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 Potenzialit à di Fisica dal Tevatron ad LHC e a Super LHC

This research outlines the potential of physics discoveries from Tevatron to LHC and Super LHC. It discusses luminosities, production cross-sections, and physics potentials in various channels, including the Standard Model, Higgs, and Beyond Standard Model. It also addresses the activities of INAF Roma1 and whether we are on the right track for future discoveries.

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 Potenzialit à di Fisica dal Tevatron ad LHC e a Super LHC

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  1.  Potenzialità di Fisica dal Tevatron ad LHC e a Super LHC Daniele del Re Universita’ di Roma “La Sapienza” and INFN Roma V3

  2. Outline • Brief intro on Tevatron and LHC • Discussion on luminosities, production cross sections and physics • Physics potentials per channel • Standard Model • Higgs • Beyond Standard Model • INFN Roma1 activities • Are we on the right track for next years discoveries? Daniele del Re (La Sapienza & INFN)

  3. High Energy Physics p p High energy production of particles with large mass • Vector bosons, top, Higgs, new particles Needed for • Standard Model precision tests, discover Higgs, spot New Physics Lumi to date ~ 3.6 1032cm-2s-1 Daniele del Re (La Sapienza & INFN)

  4. Luminosity Matters Cross section depends on beam energy Large variation from Tevatron to LHC. Important consequences for discovery Daniele del Re (La Sapienza & INFN)

  5. Expected Luminosities Tevatron Now more than 6fb-1 on tape. By year 2011 between 8 and 9.5fb-1. Run also in 2011? LHC 2009-2010: 10 TeV run. O(100pb-1) to be accumulated Later: 14 TeV, instant lumi few 1033cm-2s-1 → 1034cm-2s-1,i.e. 0(10-50fb-1)/year SLHC after 2017?? Daniele del Re (La Sapienza & INFN)

  6. SM Measurements: Still Cool Lots of physics goals: • Electroweak parameters: mtop, mW, ΓW, sin2θW and couplings  SM precision test and consistency • Direct sensitivity to new physics (e.g. rare top decays.. ) • High precision cross sections to test QCD predictions • Constraints on parton density functions • Single top production • Measure background to many physics channels Daniele del Re (La Sapienza & INFN)

  7. SM at Tevatron: W Mass Analysis basics: • Leptons in central region • Use of pTlepton and nT from missing energy • MW correlated with transverse mass New CDF measurement in preparation Daniele del Re (La Sapienza & INFN)

  8. SM at Tevatron: Top Decays (BR(t →Wb) ~ 100%) • Dilepton: two isolated, high PT leptons • l+jets: one lepton from one W (analyzed in tagged and untagged modes) • All-jets: must be b-tagged to control BG’s Event based additional constraints from kinematics Main systematics from Jet Energy Scale Combined fit to reduce uncertainty Daniele del Re (La Sapienza & INFN)

  9. Single Top Difficult analysis • Small cross section and large bkg Selection • High pT isolated e or m • MET from neutrino • 2 or 3 jets (at least 1 b-tagged jet) Intensive use of multivariate analysis Daniele del Re (La Sapienza & INFN)

  10. Rediscover SM at LHC SM process as benchmark to commission new experiments. Clean processes with well predicted s“standard candles” for: • MC tuning; • Lepton identification/trigger inefficiencies • Electron/Muon/Jets/MissingET energy scales and resolutions Cross sections • Z,W ~6 times larger than Tevatron • ttbar~100 times larger than Tevatron Start-up • Z and W inclusive cross sections and W/Z+jets measurements Masses • W and Z masses with techniques similar to Tevatron’s ones After 1 fb-1: sstat(MW)~40MeV, sstat(Mtop)~300MeV Daniele del Re (La Sapienza & INFN)

  11. An example: Z+jet/W+jet Made in ROME • Test of factorization, QCD, parton showering • Detailed check on background to most of the analyses. • To reduce systematics, measure ratios and ratio of ratios • By-products • Use of Z as candle for jets+Z→nn background CMS # of calorimetric jets CMS 100 pb-1 # of calorimetric jets Daniele del Re (La Sapienza & INFN)

  12. Higgs Intro • In the SM electroweak symmetry broken via the Higgs mechanism • W and Z bosons acquire mass, photon remains massless • Higgs not yet seen • Limits for the Higgs bosons from direct searches and global EW fits Daniele del Re (La Sapienza & INFN)

  13. Higgs Branching Ratios Low mass: • b-bbar dominated. Select events with associated production to reject QCD bkg • other channels: tt and gg important in the intermediate mass region ~130GeV High mass: • WW and ZZ mode only Leptons and vector boson reco provide largest discovery potential BR BR Daniele del Re (La Sapienza & INFN)

