Download
searches for supersymmetry at cdf n.
Skip this Video
Loading SlideShow in 5 Seconds..
Searches for Supersymmetry at CDF PowerPoint Presentation
Download Presentation
Searches for Supersymmetry at CDF

Searches for Supersymmetry at CDF

146 Vues Download Presentation
Télécharger la présentation

Searches for Supersymmetry at CDF

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Searches for Supersymmetry at CDF Wisconsin HEP Seminar Madison, 31 October 2006 Giulia Manca, University of Liverpool

  2. Outline • Supersymmetry • Searching for SUSY at CDF • Chargino and Neutralino • Di/Trileptons • Adding more leptons… • Conclusions • Outlook Giulia Manca, University of Liverpool

  3. Supersymmetry: what ? Standard Model Particles Susy Particles g Higgsino Higgs Higgs ~ G  e  ~ e  G  G Graviton Gravitino Leptons Force particles Sleptons Susy Force particles Quarks Squarks Extends the Standard Model (SM) by predicting a new symmetry: spin-1/2 matter particles (fermions) <=> spin-1 force carriers (bosons) Giulia Manca, University of Liverpool

  4. Supersymmetry: what ? broken  Standard Model Particles Susy Particles g Higgsino Higgs ~ Higgs ~ G  e  ci ~ e  G  G Graviton Gravitino Leptons Force particles Sleptons Susy Force particles Quarks Squarks c0i 4 neutralinos ~ New Quantum Number R-Parity If Rp conserved Lightest SParticle (LSP) stable! +1 (SM particles) 2 charginos -1 (Susy particles) Extends the Standard Model (SM) by predicting a new symmetry: spin-1/2 matter particles (fermions) <=> spin-1 force carriers (bosons) Giulia Manca, University of Liverpool

  5. Supersymmetry: why ? ~ ->LSP f H H f With SUSY H H Standard Model f Limitations of Standard Model SUSY • Stabilisation of Higgs mass at EW scale • Couplings don’t unify at one scale • Dark Matter • Dark Energy • Neutrino masses • Gravity Giulia Manca, University of Liverpool

  6. Supersymmetry: The Challenge 10    tt 1 10-1 100 events in 1 fb-1 (pb) 10-2 T. Plehn, PROSPINO (fb) 10-3     1012 q g c c± Compared to: 7.5x106 Zs, 7,000 t-antitop and 5,000 WZ 104 Dibosons SUSY 10 100 150 200 250 300 350 400 450 500 mass(GeV/c2) • VERY SMALL cross sections !! Giulia Manca, University of Liverpool

  7. Supersymmetry: how ? Rp : LSP c c± Wide range of signatures: look for SuSy specific signatures or excess in SM ones; examples: • Large Missing Energy ET AND: • Isolated leptons • Multijets …and many more! Giulia Manca, University of Liverpool

  8. mSugra: a working model hep-ph/9311269 • SUSY broken through gravity • Five parameters: • m0:common scalar mass at GUT scale • m1/2:common gaugino mass at GUT scale (i.e. M1(GUT)=M2(GUT)=M3(GUT)= M1/2 ) • A0: common trilinear scalar interaction at the GUT scale (Higgs-sfermionR-sfermionL) • tan: ratio of Higgs vacuum expectation values • Sign(), the higgsino mass parameter (determined by EWSB) • Lightest supersymmetric particle(LSP) is the 01, stable Running masses (GeV/c2) GUT scale EW scale log10(Q) (GeV) Tevatron Giulia Manca, University of Liverpool

  9. mSugra Existing Limits : LEP • LSP > MZ/2 • Chargino > 103 GeV/c2 (heavy sneutrinos); • Sleptons > 90-100 GeV/c2 for M(01)<M(R); 103 Giulia Manca, University of Liverpool

  10. Searching for Chargino and Neutralino at

  11. The signature Chargino-Neutralino production : Striking signature THREE ISOLATED LEPTONS If Rp conserved, LARGE MISSING TRANSVERSE ENERGY from the stable LSP+ • Low background • Easy to trigger LITTLE MODEL DEPENDENCE GOLDEN SIGNAL AT THE TEVATRON !! Giulia Manca, University of Liverpool

  12. Chargino-Neutralino production… 10 W* 1 10-1 (pb) 10-2 T. Plehn, PROSPINO 10-3 100 150 200 250 300 350 400 450 500 mass(GeV/c2) • Low cross section (weakly produced) c c± t-channel interferes destructively Giulia Manca, University of Liverpool

  13. …and decay Z* W* Leptons of 3rd generation are preferred Chargino Decay Leading lepton Next-To-Leading lepton Neutralino Decay Third lepton M12=180, M0=100, tan=5, A0=0,>0 M(1±)~113 GeV/c2 Giulia Manca, University of Liverpool

  14. Finding SUSY at CDF CENTRAL REGION =0 =1 Muon system =2 Drift chamber Em Calorimeter Had Calorimeter Giulia Manca, University of Liverpool

