physics of hadron colliders: lecture 4 – heavy flavors

50
Physics of Hadron Colliders: Lecture 4 – Heavy Flavors Joseph Kroll University of Pennsylvania 21 June 2004

Upload: clarke-newman

Post on 04-Jan-2016

49 views

Category:

Documents


4 download

DESCRIPTION

Physics of Hadron Colliders: Lecture 4 – Heavy Flavors. Joseph Kroll University of Pennsylvania 21 June 2004. Tevatron Makes Progress Every Week. Another Record Store: CDF: 9.0 £ 10 31 cm -2 s -1 D Ø: 7.5 £ 10 31 cm -2 s -1. The Competition for B Physics. KEK. Context. - PowerPoint PPT Presentation

TRANSCRIPT

Page 1: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

Physics of Hadron Colliders:Lecture 4 – Heavy Flavors

Joseph Kroll

University of Pennsylvania

21 June 2004

Page 2: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 2

Tevatron Makes Progress Every Week

Another Record Store:CDF: 9.0 £ 1031 cm-2s-1

DØ: 7.5 £ 1031 cm-2s-1

Page 3: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 3

The Competition for B Physics

KEK

Page 4: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 4

Context

You have all heard this before: “The SM is very successful, but…”

Lecture 3 addressed issues related to EW symmetry breaking

Three of the outstanding issues are1. Electroweak symmetry breaking (why MW,MZ ≠ 0)

- does the Higgs exist?- is there supersymmetry?- if neither, what is the mechanism?

2. The flavor problem- are there 3 & only 3 families?- why masses of fundamental fermions so different?- what set values & hierarchy of flavor parameters (quarks & leptons very different)

3. Violation of CP Symmetry- why does matter dominate antimatter in Universe?- is mechanism in SM correct, is it enough?

Today we will talk about addressing the flavor problem and CP violation

Page 5: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 5

The Flavor Parameters (CKM Matrix)

mass eigenstates ≠ weak eigen.

weak mass

related by Cabibbo-Kobayashi-Maskawa Matrix

V is unitary: VyV = 1 Measurements + Unitarity assuming 3 generations

PDG: K. Hagiwara et al., Phys. Rev. D66 010001 (2002) Ranges are 90% CL

Page 6: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 6

Different Parameterizations of CKM Matrix

L. L. Chau, W. Y. Keung Phys. Rev. Lett. 53, p. 1802 (1984) - used by PDG

3 £ 3 complex unitary matrix: 3 real & 1 imag. parameters ≡ 3 angles, 1 phase

notation: cij´ cosij & sij´ sinij, i, j = 1st, 2nd, 3rd generation

Advantages of this parameterization:1. Satisfies unitarity exactly2. If ij= 0, generations i & j decouple3. If 13= 23= 0, 3rd generation decouples, 12 is Cabibbo angle4. Same formulation used for lepton mixing matrix U with (£ diag[ei1/2,ei2/2, 1])

Page 7: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 7

Wolfenstein Parametrization Illustrates Hierarchy

Original reference: L. Wolfenstein, PRL, 51, p. 1945 (1983)Reference for this slide: A. Höcker et al., Eur. Phys. J. C21, p. 225 (2001); ibid, hep-ph/0406184

valid to O(6) ¼ 0.01%, = Vus = sinCabibbo» 0.2

Define:

from hep-ph/0406184

Page 8: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 8

New Measurement of Vus from KTeV

1st row of CKM matrix provides the most stringent test of unitarity:

The KTeV Collaboration, T. Alexopoulos et al., hep-ex/0406001 (sub. to PRL) – and references there in

PDG 2002

New results from KTeV These results from measuredKL semileptonic decays:f+(0) is the l form factor at q2=0

Vus = 0.2252 § 0.0008KTeV § 0.0021external

Unitarity now satisfied: 0.0018 § 0.0019

}

}Moral: well measured parameters can change

Page 9: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 9

The Unitarity Triangles

V is unitarity

geometric representation: triangle in complex plane

Im

ReVi1V*

k1

Vi2V*k2Vi3V*

k3

There are 6 triangles

Kaon UT

Beauty UT

flat

n.b. these triangles arerescaled by one of the sides

i = 1 is previous page

Page 10: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 10

The Beauty Unitary Triangle

of Chau & Keungparametrization is

Page 11: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 11

How Do Measurements Constrain Triangle?Figure courtesy of CKM Fitter group: ckmfitter.in2p3.fr – as were all of the formulas on previous slides

B0 flavor oscillations (md)constrains one side

How do B0s oscillations (ms)

fit in this picture?

