1 / 56

From the TeVatron to the LHC: What could lie beyond the SM?

From the TeVatron to the LHC: What could lie beyond the SM?. Monica D’Onofrio IFAE-Barcelona HEP Seminar, University of Oxford, 28 th October 2008. The Standard Model. Matter is made out of fermions: 3 generations of quarks and leptons Forces are carried by Bosons:

Download Presentation

From the TeVatron to the LHC: What could lie beyond the SM?

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. From the TeVatron to the LHC: What could lie beyond the SM? Monica D’Onofrio IFAE-Barcelona HEP Seminar, University of Oxford, 28th October 2008

  2. The Standard Model • Matter is made out of fermions: • 3 generations of quarks and leptons • Forces are carried by Bosons: • Electroweak: ,W,Z • Strong: gluons • Remarkably successful description of known phenomena: • predicted the existence of charm, bottom, top quarks, tau neutrino, W and Z bosons. • Very good fit to the experimental • data so far • but ... University of Oxford, 10/28/2008

  3. The missing piece: the Higgs • WOULD THE HIGGS DISCOVERY • COMPLETE OUR UNDERSTANDING OF NATURE ? What is the origin of masses?  Within SM, Higgs field gives mass to Particles (EWK symmetry breaking) SM predicts existence of a new massive neutral particle Not found yet! Theory does not predict its mass LEP limit: mH>114 GeV @ 95% CL Indirect limit from EW data: - Preferred value: mH = 84+34-26 GeV - mH < 154 GeV @ 95% CL with aS (MZ) = 0.1185±0.0026, DaS(5)had=0.02758±0.00035 University of Oxford, 10/28/2008

  4. Beyond SM: the Unknown The Standard Model is theoretically incomplete • Mass hierarchy problem •  radiative correction in Higgs sector • Unification • Dark Matter • Matter-antimatter asymmetry • Many possible new particles and theories • SuperSymmetry • Extra Dimension • New Gauge groups (Z’, W’) • New fermions (e*, t’, b’ …) • … f H DmH2 ~ L2 L = Mpl ? Can show up in direct searches or as subtle deviations in precision measurements University of Oxford, 10/28/2008

  5. Outline • Tevatron and the CDF and D0 experiments • Tevatron sensitivities: achievements understanding the SM • The SM Higgs • Searching for physics beyond SM • Supersymmetry • mSUGRA-inspired searches: • Squark/gluino • Chargino/neutralinos • GMSB-inspired searches • Diphoton+X • Delayed photon analysis • MSSM Higgs • Extra-dimension and new gauge bosons: • Search for high-mass resonances • Perspectives for the LHC University of Oxford, 10/28/2008

  6. _ The Tevatron p p CDF Highest-energy accelerator currently operational D0 Peak luminosity > 3.2 *1032 cm-2 s-1 Integrated luminosity/week  ~ 40-60 pb-1 Delivered: 5.1 fb-1 Acquired: 4.2-4.3 fb-1 (CDF/ DØ) University of Oxford, 10/28/2008

  7. CDF and DØin RunII CDF D0 Took >1 years of collisions to get to stable high efficiency Oct 08 Jan 02 University of Oxford, 10/28/2008

  8. Tevatron Sensitivities • Jet cross section measurements, heavy flavor physics, inclusive W/Z • Precision measurements (Top properties, observation of rare processes...) • New Physics searches, looking for ‘the’ unexpected Both CDF and D0 have a very rich physics program! University of Oxford, 10/28/2008

  9. Knowledge of the SM: QCD and EWK • Z(e+e-)+jets • Clean signature, low background • Test ground for Monte Carlo tools • W Mass and width • MW = 80413±48 MeV • GW = 2032±73MeV • world’s most precise single measurements! Test of Next-to-Leading Order perturbative QCD • inclusive jet cross section • Probing distances ~10-19 m • Constrains gluon PDF at high-x University of Oxford, 10/28/2008

  10. Knowledge of SM: top physics Mtop = 172.4 ± 0.7 (stat) ± 1.0 (syst) GeV/c2 • Top quark discovered at the Tevatron in 1995 • Very extensive program on top physics: • Precision measurements of top mass • Top cross sections, properties… University of Oxford, 10/28/2008

