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Chargino/ Neutralino Update

Chargino/ Neutralino Update. Yiming Li University of Oxford. Outline. SM suppression cut optimization Chargino / Neutralino separation optimization Summary & plan. SM bkg suppression cut. Signature of gaugino pair production: two acollinear boson. Previous cut: acollinearity > 10

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Chargino/ Neutralino Update

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  1. Chargino/ Neutralino Update Yiming Li University of Oxford 10 March 2009 SiD Benchmark Meeting

  2. Outline • SM suppression cut optimization • Chargino / Neutralino separation optimization • Summary & plan 10 March 2009 SiD Benchmark Meeting

  3. SM bkg suppression cut • Signature of gaugino pair production: two acollinear boson. • Previous cut: acollinearity > 10 • Not very effective, > 90% SM bkg survive • Try acoplanarity : 10 March 2009 SiD Benchmark Meeting

  4. Acoplanarity of two reco’d bosons Left: chargino selection; Right: neutralino selection Red: chargino /neutralino signal; Black: SM bkg. 10 March 2009 SiD Benchmark Meeting

  5. Boson energy – acoplanarity > 10 Left: chargino selection; Right: neutralino selection Red: chargino /neutralino signal; Blue: SUSY bkg; Black: SM bkg. 10 March 2009 SiD Benchmark Meeting

  6. Chargino/Neutralino Separation • So far box cut on 2d-mass plane. • Low purity-efficiency for neutralino • Try ‘chi square’ cut? (M1-MZ)^2+(M2-MZ)^2 < … M1 + M2 > 172 GeV 10 March 2009 SiD Benchmark Meeting

  7. Chargino/Neutralino Separation (M1-MZ)^2+(M2-MZ)^2 < 2d mass chi2 cut * Mz ^2 M1 + M2 > 2d mass cut Chi square cuts allow higher purity. But this result is a bit too optimistic since Acoplanarity cut is not implemented here… 10 March 2009 SiD Benchmark Meeting

  8. No cut on acoplanarity The same as previous page (right) Acoplanarity > 10 10 March 2009 SiD Benchmark Meeting

  9. Summary & plan • SM background is further suppressed by cutting on acoplanarity of two reconstructed gauge bosons. • Chargino /neutralino separation can be improved by optimizing the correlated di-jet masses cut. • Will try template fitting using all four samples to fit three SUSY particles masses. 10 March 2009 SiD Benchmark Meeting

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