IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 1 XXXIV International Meeting on Fundamental Physics Rick Field University of Florida (for the CDF & D0 Collaborations) CDF Run 2 Real Colegio Maria Cristina, El Escorial, Spain From HERA and the TEVATRON to the LHC Physics at the Tevatron 2 nd Lecture Heavy Quark Physics at the Tevatron

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 2 Heavy Quark Physics at the Tevatron  Charm Production at the Tevatron.  J/  and Bottom Production at the Tevatron.  Top Production at the Tevatron.

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 3 Heavy Quark Production at the Tevatron  Total inelastic  tot ~ 100 mb which is larger than the cross section for D-meson or a B-meson.  However there are lots of heavy quark events in 1 fb -1 !  Want to study the production of charmed mesons and baryons: D +, D 0, D s, c,  c,  c, etc.  Want to studey the production of B-mesons and baryons: B u, B d, B s, B c, b,  b, etc.  Two Heavy Quark Triggers at CDF: For semileptonic decays we trigger on  and e. For hadronic decays we trigger on one or more displaced tracks (i.e. large impact parameter). with 1 fb -1 ~1.4 x ~1 x ~6 x 10 6 ~6 x 10 5 ~14,000 ~5,000 CDF-SVT

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 4 Selecting Heavy Flavor Decays  To select charm and beauty in an hadronic environment requires: High resolution tracking A way to trigger on the hadronic decays (i.e. a way to trigger on tracks) CDF Primary Vertex Secondary Vertex I mpact P arameter ( ~100  m) L xy ~ 1 mm B/D decay D 0  K  The CDF Secondary Vertex Trigger (SVT) Online (L2) selection of displaced tracks based on Silicon detector hits.  At CDF we have a “Secondary Vertex Trigger” (the SVT). Collision Point

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 5 Selecting Prompt Charm Production  Separate prompt (i.e. direct) and secondary charm based on their transverse impact parameter distribution. Direct Charm Meson Fractions: D 0 : f D =86.4±0.4±3.5% D* + : f D =88.1±1.1±3.9% D + : f D =89.1±0.4±2.8% D + s : f D =77.3±3.8±2.1% B  D tail Prompt DSecondary D from B Prompt peak D impact parameter  Prompt D-meson decays point back to primary vertex (i.e. the collision point).  Secondary D-meson decays do not point back to the primary vertex. Most of reconstructed D mesons are prompt! Collision Point

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 6 Prompt Charm Meson Production  Theory calculation from M. Cacciari and P. Nason: Resummed perturbative QCD (FONLL), JHEP 0309,006 (2003). Fragmentation: ALEPH measurement, CTEQ6M PDF. Charm Meson P T Distributions CDF prompt charm cross section result published in PRL (hep-ex/ ) Data collected by SVT trigger from 2/2002-3/2002 L = 5.8±0.3 pb -1.

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 7 Comparisons with Theory  NLO calculations compatible within errors?  The p T shapes are consistent with the theory for the D mesons, but the measured cross section are a factor of about ~1.5 higher! Ratio of Data to Theory Next step is to study charm-anticharm correlations to learn about the contributions from different production mechanisms: “flavor creation” “flavor Excitation” “gluon splitting”

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 8 Bottom Quark Production at the Tevatron  Important to have good leading (or leading-log) order QCD Monte-Carlo model predictions of collider observables.  The leading-log QCD Monte-Carlo model estimates are the “base line” from which all other calculations can be compared.  If the leading-log order estimates are within a factor of two of the data, higher order calculations might be expected to improve the agreement.  If a leading-log order estimate is off by more than a factor of two, it usually means that one has overlooked something.  I see no reason why the QCD Monte-Carlo models should not qualitatively describe heavy quark production (in the same way they qualitatively describe light quark and gluon production). QCD Monte-Carlo leading order “Flavor Creation” is a factor of four below the data!  “Something is goofy” (Rick Field, CDF B Group Talk, December 3, 1999). Tevatron Run 1 b-Quark Cross Section Extrapolation of what is measured (i.e. B- mesons) to the parton level (i.e. b-quark)! CDF Run

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 9 The Sources of Heavy Quarks  We do not observe c or b quarks directly. We measure D-mesons (which contain a c-quark) or we measure B-mesons (which contain a b-quark) or we measure c-jets (jets containing a D-meson) or we measure b-jets (jets containing a B-meson). Leading Order Matrix Elements Leading-Log Order QCD Monte-Carlo Model (LLMC) (structure functions)× (matrix elements)× (Fragmentation) + (initial and final-state radiation: LLA)

