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Tau-lepton

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Tau-lepton

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  1. Tau-lepton Top-quark The 3rd generation as Probes for New Physics:The CDF case ντ Bottom-quark Aurore Savoy-Navarro, UPMC-Paris/CNRS-IN2P3 France A. Savoy-Navarro, Korea'08

  2. Synopsis • 3rd generation: WHY? • How to detect/tag them? • Probe for New Physics: the CDF case Some examples in: B Physics Top Physics Higgs BSM A. Savoy-Navarro, Korea'08

  3. WHY the 3rd generation? • The 3rd generation allows exploring important aspects of Particle Physics: the • Some key particles are made of heavy quarks (ex: the B mesons) • and/or decay into 3rd generation objects (ex: H0 but alsoZ0 →τ+τ-) • This decay channel may become even a dominant; ex: τ-lepton becomes dominant in certain BSM cases (ex: also H0 if MSSM-like) • Third generation processes are backgrounds to NP (ex: top paire production…) Heavy Flavored world A. Savoy-Navarro, Korea'08

  4. HOW TO DETECT THEM? 3rd generation objects detection has made impressive advances especially at CDF:b-tagging & triggeringτ-tagging & triggeringbut it’s quite challenging especially at hadron collidersand challenging anyway: each member of the THIRD family has its own peculiarities A. Savoy-Navarro, Korea'08

  5. L00 + μvertex ISL: intermediate Si tracker Si vertex trigger: SVT The detection of 3rd generation objects need ALL the components of a detector Central Outer gaseous Tracker (COT) Part of the Muon detector Plug calorimeter A. Savoy-Navarro, Korea'08

  6. XFT – Level 1 all trckpT>1.5 GeV σ(1/pT) = 1.7%/GeV σ(φ0) = 5 mrad 96% efficiency XFT here SVT – Level 2 all trck pT>2 GeV σ(IP) = 35 μm, σ(1/Pt) = 0.3 % σ (φ0)=1 mrad SVX read out after L1 SVT here Two Track Trigger (TTT) IP>100 μm L3 plot 2001 Events 800 400 0 Ks 1.8 1.85 1.9 GeV/c2 D0 D0 Very important contribution of Tracker in CDF Trigger Architecture Upgrade: 3D tracks 7.6 MHz Crossing rate L1 pipeline 42 clock cycles L1 L1 • 7.6 MHz Synchromous Pipeline • 5.5 μs Latency • 30 kHz accept rate Upgrade: processing time L2 buffer 4 events L2 L2 • Asynchromous 2 Stage Pipeline • 20 μs Latency • 1000 Hz accept rate DAQ buffers L3 Farm L3: CPU farm Full event Reconstruction Speed-optimized offline code Mass Storage (~100 Hz)‏ A. Savoy-Navarro, Korea'08

  7. Gaseous tracking chamber rebuilt from run I to run II to cope with luminosity x100 and for the first time a tracking LV1 trigger: eXtremelyFastTracker COT axial layers Good hit patterns are identified as segments, then segments are linked as tracks XFT 3D upgrade: Add info from stereo layers Fake rejection ~8 COT stereo layers A. Savoy-Navarro, Korea'08

  8. original system p p Fraction of ev. event + underlying event + pile-up upgraded system 0 20 60 100 140 180 Luminosity (xE30)‏ Original SVT turned off above 90xE30 Upgraded SVT can run @high Lumi Upgrade SVT for luminosity At 3x1032: 5 pile ups Upgrade: Faster SVT components and: 32Kpatterns → 512Kpatterns new AM. Good Data@ higher Luminosity More Data @ lower Luminosity A. Savoy-Navarro, Korea'08

  9. A dedicated new Higgs trigger & N.P. searches High luminosity gives large calorimeter occupancy (pile up) that generates fake clusters/ cluster merging (ex: red towers seen as one single cluster) Ten orders of magnitude to fight against!! H A. Savoy-Navarro, Korea'08