  15. The Missing Energy (MET) e  Number of Events / 2 GeV  Missing Transverse Energy (MET) Missing Transverse Energy (GeV) Real MET • Particles escaping detection Fake MET • Muon pT or jet ET mismeasurement • Instrumental effects • Cosmic ray muons • Mismeasurement of the vertex Giulia Manca, University of Liverpool

  16. Trileptons Analyses

  17. The Data Mar02-Oct05 0.7-1 fb-1 Giulia Manca, University of Liverpool

  18. Leptons to discover SUSY:The SM Calibration Samples  Low pT leptons High pT leptons • Lepton ID efficiencies • Trigger efficiencies • Calorimeter Calibration • Lepton E and P Scale • Luminosity Giulia Manca, University of Liverpool

  19. Analyses Overview  - Z* W*  +  + W*  No third lepton requirement => Higher acceptance Use e/mu only =>Very small backgrounds Sensitive to taus as 3rd lepton => Keeps acceptance at high tan Giulia Manca, University of Liverpool

  20. Like-Sign Dileptons  - Z* W*  +  + W*  • Sensitive to both chargino-neutralino and squark-gluino production • Ask for 2 high-pt (20,10) isolated leptons of the same charge • Main background : conversions! Giulia Manca, University of Liverpool

  21. Backgrounds e- e+ e-   e+ e   Backgrounds: how to reduce them? • HEAVY FLAVOUR PRODUCTION • Leptons mainly have low pT • Leptons are not isolated • MET due to neutrinos • DRELL YAN PRODUCTION + additional lepton • Leptons have mainly high pT • Small MET • Low jet activity • DIBOSON (WZ,ZZ) PRODUCTION • Leptons have high pT • Leptons are isolated and separated • MET due to neutrinos irreducible background Giulia Manca, University of Liverpool

  22. Jets Faking Leptons Electron Fake rate per Jet Inclusive Jet Sample L= 380 pb-1 • Et>20 • Et>50 • Et>70 • Et>100 ~10-4 • Inclusive Jet Triggers: • Et>20 • Et>50 • Et>70 • Et>100 ET (GeV) Inclusive Jet Sample with different trigger thresholds used to extract Fake rates and test Jet Energy Scale Giulia Manca, University of Liverpool

  23. s Analysis Strategy COUNTING EXPERIMENT • Optimiseselection criteria for best signal/background value; • Definethe signal region and keep it blind • Test agreement observed vs. expected number of events in orthogonal regions (“control regions”) • Look in the signal region and count number of SUSYevents !! • (Or set limit on the model) Giulia Manca, University of Liverpool

  24. The Basic Selection • Two leptons preselection • 1st lepton: 20(15,5), 2nd 10(8,5) GeV/c • Invariant Mass • reject resonances •    • reject Drell-Yan • Low jet activity • reject ttbar,W+jets,Z+jets • High Missing Transverse Energy • further Drell-Yan rejection Minimal number of cuts to keep analysis simple while rejecting the most overwhelming backgrounds Giulia Manca, University of Liverpool

  25. Selection criteria: (I) Mass Rejection of J/,  and Z Dielectron events Asking for the third lepton… DiElectron Mass(GeV/c2) • M<76 GeV & M>106 GeV • M> 15 (20,25) GeV • min M< 60 GeV (dielectron+track analysis) DiMuon Mass(GeV/c2) Giulia Manca, University of Liverpool

  26. (II) ( , ) and Jet Veto Rejection of DY and high jet multiplicity processes Number of Jets Et>20 GeV (e,e) (o) Number of events Sum Et of Jets (GeV) Giulia Manca, University of Liverpool

  27. (III) MET selection Further reducing DY by asking MET > 15 GeV …Still BLIND ! Giulia Manca, University of Liverpool

  28. Understanding of the Data:The Control Regions MET ?? SIGNAL REGION Diboson 10 15 DY +  Z + fake 15 76 106 Invariant Mass Control regions defined as a function of M(  ) and MET: • Each CONTROL REGION is investigated: • with different jet multiplicity check NLO processes • with 2 leptons requirementgain in statistics • with 3 leptons requirementsignal like topology Giulia Manca, University of Liverpool

  29. Control Regions for Trilepton Analyses ?? SIGNAL REGION 15 10 15 76 106 M(  ) Testing Control Regions with two leptons L=1 fb-1 • Drell-Yan • Dibosons • Heavy Flavors - SUSY • DATA MET N events/2 GeV/c 2 CDF Run II Preliminary, L=1 fb-1 Dielectron Invariant Mass(GeV/c2) MET (GeV) • Drell-Yan • WZ • ZZ • ttbar • WW • Fakes -SUSY • DATA LS-dilepton analysis has additional Control Regions to test conversion removal Dimuon PT(GeV/c) Giulia Manca, University of Liverpool