  14. Higgs: Tevatron vs LHC Different production modes (because of qq vs qqbar) • At Tevatron non-negligible W/Z associated production (Higgs + Z/W). Only mode used for low mass searches • At LHC large vector boson fusion mode (Higgs + 2 jets). Given larger backgrounds and large statistics LHC uses cleanest Higgs decay modes, i.e. no use of H→bb Tevatron LHC Daniele del Re (La Sapienza & INFN)

  15. Higgs at Tevatron: Analyses S/B~1/40 Low mass: • b-tagging • Multivariate analysis (neural networks) • Use topology constraints (in neural network NN) High mass: • Trigger on leptons • Perform analysis on different samples • Opposite-sign leptons • 0jets for gg fusion • 1,2 jets for other production modes • Same-sign leptons • H(WW)W → l+ l- X • Intensive use of multivariate analysis Daniele del Re (La Sapienza & INFN)

  16. Higgs at Tevatron: Exclusion all M Excluded Higgs in 160GeV<mH<170GeV range Daniele del Re (La Sapienza & INFN)

  17. Exclusion Potential Impressive exclusion potential for the near future If ~10fb-1 on tape all masses down to 115GeV could be tested Daniele del Re (La Sapienza & INFN)

  18. Higgs Analysis Improvements: HF Tagger Made in ROME • Identification of heavy flavor jets on real data in CDF • Statistical separation of fraction of b in Z+j events (2 fb-1) s(Z+b) = 0.57 ± 0.12 ± 0.09 pb Work in progress: • To be used in ZH→nnbb and WZ→lnjj analyses Daniele del Re (La Sapienza & INFN)

  19. Higgs at LHC At low mass (MH< 2MZ) • Dominant bb; huge QCD background • H→tt accessible through VBF • H→WW(*) accessible through gluon-gluon fusion and VBF • H→gg: low BR (decays through top and W loops); thanks to excellent γ/jet separation and γ resolution very significant • H →ZZ*→4l also accessible For higher masses • H→WW and H→ZZ→4l final-states Daniele del Re (La Sapienza & INFN)

  20. Higgs at LHC: Some Examples Made in ROME Made in ROME H → WW → ln ln • 2 opposite-sign isolated and identified leptons • Kinematical and MET cuts • No central jets • Cut based & multivariate H → ZZ→ 4l • Very clean signal (4e,4μ,2e2μ) • high BR except at mH ≈ 2 mW • Excellent mass resolution (1.5 – 2 GeV for MH= 130 GeV) Daniele del Re (La Sapienza & INFN)

  21. Higgs at LHC: Some Examples Made in ROME H → gg • Important for low mass searches • Reducible background • QCD, g+jet • Irreducible background • gg Selection • g isolation • Kinematics Fit to invariant mass Mgg • em calorimeter nice resolution s(M)/M~0.7%(CMS) s(M)/M~1.2%(ATLAS) CMS Daniele del Re (La Sapienza & INFN)

  22. Higgs at LHC: Combined Results ATLAS and CMS have similar Higgs discovery potential • With 5 fb-1 5σ discovery for mH in [~130, ~450] GeV • With 1fb-1 possible observation in H→ WW (but in Tevatron excluded region) • Combining results further reduces lumi needed Daniele del Re (La Sapienza & INFN)

  23. CMS projection at 10TeV Daniele del Re (La Sapienza & INFN)

  24. Higgs: Considerations • Tevatron: large exclusion potential in next two years of data analysis for MH<200GeV • Combinations and NN • OK for exclusions • Really questionable for discovery… • If Higgs not observed by Tevatron • LHC needed to push to larger masses • If hints of Higgs before end of 2010 • Hard to make a claim with NN-based analysis • LHC needed to have real confirmation  LHC still crucial for Higgs discovery! After discovery SLHC can play an important role to determine Higgs properties (couplings and rare decays) Daniele del Re (La Sapienza & INFN)

  25. Beyond SM: Scenarios Limitations of the Standard Model • Hierarchy problem • Couplings don’t unify at one scale • Dark matter, Dark Energy • Neutrino masses Possible extensions of SM • Supersymmetry • Extra Dimensions • New Gauge groups • Model inspired searches • Theory tells where to look • Model dependent optimization • Limits on theory parameters • Signature-based searches • Optimize selection to reduce backgrounds Daniele del Re (La Sapienza & INFN)

  26. SuperSymmetry Adds to each SM fermion (boson) a bosonic (fermionic) partner. • R-parity can be conserved (RPC) or violated (RPV) • RPC implies: - SUSY particles produced in pairs - stable and neutral lightest SUSY particle (LSP) - no proton decay • LSP is a good candidate for cold Dark Matter MSSM Lagrangian depends on 105 parameters mSUGRA requires only 5 parameters - Also other SUSY models exist: GMSB, … Daniele del Re (La Sapienza & INFN)

