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What I aim for today ...

Single leptonic SUSY searches Robert Schoefbeck (Hephy Vienna) Physics in progress, March 4th, 2010. What I aim for today. to update the non-analysts at our Institute on what we‘re currently working on

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What I aim for today ...

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  1. Single leptonic SUSY searchesRobert Schoefbeck (Hephy Vienna)Physics in progress, March 4th, 2010

  2. What I aim for today ... • to update the non-analysts at our Institute on what we‘re currently working on • to give an overview for our friends (who are analysts) at Budapest and Debrecen on what the Vienna Susy Group does.

  3. just briefly ... • Intro – What are we looking for? • An example study: ABCD in kinematical MET-significance and HT2 • Uncertainties in early leptonic SUSY • OSETs – a general tool for some fb-1 • Plans

  4. 1. What are we looking for? • Result of a systematic quantitative search • (9 x Ω Moon): doi:10.1038/nature05497 • behaves like matter • interacts only weakly Colliding cluster MACSJ0025 Hubble/Chandra NASA/ESA “Weak lensing" A.Einstein middle/pink: ordinary matter blue lobes: gravitationally int.

  5. How can we see DM in the detector? SUSY-model The simplest models with supersymmetry in accordance with experiment predict good dark matter candidates. The details of the mass spectrum are not set, however. large amounts of MET The LSP interacts weakly in many models!

  6. Discovery reach for different integrated luminosities (PTDR-II) bird’s eye view: (early) SUSY at CMS total SUSY production cross section (PTDR-II) varies over many magnitudes

  7. LHC: startup due in November March future 2 x 7TeV (2 x 5TeV) 2 x 3.5TeV you are here Early descoping: Bent Pyramid of Sneferu c. 2600 BCE (LeComte)

  8. Start-up & early data Until startup: prepare for data-taking SUSY is a possible early discovery However, MC simulation of background in regions where SUSY is suspected suffers from high uncertainties, especially in the tails Estimation of the background from data is a vital necessity

  9. Overview: early SUSY searches at CMS • Don’t be model-dependent, look for general signatures! • SUSY Hadronic Reference Analyses • Exclusive n-jet analyses Dijets + Multijets • Inclusive ≥3 jet analysis InclusiveJets • photon+MET analysis Diphoton+X • Diphoton+Jet+MET, Photon+JET+MET • SUSY Lepton Reference Analyses • Single-lepton analysis SingleLepton_e, SingleLepton_mu • Same-sign dilepton analysis (ee, emu, mu-mu, mu-tau) • Opposite-sign dilepton analysis • Trilepton analysis Trilepton • Dilepton + photon

  10. lep. search: SUSY=JETS+MET and the lepton vetoes QCD • what are the backgrounds? • t-tbar • 9.000 events in the first 100pb-1 • if one of the W decays leptonically, the bkg is irreducible • W->tau decays and tau-conversions • different Bkg-physics in different MET-regions • W+Jets • depending on pre-selection 10-50% • fewer jets, produced less centrally • QCD • is always there • small CS in the one-lepton mode but not very well understood, especially the tails • Guiding principle is • *not* to optimize discovery reach. t-tbar signal

  11. physics objects: “as loose as possible, as tight as necessary” jets at least three jets pT > (50,50,50) GeV (corrected) |η| < (2.4, 2.4, 2.4) fem < (0.9, 0.9, 0.9) MET (missing transverse energy) ET > 100 GeV , 200GeV<ET mT (trans. mass of rec. W=lep+MET) 50<mT<100, 100<mT Muon selection „GlobalMuonPromptTight“ pT>20 GeV and |η|<2.1 RelIso < 0.1, ECalIso < 4 GeV, HCalIso < 6 GeV, |d0|<0.2cm, Nhits>11 Electron selection „eleIdRobLoose“ (rej. = 96.65%, eff = 26.0%) pT>20 GeV and |η|<2.5 CaloRelIso < 0.1 Electron selection (veto) „eleIdRobTight“ (rej. = 99.76%, eff = 12.2%) pT>20 GeV and |η|<2.5 RelIso < 0.1 |d0|<0.2cm , w/ to the beam spot Summary: Typical event selection: 3 hard jets 1 Muon, no Electron Large MET mT: trans. mass (l,MET):

  12. control- region A, C signal- region B, D blue:predicted Bkg. in D black: true Bkg. Estimating the Background: the ABCD method • assumptions: • Bkg. dominates in A, B and C • possible problems: • signal contamination • in A, B and/or C • correlations • feature of leptonic searches: • few (>2) variables with some disc. power

  13. towards the real world • Naive ABCD in early single-leptonic searches is not trivial due to correlations and signal contamination in most pairs of variables. • For example, MET and mTdiscriminate very well but correlate, which is a hard to tackle problem with limited statistics. • MET-significance and HT2 are uncorrelated (to a few %) • Signal contamination will dominate systematics • I will now • give a brief overview of the method • and how it depends on different systematic uncertainties.

