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Searches for Gauge-Mediated SUSY Breaking Topologies in e + e - Collisions at LEP2

OPAL Dispatch : DP1881 Comments to : Naoko.Kanaya@cern.ch, Katja.Klein@cern.ch, Robert.McPherson@cern.ch, Christoph.Rembser@cern.ch Comments by : 20 October 2004 12:00

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Searches for Gauge-Mediated SUSY Breaking Topologies in e + e - Collisions at LEP2

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  1. OPAL Dispatch :DP1881 Comments to :Naoko.Kanaya@cern.ch, Katja.Klein@cern.ch, Robert.McPherson@cern.ch, Christoph.Rembser@cern.ch Comments by :20 October 2004 12:00 OPAL GMSB WG : G.Benelli, E.Duchovni, P.Giacomelli, M.Hamann, N.Kanaya, K.Klein, P.Krieger, T.Marchant, R.McPherson, S.Mihara, K.Nagai, C.Rembser, D.Toya, P.Tran, I.Trigger, G.Wilson, T.Wyatt Editorial Board :S.Braibant, P.Ferrari, M.Gruwe, E.Gross, T.Schoerner More Information :http://rembser.home.cern.ch/rembser/eb_gmsb/eboard.html Searches for Gauge-Mediated SUSY Breaking Topologies in e+e- Collisions at LEP2 OPAL Thursday Meeting 21 October 2004

  2. Case strong • But related to mass? • Planck scale?? • Here, case for EW scale new physics ... Case for Physics “BSM” • Quark/Lepton generations •  Compositeness? Substructure? Strings? •  Common sub-elements quarks/leptons? • Matter-Antimatter asymmetry • CPV in SM (K,B) + Big bang: • Not enough to explain observations • F.T. of cosmological constant • Higgs energy density  1050 GeV/cm3 • Observationally: < 10-4 GeV/cm3 • Fine-Tuning of Higgs mass • Particle loop corrections to MH ~L2 • If theory cut-offL ~ O(MP) • Fine tuning of corrections 1 : 1020 needed Rob McPherson

  3. dM2H (200 GeV)2 M2H(tree) 0 dM2H(top) Higgs F.T.: TeV scale new physics Take MH = 200 GeV & scale cut-off L 10 TeV • Top loops: • W/Z loops: • H loops: Process dM2H  -100 M2H  10 M2H • Fine tuning too large L < 10 TeV • Two choices • Cut off theory • Cancel loops  5 M2H Rob McPherson

  4. t b q* { } W1 W2 W3 u d u d c s c s t b t b COMPOSITE? MORE? ( ) ( ) ( ) ( ) ( ) ( ) B nL L l* EWSB ne e ne e nmm nmm ntt ntt n* ( ) ( ) ( ) ( ) ( ) ( ) H { W Zg} Z LQ Fine ~ ~ ~ ~ ~ ~ SUSY W Zg Tuning ~ ~ ~ SUSY mSUGRA ~ ~ ~ GMSB h H H ~ ~ ~ 2HDM AMSB ~ ~ ~ h H A H (RPV ?) Higgs triplets, little Higgs Low Scale Gravity TechniColour Non Commutative Geometry Extra Dimensions Roadmap: Beyond the S.M. Rob McPherson

  5. Favourite TeV scale new physics: SUSY t b q* { } W1 W2 W3 u d c s t b COMPOSITE? MORE? ( ) ( ) ( ) B nL L l* EWSB ne e nmm ntt n* ( ) ( ) ( ) H { W Zg} Z LQ ~ ~ ~ ~ ~ ~ u d c s t b SUSY W Zg ( ) ( ) ( ) ~ ~ ~ SUSY mSUGRA ~ ~ ~ GMSB h H H ~ ~ ~ Fine 2HDM ne e nmm ntt ( ) ( ) ( ) AMSB Tuning ~ ~ ~ h H A H (RPV ?) H (eg:TRIPLET) Low Scale Gravity TechniColour Non Commutative Geometry Extra Dimensions Rob McPherson

  6. Why SUSY?  - • Top loops: • W/Z loops:  - etc. • SUSY perturbatively cancels divergences so long as sparticle masses not too high • Can avoid all precision EW constraints Rob McPherson

  7. ~   } ` ~ ~ h,H,A h,H ~ Z Z0 ~ } H± H± Enlarged ~ 01-4 ~ W± W± ~ g g ~ { ~ ~ l1,2 lL,R lL,R ±1,2 ~ L L { ~ ~ q 1,2 q L,R q L,R ~ goldstino G G ~ G (s)particles List “General” MSSM Rob McPherson