  27. SUSY: topology p p ~ c01 ~ ~ ~ q c02 ~ g q q • Event topology • High-pT jets from squark/gluino decays • Large ETmiss from LSP • High-pT leptons from gaugino/slepton • High-pT b-jets/t-jets (depending on model) In RPC models, chains end up with the LSP Daniele del Re (La Sapienza & INFN)

  28. Exotica and High Mass Gauge Bosons • New gauge bosons predicted bymany extensions of the Standard Model with extended gauge symmetries: • Super-string inspired and GUT theories; • Left-Right Symmetric Models based on the gauge group SU(3)CxSU(2)LxSU(2)RxU(1)B-L predicting substructures of the known “elementary particles”; • Little Higgs Models. • Produced via Drell-Yan process • Stringent limits from precision EW experiments and direct searches • Signature: two high pt leptons. Peak in invariant mass Daniele del Re (La Sapienza & INFN)

  29. Beyond SM: Tevatron Results Searches in both SUSY and high mass resonances Real limit is the beam energy. Can’t explore large sparticle/new VB masses Two examples: SUSY in tri-leptons Z’→2leptons Daniele del Re (La Sapienza & INFN)

  30. LHC SUSY Made in ROME Made in ROME SUSY ingredients: MET + high pt jets Different final states analyzed • Purely hadronic • 1 lepton • 2 leptons • 2 photons • ... Different models/scenarios e.g.mSugra, GMSB, … Look for SUSY Higgs (charged and neutral) too CMS Daniele del Re (La Sapienza & INFN)

  31. LHC Z’ Made in ROME • 2 opposite sign charged leptons with high pT (hundreds of GeV) • low jet multiplicity, no real MET • Drell-Yan is the irreducible background Z’ → ee channel • good Mee resolution • saturation effects at high energy Z’ → μμ channel • Mμμ resolution ~10 times worse in signal region, resolution affected by misalignment at start-up Comparable sensitivity Daniele del Re (La Sapienza & INFN)

  32. Exotica Examples: Hidden Valley Made in ROME • Hidden Valley (HV) Scenarios predict long-lived neutral states with decay lengths comparable to LHC detector • Example with Higgs production • Implemented ad-hoc triggers based on HCAL, muon detector and inner tracker O(10%) efficient • Thousands of triggered events with lifetime > 1m in 100pb-1 ATLAS Daniele del Re (La Sapienza & INFN)

  33. Beyond the Beyond: SLHC • Increase mass reach • Production of new particles. Gluino e squark masses up to 3TeV • Z’ discoverable up to 5-6TeV • SUSY properties • Masses of SUSY particles from kinematics (lepton-jet invariant masses) and spin • Higgs couplings • H → μμ • WW,WZ scattering • In general: • If discovery: a lot to understand, more stat needed • If no discovery: higher masses to check, more stat needed Daniele del Re (La Sapienza & INFN)

  34. LHC Readiness to Expected • At start-up uncertainties driven by knowledge of physics objects reconstruction • Plot: an example of Mtop-Jet Energy Scale correlation • LHC to be ready to first year physics calibrating jets, MET, leptons, photons • Energy scale • Resolutions • Efficiencies • SM processes needed • Invest time now to tune methods based on data control samples Daniele del Re (La Sapienza & INFN)

  35. Leptons, Photons, JETs and MET Made in ROME Physics object calibration examples Leptons Use of Z→ll and tag-and-probe approach • tight requirements on one lepton • other used as probe to measure ID Photons Energy scale calibration using p0’s JETS Di-jet, g/Z+jet events to calibrate Use of balance in transverse plane MET Find ad hoc control samples. Use of multijet events Z CMS Daniele del Re (La Sapienza & INFN)

  36. LHC Readiness to Unexpected The example of the multi-muon events at Tevatron. • Significant sample of events with at least one of the muon candidates is produced outside of the beam pipe New physics? Reconstruction effect not under control? Extra event not simulated? …and Tevatron is running since ages, detector calibrations well known How many “multi-muon events” cases at LHC startup? Reduced by well-established calibration of physics object, relying very little on MC. CDF Daniele del Re (La Sapienza & INFN)

  37. Conclusions Tevatron: Will dominate SM measurements for a while. Higgs can be excluded (m<200GeV) in the next two years. Higgs discovery is hard. LHC: • Crucial for Higgs search. • Wide number of possible beyond-SM scenarios will also be explored. • Ready to (un)expected. Crucial role of calibrations SLHC (if any) • Deeper understanding of Higgs and New Physics discoveries • (or/and) Extend searches to larger energies INFN Roma1 plays active role in physics analysis • Well balanced effort among Standard Model, Higgs, Beyond SM, exotica analyses and calibration (understanding) of physics objects See next slide Daniele del Re (La Sapienza & INFN)