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 10 Other Sources of Heavy Quarks  In the leading-log order Monte-Carlo models (LLMC) the separation into “flavor creation”, “flavor excitation”, and “gluon splitting” is unambiguous, however at next to leading order the same amplitudes contribute to all three processes! Next to Leading Order Matrix Elements “Flavor Excitation” (LLMC) corresponds to the scattering of a b-quark (or bbar-quark) out of the initial-state into the final-state by a gluon or by a light quark or antiquark. “Gluon-Splitting” (LLMC) is where a b-bbar pair is created within a parton shower or during the the fragmentation process of a gluon or a light quark or antiquark. Here the QCD hard 2- to-2 subprocess involves only gluons and light quarks and antiquarks. Amp(gg→QQg) = ++  (gg→QQg) = 2 and there are interference terms!

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 11 Inclusive b-quark Cross Section  Data on the integrated b-quark total cross section (P T > PTmin, |y| < 1) for proton-antiproton collisions at 1.8 TeV compared with the QCD Monte-Carlo model predictions of PYTHIA (CTEQ3L, PARP(67)=4). The four curves correspond to the contribution from “flavor creation”, “flavor excitation”, “gluon splitting”, and the resulting total. Total “Flavor Creation” “Flavor Excitation” “Gluon Splitting” Tevatron Run 1 b-Quark Cross Section

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 12 All three sources are important at the Tevatron! Conclusions from Run 1  All three sources are important at the Tevatron and the QCD leading-log Monte-Carlo models do a fairly good job in describing the majority of the b-quark data at the Tevatron.  We should be able experimentally to isolate the individual contributions to b-quark production by studying b-bbar correlations find out in much greater detail how well the QCD Monte-Carlo models actually describe the data.  One has to be very careful when the experimenters extrapolate to the parton level and publish parton level results. The parton level is not an observable! Experiments measure hadrons! To extrapolate to the parton level requires making additional assumptions that may or may not be correct (and often the assumptions are not clearly stated or are very complicated). It is important that the experimenters always publish the corresponding hadron level result along with their parton level extrapolation.  One also has to be very careful when theorists attempt to compare parton level calculations with experimental data. Hadronization and initial/final-state radiation effects are almost always important and theorists should embed their parton level results within a parton-shower/hadronization framework (e.g. HERWIG or PYTHIA). “Nothing is goofy” Rick Field, Cambridge Workshop, July 18, 2002

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 13 PT Asymmetry  Predictions of PYTHIA (CTEQ4L, PARP(67)=1) for the asymmetry A = (PT 1 -PT 2 )/(PT 1 +PT 2 ) for events with a b-quark with PT 1 > 0 GeV/c and |y 1 | 5 GeV/c and |y 2 | < 1.0 in proton-antiproton collisions at 1.8 TeV. The curves correspond to d  /dA (  b) for flavor creation, flavor excitation, shower/fragmentation, and the resulting total. “Flavor Creation” “Flavor Excitation” “Gluon Splitting”

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 14 Distance R in  -  Space  Predictions of PYTHIA (CTEQ4L, PARP(67)=1) for the distance, R, in  -  space between the b and bbar-quark with PT 1 > 5 GeV/c, PT 2 > 5 GeV/c, and |y 1 |<1 in proton- antiproton collisions at 1.8 TeV. The curves correspond to d  /dR (  b) for flavor creation, flavor excitation, gluon splitting, and the resulting total. “Flavor Creation” “Flavor Excitation” “Gluon Splitting”

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 15 Distance R in  -  Space  Predictions of PYTHIA (CTEQ4L, PARP(67)=1) for the distance, R, in  -  space between the b and bbar-quark with |y 1 |<1 and |y 2 |<1 in proton-antiproton collisions at 1.8 TeV. The curves correspond to d  /dR (  b) for flavor creation, flavor excitation, shower/fragmentation, and the resulting total. “Gluon Splitting”

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 16 Azimuthal Correlations  Predictions of PYTHIA (CTEQ4L, PARP(67)=1) for the azimuthal angle, , between a b- quark with PT 1 > 5 GeV/c and |y 1 | 0 GeV/c and |y 2 |<1 in proton- antiproton collisions at 1.8 TeV. The curves correspond to d  /d  (  b/ o ) for flavor creation, flavor excitation, shower/fragmentation, and the resulting total.

