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Search for RPV-SUSY in the e+e+tau’s channel from decays with coupling

Search for RPV-SUSY in the e+e+tau’s channel from decays with coupling. Anne-Catherine Le Bihan Francois Charles Institut de Recherches Subatomiques Strasbourg. R-parity violating supersymmetry. Extension of MSSM superpontential : Violates conservation of R-parity :

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Search for RPV-SUSY in the e+e+tau’s channel from decays with coupling

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  1. Search for RPV-SUSY in the e+e+tau’s channel from decays with coupling Anne-Catherine Le Bihan Francois Charles Institut de Recherches Subatomiques Strasbourg

  2. R-parity violating supersymmetry Extension of MSSM superpontential : Violates conservation of R-parity : Susy particles produced in association via gauge couplings, mainly Followed by decay through RPV coupling Final state : 2 LSP decays with coupling : => 2 ’s + 2 electrons or 3 ’s + 1 electron or 4 ’s and MET => Look for 2 isolated electrons + at least 1 hadronic tau Summer Physics Workshop 04

  3. Data sample Preselection : 2EM CSG skim, fixed with d0correct v6 - v6-a Trigger : single EM and Di-EM Bad calo runs, bad met and ring of fire lumi-blocks removed Duplicated events and bad sam files removed Luminosity computed with lm_access : = 223.5 pb-1 Remove events with electrons in bad cal regions : = 198. 7 pb-1 Summer Physics Workshop 04

  4. can be lighter than : • -> : 100 % • -> : 100 % • => higher tau final state multiplicity RPV signal Points generated with susygen v03-00-43 , 133 = 0.003: Summer Physics Workshop 04

  5. Cut flow of the analysis 1) 2 electrons 18 < M(ee) < 80 Gev/c2 2) at least 1 hadronic tau (decay mode or ) outside the ICD region M0 =80 m1/2 =170 Mee 3) > 1.5 MET M0 =80 m1/2 =170 M0 =80 m1/2 =170 Summer Physics Workshop 04

  6. 2 electrons preselection : M(e,e)>18 GeV/c^2 • Electron Id cuts : • iso < 0.15 • emf > 0.9 • HMx8 < 50 • likelihood >0.3 • |z_e - z_vtx|<1. cm • pT>10 GeV/c • |z_vtx|<60 cm Definitions : loose electron : all id cuts except likelihood tight electron : all id cuts Summer Physics Workshop 04

  7. Missing Et strategy • Signal exhibits moderate • DY Z->ee is characterized by low Usefull variable is : takes into account statistical flucuation of qcd jets energy mismeasurement MET ( GeV) Missing ET definition : • METB_CORR_CALOMU • corrected in MC with pT electron smearing • smear METx (resp. METy) with (3./MET+0.45*METxy)*METx/MET Summer Physics Workshop 04

  8. Use allmost all EM and Di-EM triggers , v8-v12 Use Ulla’s method to determine the turn-on function : -> compare MC/data for events with 2 electrons, 15<M(ee)<60, met<10 Freq((pT-12.2)/sqrt(pT*0.66)) pT of leading electron (Gev/c) Trigger efficiency Summer Physics Workshop 04

  9. Data/MC electron Id efficiencies use tag and probe method on tight electron + track invariant mass: _CC(data) : 81 %  _CC(MC): 86 % _EC(data) : 67 % _EC(MC): 93% Likelihood efficiency : use tag and probe method on tight electron + loose electron invariant mass: _CC(data) :89%  _CC(MC):97% _EC(data) :68% _EC(MC):65% Summer Physics Workshop 04

  10. QCD background estimate • Define multi-jet QCD background sample by inverting the cut on Hmatrix and likelihood for both electrons • .Use a likesign sample to estimate the QCD background : NQCD = 2* (N_ES(data) - N_ES(MC) ) (assume equiprobable sign distribition OS/ES in QCD) • Don’t use directly the likesign sample to describe the QCD background since signal can contain like sign events • Scale the QCD sample with inverted Hmatrix and likelihood to NQCD. Summer Physics Workshop 04

  11. Tau identification in hadronic finalstates • A tau candidate consists of : • a calorimeter cluster found by simple cone algorithm • cone size R=0.3, isolation cone R =0.5 • EM sub-clusters • Tracks in 0.5 cone consistent with tau mass • The tau condidates are classified into 3 categories : • type 1 : -> : 1 track CAL cluster no EM sub-cluster • type 2 : -> : 1 track Cal cluster and EM sub-cluster • type 3 : 3 prongs : at least 2 tracks Use 3 neural networks, one for each type, based on shower shape, isolation, core, energy fraction, sub-clusters in EM3, to separate taus from QCD background. Summer Physics Workshop 04

  12. Other background than QCD jets ?Electron contamination Apply a veto on a tau candidates matched to a tight electron. Are still loose electron misidentified as taus ? Tag and probe method on loose electon in Z peak : 41.8  0.6 % misidentified as tau Use additional NN to remove electron contamination : 7.2 0.3 % misidentified as tau Loose electron: all id cuts except likelihood Summer Physics Workshop 04

  13. pT oftau candidate Hadronic taus in p14 data ? NN efficiencies ? • Select sample with 1isolated +  ,  ( )>2.7, 20<|M()|<60, n <2, pT()>14 , pT()>8 •  Candidate : R>0.7 and NN(e)>0.9 • Enriched sample of Z->-> • and  have opposite sign • Background sample :  and  have same sign • Estimate the Z->content : fit PT of tau candidate for type 1 and 2 only Check fit on calorimeter and tracking quantities used to discriminate between taus and QCD jets / check behaviour after NN cuts Summer Physics Workshop 04

  14. (ET(tower1)+ET(tower2))/ET Check fit on NN input variables (1) Cluster width : after NN cut Summer Physics Workshop 04

  15. Check fit on NN input variables (2) cluster isolation pT(R=0.5)-pT(R=0.3)/pT(R=0.3) after NN cut Summer Physics Workshop 04

  16. Check fit on NN input variables (3) Tracking combined variables after NN cut after NN cut Summer Physics Workshop 04

  17. pT and  after NN cuts Data/MC scale factor for tau identification : 0.90.1 Summer Physics Workshop 04

  18. Estimate of NN efficiency on QCD jets Efficiency ratio data/MC for real qcd jets was estimated in the dielectron data sample : The number of taus in the Z peak mass region (requiring 2 OS electrons ) was compared to MC Zee. This shows good agreement and we obtain a ratio for the QCD jet efficiency factor betweenMC and data equal to 1 Summer Physics Workshop 04

  19. e+e+tau selection : • Tau Id cuts : • (e,)>0.1, (,)>0.1, pT()>7 GeV/c • Cut of 0.9 on neural networks for QCD background • Cut of 0.9 on neural network for electron background • Cut on where is the energy deposited in the CH calorimeter in a 5x5 window around the  track : against  background Summer Physics Workshop 04

  20. Selection of e+e+’s final states Acceptance : Expected events in 198.7 pb-1 : Summer Physics Workshop 04

  21. Comparison Data / SM-background : Summer Physics Workshop 04

  22. The very preliminary results so far … tan=10, >0, A0=0, m0=80 Summer Physics Workshop 04

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