  10. The upgraded Calorimeter Triggercourtesy of Simone Donati - 24x24 Calorimeter towers E(em), E(had) sent to L2 CPU @full resolution (10 bit) - Jet, e/g clustering, MET computed with offline-style algorithm (immune to pileup). - Use fixed cone algo:DR=√(Df2 + Dh2)=0.7 jet axis f h 10 bit E(em), E(had) L2Cal (4 Pulsar crates) L2 CPU A. Savoy-Navarro, Korea'08

  11. The L1MET Upgrade Wedge Energy Tr Same Custom Hardware used to calculate Met/SumEt for L1 Met Reconstruction to L1: Same L2 Resolution! L1MET Pulsar Pulsar Merger NEW! L2cal Pulsar x6 Trigger Tower Energy ( 4 S-LINK cables) Pulsar Merger Pulsar Merger L2Cal Pulsar x6 Trigger Tower Energy (288 LVDS Cables) Pulsar Merger L2 PC performs clustering and Met calculation Pulsar Merger L2Cal Pulsar x6 Commissioning Ongoing Courtesy Laura Sartori

  12. Etmiss 25 L1 commissioning Effects of latest trigger upgrades on L1 and L2: 2 examples After L1 upgrade Before L1 Upgrade After L2Cal Upgrade Before L2Cal Upgrade Jet40 L2 upgrade since Nov07 L2 Cross Section (nb) This impacts also on the τ- triggers Courtesy Laura Sartori A. Savoy-Navarro, Korea'08 Instantaneous Luminosity (x 1030 cm-2 s-1)

  13. τ IDENTIFICATION only possible in hadronic decay BR=50% τ+→π+[π-π+]ντ (n π0) BR=14% Tagging and triggering based on: An inner cone, shrinking with energy, 1 or 3 good tracks A. Savoy-Navarro, Korea'08

  14. Primarily designed to trigger low Pt multileptons Including τ’s Davis, LPNHE, PISA, Rutgers, TA&M installed in 2002 A. Savoy-Navarro, Korea'08

  15. A. Savoy-Navarro, Korea'08

  16. MATTER ANTIMATTER b b s s Bs 0 Bs 0 The Bs-world: Bs mesons = {bs} bound states NEW PHYSICS? Transitions Matter ↔Antimatter via: The flavour eigenstates are linear combinations of mass and lifetimes eigenstates • Bs sector is defined by 5 parameters: • Masses: mH, mL • Lifetimes: ΓH, ΓL (Γ=1/τ), • Phase:βs • Bs observables:Δms = mH-mL≈2IM12I defines the mixing oscillation frequency • Different Lifetimes: ΔΓs=ΓL-ΓH ≈2 IΓ12I cos Φs • CPV: ΦsSM = arg(-M12/ Γ12) ≈ 4x10-3 rad (SM) Thus small value predicted by SM A. Savoy-Navarro, Korea'08

  17. Dms measurement ms = 17.77±0.10(stat)±0.07(syst) ps-1 PRL. 97, 242003 (2006) Extracted parameters dominated by theoretical errors; Need more from LQCD 1 fb-1 |Vts / Vtd|= 0.2060 ± 0.0007 (exp)+0.0081(theo) -0.0060 (5.4s significance) CDF present focus DGS=GH-GL, G= (GH+GL)/2 and βs ALL in ONE process βs = phase of b→ccs transition accounts for decay & mixing+decay= 2.20(SM prediction) If NP occurs in mixing: Φs = ΦsSM + ΦsNP and 2βs = 2βsSM – ΦsNP  standard approximation: Φs = -2βs A. Savoy-Navarro, Korea'08

  18. Flavour-tagging performance Same tagging used successfully for mixing-frequency measurement Opposite Side:looks at decay of the ‘other’ b-hadron in the event Same Side:exploits the charge/species correlations with associated particles produced in hadronization of reconstructed B0s meson OST efficiency 96 +/- 1% OST dilution: 11 +/- 2% SST efficiency 50 +/- 1% SST dilution 27 +/- 4% Total εD2 ~ 4% Output: decision (b-quark or antib-quark) and the probab. of being correct A. Savoy-Navarro, Korea'08