  30. LS-Dileptons Control Regions ee-like sign L=1 fb-1 L=1 fb-1 Very good agreement between SM prediction and observed data -like sign Zmass EWK low DY Zmass Conversions EWK low DY L=1 fb-1 Signal-like but opposite sign Conversion- like control-region Giulia Manca, University of Liverpool

  31. Systematic Uncertainty • Major systematic uncertainties affecting the measured number of events ee+lepton (high-pt) • Signal • Lepton ID 3.6% • Muon ID 0.8% • Background • Fake lepton estimate method 9.6% • Jet Energy Scale 4.6% • Common to both signal and background • Luminosity 6% • Theoretical Cross Section 7-10% • PDFs 2% Z->ee MC Number of events Missing Et (GeV) Giulia Manca, University of Liverpool

  32. Let’s look at the signal region !

  33. Results ! ? Look at the “SIGNAL” region LS dileptons Low-Pt trileptons High-Pt trileptons Giulia Manca, University of Liverpool

  34. Results ! Look at the “SIGNAL” region • WZ • ZZ • HeavyFlavor • DY+gamma • Fakes -SUSY • DATA N events/5 GeV/c2 Giulia Manca, University of Liverpool

  35. Results ! Look at the “SIGNAL” region Giulia Manca, University of Liverpool

  36. Trimuon Event Giulia Manca, University of Liverpool

  37. Highest lepton-pt event In the ee like-sign analysis, we observe one interesting event e- : 103 GeV MET : 25 GeV e+ : 5 GeV e- : 107 GeV  : 15 GeV Giulia Manca, University of Liverpool

  38. Limit • No SUSY :( • Combined all analyses to obtain a limit on the mass • of the chargino in mSugra-like scenario • with M(e)=M()=M() • slepton masses ~ neutralino masses • Observed limit: • M(1) ~ 127 GeV/c2 • xBR ~ 0.25 pb ~ ~ ~ • Sensitive up to masses • M(1) ~ 140 GeV/c2 • xBR ~ 0.2 pb D0 limit in similar scenario (but more Luminosity): M(1) > 140 GeV/c2 Beyond LEP and Tevatron Run I ! Giulia Manca, University of Liverpool

  39. Looking at different models… But : the limit we can set depends on the model ! In “standard” mSugra Sensitive to chargino masses of ~ 116 GeV/c2 Not able to exclude this particular region of parameter space with these results … Giulia Manca, University of Liverpool

  40. The differences in the models In Standard mSugra the BR into taus is enhanced smaller acceptance Giulia Manca, University of Liverpool

  41. From trileptons to multileptons…

  42. If R-Parity violated sparticles : Do not need to be pair-produced Can decay into SM particles Extra terms in the Super-Potential of the type : violates Lepton violates Baryon number conservation number conservation ’”couplings of the RPV vertex; R-Parity Violating SuperSymmetry  l121 ~ ~  e  0 1 e- 1 2 1 Giulia Manca, University of Liverpool

  43. R Parity Violation  ~ e  e- • RPV can be tested in Production and Decay of SUSY particles RPV decay of LSP(c01) At least four leptons in final state ! • l121 ->(eeee,eeem,eemm) +nn • l122 ->(mmmm,mmme,mmee) +nn Only one λijk ≠ 0: at the time LSP assumed to decay within the detector ( |d0|<0.02 cm ) Giulia Manca, University of Liverpool

  44. Backgrounds • Similar backgrounds to trileptons analyses • Challenge: conversions • Sensitive to all new physics with >4 leptons in the final state!! Luminosity = 346 pb-1 Fake leptons Giulia Manca, University of Liverpool

  45. Control Regions • Chosen changing the requirements on the lepton selection criteria, delta-phi, invariant mass Dielectron events Trilepton events Giulia Manca, University of Liverpool

  46. 26 total control regions By lepton type Inside & outside Z window Number of leptons Fail Df cut Plot shows relative agreement of all control regions. Error bars = ±1σ Line = perfect agreement Control Region Overview Giulia Manca, University of Liverpool

  47. Signal Regions Signal regions are consistent with background and no signal Giulia Manca, University of Liverpool

  48. Event Display Giulia Manca, University of Liverpool

  49. Limits ! ~ m(c+1) >203 GeV/c2 ~ m(c+1) >186 GeV/c2 l122>0 l121>0 D0 Limits : 122 >0 :m(c+1) >229 GeV/c2 121 >0 :m(c+1) >231 GeV/c2 Giulia Manca, University of Liverpool

  50. Summary and Outlook: Chargino and Neutralino in mSugra Multileptons signatures: • CDF analysed first bunch of data and observed no excess • Set limit already beyond LEP results ! (although model dependent ) • 1.5 fb-1 of data collected and ready to be analysed • With 4-8 fb-1 by the end of RunII we should be sensitive to Chargino masses up to ~250 GeV andsxBR~ 0.05-0.01 pb !! Ellis, Heinemeyer, Olive, Weiglein, hep-ph\0411216 Favoured by EW precision data One e like sign event… Giulia Manca, University of Liverpool