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Z 0 →µµ and Charged tracks

V.Nikolaenko, IHEP Protvino Used Z0+jets AOD DataSets after ALPGEN Produced D3PD using EWPA vsn 3.32 Np0_merge_tid060297_tid060298.root Np1_merge_tid060726_tid060727.root Np2_merge_tid060299_tid060300.root Np3_merge_tid060728_tid060729.root Np4_merge_tid061150_tid061151.root

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Z 0 →µµ and Charged tracks

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  1. V.Nikolaenko, IHEP Protvino Used Z0+jets AOD DataSets after ALPGEN Produced D3PD using EWPA vsn 3.32 Np0_merge_tid060297_tid060298.root Np1_merge_tid060726_tid060727.root Np2_merge_tid060299_tid060300.root Np3_merge_tid060728_tid060729.root Np4_merge_tid061150_tid061151.root Np5_merge_tid060301_tid060302.root Z0→µµ and Charged tracks

  2. LHC predictions (R.Field) Rick Field – Florida/CDF/CMS

  3. Sectors in trans. plane

  4. Generated track dens. (O.Zenin)

  5. Expected statistics • At √s=10 TeV and LUMI=100 ev/pb • Z0→µ+µ- and partons at pt>20 GeV • Z incl N= 114 300 PYTHIA • Z+Np0 90 000 AlpgenJimmy LO • Z+Np1 20 500 • Z+Np2 6 900 • Z+Np3 2 200 • W+Np0 2155 000 • WZ+ZZ c.s. at 14/10/7 TeV→ 50/31/18 pb

  6. StacoMuons and Z0 (Np=0)

  7. muons and Z0 • Page 6: a) muons pseudorapidity ( Np0 ) • b) m(µ+µ- ) • 81.2<m(µ+µ- )<101.2 used as Z0; • c) Pt of reconstructed Z0; • d) rapidity Y of Z0;

  8. Tracks classification

  9. Number of tracks and muons association

  10. Tracks and muons • Events in the Z0 mass band kept; • Page 9 • a) Np0 sample, total number of tracks and the number of tracks used in Vert Fit • b) the same for Np3 sample; • c) φ-angle difference between µ and track • d) η-difference ( in degres) • Muon tracks are excluded from track sample (if both diff. of φ and η less than 0.5 deg.)

  11. Selected “Primary” tracks

  12. Tracks φ and impact parameter

  13. Tracks distributions • Page 12: • a) distribution on the φ-angle is NOT flat; • this is strange. • b) a clear correlation between d-impact parameter and the φ-angle is observed • Comment: the d-impact parameter at AOD is calculated for the “vertex” at (X,Y)=(0,0); • It should be recalculated for the reconstructed prim. vertex

  14. Beamspot in (X,Y) plane Beamspot is shifted

  15. METFinal for Np0 sample pt and φ-distribution for the missing mom. vector; the φ-distribution is NOT flat

  16. Tracks and Z0 in the central region • Selection criteria applied for next distributions: • -0.5 < η(Z0)< 0.5; • -1.0 < η(track)< 1.0;

  17. N tracks in sectors w.r.t. Pt of Z0

  18. Mean sum of tracks Pt in sectors vs pt of Z0

  19. Mean charged multiplicity, Z0 at -0.5<η<0.5

  20. <Σ| pt |> in Towards sector

  21. <Σ| pt |> in Transverse sectors

  22. <Σ| pt |> in Away sector

  23. <Σ| pt |> in Away sector for tracks and jets

  24. Summary • A dependence of “primary” track reconstruction efficiency on the φ angle is observed; also MET φ distribution is not flat. • Expected correlation between the Pt of Z0 and tracks Pt sum in the Away sector is seen. • To do: • -Reconstruction efficiency and purity should be studied in details • -Look for BG MC samples

  25. References • WZ+jets meetings 16 Apr (A.Miagkov), 21 Jul (O.Zenin) http://indico.cern.ch/conferenceDisplay.py?confId=60149 and confId=47812 • Joined CMS-ATLAS-LHCb-ALICE meeting http://indico.cern.ch/conferenceDisplay.py?confId=65178 • ATLAS UE-study page in preparation: https://twiki.cern.ch/twiki/bin/view/AtlasProtected/UnderlyingEvent

  26. Backup slides Mean track energy vs R-parameter (in degrees)

  27. Suggested UE Reference Plots (with Min-Bias Trigger) • Average Nchg and average PTsum in the "toward", "away", "transverse" region as defined by the leading charged particle, PTmax, • and as defined by the leading charged particle jet, chgjet#1, (anti-KT algorithm, d = 0.5) with PTmin = 0.5 GeV/c and PTmin = 0.9 GeV/c and |eta|< 1

  28. Suggested ATLAS/CDF plots from early LHC data (cont.) • The average Nchg and average PTsum in the "toward", "away", "transverse" region would be plotted versus the PT of the object that was used to define the three regions (i.e. PTmax or PT(chgjet#1)).

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