1 / 42

Tevatron Searches for Higgs and SUSY

Tevatron Searches for Higgs and SUSY. Dan Claes. for the. and. collaborations. Hadronic Structure 2007 September 3-7 Comenius University Study and Congress Center Modra-Harmónia, Slovakia. Searches for contributions to observed events by Higgs decays as well as

lethia
Download Presentation

Tevatron Searches for Higgs and SUSY

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Tevatron Searches for Higgs and SUSY Dan Claes for the and collaborations Hadronic Structure 2007 September 3-7 Comenius University Study and Congress Center Modra-Harmónia, Slovakia

  2. Searches for contributions to observed events by Higgs decays as well as new phenomena beyond the Standard Model are intensifying as the Tevatron data set grows. Chicago  p p 1.96 TeV Booster p CDF DØ Tevatron p p source Main Injector & Recycler CDF Proton-antiproton collider operating at COM energy of 1.96 TeV

  3. Collider Run II Integrated Luminosity ~3 fb-1 recorded! All the results shown today are based on analysis of 1+ fb-1 Collider Run II Peak Luminosity 4-8 fb-1 by 2009 • Will run for at least two more years!

  4. Higgs production at the Tevatron t H g t g t have seen evidence for single top! one in ~1012 events could be a Higgs boson! q W/Z W/Z q H

  5. Nature appears to respect gauge invariance masslessness Through electroweak symmetry breaking within the complex scalar field, V(), of the Higgs the gauge bosons W,Z acquire mass and a spin-0 Higgs boson appears, its own mass unspecified though theoretical considerations do constrain it. Higgs self-coupling diverges Allowed unstable vacuum

  6. mH>114.4 GeV/c2 at 95% confidence Direct searches reveal The latest LEP Electroweak Working Group fit yields a preferred value of: A Standard Model Higgs should be LIGHT! A light Higgs might be around the corner (if the SM is correct) mH < 144 GeV at 95% confidence limit

  7. H->WW Excluded at LEP Most sensitive searches: bb mH<135 GeV/c2 • produced with W or Z boson • decay to b quark pair mH>135 GeV/c2 Analysis Strategy mH < 135 GeV WH/ZH + H bb mH > 135 GeVGluon fusion + HWW Background top, Wbb, Zbb WW, DY, WZ • direct ggH production • decays to W boson pair

  8. electron/muon neutrino Selection - one or two tagged b-jets - e or m with pT > 15 GeV - ET > 20 GeV DØ: 4 non-overlapping samples - e or m with - 1 “tight” or 2 “loose” b-tags CDF: 2 exclusive samples using different b-tagging algorithms

  9. Limits set cutting on NN output: DØ exp, obs CDF exp, obs 95/SM = 9.05, 11.19.95, 10.1

  10. ZH bb b jet Selection: - two acoplanar jets (exactly 2 – CDF) - ≥ 1 tagged b-jets (CDF) 2 tagged b-jets (DØ) - ET > 55 GeV (CDF) 50 GeV (DØ) b jet

  11. ZH bb Backgrounds : - W+heavy flavour jets - Z +heavy flavour jets - top pairs

  12. Look for enhanced production of Zs: e, e, • Selection: • require two isolated muons or • electrons in Z mass window • -one or two tagged b-jets CDF - corrects its b-jets with ET projections

  13. Separate NN trained to reject two main background processes: 2 ‘loose’ b-tags 1 ‘tight’ b-tag Z + jets top pairs 95/SM at MH = 115 GeV 20.4 exp 16 17.8 obs 16

  14. → hadrons → e or  → e or  ee same charge di-lepton mass Selection: - 2 isolated leptons (pT > 15 GeV) (electrons and/or muons)‏ - kinematic likelihood selection e like-sign!  , m , ET or  min T “flips”: charge mis-identification estimated from data: : solenoid vs toroid e: solenoid vs (track,calorimeter) 

  15. L = 1 fb-1 95/SM ~ 18 for MH = 160 GeV

  16. Selection: - two isolated leptons - large ETmiss - Less than 2 jets (>15 GeV) CDF leptons will tend to align If WW comes from a spin-0 Higgs Higgs: small( ) WW: large( )

  17. Matrix Element Technique most sensitive at high masses

  18. SUMMER 2006 • Combines sixteenmutually exclusive final states for WH, ZH, WW - 10.4  SM at mH=115 GeV - 3.8  SM at mH=160 GeV • Today I’ll report on recent progress • updated CDF & DZero low & high mass 1+ fb-1 analyses

