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Top quark mass measurement in CDF at Run II

Top quark mass measurement in CDF at Run II. Introduction Overview of the measurement Quick review of Run I results Measurement with CDF at Run II Toward the goal Summary. T.Maruyama for CDF collaboration ( JSPS fellowship / Univ. of Chicago).

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Top quark mass measurement in CDF at Run II

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  1. Top quark mass measurement in CDF at Run II • Introduction • Overview of the measurement • Quick review of Run I results • Measurement with CDF at Run II • Toward the goal • Summary T.Maruyama for CDF collaboration ( JSPS fellowship / Univ. of Chicago)

  2. Introductionwhy is the top mass interesting? 1. Top mass is a basic Standard Model parameter. 2.Top is heavy (~ 175 GeV) Yukawa coupling ( Mt / v) ~ 1. -- this is only elementary fermion with a mass near the Electro-Weak Symmetry breaking scale. -- If we can measure strength of this coupling (i.e. ttH), a test of the Standard Model of the Higgs sector can be performed. it will be possible in the future.

  3. 3. Precise top quark mass measurement can pin down Higgs mass. (within Standard Model framework: together with W boson mass precise measurement) 2 d Mw { Mt, ln(M ) } H Tevatron top mass direct measurement can be compared toEW Indirect prediction via radiative correction. Next Target is to predict Higgs mass using precise top mass.

  4. Goal of Run II Current Higgs mass constraint Top quark mass ~ 2 – 3 GeV W boson mass ~ 30 – 40 MeV d M / M ~ 35% H H

  5. 2. Overview of the measurement: (Top quark production at the Tevatron) Since Tevatron is p p collider, q q annihilation is dominant process. (~ 85%) Total cross section of t t production is 5.8 – 7.4 pb. (theory: hep-ph/0303085 M.Cacciari et al) at = 1.96 TeV.

  6. Top quark decay “t -> W + b” is the dominant process. (V ~ 1, M > M + M ) tb b t W Today’s talk concentrates on these mode because they were most precise ones in Run I and give the earliest result for Run II ( t t  WbW’b  (l nb) (qqb) )

  7. Overview of the measurement: Event selection lepton+jets analysis event selection criteria: event passes high-P electron or muon triggers lepton E >20GeV, missing E >20GeV. 3 jets with ( E >15GeV, | h |<2.0 ) and a 4th jet with (E >8GeV, | h |<2.4: Run I), (E >8GeV, | h |<2.0: Run II) For Run I, b-tag analysis: >= 1 jet tagged as a b from lifetime (SVX) or semi-leptonic(SLT) analysis ignoring tags: 4 jets satisfy tight criteria(E >15GeV). For Run II, analysis ignoring tags: 4 jets satisfy tight criteria ( tagged analyses are coming) T T T T T T T

  8. 4.Overview of the measurement: technical details A kinematic fit is applied to each event under the hypothesis of top decay: p p  t t X  W b W b X  ln b j j b X constraints: tagged jet(s) is assigned to b-quark. M = M = M M = M Best c combination is used. Top mass for each event is reconstructed here. In each data set, backgrounds are estimated: QCD W+heavy flavor (bb, cc), non-W, SVX mistag, etc. A likelihood technique is employed to determine the top mass. - + 1 2 ln jj W t t 2 There are 24 combs. (12: jet – parton match, 2: neutrino Pz )

  9. 3. Quick review of Run I measurement Lepton + jets mode 2 SVX tag: 170.1+-9.3 GeV (5 obs, 5+-3% BKG) 1 SVX tag: 178.0+-7.9 GeV (15 obs, 13+-5% BKG) SLT tag : 142.0+33-14 GeV (14 obs, 40+-9% BKG) No tag : 181.0+-9.0 GeV (42 obs, 56+-16% BKG) Trading of stat., BKG, jet assignment Lepton+jets mode combined: 175.9 +- 7.1 GeV Tevatron combined: 174.3 +- 5.1 GeV

  10. 4.Measurement with CDF in Run II: Tevatron upgrade Tevatron upgrade: new main injector new recycler ring improved p source and booster Instantaneous luminosity goal  10 times Run I In addition, beam energy increased 900 ->980GeV This provides 30-40% cross section increase. Today’s talk until Jun-03 Delivered ~130pb-1 Tape ~100pb-1 Detector OK ~ 72pb-1 ~130pb-1 Detector OK ~ 56pb-1 ~110pb-1 (w/ SVX) comments early part since Jan-03 of Run II tape/del ~85% when detectors good/tape were ~95% commissioned. (typically) Run IIa integrated luminosity (-Jun/2003) Mar-02 Jan-03 Today’s talk commissioning

  11. 4. Measurement with CDF in Run II: detector upgrade Up to | h |=1.5 | h | out to 2.0 New DAQ and Silicon Vertex Trigger (online impact parameter trigger : SVT) was also newly installed.

  12. Measurement with CDF in Run II: results from lepton+jets mode (no btag) Run II starts measuring top mass !! Lepton + jets mode with no b-tag (but 4 tight jet) sample gives the first result: 171.2 +-13.4(stat.) +-9.9(sys.) GeV Selection criteria are the same as mentioned before. Results with b-tag coming soon.

  13. 4. Measurement with CDF in Run II: lepton + jets mode 57 b-tag sample with 3 tight jets (E >15GeV, | h | <2.0) + 1 loose jet ( E > 8GeV, | h | <2.0) T T

  14. 5. Toward the goal: Uncertainties Run I Run II (preliminary) Stat. Error 4.8GeV ~14.0GeV (combined) (one mode) Jet Energy scale 4.4GeV 9.3GeV ISR/FSR 2.6GeV 2.4GeV Background shape 1.3GeV 0.3GeV PDF 0.3GeV 1.8GeV MC generators 0.1GeV 1.8GeV Jetenergy scale: understanding of calorimeter response for CDF II is under way. Since this winter, we have significant improvement. (comparable value to Run I by next winter conference) PDF, generators: Estimated method and MC are different from Run I. We have to check this continuously.

  15. 5. Toward the goal: Improvement of systematics • (0) Careful detector maintenance and calibration is needed. • Number of control sample (stat.) will be increased. • At 2 fb-1, number of events is: • 20(luminosity) x 1.3(xsec) x detector acceptance > 26 times Run I • (i.e. SVX tag events: > 520 events) • (2) Jet Energy Scale: • -- Gamma jet E balance is a basic tool for in-situ calibration. • (see next slide: 2002-ICHEP result) • -- Calibration of b-jet energy scale using Z  b b process • with new track impact parameter trigger (SVT) • -- Z boson and jet E balance with high stat. is available. • -- Increasing double b-tag events will allow in-situ W mass • calibration for top quark decay. • (4) ISR / FSR: • -- Experimental study of gluon radiation (with MC) • (5) Background shape: • -- Z + 4 jets data is useful to uderstand the W+4j background. T T

  16. 6. Summary • CDF restarts the top quark mass measurement using upgraded • Tevatron and detector. • Preliminary value using no b-tag and 4 jet sample is • 171.2 +14.4-12.5 (stat.) +- 9.9 (syst.) GeV. • Result using b-tagged events as well as the first Run II • dilepton result, will be available soon. • Toward the Run IIa goal, we have many things to do. • A major focus is reducing the jet energy uncertainty. • CDF Run IIa will provide an important indirect Higgs mass • constraint via the top mass measurement.

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