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Investigation of cut slength/error

Investigation of cut slength/error. outlines. In many papers about charm measurements, a cut on the decay length significance is used. For ex : http://www-zeus.desy.de/physics/phch/conf/ichep06/hfl/9/ZEUS-prel-06-016.ps The decay length is defined as :. D0Tree.

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Investigation of cut slength/error

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  1. Investigation of cut slength/error

  2. outlines • In many papers about charm measurements, a cut on the decay length significance is used. • For ex : http://www-zeus.desy.de/physics/phch/conf/ichep06/hfl/9/ZEUS-prel-06-016.ps • The decay length is defined as :

  3. D0Tree • What we have in D0Tree is the length from TCFIT and its error • I also calculated Lxy (with the same definition) using the helix swimming to determine the secondary vertex and included in the tree • But I don’t calculate/include the errors • Idea : as this cut was used in another experiment (and has shown its efficiency), try to use a similar one • Test : compare slength from TCFIT with Lxy • I’m using a pure D0 sample

  4. No cut on probability

  5. Prob>.01

  6. Prob>.1

  7. Prob>.5

  8. comments • Using at least a minimal cut on probability of TCFIT, slength and Lxy seems pretty agree in the ‘physical’ range of D0 decay length (<1mm) • Lxy shows some large values : can look if using another method to determine the secondary vertex position (Kfparticle for example) gives better agreement • can use slength and its error as a substitute to Lxy. • Next : verify with the realp pT D0 in hijing

  9. Slength/error vs pT of D0 <slength/error> = 0.26 + 0.24pT  slength/error = 1.38 + 0.16pT

  10. Slength/error vs pT of D0 (power law pT) • Linear fits not really good because of law statistic

  11. HERA-II specifications (ZEUS detector • ep collisions • Reconstruction of D+ • Pre selection of tracks (pT(kaon)>.65GeV , pT(pions)>.45GeV) • D+ candidates with pT>3GeV/c only accepted • Vertex detector : • 600 single sided silicon detectors in 3 barrels

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