  19. Combines sixteen mutually exclusive final states for WH, ZH, WW 7.7  SM at mH=115 GeV 1.4  SM at mH=160 GeV

  20. Higgs Bosons Beyond the Standard Model The Standard Model assumes a single complex Higgs doublet generates W/Z masses and a massive chargeless spin-0 boson, the Higgs, H • Hu/Hd couple to up- and down- type quarks • tanβ is the ratio of their vev’s tanβ= <Hu>/<Hd> • EWSB results in 4 massive scalar (h, H, H±) and one massive pseudoscalar (A) Higgs bosons () 2HDM: 2 Higgs Doublet Models • fully parameterized • (at tree level) by tanβ, mA • with radiative corrections • that depend on stop mixing Minimal Supersymmetric Model At large tan enhanced f0bb and f0tt couplings mean large Higgs production rates at hadron colliders!

  21. Fermiophobic Higgs Decaying to 3g A production mechanism unique to hadron colliders is accessible to the Tevatron provided mH is not too large! For tan b> 1, mH < 200 GeV and mh< 90 GeV B(h )  1 and B( HhW )  1 • Background rates in 3g final state are very low • measured fake rates for Zg or Wgg • tri-photon production extrapolated from di-photon sample No obvious structure in diphoton mass spectrum Optimizing selection on 3s ET >30, 25, 25GeV 0events observed 1.1  0.2expected background

  22. Fermiophobic Higgs Decaying to 3g Optimizing final selection on 3s ET >30, 20, 25GeV and pT > 25 GeV rejects background LEP2 limits of 108 GeV/c2 assumed SM coupling hf VV

  23. Fermiophobic Higgs in 2g+ X 1.1 fb-1 Selection: 2 photons (pT > 25 GeV) Background: , +jet and jet+jet mh>92GeV at 95% CL

  24.  b (b) bb b(b) Search At high tan Br(H/Abb)  90%, but swamped by QCD background  0 b Look for associated production with bs. b g Selection: - 3 b-tagged jets‏ - look for a signal in the invariant mass of two leading jets g b  0 b g The shape from double–tagged events ( mis-tagged rate) Normalized to the 3b-tagged sample outside the signal mass window. ALPGEN MC

  25.  b (b) bb b(b) Search • CDF found two useful discriminators • m12 (invariant mass, 2 leading jets) • mdiff = mass of the tracks assigned to jet from the displaced vertex 0.980 fb-1 0.90 fb-1

  26. Neutral MSSM Higgs  had Main backgrounds: Z (irreducible), W+jets, Zee,, mulijet, di-boson DØ: -channel only CDF: e, , e+ channels • 1 isolated  • separated from • opposite sign • hadronic  • isolated e or  • separated from • opposite sign • hadronic  • set of 3 NNs discri- • minate  from jets • variable-size cone algorithm for  > 55 GeV • mvis < 20 GeV removes • remaining W background • Ws removed by a cut on the MET • projected on the bisector between s.

  27. Neutral MSSM Higgs  had Small excess in CDF’s e+ channel • but < 2 effect • not observed in CDF e channel While DØ is in good agreement with SM

  28. Neutral MSSM Higgs  had Both experiments give similar results: in the 90<mA<200 GeV region tan> ~40-60 excluded for the no-mixing and mhmax benchmarks

  29. SUPERSYMMETRY Particle Name Symbol Spartner Name Symbol gluon g gluino g charged Higgs H+ chargino 1,2 charged weak boson light Higgs h neutralino 1,2,3,4 heavy Higgs Hpseudoscalar Higgs Aneutral weak boson Z photon  quark q squark qR,L lepton l slepton lR,L ~ ~ 0 ~  ~ ~ • The LightestSupersymmetricParticleprovides • ET if the LSP is stable and R-parity is conserved • photons and ET if the LSP is a gravitino and NLSP a neutralino • long-lived particles if the LSP decays weakly • SUSY particles are heavy • high pT final state objects