  14. Robert Schoefbeck (HEPHY Vienna) 2. ABCD in MET-sig. and HT2 MET-significance:“MET over the square-root of the total scalar sum of pT”HT2 : “Scalar sum of pTs with hardest jet removed” where I consider jets if |η|<2.4 and pT>40GeV and Vjet-muons with pT>10GeV(somewhat preliminary).

  15. Robert Schoefbeck (HEPHY Vienna) • HT2 of Bkg-Components • The Bkg-samples • show similar tails. • SingleTop and QCD are small • Limited statistics for the tail of WJets HT2

  16. Robert Schoefbeck (HEPHY Vienna) MET-sig of Bkg-Components The composition of TTbar/WJets slightlyvaries over MET-sig but this variation is to some extent independent of HT2. QCD&singleTop ~O(small) MET-sig

  17. Robert Schoefbeck (HEPHY Vienna) Binned distributions of total Bkg., 10TeV HT-2 met-sig Limited statistics in the (highest) tails, very well-tempered behaviour, though. More plots in the backup and in my talk on Dec. 3rd.

  18. Robert Schoefbeck (HEPHY Vienna) Total Background on a log-scale Independent exp. variables have parallel contour lines; Fulfilled quite well ( ). Control: 3<MET-sig<6 150<HT2<300 Signal: 8<MET-sig 350<HT2 quick check of robustness (see later): Include shaded area to B,D and C (red arrows) HT2 B D CUT-BD A C MET-sig CUT-AB

  19. Robert Schoefbeck (HEPHY Vienna) example: LM2 on a linear scale HT2 D B C A MET-sig

  20. Robert Schoefbeck (HEPHY Vienna) find a working point (axis = cut values, fixed excluded regions, LM1) double ratio (A/B)/(C/D) on Bkg relative statistical error CUT-BD CUT-BD CUT-AB CUT-AB “significance” (est. Signal / sigmastat+sys) signal events in D

  21. Robert Schoefbeck (HEPHY Vienna) Results at 100pb-1 True BG in D: 13.1 Events Except for LM0 these variables seem to work quite well. Sig.Cont. is the main remaining problem, of course.

  22. 10TeV LM1 LM0 total Bkg HT-2 HT-2 HT-2 met-sig. met-sig. met-sig. 7TeV total Bkg, log scale LM0 LM1 HT-2 HT-2 HT-2 met-sig. met-sig. met-sig.

  23. Robert Schoefbeck (HEPHY Vienna) 3. What are my uncertainties?

  24. Robert Schoefbeck (HEPHY Vienna) Robustness: Including dead areas in D cut on met-sig in „D“ cut on HT2 in „D“ Example: LM2 RED: true Bkg in D, Black: estimated background in D Varying region D according to the red arrows on the previous slided, there is only a very small dependence on the HT2 cut-value (left) and an almost constant term in the relative error as function of region-D cut on met-sig (right).

  25. signal contamination and JES true Bkg. subtracted estimated Bkg.-events JES sig.Cont. sig.Cont. Signal contamination gives a bias for every signal hypothesis (Middle Bin). Conservative: Treat it as an sys. unc. for which the width of the band is a good measure. Other Bins: Dependence on JES The true Bkg changes but the estimation follows nicely (slope is corrected). same as left, with true background subtracted Estimate sys. uncertainty from JES : fromthe variation of the width

  26. measure efficiency of lepton-isolation cut (1) mass[GeV] • Monitoring lepton-iso efficiency with tag and probe using Z+Jets • tag a RA4 muons • Select looser probe-muon (RA4-preselection without rel-iso cut) and • require opposite muon-charges and M(mu,mu) = MZ +/- 10GeV • measure efficiency of rel.iso-cut binned in pt, eta and njets • extrapolate to higher jet-multiplicites and compare with generator efficiency • done by Gregor Kasieczka, more info e.g. in talk by A.J. Richards, Nov., 19th

  27. T&P results: predicting iso-cut efficiency (2) Extraploation njets Example: prediction for iso-efficiency in the low-lepton-pT (10GeV < pT < 30GeV) range and extrapolation to high jet-multiplicities. Error bars for 100pb-1. Extrapolation works well. The model fitted is εn = ε0 pn. Mainly serves as a sanity check.