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 17 Azimuthal Correlations  Predictions of PYTHIA (CTEQ5L) with PARP(67)=1 (new default) and PARP(67)=4 (old default) for the azimuthal angle, , between a b-quark with PT 1 > 15 GeV/c, |y 1 | 10 GeV/c, |y 2 |<1 in proton-antiproton collisions at 1.8 TeV. The curves correspond to d  /d  (  b/ o ) for flavor creation, flavor excitation, gluon splitting, and the resulting total. New PYTHIA default (less initial-state radiation) Old PYTHIA default (more initial-state radiation) “Flavor Creation” “Flavor Excitation” “Gluon Splitting”

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 18 Azimuthal Correlations  Predictions of HERWIG 6.4 (CTEQ5L) for the azimuthal angle, , between a b-quark with PT 1 > 15 GeV/c, |y 1 | 10 GeV/c, |y 2 |<1 in proton-antiproton collisions at 1.8 TeV. The curves correspond to d  /d  (  b/ o ) for flavor creation, flavor excitation, shower/fragmentation, and the resulting total. “Flavor Creation” New PYTHIA default (less initial-state radiation) Old PYTHIA default (more initial-state radiation)

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 19 CDF Run I Analysis Azimuthal Correlations  Run I CDF data for the azimuthal angle, , between a b-quark |y 1 | < 1 and bbar-quark |y 2 |<1 in proton- antiproton collisions at 1.8 TeV favored PYTHIA Tune A (PARP(67) = 4). Kevin Lannon DPF2002 Now published!

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 20 The Run 2 J/  Cross Section  The J/  inclusive cross-section includes contribution from the direct production of J/  and from decays from excited charmonium,  (2S), and from the decays of b- hadrons, B→ J/  + X. CDF (  b)  (J/  |Y(J/  )| < 0.6)4.08  0.02(stat)+0.36(sys)-0.48(sys) Down to P T = 0! J/  K B   J/  coming from b-hadrons will be displaced from primary vertex! 39.7 pb -1 Primary vertex (i.e. interaction point) 4.8 pb -1

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 21 CDF Run 2 B-hadron Cross Section  Run 2 B-hadron P T distribution compared with FONLL (CTEQ6M). B-hadron p T CDF (  b)FONLL (  b)  (B-hadron)29.4  0.6(stat)  6.2(sys) |Y| < 1.0  Good agreement between theory and experiment! 39.7 pb -1 Cacciari, Frixone, Mangano, Nason, Ridolfi PRD 71, (2005)

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 22 CDF Run 2 b-Jet Cross Section  b-quark tag based on displaced vertices. Secondary vertex mass discriminates flavor.  Require one secondary vertex tagged b-jet within 0.1 < |y|< 0.7 and plot the inclusive jet P T distribution (MidPoint, R = 0.7). Collision point

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 23 CDF Run 2 b-Jet Cross Section  Shows the CDF inclusive b-jet cross section (MidPoint, R = 0.7, f merge = 0.75) at 1.96 TeV with L = 300 pb -1.  Shows data/theory for NLO (with large scale uncertainties).  Shows data/theory for PYTHIA Tune A.

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 24 The b-bbar DiJet Cross-Section  E T (b-jet#1) > 30 GeV, E T (b-jet#2) > 20 GeV, |  (b-jets)| < 1.2. Differential Cross Section as a function of the b-bbar DiJet invariant mass! Preliminary CDF Results:  bb = 34.5  1.8  10.5 nb QCD Monte-Carlo Predictions: PYTHIA Tune A CTEQ5L ± 0.62 nb HERWIG CTEQ5L21.53 ± 0.66 nb ± 0.58 nb Predominately Flavor creation! Systematic Uncertainty  Large Systematic Uncertainty:  Jet Energy Scale (~20%).  b-tagging Efficiency (~8%)

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 25 The b-bbar DiJet Cross-Section  E T (b-jet#1) > 30 GeV, E T (b-jet#2) > 20 GeV, |  (b-jets)| < 1.2. Preliminary CDF Results:  bb = 34.5  1.8  10.5 nb QCD Monte-Carlo Predictions: PYTHIA Tune A CTEQ5L 38.7 ± 0.6 nb HERWIG CTEQ5L21.5 ± 0.7 nb ± 0.6 nb + Jimmy35.7 ± 2.0 nb Differential Cross Section as a function of the b-bbar DiJet invariant mass! Adding multiple parton interactions (i.e. JIMMY) to enhance the “underlying event” increases the b-bbar jet cross section! JIMMY: MPI J. M. Butterworth J. R. Forshaw M. H. Seymour JIMMY Runs with HERWIG and adds multiple parton interactions!

