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Introduction to CDF

Introduction to CDF. A little history and geography The NEW machine The UPGRADED apparatus (for Run II) A few old results (Run I) Luminosity matters for Run II. Mario’s talk tomorrow : recent results, and what we will do in CDF. Fermilab (FNAL): a bit of history.

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Introduction to CDF

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  1. Introduction to CDF • A little history and geography • The NEW machine • The UPGRADED apparatus (for Run II) • A few old results (Run I) • Luminosity matters for Run II Mario’s talk tomorrow: recent results, and what we will do in CDF

  2. Fermilab (FNAL): a bit of history • Conceived and designed by R.Wilson, late ‘60s • Built in Illinois, due to senator E.Dirksen: Batavia, 1 hr W of Chicago • Originally, a 250 GeV proton synchrotron • Went up to 400 GeV, later an 800 GeV SC ring was added in same tunnel (the Energy Doubler/Saver) • Early discoveries, and not: 1973: Expt. 1A discovered and undiscovered weak neutral currents (“Alt. Neutr. Curr.”, Rubbia et al.) 1975: the Oops-Leon (6.2GeV) 1977: Leon Lederman et al., the real   • Became a 1.8 TeV p-pbar collider in the ’80s • First collisions seen in CDF in 1985. Run 0 to 1989. • Run Ia, Ib 1992-1996: 110 pb-1, top quark discovery in 1995. • Other highlights: ET spectra to 400 GeV, many B-hadron lifetimes, W mass, many limits on non-SM processes… • Upgrade of machine and detectors for Run II: 1996-2001.

  3. ... who also brought back bisons (Apr. 15, first-born baby of season) The Highrise (h=75m), also designed by R.Wilson... The lab also has a Village with accomodation for physicists (3 km from CDF and Highrise), 10 000 Canadian geese, etc

  4. CDF (at B0) D0 High Rise Tevatron 8 GeV Booster Main Injector

  5. Debuncher, accumulator rings 2 1 3 4 6 5

  6. 1. Cockroft-Walton, 750 keV 2. Linac, 400 MeV 3. Booster, 8 GeV (H- ions) (at end, H-p) 4. Main Injector, 150 GeV 5. Tevatron, 1 TeV 6. antiproton target (120 GeV) and Recycler (8 GeV)

  7. Antiproton availability is the most important factor limiting luminosity. The Run II mode of operation: • Making many antiprotons (use 120GeV protons, capture them over broad momentum interval) • 5 1012 proton bunch makes 9 107 antiprotons around p=8 Gev. Captured with Li lens. Stored in Debuncher ring. Moved to Accumulator ring. • “Cooling” the antiprotons (in Debuncher ring): • “Stochastic”cooling (Nobel to Van Der Meer): RF pickup from proton beam signals frequenccy components outside central orbit. Amplified OPPOSITE signal is fed back to THE SAME protons on the opposite side of ring (diameter < ½ circumference) and reduces deviant freq. Components. • Electron cooling (invented in Novosibirsk): electrons are easier to cool than protons, because they irradiate. A very cold beam of electrons is “mixed” with proton beam by giving it same  as protons; due to 2nd law of thermodynamics, proton beam cools. • Antiproton cycle: pre-storage:produced at 8 GeV from 120 GeV protons, debunched, cooled. Gradually stacked – for hours -into Accumulator ring . Accelerated in Main Injector. Then to Tevatron, for acceleration and luminosity. Post-storage:decelerate to 120 GeV, then to 8 Gev in Main Inj., store and cool in Recycler. Not done yet!

  8. The upgraded CDFII detector (briefly) • Necessary to: handle higher rates, shorter interbunch (132 ns). • New Si detectors: - SVX II, Si microvertex det., 3 barrels, 5 layers - Interm. Si Layers (ISL), 2 layers at higher  • New Central (Outer) drift Ch. (COT), with <130ns max. drift time AND online track processor (XFT, al LV1Trig., C.Sánchez) • Scint. Sampling calorimetry over whole  range for faster response, good hermeticity. EM (21 r.l., includes pre-shower and shower max. detectors) and Had. Calo. (3.5 ), both with uniform pattern of segmentation in . • LV2 trigger processor SVT: a VERTEX trigger, high eff. On b, c displaced vertices. Trigger on b’s is very important physics enhancement.