  28. Robert Schoefbeck (HEPHY Vienna) Jet-Smearing • Take each jet • get its resolution • raise it by some factor • smear with the additional contribution • reorder Jets • recalculate MET -> Jet smearing has practically no effect (only SM/SUSY scale)

  29. more on uncertainties Signal contamination definitely the largest issue. Although it is a bias known under a signal hypothesis, I (for now) treat it as an sys. uncertainty in statistics (~3.1 Evts@100pb-1) Jet-energy scale second largest, but ABCD subtracts leading term(~1Evts) lepton-efficiency monitoring Lepton Iso. Efficiency with T&P in Z-Events expect only very small effect (see my talk on Dec. 3rd) jet-efficiency and systematics in the low jet-pt range 30 to 50GeV needs a close look, monitor jet-efficiency with T&P in Dijets (in the making) jet-resolution re-smearing Jets with worsened resolution has very small effect (talk on Dec. 3rd) muon-trigger efficiencies The muon-trigger efficiencies with Mu5, Mu7 and Mu9 are constant over my ABCD regions within the statistical error

  30. mean significance of deviation from SM at 7TeV, including statistics + systematics, signal.cont. of (LM1-LM10) taken as systematic error used roostats::ProfileLikelyhoodCalculator, preliminary ABCD regions: 2.5 < met-sig < 4.5 and 4.5 < met-sig 250<HT-2<350 and 350<HT-2 • some points (LM1,LM3,...) much easier than others (LM2, LM7) 100pb-1 probably is too little LM0 not seen roostat sometimes crashes, cause not yet known

  31. 4. OSets: disentangle branchings and masses

  32. 827 - 777 746 - 748 724 671 580 468 465 455 267 264 141 mSUGRA LM2 (incomplete) 46% q 15% t 13% b 26% b 53% q 12% t 46% t 15% q 30% q 38% b 42% t 12% t Z 24% t 85 % τν 15% W

  33. mq mg mC mN OSET LLM 100% → tb LM1: mq ∼ 550, mg ∼ 600, mC ∼ 180, mN ∼ 100 LM2: mq ∼ 760, mg ∼ 830, mC ∼ 270, mN ∼ 140 LM8: mq ∼ 800, mg ∼ 740, mC ∼ 230, mN ∼ 120 100% → q 100% → ν τ

  34. well modeled!

  35. 5. What to do next • prepare for 10 pb-1 Lepton commissioning effort (WK), maybe Dijet T&P • ~ by beginning of April • prepare for 100 pb-1 Complete systematicsstudies at 7TeV for ABCD • Determine “OSET reach” including backgrounds & detector • ~June/July • prepare for 1 fb-1 Join analysis: • e.g. Met-sig vs. HT-2 has a hadronic counterpart • which might work equally well; combine with exclusive • event selections like RA1, RA2 • e.g. fit OSets to different n-lepton bins at the same time • ~Autumn tasks I ommitted: Vertexing, secondary vertex finding efficiency , also related to (W.Waltenberger, D.Liko, C. Thomay) b-Tagging (W.Adam) maintenance of SUSY-PAT recipe and patification for the SUSY group

  36. Robert Schoefbeck (HEPHY Vienna) BACKUP

  37. Robert Schoefbeck (HEPHY Vienna) met-sig. for signals (only lower cut) A+B C+D C+D A+B MET-sig MET-sig typically, expect at least signal ~ O(Bkg) in signal region; (Note that this is summed over HT2-regions, as indicated)

  38. Robert Schoefbeck (HEPHY Vienna) HT2 for signals (only lower cut) B+D A+C A+C B+D HT2 HT2 Again, this is summed over met-sig.-regions, Thus a small signal (e.g. LM2) in this plot need not be a problem (details->backup)

  39. Robert Schoefbeck (HEPHY Vienna) MET for different Backgrounds Cuts applied: preselection MET-Sig > 3 HT2 > 150 (lower region-cuts) MET

  40. Robert Schoefbeck (HEPHY Vienna) HT2 for Bkgs in AB and CD C A B D HT2 HT2

  41. Robert Schoefbeck (HEPHY Vienna) MET-Sig for Bkgs in AC and BD B A D C MET-sig MET-sig

  42. Robert Schoefbeck (HEPHY Vienna) HT2 for total Bkg. & signals in A,B & C,D C A B D HT2 HT2

  43. Robert Schoefbeck (HEPHY Vienna) MET-sig for total Bkg. & signals in A,C & B,D B A D C MET-sig MET-sig

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