  11. Knowledge of SM: rare processes • DiBoson cross sections D0:s + t = 4.7 ± 1.3 pb CDF: s + t = 2.0-2.7 pb (± 0.7 pbper analysis) Measurements of W/Zg, WW and WZcross sections Consistent with NLO calculation ZZ production  Evidence at CDF Observation at D0!! Consistent with NLO calculation: 1.4 ± 0.1 pb The focus is now to uncover the unknown University of Oxford, 10/28/2008 Evidence of Single top production

  12. Needle in the haystack  Model-inspired searches • Theory driven • Model-dependent optimization of event selection • Set limits on model parameters  Signature-based searches • Signature driven • Optimize selection to reduce backgrounds • Event count; event kinematics Every measurement we make is an attempt to find New Physics When searching for a needle in a haystack, the hay is more important than the needle... Many searches are extensions of SM measurements. University of Oxford, 10/28/2008

  13. The SM Higgs Boson

  14. SM Higgs Production and Decay • Direct production gg→H • Highest Production rate • Largest background • Associated production ZH/WH • Leptonic vector boson decay helps for triggering and signal extraction MH (GeV/c2) • Low Mass (MH<135 GeV/c2) • H→bb mode dominates •  WHlbb, ZHbb , ZHllbb • VBF Production, VHqqbb, H(with • 2jets), H, WH->WWW, ttH • High Mass (135<MH<200 GeV/c2) • H→WW mode dominates University of Oxford, 10/28/2008

  15. Higgs→WW*→ll • Most sensitive channel for high mass Higgs • gg →H → WW* and W(Z)H → W(Z)WW* • Unbalanced transverse energy (MET) from n • 2 leptons: e,,→e, (must haveopposite signs) • Key issue: Maximizing lepton acceptance • Primary backgrounds: Drell-Yan, WW • Higgs is scalar  leptons travel same direction • In t-channel WW, W are polarized along the beam direction • Use Matrix Element and Neural Network methods Results at mH = 165GeV : 95%CL Limits/SM University of Oxford, 10/28/2008

  16. SM Higgs limits CDF/D0 combination: High mass only Exp. 1.2 @ 165, 1.4 @ 170 GeV Obs. 1.0 @ 170 GeV Tevatron exclude at 95% C.L. the production of a SM Higgs boson of 170 GeV Low mass combination difficult due to ~70 channels: Expected sensitivity of CDF/DØ combined: <3.0xSM @ 115GeV A 15 GeV window [162:177] excluded @ 90% CL University of Oxford, 10/28/2008

  17. Searches Beyond SM Supersymmetry

  18. Supersymmetry • New spin-based symmetry relating fermions and bosons: Q|Boson> = Fermion Q|Fermion> = Boson gaugino/higgsino mixing • Minimal SuperSymmetric SM (MSSM): • Mirror spectrum of particles • Enlarged Higgs sector: two doublets with 5 physical states • Naturally solve the • hierarchy problem • Define R-parity = (-1)3(B-L)+2s • R = 1 for SM particles • R = -1 for MSSM partners If conserved, provides Dark Matter Candidate (Lightest Supersymmetric Particle) University of Oxford, 10/28/2008

  19. gravity SUSY breaking (hidden sector) MSSM (visible sector) or Gauge fields, loop effects…. Symmetry breaking No SUSY particles found yet: • SUSY must be broken • More than 100 parameters even in minimal (MSSM) models • Breaking mechanism determines phenomenologyand search strategy at colliders: • Direct searches or subtle deviations in precision measurements mSUGRA, GMSB, …. choose a model  Constrained MSSM models used as benchmark University of Oxford, 10/28/2008

  20. Sparticles mass and cross sections 1. Unified gaugino mass m1/2 2. Unified scalar mass m0 3. Ratio of H1, H2 vevs tanβ 4. Trilinear coupling A0 5. Higgs mass term sgn() • in mSUGRA, new superfields in “hidden” sector • Interact gravitationally with MSSM • 5 parameter at GUT scale T. Plehn, PROSPINO (pb) m (GeV) • Squarks and gluinos are heavy • Sizeable Chargino/neutralino cross sections M(+) ~ M(02) ~ 2M(01) M(g) ~ 3M(+) In R parity conservation scenario, the LSP is the neutralino (c01 ) ~ University of Oxford, 10/28/2008