  30. Minimal Supersymmetric SM Extension adding the fewest new particles • 2 Higgs doublet h0 H0 A0 H+ • and described by 4 parameters M1U(1) M2U(2) gaugino mass parameter at EW scale mhiggsino mass parameter tanb ratio of VEV of Higgs doublets • scalar sector described by MANYmass parameters • different SUSY breaking different class of models SUSY Symmetry Breaking SUGRA( ~ 10 11 GeV) MSSM Assumptions: • 5 free parameters mocommon scalar mass m1/2common squark mass Ao trilinear coupling tanb sign(m) • SUSY particles are pair produced • Lightest SUSY particle (LSP) is stable • Lightest SUSY particle is

  31. Stop  charm + ET ~ with 0 as LightestSupersymmetricParticle and and pair production R-parity Search for: 2 charm jets plus Missing ET Pre-selection: 2 jets, pT > 40(20) GeV Lepton, track vetos δφ(jj) < 165o δφmax- δφmin < 120o δφ(j,ET) > 50o A=(ET-HT)/(ET+HT)>-0.05 ET> 60 GeV then flavor tag (>= 1 jet)

  32. Stop  charm + ET Finally optimize mass-dependent cuts on HT and P = max + min For HT>140 P<320 SM process Number of events Wl+jets 20.62  2.34 Z+jets * 13.23  1.76 Wl +HF (bb, cc) 11.94  1.06 Z+HF (bb, cc) 11.60  0.78 WW,WZ,ZZ 2.70  0.27 tt 2.17  0.07 Single top 1.76  0.05 Zll(e,,)+jets 0.12  0.09 Zll(e,,)+ HF (bb, cc) 0.09  0.04 Total BKG 64.213.22 Data 66 *use Zee+jets to normalize Zvv+jets

  33. Search for Long-lived Stop CDF Electromagnetic Calorimeter (EM) Some models predict long-lived massive particles due to: – weak coupling (e.g., NLSP in SUSY models with GMSB) – Kinematic constraints (chargino in SUSY with AMSB) – New symmetry (gluino in split-SUSY, LSP stop in ED models) A long-lived, charged massive particle (CHAMP) appears as a “slow” muon. TOF Hadronic Calorimeter Tracking Chamber Muon Detector – High PT, low velocity, highly ionizing “muon” – Measure velocity () via TOF detector + timing from tracking detector – Calculate mass from momentum and  Control Region dominated byW Data Signal Region

  34. Search for Long-lived Stop • Signal region: no candidates with m>120 • consistent with expected background Prospino2 Exclude stable stop with m<250 GeV/c2 at 95%CL

  35. Squarks/Gluinos  jets + ET Assuming R-partity is conserved, squarks and gluinos can decay directly into the LSP (01). or cascade down to the LSP The dominant signature for ppqq, qg, gg + Xisjets+ET    Separate 2-jet, 3-jet and >3-jet analysis. At least 3 jets ET > 25 GeV and ET > 25 GeV

  36. Squarks/Gluinos  jets + ET 1.4 fb-1 Mgluino < 290 for any Mq ~ Mgluino < 380 excluded for Mg ~ Mq A0=0 tan = 5 <0 ~ ~

  37. Squarks/Gluinos  jets + ET 0.96 fb-1 ~ ~ Mgluino < 402 excluded for Mg~Mq Mgluino < 309 excluded – any Mq A0=0 tan = 3 <0 ~

  38. Squarks  had + jets + ET τ- A0 = -2m0 tan = 15  < 0 enhanced  decay • Selection: • 2 or more jets ET > 35 GeV • ET > 75 GeV • at least one hadronic  • Optimization: • ET > 175 GeV • > 325 GeV

  39. Squarks  had + jets + ET Predicted Yields Signal (m0,m½) ( 80,160) 4.70.4 (100,150) 7.10.6 Background 1.7 Data 2 LEP2 slepton searches LEP2 chargino searches Translating to

  40. Chargino/NeutralinoTrileptons Production of 1 02 will lead to trileptonfinal stateswithET perhaps thecleanestsignature of supersymmetry. Dominant backgrounds: Dibosons and Drell-Yan with converting bremsstrahlung photon • Limits set on Br as a • function of  mass • Results interpretted within • select mSUGRA scenarios ~ ee+track Large  and Br Maximal 3 ~

  41. Chargino/NeutralinoTrileptons Final Selection Signal: 1-2 events Background: 1  0.3 Data: 0 DØee+track: DØ Combined Limit (5 analysis) : DØ Combined Limit (14 analysis) :

  42. Conclusions

More Related