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 26 b-bbar DiJet Correlations  The two b-jets are predominately “back-to- back” (i.e. “flavor creation”)!  Pythia Tune A agrees fairly well with the  correlation! Differential Cross Section as a function of  of the two b-jets! Tune A! Not an accident!

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 27 Top Production at the Tevatron  Top quark discovered in 1995 by CDF and DØ.  Not a surprise: SM quark sector now complete.  Now study the detailed properties of the top: Charge. Lifetime. Branching ratios. W-boson helicity.  Make precision measurements: Cross-sections now 12%! Mass now 2%!  Measure single top production!

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 28 Top Decay Channels  m t >m W +m b so dominant decay t  Wb.  The top decays before it hadronizes.  B(W  qq) ~ 67%.  B(W  l ) ~ 11% l = e, 

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 29 Dilepton Channel (CDF)  Backgrounds: Physics: Drell-Yan, WW/WZ/ZZ, Z   Instrumental: fake lepton  Selection: 2 leptons E T > 20 GeV with opposite sign. >=2 jets E T > 15 GeV. Missing E T > 25 GeV (and away from any jet). H T =p Tlep +E Tjet +ME T > 200 GeV. Z rejection.  (tt) = 8.3 ± 1.5 (stat) ± 1.0 (syst) (lumi) pb 65 events 20 events background

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 30 Lepton+Jets Channel (CDF) Kinematics  Selection: 1 lepton with p T > 20 GeV/c. >= 3 jets with p T > 15GeV/c. Missing E T > 20 GeV.  Backgrounds: W+jets QCD spherical central binned likelihood fit  Use 7 kinematic variables in neural net to discriminate signal from background! One of the 7 variables!  (tt) = 6.0 ± 0.6 (stat) ± 0.9 (syst) pb Neural net output!

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 31 Lepton+Jets Channel (CDF) H T >200GeV 2 b tags b-Tagging  Require b-jet to be tagged for discrimination. Tagging efficiency for b jets~50% for c jets~10% for light q jets < 0.1% 1 b tag ~150 events Small background!  (tt) = 8.2 ± 0.6 (stat) ± 1.1 (syst) pb ~45 events

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 32 All Hadronic Channel (DØ)  Selection: >=6 jets with p T > 15 GeV/c. >=1 b tagged. NN discriminant > 0.9.  Huge QCD background! Geometric mean of 5 th and 6 th leading jet E T  Use 6 kinematic variables in neural net to discriminate signal from background! One of the 6 variables!

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 33 Tevatron Top-Pair Cross Section Bonciani et al., Nucl. Phys. B529, 424 (1998) Kidonakis and Vogt, Phys. Rev. D68, (2003) Theory CDF Run 2 Preliminary

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 34 New CDF M top Results CDF Lepton+jets: M top (template) = ± 2.5 (stat. + jet E) ± 1.3 (syst.) GeV M top (matrix element) = ± 2.5 (stat. + jet E) ± 1.4 (syst.) GeV M top (L xy ) = (stat.) ± 5.6 (syst.) GeV CDF Dilepton: M top (matrix element) = ± 4.5 (stat.) ± 3.1 (jet E. + syst.) GeV Transverse decay length!

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 35 Top Quark Mass Summer 2005 Dilepton: CDF-II M top ME = ± 5.5 GeV Lepton+Jets: CDF-II M top Temp = ± 2.8 GeV CDF-II M top ME = ± 2.9 GeV CDF Combined: M top CDF = ± 1.6 ± 2.2 GeV = ± 2.7 GeV New since Summer 2005

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 36 Top Cross-Section vs Mass Tevatron Summer 2005CDF Winter 2006 Updated CDF+DØ combined result is coming soon! CDF combined

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 37 Is Anything “Goofy”?  Possible discrepancy between l + jets and the dilepton channel measurements of the top mass??  Is it statistical? ME(dilepton) vs Templ(l+jets):  2 = 2.9/1, Prob = 0.09 (accounts for correlated systematics).  Is there a missing systematic?  This is probably nothing, but we should keep an eye on it!