  8. Why not SUSY? • SUSY: M(particle) = M(sparticle)  should have seen it! • SUSY must be a broken symmetry • General MSSM: > 100 new parameters... •  Entire parameter space has unfortunate features ... RPV: Additional unpleasant features General SUSY: different particle masses + mixing  LFV, FCNC • SUSY Model construction: • Ignore SUSY details, but pick mediation mechanism • Mediation must not induce mixing  LFV, FCNC etc. • Either R-Parity conservation or (very?) artificial ltuning Rob McPherson

  9. FCNC problems Fix in mSUGRA 4(+1) Params SUSY/GUT: sin2qW CDM Candidate 0 Decay chains to 0 SUSY “Missing Energy” signature No severe FCNC, LFV CDM difficult (warm?) NLSP 0 or l Decay chains to NLSP then to G Extra g orl Arbitrary suppression Lifetime Signatures Minimal model 5(+1) Par. Visible e,m,t,...,W,Z ~ ~ ~ ~ ~ e,m,t,...,W,Z SUSY Breaking (Mediation) Gravity Gauge F~ 1011 GeV 103<F<1010 GeV Hidden SUSY ~ ~ (heavy G) (light G) M M~MP~1018 GeV 103<M<1015 GeV ~ ~ ~ ~ ~ Rob McPherson

  10. ~ ~ ~ ~ l l G 0  g G Gauge Mediation: Searches ... ct ~ 0 : l l+ ET4x l +ETt t+(l t l t)+ET 0 < ct <  : 2x Kink/IP+ET2xl+2x Kink/IP+ ET2x Kink/IP+ (l t lt)+ ET ct ~  : 2x stable 2xl + 2x stable 2x stable + (ltlt) ct ~ 0 : g g+ ET Jets / l +g g +ETl l+ g g+ET 0 < ct <  : n.p. g+ET Jets /l+ n.p.g+ ETl l+ n.p. g + ET ct ~  : + ETJets / l + ETl l + ET Rob McPherson

  11. Rob McPherson

  12. GMSB PR Dispatch • Summarize all relevant OPAL searches • Brief descriptions of analyses published in other PR • More detailed description of analyses published here first • Discuss combination strategy • Particularly handing signal+background overlap for different NLSP lifetime analyses •  Model independent results • Cross-section limits in each channel valid for all NLSP lifetimes • Model depend limits • Detailed scans in GMSB parameter space 42 Pages of text 20 Pages of figures Rob McPherson

  13. ~ ~ ~ ~ l l G 0  g G Selection: > 2 leptons + ET ct ~ 0 : l l+ ET4x l +ETt t+(l t l t)+ET 0 < ct <  : 2x Kink/IP+ET2xl+2x Kink/IP+ ET2x Kink/IP+ (l t lt)+ ET ct ~  : 2x stable 2xl + 2x stable 2x stable + (ltlt) ct ~ 0 : g g+ ET Jets / l +g g +ETl l+ g g+ET 0 < ct <  : n.p. g+ET Jets /l+ n.p.g+ ETl l+ n.p. g + ET ct ~  : + ETJets / l + ETl l + ET Rob McPherson

  14. Selection: > 2 leptons + ET • See: TN712 for details • Standard SUSY preselection • Kinematic cuts removing (in)famous low multiplicity excess • facop, |cosqmiss|, Evis • Require at least 4 jets consistent with parton lepton (e,m,t) • 5 data events with 4.2 ± 0.3 (stat) +1.4/-0.4 (syst) expected • Use this for 6-lepton final states, e  50% • Additional cut on fraction of energy outside of “lepton jets” • 2 data events with 2.8 ± 0.3(stat) +0.9/-0.3(syst) expected • Use this for 4-lepton final states, e  50% equal BR, 40% 4xt • Largest systematic errors • Background: Generator comparisons: 10% 4f, 40% M.P. Modeling of cut variables: +31.5/-5.6 % • Signal: Modeling of cut variables: ±4% Rob McPherson

  15. Selection: > 2 leptons + ET Rob McPherson

  16. ~ ~ ~ ~ l l G 0  g G Selection: Large Impact Parameter ct ~ 0 : l l+ ET4x l +ETt t+(l t l t)+ET 0 < ct <  : 2x Kink/IP+ET2xl+2x Kink/IP+ ET2x Kink/IP+ (l t lt)+ ET ct ~  : 2x stable 2xl + 2x stable 2x stable + (ltlt) ct ~ 0 : g g+ ET Jets / l +g g +ETl l+ g g+ET 0 < ct <  : n.p. g+ET Jets /l+ n.p.g+ ETl l+ n.p. g + ET ct ~  : + ETJets / l + ETl l + ET Rob McPherson