Why is ms consideredone of the most important Run II measurements?

Aside: a key issue is to pickexperimental quantities thatcan be related to CKM para.without large theory errors

Page 12: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 12

Neutral Meson Flavor Oscillations

Page 13: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 13

Neutral B Meson Flavor Oscillations

Flavor oscillations occur through2nd order weak interactions

e.g.

Same diagrams and formula for ms for Bs except replace “d” with “s”

All factors known well except “bag factor” £ “decay constant”

md = 0.489 § 0.008 ps-1 (2%) (PDG 2002) from Lattice QCD calculations – see hep-ph/0406184

From measurement of md derive |V*tbVtd|2

Page 14: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 14

B Meson Flavor Oscillations (cont)

If we measure ms then we would know the ratio ms/md

Many theoretical quantities cancel in this ratio, we are left with

from Lattice QCD calculations – see hep-ph/0406184

Since Vts ¼ Vcb this gives us our side Rt

This is why ms ishigh priority in Run II

Page 15: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 15

Current Status of ms

Results from LEP, SLD, CDF I ms > 14.5 ps-1 95% CL

see http://www.slac.stanford.edu/xorg/hfag/osc/winter_2004/index.html

Amplitude method:H-G. Moser, A. Roussarie,NIM A384 p. 491 (1997)

Page 16: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 16

CP Violation Through Mixing in B Decays

Examples

yields sin2

Weak phase in Vts very small very small SM CP asymmetry

Large asymmetry unambiguousevidence of new physics(B0 ! K0)

must know ms to observe

Page 17: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 17

B Physics at Hadron Machines

Strong interaction produces bb pairs

Example of lowest order (LO) s2

Example of next leading order (NLO) s3

NLO contribution comparable to LO contributionsee P. Nason, S. Dawson, R. K. EllisNucl. Phys. B273, p. 49 (1988)

called “flavor creation”

“gluon splitting”

“flavor excitation”

b pairs produced close in y

Page 18: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 18

B Physics at Hadron Machines (cont.)

b quarks then fragment to B hadrons

B factories running on Y(4S) only produce lightest B mesons

Hadron colliders (and e+e- colliders running above Y(4S)) produce other B’s

fragmentation is hard: B hadron gets large fraction of b quark E

Many unique B measurements at hadron colliders

e.g., ms, Bs rare decays, observation Bc, b lifetime

Page 19: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 19

B Production at Tevatron

The inclusive b cross-section is enormous: on the order of 100b

For L = 1031 cm-2s-1 (1032) £ L = 1kHz (10kHz)

Much of this not useful (trigger, acceptance, analysis selection criteria)The useful cross-section is order 10b

This is still well above production cross-section at B Factories, Z pole

The CDF Collaboration, D. Acosta et al., Phys. Rev. D65, 052005 (2002)

B factory rate: L = 1034 cm-2s-1 £ L = 10 Hz

£ L » 100 Hz

Page 20: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 20

B Production Tests QCD

Measurement of B production an extremely interesting test of QCDThere is an outstanding disagreement between theory and data

The CDF Collaboration, D. Acosta et al., Phys. Rev. D65, 052005 (2002)

Data factor 2 – 3above theory

Recent theoretical workhas reduced discrepancy:b ! B frag. model

Measurement of production fractions (fd, fu, fs, fbaryon, fB**) interesting tooAlso necessary for absolute branching fractions & other studies