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 38 Future Top Mass Measurements  Expect significant reduction in jet energy scale uncertainty with more data.  Today we have CDF-II M top (Temp) = ± 2.8 GeV (~0.7 fb -1 ).  CDF should be able to achieve 1.5 GeV uncertainty on top mass! Systematic Source Uncertainty (GeV/c 2 ) ISR/FSR0.7 Model0.7 b-jet0.6 Method0.6 PDF0.3 Total1.3 Jet Energy2.5

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 39 Constraining the Higgs Mass  Top quark mass is a fundamental parameter of SM.  Radiative corrections to SM predictions dominated by top mass.  Top mass together with W mass places a constraint on Higgs mass! Tevatron Run I + LEP2 This spring? Summer GeV Higgs very interesting for the Tevatron!

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 40 Top Quark Charge +2/3 or -4/3?  t  Wb but W + b or W - b? Check to see if Q = +2e/3 (as expected) or Q = -4e/3 (i.e. exotic quark).  DØ uses Lepton+Jets double-tag sample.  2 fit for paring of leptonic b. JetQ for flavor tagging b jet. Likelihood ratio test. b bdduu B0B0 -- 2e/3 -4e/3 370 pb events 34 top Measure  data = 11.5 exclude -4e/3 hypothesis to 94% CL exclude +2e/3 hypothesis to 66% CL.

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 41 W-Boson Helicity (DØ)  In SM (V-A coupling of tWb) only 2 helicities allowed: f + =0, f - ~0.3, f 0 ~0.7.  DØ uses both the cos  * (in Lepton+Jets) and lepton P T (in dilepton) variables to measure f + (fix f 0 ). Combined Result f + = 0.04 ± 0.11 (stat) ± 0.06 (syst) 0.0 < f + <0.25 at 95%CL

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 42 Top: Charge, Branching, Lifetime, W Helicity DØ Prelim. 365 pb -1 Top Charge  top < 1.75x s c  top < 52.5  m at 95%CL Exclude |Q| = 4/3 at 94% CL Reconstructed Top Charge (e) SM bgrnd signal f + (DØ combined) = 0.04 ± 0.11(stat) ± 0.06(syst) f + (SM pred.) = 0 signal+bgrnd 370 pb -1 hep-ex/ CDF Prelim. 318 pb -1 Top Lifetime Impact Parameter (  m) Everything consistent with the Standard Model!

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 43 Other Sources of Top Quarks ~85% g g Strongly Produced tt Pairs  Dominant production mode  NLO+NLL = 6.7  1.2 pb  Relatively clean signature  Discovery in 1995 ElectroWeak Production: Single Top  Larger background  Smaller cross section  ≈ 2 pb  Not yet observed! ~15%

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 44 Single Top Production s-channelt-channelAssociated tW Combine (s+t) Tevatron  NLO 0.88  0.11 pb1.98  0.25 pb ~ 0.1 pb LHC  NLO 10.6  1.1 pb247  25 pb pb CDF< 18 pb< 13 pb< 14 pb D0< 17 pb< 22 pb B.W. Harris et al.:Phys.Rev.D66, T.Tait: hep-ph/ Z.Sullivan Phys.Rev.D70: Belyaev,Boos: hep-ph/ Run I 95% C.L. (m top =175 GeV/c 2 ) s-channelt-channel tW associated production

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 45 New Single Top Results from CDF  To the network 2D output, CDF applies a maximum likelihood fit and the best fits for t and s-channels are: t-channel:  < % C.L. s-channel:  < % C.L. The new CDF limits!

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 46 Single Top at the Tevatron  The current CDF and DØ analyses not only provide drastically improved limits on the single top cross-section, but set all necessary tools and methods toward a possible discovery with a larger data sample!  Both collaborations are aggressively working on improving the results! 95% C.L. limits on single top cross-section Single Top Discovery is Possible in Run 2 !!!! Channel CDF (696 pb -1 ) DØ (370 pb -1 ) Combined3.4 pb s-channel3.2 pb5.0 pb t-channel3.1 pb4.4 pb (2 pb) (0.9 pb) (2.9 pb) Theory!

IMFP Day 2 April 4, 2006 Rick Field – Florida/CDF/CMSPage 47 Top-AntiTop Resonances  CDF observed an intriguing excess of events with top-antitop invariant mass around 500 GeV! Phys.Rev.Lett. 85, 2062 (2000) CDF Run 1 Excess is reduced!