  17. Selection: Large Impact Parameter • See: K.Klein’s PhD thesis for details, linked from http://rembser.home.cern.ch/rembser/eb_gmsb/eboard.html • charged-track driven analysis • Primary charged tracks: “good tracks” with |d0| < 0.05 cm • Secondary charged tracks: “good tracks” with |d0| > 0.05 cm • Other tracks charged tracks: rest • Place different requirements on number of each type of track for different channels • Direct NLSP production: 2 secondary, no primary • 4-lepton: 2 secondary, 2 primary etc. • Additional cuts to remove cosmic, unmodelled backgrounds ... • charge conservation, TOF cuts, longitudinal IP, Mvis • Good agreement between data and background expectation • Largest systematic errors • Backgrounds: MC statistics as large as 50% track-resolution (smearing) usually smaller than MC stats (but for single √s can be 100% due to small MC stats) Rob McPherson

  18. Selection: Large Impact Parameter Rob McPherson

  19. ~ ~ ~ ~ l l G 0  g G Selection: Kinked Tracks ct ~ 0 : l l+ ET4x l +ETt t+(l t l t)+ET 0 < ct <  : 2x Kink/IP+ET2xl+2x Kink/IP+ ET2x Kink/IP+ (l t lt)+ ET ct ~  : 2x stable 2xl + 2x stable 2x stable + (ltlt) ct ~ 0 : g g+ ET Jets / l +g g +ETl l+ g g+ET 0 < ct <  : n.p. g+ET Jets /l+ n.p.g+ ETl l+ n.p. g + ET ct ~  : + ETJets / l + ETl l + ET Rob McPherson

  20. Selection: Kinked Tracks • See: OPAL PN504 for details • charged-track driven analysis • Primary charged tracks: |d0| < 5 cm, |z0| < 20 cm, Pt > 110 MeV, no Calo,m • Secondary charged tracks: |d0| > 2.5 cm, Pt > 110 MeV, no SI, CV • Other tracks charged tracks: rest • Define kink as primary track intersecting with secondary track inside detector • Demand at least one kink • Additional cuts depending on channel • number of tracks, track Pt, kink vertex location, effective mass of kink, number of secondary tracks per kink • Expected background dominated by 2-photon events with hadronic interactions • Good agreement between data and background expectation in all selections • Largest systematic errors • Backgrounds: MC statistics as large as 50% Track-resolution (smearing) usually smaller than MC stats (but for single √s can be 100% due to small MC stats) Rob McPherson

  21. Selection: Kinked Tracks Rob McPherson

  22. ~ ~ ~ ~ l l G 0  g G Selection: ~ Stable Charged Tracks ct ~ 0 : l l+ ET4x l +ETt t+(l t l t)+ET 0 < ct <  : 2x Kink/IP+ET2xl+2x Kink/IP+ ET2x Kink/IP+ (l t lt)+ ET ct ~  : 2x stable 2xl + 2x stable 2x stable + (ltlt) ct ~ 0 : g g+ ET Jets / l +g g +ETl l+ g g+ET 0 < ct <  : n.p. g+ET Jets /l+ n.p.g+ ETl l+ n.p. g + ET ct ~  : + ETJets / l + ETl l + ET Rob McPherson

  23. Selection: ~ Stable Charged Tracks • See: TN738 and M.Hamann’s PhD thesis for details, linked at http://rembser.home.cern.ch/rembser/eb_gmsb/eboard.html • Improved reconstruction allowing CJ hits with saturated dE/dX to be used • Demand at least one good charged track with non-Standard-Model dE/dX • Other cuts to reduce gamma-gamma and other backgrounds • Eecal/√s, PZ/P, Ptrack in event, isolation around anomalous track • But limited cuts on calorimeters and charged track multiplicity •  sensitivity to single high dE/dX tracks, multi-track events, ... • Depend on Monopole trigger (present in Y2K run) for efficiency for the saturated dE/dX events (track trigger does not necessarily select these events) • 0 data events selected, 0.78 ± 0.38 (stat) ± 0.10 (syst) expected • Typical selection efficiencies: to 95% for particles with M ~ Ebeam • Largest systematic errors • Track measurement errors : ± 10% • dE/dX uncertainties : ± 5% Rob McPherson

  24. Selection: ~ Stable Charged Tracks Rob McPherson

  25. ~ ~ e e  t t (t = 10-6 s), √s = 208 GeV Efficiency: ~ Stable Charged Tracks Rob McPherson

