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Missing Transverse Energy Requirements from SUSY searches Dan Tovey, University of Sheffield

Missing Transverse Energy Requirements from SUSY searches Dan Tovey, University of Sheffield. Motivation. ~. c 0 1.

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Missing Transverse Energy Requirements from SUSY searches Dan Tovey, University of Sheffield

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  1. Missing Transverse Energy Requirements from SUSY searchesDan Tovey,University of Sheffield 1

  2. Motivation ~ c01 • R-Parity conserving SUSY models provide an explanation for the existence of Dark Matter in the universe  stable, neutral, Lightest Supersymmetric Particle (often lightest neutralino). • Invisible DM particles pair-produced in LHC collisions  MET. • MET / DM particle production main signature for RPC SUSY. MET ~ c01 2

  3. Non-Gaussian Tails Dietrich et al. • Inclusive SUSY searches typically impose hard cuts on jets and MET (>100 GeV). • Early data potentially exceeds Tevatron reach. • Non-gaussian MET tails enhance QCD jet backgrounds  hard to model  dangerous! • Priority (1): Minimise tails / event cleaning • CSC studies: HF (real MET) dominated tail • Priority (2): Understand remainder • Data-driven strategies 14 TeV rel11 CSC simulation: J5 sample 3

  4. Impact of LAr LVPS Problems • Impact on events passing CSC inclusive 0-lepton SUSY cuts • Uses LAr cell killer (Feng, Choudalakis) • Biggest impact on QCD jet background (fake MET) • Remediation with MET f cuts studied Gray + Hughes, SUSY ETmiss subgroup, 15th April 4

  5. Event Cleaning Duxfield • Rejection of non-collision tails (calo problems, coherent noise, beam-halo, beam-gas, cosmics) • Cell masking + interpolation • Jet EM/charged fraction • EMBPS quantities • Calo timing • Etc. • Rejection of badly-measured events (event pile-up, jet punch-through, dead material losses etc.) • PrimVtx position / object match • MuSpecShower • Jet fiducialisation / dead regions • Jet-MET f correlations • Etc. min(Δφ1, Δφ2, Δφ3) Kataoka, Asai • blue: QCD • green: tt, W, Z • red: SUSY(SU3) 0.2 Min(Df1,Df2,Df3) 5

  6. Jet Tail Estimation jets MET Duxfield CSC SUSY-3 • Use “Mercedes” events where MET vector associated with one jet. • Measure jet resolution tail comparing jet pT with MET: • Use g+jet and dijet events to measure full response function with correct tail normalisation • Recent studies to develop prescaled acolinear jet trigger: maximise stats CSC SUSY-3 6

  7. MET Tail Estimation Duxfield • Use in MC or smear multi-jet events to reproduce MET tail. • Sensitive to both ‘fake’ MET and ‘real’ MET (neutrinos) collimated in jet direction • SUSY: provides useful measure of both components together • Jet/ETmiss: Could provide a useful diagnostic tool if components can be separated CSC SUSY-3 CSC SUSY-3 7

  8. Impact of Resolution 14 TeV • Example: jets + MET + 1-lepton • Most promising channel for early data • Reject QCD jet background with lepton requirement • Background dominated by semi-leptonic ttbar and W(ln)+jets • Reject with mT(ln) > 100 GeV cut. • Significant background remains: MET mis-measurement dominates mT < 130 GeV region. • Resolution improvements directly improve S/B • Gaussian performance more important for measurements … Zhuang 10 TeV 8

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