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D0 Analysis in cucu200GeV using Micro Vertex Code

D0 Analysis in cucu200GeV using Micro Vertex Code. Analysis Meeting @ BNL September 24, 2008 J.Bouchet, J.Joseph, S.Margetis Kent State University. Cuts Used in MuKpi macro. pure D 0 : 950 MuDst files (400 possible D 0s per file) - |Zvertex| < 20 cm - NTpcHits > 15

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D0 Analysis in cucu200GeV using Micro Vertex Code

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  1. D0 Analysis in cucu200GeV using Micro Vertex Code Analysis Meeting @ BNL September 24, 2008 J.Bouchet, J.Joseph, S.Margetis Kent State University

  2. Cuts Used in MuKpi macro • pure D0 : 950 MuDst files (400 possible D0s per file) - |Zvertex| < 20 cm - NTpcHits > 15 - |η| in SSD acceptance, ie |η| <1.2 - pT > 0.1 GeV/c - decay length < 700μm • D0Mix: 1D0 embedded in Cu+Cu Hijing event, 290 files with 400 events. - same cuts as above • Real Data: Cu+Cu@200GeV MinBias (P07ic) : - ran over 20,000 files - dEdx cuts + same cuts as in pureD0 • The macro associates positive and negative tracks to reconstruct • the invariant mass

  3. Pure D0 Sample Resolution 0.589% No Cuts Resolution:0.589% • The Reconstruction Microvertex Code[MuKpi.C ] reconstructs D0 parameters pretty well in pure D0 sample. • Cuts on TpcHits(>20) and SiHits (SvtHits>0&SsdHits>0 )for pos and neg daughter tracks removes almost every bad associations in pure sample.

  4. D0Mix(No Cuts) Real-all associations Fake-rotation of pion Real Fake Seems to be working with a cut on the Number of Tracks. We see a small correlation for mass =1.86 and the low multiplicity

  5. Background Subtraction A Gaussian is fitted to the signal and a zero degree polynomial to the background.

  6. Looking at some attempted cuts in MuKpi.C with pure D0 and D0Mix sample DCA of the Tracks Pure D0 D0 Mix In order to remove fake association we can do a cut on dca, |DCApos – DCAneg|< 0.1 With the help of silicon detectors there is more precision in DCAs and hence a more fine tuned cut in the analysis.

  7. D0 Mass with cut on Dca Dca cut is applied in both longitudinal and transverse directions.

  8. Angle(made by Kaon in the CM frame) analysis in pure and D0Mix (For Ntracks<50) Angle made by K- in the CM Frame Pure D0 D0 Mix A cut (|angle|< 0.8 ) can possibly remove some background .

  9. D0Mass(with a cut on the opening angle of Kaon) With a cut on the opening angle of Kaon(in the CM frame) we possibly can improve the signal. But removing the cut on NTracks leads to disappearance of the D0signal in all cases!

  10. D0Mix: Combining cuts on Ntracks, Dca, opening angle of Kaon, momenta of daughter tracks etc. Here we tried two sets of cuts to see how well it reconstructs the D0Mass from the mix sample • NoTracks <50 • |Kaon opening angle| < 0.8 • |pPos|>0.6, |pNeg|>0.6 • ChargePosTrack >0, ChargeNegTrack <0 • |dcaXY_pos – dcaXY_neg| < 0.1 • |dcaZ_pos – dcaZ_neg| < 0.1 • SsdHits(pos&neg) > 0 • SvtHits( pos&neg) > 0 • TpcHits(pos&neg) >20 • NoTracks<50

  11. D0 Mix: Mass plot and background • Mass plot with all the cuts mentioned in the previous slide • Background The shape of the Background (for each association, rotation of the pion track through π) differs from the actual mass distribution and hence the subtraction can lead to over-estimation of D0.

  12. Recalculation of Background • Tried random rotation in 2π for both daughters : same results • We tried to rotate the track around the primary vertex by rotating the pion track before doing the association. • In the following slides we look at three cuts: No of Tpc Hits, No of Si Hits and No of Tracks

  13. Fixed Rotation All associations Background

  14. Real Data With the help of analyzed cuts in pure and mix D0 sample, we can now proceed to the Real Data and apply similar cuts with appropriate values. dEdx of Real Data Red = Pi+ Blue = K-

  15. Real Data Mass plots True Fake

  16. Outlines • Analysis of D0 reconstruction based on micro vertex code (using SSD and SVT hits) to find and optimize proper cuts. • We looked at Pure and D0Mix sample. • Applied different cuts in Pure and D0Mix to enhance the signal. • Investigation of background calculation(Like sign & Mix Events) • We plan to apply the same cuts but tuned for the real data (looked at real data, but no signal so far) • We can utilize the SiliconHits to have more tight cuts on DCA

  17. BackUp slides

  18. Mass Resolution with Si and TpcHits (pure D0) TPC > 30(*) σD0M =0.01054 eff =81.5% no cut σD0M =0.01087 Si > 1(*) σD0M =0.01068 eff=44.5% TPC>30 &&Si > 1(*) σD0M =0.01030 eff=35.2%

  19. Daughter momenta(D0Mix)

  20. Daughter Characteristics

  21. Random Rotation(D0Mix)

  22. SigmaDca(D0Mix) SigmaXY_pos – SigmaXY_neg D0Mix Pure D0

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