Decay length significance SL zoom • SL = decay length / error (decay length)

  4. Inv. Mass D0 • left : invariant mass K-π+ before cut on SL • right : invariant mass K-π+ after cut on SL > 5

  5. Cut study dca<200µm SL>5 SL>10 SL>15 • Change the SL and dca pair track cut • Fit is done with pol1 function ; signal and background are evaluated in 1.84<M< 1.92 dca<100µm

  6. summary • Significance Seff = S/√(S+B) ,where • B = counts evaluated with the pol1 function • S = counts after background contribution Signal (S) background

  7. Decay length vs SL • left : decay length vs mass ; right : decay length significance vs mass • it is interesting to see that a cut on Sl seems to remove more efficiently the background (even we see a small peak at the correct inv. Mass on the left plot)

  8. Single track cut • The next plots are for the kaon track candidate • I look at some quantities for • All tracks (left panel) • Tracks where I select SL >5 and DCA pair < 200 µm (which from the plot I’ve shown before seems to select good D0 candidates) (right panel) • The beta factor for the kaon is calculated using the kaon mass assumption

  9. DCA distribution • Good kaon candidates (right) show that a min DCA cut is needed • DCA/DCA distribution • DCA is taken from the covariance matrix of track • Good kaon candidates (right) show that a cut ST =DCA/DCA could be applied

  10. DCA vs. (1/momentum) (X legend on the plot is flase) • We see the separation = min DCA cut for good kaon candidates

  11. DCA product • The product is defined as DCAXYkaon x DCAXYpion • The cos () is the cosine of the angle formed by the vector joining the primary vertex and the secondary vertex and the D0 momentum vector • As it has been shown before, the good D0 candidates exhibit a strong negative product • There is also a correlation between dcaProduct<0 and cos() > .9

  12. Summary /to do • Applying the decay length significance as a cut looks promising • Can apply another cuts (on the track level) • To do : • Correlation of cuts : for example, make the S/B map of D0 as a function of (Sl,DCA pair track) • Look at the other decays , as increasing the statistic confirm my previous results (based on less # events)

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