Page 21: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 21

Characteristics of B Production and Decay

b large, butinelastic » 103 larger

Trigger & analysis strategy:Exploit unique aspectsb production & decay

UA1 showed it was possible:b! X, b! X, b mixing

Then CDF fully reconstructed B

B-! J/ K-, J/!+-

F. Abe et al.,PRL 68, 3403 (1992)

CDF “Run 0”2.6§0.2 pb-1

Page 22: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 22

Silicon trackingDrift chamber

Lumi monitor

Hadronic Calorimetry

Muon systems

Iron shielding

Solenoid and TOF

ElectromagneticCalorimetry

CDF II

New Front-end elec. & DAQ: 7.6 MHz clock (132 ns)

Page 23: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 23

Some Key Detector Features for B Physics

• Immersed in 1.4 T axial field; covers R = 0.4 m to 1.4 m; full coverage ||<1• High redundancy drift chamber: 4 axial & 4 stereo (2o) layers – 12 wires each• Particle ID with dE/dx from time over threshold

Central Outer Tracker (COT) Resolution pT/pT = (0.15%) pT (in GeV/c)

Particle separation power from dE/dx

K/ separation > 1.4 for pT>2 GeV e/ separation = 3 for pT=1 GeV

K

e

Page 24: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 24

Some Key Detector Features for B Physics

Silicon Tracking – 3 separate detectors

1. Layer 00: (single sided) • attached to beampipe • 1.4 to 1.6cm from beam line • axial only2. SVXII: (double sided) • 87 cm length, 12 wedges in azimuth • 5 layer with 3D track reconstruction • axial+small angle stereo or axial+90o • 3 barrels (6 half barrels in trigger) • 2.4 cm inner radius, 10.6 cm outer 3. ISL: (double sided) • 1 layer at 22 cm in ||<1 • 2 layers (20 & 28 cm) 1<||<2 • axial+small angle stereo

Online impact parameter resol.47m best wedges55m average of all wedgesincludes » 30m from beam

SVTonline@ L2

Page 25: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 25

Time of Flight Detector (TOF)

• 216 Scintillator bars, 2.8 m long, 4 £ 4 cm2

• located @ R=140 cm• read out both ends with fine mesh PMT (operates in 1.4 T B field – gain down ~ 400)• anticipated resolution TOF=100 ps• (limited by photostatistics)

Kaon ID for B physics

Measured quantities:s = distance travelledt = time of flightp = momentum

Derived quantities:v = s/tm = p/v

Page 26: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 26

CDF II Trigger System

Detector

L1 trigger

L2 trigger

L3 trigger

tape

46 L1buffers

1.7 MHz bunchcrossing rate

30 kHz L1 accept

300 Hz L2 accept

70 Hz L3 accept

Hardware tracking for pT 1.5 GeV

Muon-track matching

Electron-track matching

Missing ET, sum-ET

Silicon tracking for pT>2 GeV

300 CPU’s

Jet finding

Full event reconstruction

Refined electron/muon/photon finding

>100Hz with datacompression

4 L2 buffers

courtesy E. Thomson (OSU/Penn)

(XFT)

(SVT)

Page 27: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 27

Trigger Strategy for B Physics

Exploit the characteristics of B production and decay

1. B mass relatively large decay products have relatively high pT

require pT > 1.5 – 2.0 GeV/c or larger

2. B decay produces high pT leptons (electron and muon)

B! X, e X & B! J/ X, J/!+-

3. B’s have long decay distance trigger on displaced tracks

B0s

D-s +

-

K-

K+

d0

4. Combine lepton & displaced track

Page 28: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 28

Example of Specific Trigger for B Physics

Hadronic Path – designed for B0s! D-

s+Level 1 - 2 XFT tracks with pT > 1.5 GeV - opposite charge - < 135o

- |pT1| + |pT2| > 5.5 GeV

Level 2 - confirm L1 requirements - both XFT tracks - SVT 2<15 - 120 m< |d0| <1mm - 2o < < 90o

- Decay length Lxy > 200 m

Level 3 - confirm L2 with COT & SVX “offline” quality track reco.