  19. Results PRL100, 161802(2008) Assuming the SM, the probability of observing a fluctuation as large or larger than observed in data is 15% (1.5σ) One dimensional: 0.16 < βs < 1.41 at 68% CL A. Savoy-Navarro, Korea'08

  20. ICHEP update 3200 decays, S/B~2 N.B. Analysis not yet optimized 0.28 < βs < 1.29 at 68% CL Increased dataset still hints at larger than SM values! Consistency with SM decreased 15%  7% (~1.8 σ) (first sign of new Physics soon??) www-cdf.fnal.gov/physics/new/bottom/080724.blessed-tagged_BsJPsiPhi_update_prelim/ A. Savoy-Navarro, Korea'08

  21. LOOK for 2-body B, D rare decays at CDF: • B0d,s → μμ, B0d,s → eμ, B0d,s → ee and D0→ μμ Ex: SM=> BR(Bs→μμ)~3.8x10-9 But BR enhanced by x10-103 by NP WHY: FCNC decays forbidden at tree level, proceed through loops. Higher order diagrams highly suppressed, allowing NP to manifest itself. A. Savoy-Navarro, Korea'08

  22. Each search is relative to a normalization mode • B0d K+p-,for • B0d,s ee, em • B+ J/y K+ • ForB0d,s mm • D0 p+p- • forD0 mm A. Savoy-Navarro, Korea'08

  23. B  ee, eμ signal after Lepton ID World’s best limits 90% (95%) BR limits × 108 A. Savoy-Navarro, Korea'08

  24. CDF has gained 2 orders of magnitude, now only about one order from SM A. Savoy-Navarro, Korea'08

  25. The TOP quark case Interesting and not yet well studied case (in progress) the top paire production with the top decaying into τ(see next) A. Savoy-Navarro, Korea'08

  26. Search for top into τ’s : main motivations • Good training camp for BSM searches • background of SUSY • τ dominant decay at large tan β • Goal #1: First time 3 σ observation (not yet!) • Goal #2: Check BR(t→τνb) against Standard Model • BR(WB) = 100% ? Or H+b ?? H-? A. Savoy-Navarro, Korea'08

  27. Z→ττ + jets background • 1 τ→e or μ,1 τ→hadrons • Unlike the top signal: • The 2 leptons are close • MEt points between them OR opposite to them • The τν’s energies can be reconstructed • Veto event if it satisfies the former angular requirements and M(τ,τ) < 115 GeV • This Z veto cuts 70% of Z→ττ and 8% of top signal CDF simulation >115 GeV Other major background: QCD jets faking τ-jets

  28. Results on 1.05 fb-1 • P-value: 8% • Γ(t→τυq)/ΓSM(t→τυq) < 1.5 à 95% CL (2005 result : <5.2) Impact of this result Now starting study with presently available data A. Savoy-Navarro, Korea'08

  29. Search for charged Higgs in top decay(cont’d) Explore the possibility that t → H+b with subsequent decay of H+ → c s Reconstruct event kinematics Z!Top: interesting way to look for H±Z! A. Savoy-Navarro, Korea'08

  30. b, W(*),Z(*) H H _ _ b, W,Z The many ways to produce a Higgs at CDF decay gg→H→bb dominates but huge QCD bkgd => close to IMPOSSIBLE mH>140GeV WH→lνbb ZH→llbb VH→ννbb, ν(l)bb VH→qqbb H→ττ(+jets) mH<140GeV A. Savoy-Navarro, Korea'08

  31. Neutral SM Higgs into τ-leptons Important to look at different decay mode (i.e. H→ττ, not only H→ bb). Analysis optimized for SM Higgs, but sensitive to non SM Higgs. MSSM predicts a much higher H-rate for large tanβ in gg fusion, especially in τ-decay. A. Savoy-Navarro, Korea'08