  38. Summary of Activities in Dept. • Standard Model: Tevatron: Z+b-jet. CMS: Z/W+jets, Z incl. production. ATLAS: Z→2m • Higgs: ATLAS: H→ZZ→4l. CMS: H →WW→2l2n. • SUSY: ATLAS: SUSY Higgs.CMS: GMSB in photons. • Exotica: ATLAS: Hidden Valley. CMS: Z’ → ee • Physics objects calibration: ATLAS: Z tag and CMS: Z tag and probe fo electrons. probe for muons. JET calibration using g+jet. photon calibration with p0. Daniele del Re (La Sapienza & INFN)

  39. BACKUP Daniele del Re (La Sapienza & INFN)

  40. Tevatron Detectors Daniele del Re (La Sapienza & INFN)

  41. LHC Detectors Daniele del Re (La Sapienza & INFN)

  42. What Physics? Cross section depends on beam energy Large variation from Tevatron to LHC Important consequences for discovery Limit: 0.5pb * 4 103 pb-1 = 2K events Daniele del Re (La Sapienza & INFN)

  43. Higgs at Tevatron: Exclusion at low M • Summary of exclusion limits at 115GeV for different channels. • Final result as a combination of many different results Daniele del Re (La Sapienza & INFN)

  44. Strongest Discovery Modes c0 c0 undetected • New Physics predicts undetectable particles • MET: large missing E in transverse plane identifies new physics processes ...but MET very sensitive to detector inefficiencies and bad behaviors need to keep background very low • In addition to MET: presence of other particles to identify specific final states and suppress backgrounds • leptons • jets • photons q q ~ g ~ ~ g q ~ q q q undetected Example of decay chain for low mass RPC SUSY Daniele del Re (La Sapienza & INFN)

  45. List of Experimental Priorities SUSY Will talk about these Daniele del Re (La Sapienza & INFN)

  46. Inclusive Analysis: To-do at Startup Credibility of inclusive analyses at start-up: • Tiny backgrounds (S/B > 10) after selection • Easy to disentangle signal vs bkg in inclusive distributions • Redundant measurements • Detector-wise and analysis-wise • Use of control samples for bkg shapes and resolutions • At the beginning forget about MC predictions • Keep it simple and robust • No complicated multivariate approaches Daniele del Re (La Sapienza & INFN)

  47. Points and SUSY Phenomenology • squark-gluino mass • hierarchy, decay modes Cross section dependence ~ ~ ~ ~ m(g)>m(qi) ~1fb m(g)>m(q) • SUSY production • cross section ~ ~ m(g)<m(qj) ~ ~ Large BR(c20→h0c10) BR(c2±→W±c1 0) ~ ~ ~100fb • Intermediate SUSY • particle BR (c20,c2±) ~ ~ ~1pb ~ ~ Large BR(c20→Z0c10) • BOTTOMLINE • In red, phase space region for early discoveries: • large cross sections, additional leptons in final state ~10pb ~ ~ m(g)<m(q) ~ ~ Large BR(c20→l l) BR(c2±→ln) ~ ~ Daniele del Re (La Sapienza & INFN)

  48. Triggers for SUSY Trigger improvements are under development. So far • JetMET (fully hadronic analyses) • Based on Jet Pt reco, MET, HT • L1 cuts: 1,2,3,4 large pT jets, HT, ET • HLT cuts: combinations of MET and jets with different thresholds (single Jet pT>200GeV, MET>65GeV) • Single muon • For MET+Jet+muons analyses • L1 cuts: pT>7GeV, info from DT, RPC, CSC • HLT cuts: pT>3GeV, isolation • Single electron • For MET+Jet+electrons analyses • L1 cuts: pT>12GeV, some isolation • HLT cuts: pT>15GeV, detailed isolation Daniele del Re (La Sapienza & INFN)

  49. Fully Hadronic Mode: Results • Main systematics on bkg from MET and Jet Energy Scale (~20%) Signal and background in ETmiss Low mass (LM1) S/B~20 Daniele del Re (La Sapienza & INFN)

  50. Mass Measurements ~ ~ ~ c02→ l l →c01 l+ l- • After discovery, particle properties measured and used as confirmation • Edge of dilepton invariant mass correlated with slepton and neutralino masses • Combinatorial (SUSY+SM) background (two leptons from independent chains) removed by flavor subtraction (em pairs) • 1 fb-1 example: edge = (80.4±1.4) GeV ~ l± ~ ~ c02 c01 ± l l± Daniele del Re (La Sapienza & INFN)

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