  26. ~ ~ ~ ~ l l G 0  g G Selection: g + X + ET ct ~ 0 : l l+ ET4x l +ETt t+(l t l t)+ET 0 < ct <  : 2x Kink/IP+ET2xl+2x Kink/IP+ ET2x Kink/IP+ (l t lt)+ ET ct ~  : 2x stable 2xl + 2x stable 2x stable + (ltlt) ct ~ 0 : g g+ ET Jets / l +g g +ETl l+ g g+ET 0 < ct <  : n.p. g+ET Jets /l+ n.p.g+ ETl l+ n.p. g + ET ct ~  : + ETJets / l + ETl l + ET Rob McPherson

  27. Selection: g + X + ET • See N.Kanaya’s PhD thesis for details, linked from http://rembser.home.cern.ch/rembser/eb_gmsb/eboard.html • Standard SUSY preselection • Analysis concentrates on 2 goodg • Different selections for • l lg g • Jets + g g • 3 DM regions • Jets+ l +g g • 2 DM regions • variables: facop, |cosqmiss|, Evis, Eg, gisolation • Selected events consistent with expected background • Efficiencies: typically ~ 50%, but can be ~10% in “edge” cases • Largest systematic: • g isolation cuts: studied with Z-peak data, ~ 20% for background Rob McPherson

  28. Selection: g + X + ET Rob McPherson

  29. Summary of all results Rob McPherson

  30. Combination Strategy • Use identical signal and background MC • Produce run and event lists • Define “overlap” analyses : > 0.1% overlap • Never more than 2 analyses satisfy this • Can be significant signal overlap: up to 40% • Almost never background overlap • Only exception: charginos with/without g • No data event was selected by > 1 analysis • Difficult to generate enough signal MC for all lifetimes • Use a simplifying technique for efficiency interpolation Rob McPherson

  31. ~ ~ ~ ~ l l G 0  g G Full MC Grids: ~ 7M signal events produced • Production: • Private Geant3/GOPAL build for lifetime, additional detector interactions, ... • Processed/reprocessed/fixed by constant attention from Steve O’Neale Rob McPherson

  32. Lifetime Efficiency Function • See: OPAL TN643 for details • Decay of NLSP  exp(-t / t) • Detector is sphere with fiducial volume range: • lstart  lstop • Efficiency is constant between lstart and lstop • ISR/FSR not explicitly considered • esingle = e0 x [ exp(- lstart / lmean(m1,t) – exp(- lstop / lmean(m1,t) ] • Using lifetime MC grid: • Fit for e0 , lstart , lstop • Systematic errors: • Remove each point from fit, predict esingle , measure difference • For cascade decades, pick worst case for central value Rob McPherson

  33. Efficiency function: example Rob McPherson

  34. Each channel: cross-section limits • For direct NLSP pair production • Take cross-section evolution from theory scan • For channels with cascades • Assume generic s-channel g propagator • Scalar : sb3 / s • Spin ½ : sb / s • Scan over lifetimes, intermediate masses • Pick maximum (worst case) • Combine multi-channel (with overlap as separate channels) using Tom’s code Rob McPherson

  35. Example limit: direct NLSP production Rob McPherson

  36. ~ Example: cascade decays 0witht1 NLSP Rob McPherson

  37. mGMSB Theoretical model scan - SM + 5 ½ parameters - √s = 182.7, 188.7, 191.6, 195.5, 199.5, 201.6, 205.1, 206.7, 208.1 GeV - Have Full theory scan DB (takes up most of a 60 GB disk I would like back ...) - Use Mtop = 175 GeV Rob McPherson

  38. Exclusion Limits • Direct NLSP production: • limits based only on direct production channel computed • Take lowest (worst) limit using complete theory DB scan • Valid for all lifetimes • Constraints on GMSB parameter space • Use theory scan to calculated s, BR for each channel • Compare s x BR or s x BR2 • Also calculate Higgs mass (always SM-like) for each point • Show contour for MH = 114.4 GeV (LEP combined) • Also 114.4 – 3 = 111.4 GeV to show theory error ~ 3 GeV • Also 111.4 – 5 = 106.4 GeV to show impact of Mtop error ~ 5 GeV Rob McPherson

  39. ~ ~ ~ ~ l l G 0  g G Example theory scan limits ~ ~ l 0 ~ ~ e,m THEORETICALLY INACCESSIBLE ~ (t NLSP) ~ ± MH=114.4 GeV MH=111.4 GeV MH=106.4 GeV ~ ~ ± LEP 1 l Rob McPherson

  40. What’s the message ? Rob McPherson

  41. The End Rob McPherson

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