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One Lepton Mode Background MT and new MT method (including systematic errors)

One Lepton Mode Background MT and new MT method (including systematic errors). SUSY Background meeting (CSC1&2) 27. Nov 2007 Ginga Akimoto , S.Asai, Y.Kataoka, N.Kanaya The University of Tokyo, ICEPP. Table of Contents. Update Digest of BG estimation Systematic Error Study

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One Lepton Mode Background MT and new MT method (including systematic errors)

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  1. One Lepton Mode BackgroundMT and new MT method (including systematic errors) SUSY Background meeting (CSC1&2) 27. Nov 2007 Ginga Akimoto , S.Asai, Y.Kataoka, N.Kanaya The University of Tokyo, ICEPP

  2. Table of Contents • Update • Digest of BG estimation • Systematic Error Study • BG estimation with K factor • Conclusion & Outlook I have already shown the detail of our method in the previous meeting, so I focus on the systematic errors today.

  3. I. Update 2nd Lepton (PT>10GeV) veto Def :: Effective Mass : add Lepton PT Def :: Transverse Sphericity : add Lepton Systematic Error Study of ( lepton efficiency , Energy Scale, STACO muon id selection , MC @ NLO) BG estimation with K factor Used samples are the CSC full-simulation samples (v12.0.6.5) and systematic error samples (including fast simulation) . [same to previous meeting] In Addition to these , we use ATLFAST alpgen samples to study lepton efficiency.

  4. II. Bakground Estimation : MT and new MT Method • This figure shows MT distribution of SUSY(SU3) and background processes, which is calculated with missing ET and Lepton PT. The main background processes are top and W. • MT<100GeV : Background ( top &W) enhanced Sample [Control Sample] • MT>100GeV : SUSY signal enhanced Sample [Signal Region] [MT-Method] The background distributions of One Lepton Channel are estimated with Control Sample. (detail has already shown in the previous many meetings.) Signal Region MT>100GeV Control Sample MT<100GeV

  5. II. Background Estimation (w/o SUSY) • Following figure shows missing ET distribution of background processes (and estimation with original MT method). Magenta line shows estimated background processes with MT method and black line is truth background . • # of mET>100GeV and mET>300GeV is also reproduced well. Magenta with error : estimated BG with C.S. Black line : (truth) all BG process (ttbblnln dominant) Events number is also well reproduced.

  6. II Background Estimation ( with SUSY) • Background distributions are overestimated with original MT method as following reasons if SUSY exists. (But SUSY signals are detectable with this method). • SUSY contamination in Control Sample distorts the distribution of Control Sample . It makes main discrepancy from truth BG. • In addition to the distribution, normalization factors are affected by SUSY contamination, which cannot be negligible even in lower mET region and makes the background overestimated. • To remove these contamination effects. • The distribution of the contamination is estimated with Signal Region. • The amount of the contamination is about 0.7 (times scaled Signal Region). • Normalization factor is obtained in the region of mET=[100-150GeV] in stead of mET=[100-200GeV]. • With these corrections we can estimate the background correctly. (detail has already shown in the previous meetings.)

  7. III Systematic error study : original CSC sample • This figure shows Missing ET and Effective Mass distribution (truth (black line)& estimated BG with new MT method (red line ) ). With MT and new method we can estimate the background correctly. Statistic Errors and ratio BG(estimated) over BG( truth ) is following table.

  8. III Systematic Error Study • List of Systematic Error Study • Energy scale (change mET and Jet PT by +/-5% ) • Top : LO-> NLO • STACO muon collection • Lepton efficiency 2% We checked these systematic errors

  9. III systematic error : Enegy scale x1.05 [BG] means real BG. [BG est] is estimated BG(MT w/o SUSY and new MT with SUSY). [BG(syst.)/BG(original)] is [BG] difference from original sample.

  10. III systematic error : Enegy scale x0.95

  11. III Systematic error : Top (T1) MC @ LO->NLO

  12. III Systematic error: STACO Muon Collection

  13. III Systematic error: Lepton Efficiency 2% (atlfast) These figures show mET and Meff distribution of ATLFAST. We assumed 2% lepton efficiency (Results after 2% Eff are next page).

  14. III Systematic error :Lepton Efficiency 2% (atlfast)

  15. IV. BG estimation with K factor • Following K factors are applied . • SUSY 1.5 • Top 2.02 • W/Z 1.24 • QCD 2.6

  16. V. Conclusion & Outlook • Conclusion • We applied MT / new MT methods to various systematic error sample and study other systematic errors.(STACO muon id collection, Energy Scale , Lepton Efficiency , Top NLO ) • BG estimation with K factor • In any case SUSY is detectable and estimated backgrounds are comparatively consistent with statistic errors. These methods are stable against systematic errors.

  17. Backup

  18. III Systematic : Top ME/PS PT 40GeV->15GeV

  19. III Systematic : Top renormalization scale (x0.5)

  20. III Systematic : W ME/PS PT40 - >15GeV

  21. III Systematic : W renormalization scale (x0.5)

  22. III Systematic : W pythia sample

  23. III Systematic : contamination factor The level of contamination (# of SUSY ratio : [Control Sample] over [Signal Region] ) is assumed to be 0.7 (by MC average from SU1 to SU3 CSC Full). These factors are deferent with each SUSY models by 0.1. So we changed it to 0.6 and 0.8 and applied new MT method. 0.8 :we overestimate contamination 0.6 : we underestimate contamination

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