  9. Three results from CDF, Run I: • Jet ET inclusive spectra: new physics? • W mass measurement (transverse mass) • Discovery of the top quark (1994-1995)

  10. Inclusive Central Jet Cross Section Data over ~7 orders of magnitude Run1a and 1b results consistent .. Observed deviation in tail …….. is this a sign of new physics ?

  11. SM explanation (gluon at high-x) Important gluon-gluon and gluon-quark contributions at high- Gluon pdf at high-x not well known… …room for SM explanation….

  12. CONCLUSION: • Obviously, need better knowledge of parton density functions (pdf). • tomorrow Mario will show you how to gain such knowledge. • An impressive spectrum, but no reason to get excited yet.

  13. Measuring the W mass at hadron colliders •    W production: udW (both quarks from sea at pp machines) • W decay: W  e,  and transverse massmethod • Invariant mass: M2=2E1E2(1-cos(p1p2)) • Cannot use it: only measure ET of neutrino... • Use MT instead: MT2= 2 ETe Etmiss (1-cos(12)) • In general, MT < M, but not for , where most of  is! • Fun to prove this: consider simplified case of W  e produced at rest, and decaying isotropically: then MT = MW sin and d/dMT = d/dcos · dcos/dMT = const · sin/cos ,  for  which is why d/dMT peaks at MW (Jacobian peak)

  14. W transverse mass distribution edge gives W mass .. and tail gives W width

  15. Sensitivity of lineshape to W width

  16. W mass, top mass and all that ..

  17. The long search for top: 1977-94 (from Chris Quigg) open circles– indirect estimates from fit of EW observables solid line -e+e- colliders broken line - ppbar collisions dot-dashed line - from W width from ppbar -> ( W or Z) + nothing triangles - CDF direct measurements inverted triangles - DØ direct measurements crossed box - world average

  18. Top production and decay at the Tevatron

  19. Dilepton channel Two high PT leptons (e or m) PT>20 GeV, central (-1.1<h<1.1), oppositely charged at least one of the lepton must be isolated Mee or Mmm not in Z mass region (75-105 GeV/c2) Significant missing energy from two n’s Two or more jets with ET>10 and -2.0<h<2.0 b l- n l+ b n Dilepton Channel • Dominant Backgrounds: WW, Z tt, fake leptons, Drell-Yan • Features: good signal-to-background ratio low statistics not ideal for t mass reconstruction observed: 9 events (1ee, 1mm, 7em) total background: 2.4±0.5

  20. Signature: one central and Isolated high PT lepton (e or m) missing ET from the n, (ET>20 GeV) 3 or more jets, ETjet > 15 GeV Dominant Backgrounds: Non W background (fake leptons) pp  W + n×Jets Signal region is: S/B » 1/6 Reduce the background fraction by “b-tagging” top events always contain b jets, usually W+jets events do not b l- n q b q Lepton + Jets Selection • Secondary VerteX Tagging e(SVX) ~ 42% tag b-quarks using displaced vertex • Identify semileptonic B decaye(SoftLeptonTagging) ~ 20% • tag b-quarks using semileptonic decays

  21. Top mass from lepton + jet sample • Split data into 4 exclusive subsamples with different S/B ratios SVX double tagged SVX single tagged SLT without SVX tags events non-tagged events (ET(jet4)>15 GeV)

  22. All hadronic mass CDF preliminary • No n’s - all jets are measured. • At least one SECVTX (displaced vertex) tag (S/N~1/3). • Resolution: dominate the combinatorial effect. • Kinematic fit to individual events (3C fit). • Combination with lowest c2 is chosen • Experimental mass distribution is compared to HERWIG tt MC and to back- ground samples. b q q b q q

  23. Top Mass Summary 161±20 GeV/c2 186±16GeV/c2 175.9±6.9 GeV/c2 CombinedMass

  24. LUMINOSITY MATTERS

  25. Luminosity: past and present • Run Ib (’94-’96):  = 1.5 –2.5 E31, Lint = 89 pb-1 • Run IIa (’00-…) goal:  2 E32, Lint = 2 fb-1 …currently:   5 E31, Lint 200 pb-1 for Run II – and expect Lint(2003)= 225 pb-1 • Why so low?: Recycler Ring not used (x2 less L) too few antiprotons? (x2 less ) • L better improve, else physics reach will be modest • A separate – or related? - issue: Tevatron now operating with 36x36 bunches (396 ns interbunch), but it was expected to be capable of 108x108 bunches (132 ns interbunch): 396 ns interbunch,  = 2 E32<Ncoll> = 3132 ns interbunch,  = 1 E32 <Ncoll> = 2

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