At Level 3 usingtrigger criteria

Page 29: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 29

CDF = “Charm Detector @ Fermilab”

Most of that charm is prompt charm, i.e., not from B ! DX

We proved that using the D impact parameter - prompt charm points back to the PV (within resolution) - charm from B do not point to PV

Prompt B ! D

Measure d0 resolution in prompt peakapply to model of B! DX

Prompt fraction: (86.6 § 0.4 (stat.))%Systematic error 3-4%

CDF II, D. Acosta et al., PRL 91, 241804 (2003) & C. Chen (UPenn) Ph. D. Dissertation, fermilab-thesis-2003-14

Page 30: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 30

CDF II, D. Acosta et al., PRL 91, 241804 (2003) & C. Chen (UPenn) Ph. D. Dissertation, fermilab-thesis-2003-14

Data above theory – much less discrepancy than Run I B cross-section vs. theory

Measurement of Prompt Charm Production

1st PRL fromTevatron in Run II

Page 31: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 31

CDF II B Cross-section from B! J/ X

Measure (B) down to pT(B) = 0

Use B! J/ X, J/! +-

- Trigger on dimuon - Get clean J/ signal - Use t (Lxy) to separate B from prompt - B fraction varies from 10 – 40%

Agreement with theory has improved - CDF II data consistent with Run I - theory changed - updated parton distribution functions - updated b quark fragmentation

Page 32: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 32

Experimental Steps for Measuring Bs Mixing

1. Extract B0s signal – decay mode must identify b-flavor at decay (TTT)

Examples:

2. Measure decay time (t) in B rest frame (L = distance travelled) (L00)

3. Determine b-flavor at production “flavor tagging” (TOF)

“unmixed” means production and decay flavor are the same

“mixed” means flavor at production opposite flavor at decay

Flavor tag quantified by dilution D = 1 – 2w, w = mistag probability

Page 33: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 33

Measuring Bs Mixing (cont.)

4. Measure asymmetry

these formulas assume perfect resolution for t

Asymmetry is conceptual: actually perform likelihood fit to expected“unmixed” and “mixed” distributions

Page 34: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 34

Comment on : Time Integrated Mixing

is the time integrated mixing probability

In principle, a measurement of determines m - the first Bd mixing measurements were measurements - d = 0.181 § 0.004 (PDG 2002) - this does not work for Bs: s = 0.5 (the limit as x!1)

A measurement of

is very interesting

Page 35: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 35

Example of Bs Oscillations

Example of Asymmetrywith lots of statisticsms = 20 ps-1

Illustrated are - tagging reduces statistics dilution reduces amplitude - decay length resolution damps amplitude further - momentum uncertainty damps amplitude more as decay time t increases

Large ms: Bs! Ds l no goodneed fully reconstructed decayse.g., Bs! Ds

Figures courtesy M. Jones (Penn/Purdue)

Page 36: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 36

B+, Bd, Bs Signals I. K. Furic Ph. D. Dissertation MIT (2004)

We see signals with good S/B:rate is about 1/10th expected

Results of this analysis

Page 37: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 37

Common B Meson Selection Criteria

slide courtesy of I. K. Furic (MIT/EFI Chicago)

Page 38: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 38

Background Dominated by Heavy Flavor

Peaked structure in B+ background is due to D* polarization

Extensive simulation required to study complex background shape

Very little of the reflections/partially reconstructed decays leak into signal

Page 39: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 39

What About Measuring B Lifetimes?

Lifetime bias from trigger complicates lifetime measurement in B ! D

Must solve this problem eventually for the Bs mixing analysis – in progress

Have measured lifetimes in B! J/ K (dimuon trigger – no bias)Fit mass and lifetime distribution simultaneously

Example: B+! J/ K+ B+ = 1.662 § 0.033 (stat) § 0.008 (syst) ps

240 pb-1

Page 40: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 40

Bs! J/ 240 pb-1

Decay interesting for CP Violationand search for new physics

CP analysis requires knowingCP composition (% even)

Preliminary tranversity analysisindicates predominantly CP evenin agreement with Bd! J/ K*

K. Anikeev, MIT, Ph. D. Thesis, in preparation

Page 41: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 41

B Flavor Tagging

We quantify performance with efficiency and dilution D

= fraction of signal with flavor tag

D = 1-2w, w = probability that tag is incorrect (mistag)