  21. Inclusive search for squark/gluino mSUGRA: Low tan b scenario (=5 for CDF, = 3 for D0) Assume 5-flavors degenerate q Final state: energetic jets of hadrons and large unbalanced transverse energy(due to presence of c0) ~ q ~ ~ ~ c c 0 0 g q g ~ A0 = 0, m<0 M0 [0,500 GeV/c2] m1/2  [50,200 GeV/c2] q 0 c ~ ~ q q ~ ~ c c 0 0 ~ ~ q q g g q ~ Mq ~ Mg qg final state dominates  3 jets expected ~ q ~ ~ ~ ~ c c 0 0 ~ q g ~ q q q ~ ~ q q 0 0 c Mq > Mg gg final state dominates  4 jets expected ~ ~ ~ ~ ~ ~ c c 0 0 Mq < Mg qq final state dominates  2 jets expected ~ ~ ~ q ~ ~ q q 3 different analyses carried out with different jet multiplicities Final selection based on Missing ET , HT = S (ETjets) and ET jets University of Oxford, 10/28/2008

  22. DiBoson Background rejection Data sample Cleanup • at least one central jet with |h|<1.1 • minimum missing ET of 70 GeV • Reject beam-related backgrounds and cosmics Rejection of SM processes QCD-multijet: ET due to jet energy mismeasurement. W/Z+jets with Wl or Z, DiBoson and tt production: Signaturesvery similar to SUSY Define signal region based on selections that maximize background rejection University of Oxford, 10/28/2008

  23. QCD multijet rejection Missing ET from mis-reconstructed jets  Collinear with one of the leading jets  Apply cuts on Df (missingET-jets) • CDF: remaining QCD-bkg estimatated from Monte Carlo. • Control checks in enhanced QCD-sample • DØ : QCD-bkg extrapolated in data by exponential fit function Df(MET-jets) cut reversed for at least one of the leading jets University of Oxford, 10/28/2008

  24. Z/g* n q n g q g n W q l t b q’ W q q t b Top and Boson+jets rejection Control region • Genuine Missing ET in the event • Suppressed vetoing events with: • jetElectromagnetic fraction > 90%, to reject electrons mis-identified as jets • isolated tracks collinear to missing ETto reject undetected electrons/muons • Modeled using Monte Carlo • Normalized to NLO cross section • Define control regions reversing lepton vetoes  checks of background estimations • Understanding these processes is fundamental Control region University of Oxford, 10/28/2008

  25. DATA vs SM predictions DØ CDF Good agreement between Observed and Expected events Systematic uncertainties dominated by Jet Energy scale University of Oxford, 10/28/2008

  26. Exclusion limits: Mg -Mq andM0-M1/2 plane ~ ~ Similar results for CDF and DØ 95% C.L. Exclusion limit Results can be interpreted as a function of mSUGRA parameters LEP limit improved in the region where 70<M0<300 GeV/c2and 130<M1/2<170 GeV/c2 ~ ~ For Mg=Mq → M > 392GeV/c2 Mg > 280 GeV/c2 in any case ~ University of Oxford, 10/28/2008

  27. Lepton ET Search for chargino/neutralino mSUGRAc02c±1 pair production Signature: three leptons and ET • Small cross sections (~0.1-0.5 pb) • Very low background: • Drell-Yan • Diboson(WW, WZ/*, ZZ/*, W) • Top pair production • QCD-multijets, W+jets (misidentified leptons) e,m,tLept, tHadr • CDF: 5 exclusive channels • combinations of “tight” (t) and “loose” (l) lepton categories • 3-leptons (e,m,tLept) • 2-leptons (e,m,tLept) + iso-track T (tHadr) • Ordered in terms of S/B • DØ: 4 analyses carried out • ee+IsoTrk, mm+IsoTrk, em+IsoTrk, Same-sign mm ttt tlT ttl tll ttT University of Oxford, 10/28/2008

  28. 3 tight leptons selection c02c±1 results 47 Dilepton and trilepton control regions defined to test SM predictions CDF Signal region: Missing ET > 20 GeV + topological cuts Njet=0,1 and ETjet < 80 GeV DØ (4 channels) mSUGRA Benchmark: m0=60 GeV/c2, m1/2=190 GeV/c2, tan=3, A0=0, >0 Data Observed : 3 SM Expected: 4.1  0.7 Good agreement between data and SM prediction  set limit University of Oxford, 10/28/2008

