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

2. 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 8/13/20082

3. Std M T -method 8/13/20083 Here example on: m0 180, m12 330 Next steps: 1.Apply one of Meff cuts (0.4, 0.8, 1.2, 1.6 TeV), 2.count remaining data and est SM evts, 3. calc significance …

4. Std M T -method 8/13/20084 SM underestimated in signal-free (xsec) regions SM overestimated in high xsec signal region True for all four MEFF cuts

5. Std M T -method 8/13/20085 M0 540, M12 510 point Norm est/truth : 91.7 % M0 900, M12 930 point Norm est/truth : 91.1 %

6. Std M T -method 8/13/20086 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 M T -method 8/13/20087 Take SM eff for each quadrant (A,B,C,D) from MC Calc norm from data, as follows AB CD A = ε SM A N SM + ε Sig 1 (1- ε Sig 2 ) (N -N SM ) B = ε SM B N SM + ε Sig 1 ε Sig 2 (N -N SM ) C = ε SM C N SM + (1-ε Sig 1 ) (1- ε Sig 2 ) (N -N SM ) D = ε SM D N SM + (1-ε Sig 1 ) ε Sig 2 )(N -N SM ) And N = A+B+C+D Solve for N, N SM, ε Sig 1, ε Sig 2 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 !

8. Advanced M T -method 8/13/20088 Estimated SM plot: shape from MC, norm from bg estiamtion -> ‘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 M T -method 8/13/20089 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 estimated SM evts are negative !!!

10. Advanced M T -method 8/13/200810 M0 180, m12 150, Meff_cut 1.2 TeV Estimated SM evts : not a number (nan) M0 60, m12 150, Meff_cut 1.2 TeV SM evts est/truth : 177.6 % M0 300, m12 150, Meff_cut 1.2 TeV Estimated SM evts : -2.8 truth SM evts : 11.0 ???

11. Advanced M T -method 8/13/200811 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 ? 8/13/200812

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