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Data-driven BG estimation on mSUGRA grid

Data-driven BG estimation on mSUGRA grid. CAT SUSY, Aug 13 2008 Moritz Backes & Till Eifert UoG. Std M T -method. Project data (=SUSY+SM) from low-M T to high-M T Scale norm of projection by ratio of M T in low MET (100-150 GeV ) Correlations not taken into account.

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Data-driven BG estimation on mSUGRA grid

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  1. Data-driven BG estimation on mSUGRA grid CAT SUSY, Aug 13 2008 Moritz Backes & Till Eifert UoG

  2. Std MT-method • Project data (=SUSY+SM) from low-MT to high-MT • Scale norm of projection by ratio of MT in low MET (100-150 GeV) • Correlations not taken into account

  3. Std MT-method Here example on: m0 180, m12 330 Next steps: • Apply one of Meff cuts (0.4, 0.8, 1.2, 1.6 TeV), • count remaining data and est SM evts, • calc significance …

  4. Std MT-method • SM underestimated in signal-free (xsec) regions • SM overestimated in high xsec signal region • True for all four MEFF cuts

  5. Std MT-method • M0 540, M12 510 point • Norm est/truth : 91.7 % • M0 900, M12 930 point • Norm est/truth : 91.1 %

  6. Std MT-method • Discovery reach therefore increased w.r.t. SM from MC ! • Here, assumed systematic on SM of 20% • SM from MC, 20% sys on W, Z, tops, 50% on QCD (~no contribution in 1-lepton)

  7. Advanced MT-method • Take SM eff for each quadrant (A,B,C,D) from MC • Calc norm from data, as follows • A = εSMANSM + εSig1 (1- εSig2) (N -NSM) • B = εSMB NSM + εSig1 εSig2(N -NSM) • C = εSMC NSM + (1-εSig1 ) (1- εSig2) (N -NSM) • D = εSMD NSM + (1-εSig1 ) εSig2)(N -NSM) • And N = A+B+C+D • Solve for N, NSM, εSig1 , εSig2 A B • Takes SM correlations into account • Using Meff instead of MET, we can adjust the cut to agree with final Meff cut (0.4, 0.8, 1.2, 1.6 TeV) • Thus, SM evts in B is what we want ! C D

  8. Advanced MT-method • Estimated SM plot: shape from MC, norm from bgestiamtion -> ‘data’ • Very good result : norm est / truth = 100.65% • Here, an Meff cut of 1.2 TeV has been applied (not seen in plot, but used in estimation method!)

  9. Advanced MT-method • SM correctly estimated in signal-free (xsec) regions • SM wrongly estimated (mainly too low) in high xsec signal region • The higher the MEFF cuts, the bigger the problematic region • Note, in some cases the estimatedSM evts are negative !!!

  10. Advanced MT-method • M0 180, m12 150, Meff_cut 1.2 TeV • Estimated SM evts : not a number (nan) • M0 300, m12 150, Meff_cut 1.2 TeV • Estimated SM evts : -2.8 • truth SM evts : 11.0 • M0 60, m12 150, Meff_cut 1.2 TeV • SM evtsest/truth : 177.6 % ???

  11. Advanced MT-method • Discovery reach seems very similar (since we cut off at 7 sigma AND we have four Meff cuts to pick the best) • Here, assumed systematic on SM of 20% • SM from MC, 20% sys on W, Z, tops, 50% on QCD (~no contribution in 1-lepton)

  12. Go on … • Write things together • Correlations in std MT-method ? Change from MET -> MEFF as well ? • For advanced MT-method: • Show that we can control problematic estimates by plot: est. SM evts as func of MEFF, MT cut • If ~ constant -> OK • Otherwise -> problematic • Agrees with problematic points on grid ? • Study effect of systematic errors: • Vary MC shape (change SM eff of quadrants) • What else ?

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