  29. Excluded region in mSUGRA excluded region in mSUGRA m0-m½ space for tan(β)=3, A0=0, μ>0 m0 = 60 GeV/c2 Exclude mc±1< 145 GeV/c2 ~ ~ ~ Small Dm = m(c20 )-m(l), soft leptons from c20 decay  Loss in acceptance, no exclusion University of Oxford, 10/28/2008

  30. Gauge Mediated Symmetry Breaking • SUSY breaking at scale L (10 -100 TeV). Mediated by Gauge Fields (“messengers”) • Gravitino very light (<< MeV) and LSP • Neutralino or slepton can be NLSP • If NLSP is neutralino In Rp conservation scenario:  2 NLSP  2g + MET (+X) in final state Snowmass p8 spectra CDF Run I (taken from N. Ghodbane et al., hep-ph/0201233) University of Oxford, 10/28/2008

  31. gg+Missing ET • Assuming c01 (NLSP) short-lived • Very low SM background • Zgg nngg, Wgg lngg • Understanding of instrumental background challenging: • Mis-measured ET: use multijet data sample • e g misidentification: use W(en)g data 2 photons pTg > 25 GeV, |hg|<1.1 ET> 60 GeV 3 events (SM: 1.60.4) University of Oxford, 10/28/2008

  32. Delayed Photons • c01 life-time undetermined in GMSB  long-lifetime can be in ~ns range • Final state: Delayed photon+ET +jets  ET> 40 GeV, pTg>25 GeV, ETjet > 35 GeV  |h(g)|<1.1, |h(jet)|< 2. Observed 2 events SM Expect.: 1.30.7 M(c01)>101 GeV @ 5 ns tc(g) in [2-10] ns range University of Oxford, 10/28/2008

  33. MSSM Higgs

  34. Neutral MSSM Higgs • In MSSM, two Higgs doublets • Three neutral (h, H, A), two charged (H±) • Properties of the Higgs sector largely determined by mA and tanb • Higher-order effects introduce other SUSY parameters • Large Higgs production cross section at large tanb. Higgs decays: BR(bb) : ~90% Huge QCD background BR(tt) :~10% University of Oxford, 10/28/2008

  35. BSM Higgs:  • CDF and DØ  channel •  pure enough for direct production search • DØ adds associated production search: bb • Key issue: understanding  Id efficiency • Large calibration samples: W for Id optimization and Z for confirmation of Id efficiency mA=140 GeV/c2 • No Evidence for SUSY Higgs • Limits: tan vs mA •  generally sensitive at high tan CDF:  University of Oxford, 10/28/2008

  36. Searches Beyond SM • More ‘Exotic’ models… • - Extra-Dimensions • New Gauge bosons

  37. Search for high mass resonances Example of di-lepton events Transverse plane • Advantage • Sensitive to many BSM scenarios: • Extra-Dimensions • Extended SUSY-GUT groups • (SO(10),E6,E8...leading to additional gauge bosons, Z' and W') • R-parity violating SUSY • and more... • Di-lepton resonances have a strong track record for discovery → J/ψ, Υ, Z • Enlarge the possible final states looking also in dijet,ditop or dibosons! • Construct the pair invariant mass and look for any excesses in the high mass spectrum University of Oxford, 10/28/2008

  38. Extra-Dimensions M2Planck ~ Rn(MD)n+2 ,MD ~ 1 TeV ‘Solves’ the hierarchy problem by postulating that we live in more than 4 dimensions. • Large Extra Dimensions: Arkani-Hamed, Dimopoulos, Dvali (ADD) • Gravity propagate in ndadditional spatial dimensions compactified at radius R • Effective Planck scale: • no narrow resonances, SM particles pair production enriched by exchanged gravitons • Randall-Sundrum model: Only one extra dimensions (wraped) limited by two 4-dimensional brains. • SM particles live in one of the brains. • Graviton can travel in all 5 dimensions, appears as Kaluza-Klein towers • dimensionless coupling (k/MPl) free parameter University of Oxford, 10/28/2008

  39. CDF: Central-Central (|1,2|<1) or Central-Forward (||<2) e+e- pair with ET>25 GeV D0: EM objects pair (e+e- or gg), CC: |1,2|<1.1, CF 1.5<||<2.4 Major Backgrounds: DrellYan QCD (including W+jets) Resonance search performed in mass range 150-1000 GeV/c2 No evidence for narrow resonances  set limits Search for High Mass e+e-/gg Resonance CDF Search for RS Gkk resonance University of Oxford, 10/28/2008