Statistical error A on asymmetry A (N is number of signal)

statistical error scales with D2

Page 42: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 42

Some More Detail

Aside:Total D2 ¼ 30%at the B factories

Page 43: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 43

Two Types of Flavor Tags

Opposite side

Same side Based on fragmentation tracks or B**

+ Applicable to both B0 and B0s

− other b not always in the acceptance

− Results for B+ and B0 not applicable to B0s

+ better acceptance for frag. tracks than opp. side b

Reminder: for limit on ms must know D

Produce bb pairs: find 2nd b, determine flavor,infer flavor of 1st b

Page 44: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 44

Types of Opposite Side Flavor Tags

Lepton tags

Jet charge tag

Kaon tag

mistags from

Run II: for muons: D2 = (0.66 § 0.19)%

jet from b (b) has negative (positive) charge on average

Run II:D2 = (0.419 § 0.024)%

expect comparable for elec.

low high D

high low D

Largest D2 @ B factories Run II: no useful tag yet(have seen D, too low)

TOF

Page 45: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 45

Performance of OST’s is Poor – Why?

Part of the problem is acceptance of opposite side b

Generator Level study from K. Lannon, Ph. D. Dissertation, Illinois, 2003

Also opposite-sideB hadron can mix:D = 1 – 2 = 0.76

Page 46: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 46

Same Side Flavor Tags

Based on correlation betweencharge of fragmentation particleand flavor of b in B meson

Decay of P-wave mesonsB** also contributesto B0, B+ (not B0

s)

Expected correlationsdifferent for B+, B0, B0

sTOF

Page 47: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 47

Results on Same Side Flavor Tag

Select track in R = 0.7 around Bwith minimum pT(rel) wrt B + track

Apply to B0! J/ K*0, D-+

Run II: measure D and md simultaneously

Find = 66.0 § 0.6 D = 12.4 § 3.3 D2 = 1.0 § 0.5 (all in %, stat error only)

md = 0.55 § 0.10

Page 48: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 48

Run I: Understood SST Well

MC explained D+ vs. D0

Data vs.Tuned MCExcellentAgreement

We have to use MC for D of SSKT for limit

F. Abe et al.,PRD 58, 032001 (1999)

Page 49: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 49

Summary: Bs Flavor Oscillations

We have a long way to go - rates are far below expectations - tagging is far below expectations - lifetime resolution not as good as expected – not as critical yet

BUT we are making progress and there is plenty of reason to be optimisticThe potential significance of a measurementcan be estimated using the following formula

Page 50: Physics of Hadron Colliders: Lecture 4 – Heavy Flavors

21 June 2004 Joseph Kroll University of Pennsylvania 50

Acknowledgements

Thanks to organizer Xin Wu (Geneva) & to co-lecturer Paris Sphicas (Athens)

Special thanks to Marjorie Shapiro (Berkeley) for a copy of her 1999 CERNAcademic Lectures & to Evelyn Thomson (OSU/Penn) for discussions onTevatron top physics

Many of my colleagues in CDF provided information including Konstantin Anikeev (MIT),David Ambrose (Penn), Chunhui Chen (Maryland), Frank Chlebana (FNAL), Nathan Eddy (FNAL), Stefano Giagu (INFN-Roma), Chris Hays (Duke),Beate Heinemann (Liverpool), Matt Herndon (JHU), Joey Huston (MSU),Jaco Konigsberg (Florida), Ashutosh Kotwal (Duke), Stephanie Menzemer (MIT),Rolf Oldeman (INFN-Roma), Manfred Paulini (CMU), Kevin Pitts (Illinois),Sal Rappoccio (Harvard), Marco Rescigno (INFN-Roma), Rob Roser (FNAL),Rick Snider (FNAL), Brian Winer (OSU), Peter Wittich (Penn), Kohei Yorita (Waseda)

also Paul Derwent (FNAL), Jens Erler (UNAM), Paul Keener (Penn), Paul Langacker (Penn), Michelangelo Mangano (CERN), Jackie Mileski (Penn), Ron Moore (FNAL), Mary Scott Thomas (Penn)

Finally, special thanks to my wife Monica Kroll for her support