  32. Search for a SUSY Higgs into 2 τ’s • σ(MSSM) ~ σ(SM) x tan2β • ττ signal: lower background • τ-BR increases with tanβ A. Savoy-Navarro, Korea'08

  33. The many ways to search for Higgs at CDF the high mass case: H→WW→lνlν The physics backgrounds Analyse strategy: 0 jet events WW/WZ WW/WZ W+Jets/γ 1 jet events ≥ 2 jet events And: Drell-Yan, ttbar, single top, Multijets all these processes are well measured A. Savoy-Navarro, Korea'08

  34. 0-jet evt 1-jet evt 2+ jet evt NN with different inputs are trained for each case Anti-b tagging is added in the ≥ 2 jets case, in order to get rid of the ttbar background The results obtained for each of these 3 cases arethen combined, and the CDF result is A. Savoy-Navarro, Korea'08

  35. CDF result on 3 fb-1 of data (See Rob Roser’s talk) σ x BR (H→WW*) expected limit 1.66 times SM for a Higgs mass of 165 GeV; Observed 1.63 CDF & D0 combined exclude m(H0) =170 GeV at 95% CL A. Savoy-Navarro, Korea'08

  36. A minimally supersymmetric world ? proposes a new symmetry Fermions ↔ Bosons A. Savoy-Navarro, Korea'08

  37. Ex 2: SUSY Trileptons searchusing lepton+track trigger Backgrounds CDF selection: Dominant if Large tan β A. Savoy-Navarro, Korea'08

  38. A. Savoy-Navarro, Korea'08 Courtesy Sourabh Dube

  39. 100 A. Savoy-Navarro, Korea'08 Courtesy Sourabh Dube

  40. 100 A. Savoy-Navarro, Korea'08 Courtesy Sourabh Dube

  41. Ex 2:Searches for sbottom quark If large tan b, light sbottom is expected Dedicated searches for b production (B.R. (bb c0) = 100%) direct pair production or b from gluino decays sgg ~ 10 sbb , consider region and mass(gluino) > mass(sbottom) Final state: ET + 4 b-jets b ~ ~ ~ b c c 0 0 ~ ~ ~ ~ g g b ~ b ~ ~ ~ ~ ~ ~ c c 0 0 ~ ~ g g ~ b b B-tag algos • Main background processes: • QCD-multijets • light-flavor jets tagging (“mistag”) • Top production, W/Z+jets, diboson •  Predictions tested in Control Regions A. Savoy-Navarro, Korea'08

  42. Exclusion limits Excluded s above 0.1 pb (M(g) ~ 350 GeV/c2) Translated into limits on the gluino-sbottom mass plane ~ ~ Sbottom masses up to 300 GeV/c2 are excluded for M(g)<340 Gev/c2 A. Savoy-Navarro, Korea'08

  43. Ex 3: Search for RpV-SUSY Top Quarks decaying to a b-quark and a τ-lepton (all 3 in one) Based on (only) 322 pb-1 of data collected by lepton+track triggers Look for channels with one τ decaying leptonically and the other hadronically. Expected 2.26+0.46-0.22 events; observed 2 . A. Savoy-Navarro, Korea'08

  44. stop→τb event Upper limit on σ(production) If Br(stop-->τ b) = 100%, Lower limit M(stop)i=155 GeV/c2 (assuming NLO cross-section for stop pair production). If theoretical  uncertainties due to PDF's + factorisation scale taken into account, imit =151 GeV/c2 A. Savoy-Navarro, Korea'08

  45. Concluding remarks: perspectives • CDF has been instrumental in developing the tools (hard-software) to exploit the potential of the 3rd generation to tackle New Physics • This is a particularly “high-tech Physics”: Theory, detector, analysis points of view • Identifying these tricky objects (3rd family not and easy family…) in real time is a preriquisit especially in hadron colliders • The future is in an heavy flavored world: LHC experiments must address very soon this issue and upgrade their detecting capacity consequently • In this aspect also CDF is a precursor and pioneer: breakthroughs may still be expected A. Savoy-Navarro, Korea'08