  40. Exclusion limits • CDF (D0) exclude RS graviton with mass below 850 (900) GeV/c2 for k/MPl=0.1 • Can interpret results in term • of several other scenarios • Limits on extended gauge groups theories: SM-like Z’: 966 GeV/c2 • Limits on effective Planck scale in LED: • Expect a cross section enhancement above SM • Use gg, e+e- 1.29 - 2.09 TeV depending on number of ED University of Oxford, 10/28/2008

  41. Di-muon resonances Spin 1 Z’-like limits For the first time beyond one TeV for SM-Z'! Spin 0 (RPV sneutrinos): mass limits up to 810 GeV Spin 2 ( RS Graviton): mass limits up to 921 GeV • Looking for narrow dimuon resonance decaying • Could have spin 0, 1 and 2 • Search in 1/mμμin which detector resolution is ~const:  17% inverse mass resolution at 1 TeV  construct templates for several signal hypothesis, add bkg and compare to data University of Oxford, 10/28/2008

  42. and more! Every final state is currently investigated!!! • dijet resonances • Limits on several models, up to 1.2 TeV! • ditop resonances • limits on massive gluons and leptophobic Z' (Mz' > 760 GeV) • W' in tb(+c.c.) or en final state • world's best limit MW'→ en> 1 TeV • searches for t' or b' • fourth generation quarks not excluded by EWK • interesting tails in t' → Wq • mt' > 311 GeV University of Oxford, 10/28/2008

  43. 8.75 fb-1 7.29 fb-1 today Highest Int. Lum Lowest Int. Lum Final remarks Projection curves FY10 start In case we don’t find new particles @ Tevatron…. ~ 1.8 fb-1 delivered in FY08 FY08 start University of Oxford, 10/28/2008 CDF and D0 have a wide and rich program of searches for SUSY. No evidence yet, but.. expect to collect and analyze up to 8 fb-1 of data in the next years.

  44. 7 TeV + 7 TeV The Future …. now almost present The Large Hadron Collider (LHC) Proton- Proton Collider ATLAS CMS First Event (9/10/2008)! University of Oxford, 10/28/2008

  45. Roadmap to discovery Higgsdiscoverysensitivity (MH=130~500 GeV) Explore SUSY to m ~ TeV Precision SM measurements 1 fb-1 Sensitivity to 1-1.5 TeV resonances → lepton pairs Understand SM backgroundfor SUSY and Higgs Jet energyscalecalibration 100 pb-1 Detector calibration Use SM processes as “standardcandles” 10 pb-1 time 100 pb-1 • High-pT lepton resonances may provide the first signal of New Physics: • Less sensitive to calorimeter performance University of Oxford, 10/28/2008

  46. ATLAS preliminary Jets measurements @ LHC Ze+e- 50 pb-1 Jet energy scale largest source of systematic error initial uncertainty ~ 5-10% Need to reduce error for QCD test LHC (s = 14 TeV) 10 events with Ldt = 20 pb-1 Ldt=1fb-1 Tevatron measure W/Z + jet(s) cross-section γ/Z+jets calibration signal University of Oxford, 10/28/2008

  47. RP-conserving mSUGRA ATLAS preliminary pTjets+ETmiss(GeV) SUSY@LHC Excl The LHC is built to discover SUSY If there, we will find it relatively soon An example: squark-gluino production • But it will take a bit of time: • commissioning phase to understand detector performance and “re-discover” the SM University of Oxford, 10/28/2008

  48. ATLAS preliminary H  ZZ*  4l 30 fb-1 The “golden” channel SM Higgs: a challenge! Required luminosity for 95% C.L. exclusion For low mass of ~120 GeV need to combine many channels with small S/B or low statistics (H  , H→, H ZZ*  4l, H→ WW*→ll ) ATLAS preliminary most promising in the range 150-180 GeV, again with H → WW* →ll  almost excluded at the Tevatron! University of Oxford, 10/28/2008

  49. Conclusions "Whatever" is beyond the Standard Model, these are exciting times for high energy physics! LHC TeVatron? University of Oxford, 10/28/2008

More Related