lecture 2: university of chicago july 10, 2006 rick field – florida/cdfpage 1 university of...

Lecture 2: University of Chicago July 10, 2006

Rick Field – Florida/CDF

University of ChicagoUniversity of Chicago

Rick FieldUniversity of Florida

CDF Run 2

Enrico Fermi Institute, University of Chicago

Lecture 2: Things I would Like toSee Measured at the Tevatron

Heavy Quarks, Bosons, & Photons



Heavy Quark & Boson Heavy Quark & Boson Production at the TevatronProduction at the Tevatron

Total inelastic tot ~ 100 mb which is 103-104 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+, D0, Ds , c , c , c, etc.

Want to studey the production of B-mesons and baryons: Bu , Bd , Bs , Bc , 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 1014

~1 x 1011

~6 x 106

~6 x 105

~14,000 ~5,000

CDF-SVT



Selecting Heavy Flavor DecaysSelecting 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

Impact Parameter ( ~100m)

Lxy ~ 1 mm

B/D decay

D0 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



Selecting Prompt Charm Selecting Prompt Charm ProductionProduction

Separate prompt (i.e. direct) and secondary charm based on their transverse impact parameter distribution.

Direct Charm Meson Fractions:Direct Charm Meson Fractions:

DD00: f: fDD=86.4±0.4±3.5=86.4±0.4±3.5%%

D*D*++: : ffDD=88.1±1.1±3.9%=88.1±1.1±3.9%

DD++: f: fDD=89.1±0.4±2.8%=89.1±0.4±2.8%

DD++ss: f: fDD=77.3±3.8±2.1%=77.3±3.8±2.1%

BD tail

Prompt D Secondary D from B

Promptpeak

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



Prompt Charm Meson ProductionPrompt 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 PT Distributions

bpD

bpD

bpD

bpD

Ts

T

T

T

22.005.075.0)1|Y|GeV,8,(

7.01.03.4)1|Y|GeV,6,(

8.01.02.5)1|Y|GeV,6,*(

5.12.03.13)1|Y|5.5GeV,,( 0

CDF prompt charm cross section result published in PRL (hep-ex/0307080)

Data collected by SVT trigger from 2/2002-3/2002

L = 5.8±0.3 pb-1.



Comparisons with TheoryComparisons with Theory

NLO calculations compatible within errors? The pT 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”



Bottom Quark Production Bottom Quark Production at the Tevatronat 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).

Integrated b-quark Cross Section for PT > PTmin

1.0E-03

1.0E-02

1.0E-01

1.0E+00

1.0E+01

5 10 15 20 25 30 35 40

PTmin (GeV/c)

Cro

ss

Se

cti

on

(b

)

Pythia Creation

Isajet Creation

Herwig Creation

D0 Data

CDF Data

1.8 TeV|y| < 1

CTEQ3L

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 1 1999



Sources of Heavy QuarksSources 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).

Proton AntiProton

“Flavor Creation” Q-quark

Q-quark

Underlying Event Underlying Event

Initial-State Radiation

Leading Order Matrix ElementsLeading-Log Order

QCD Monte-Carlo Model (LLMC)

Dbjpip FbkijdGGBd )()(

(structure functions) × (matrix elements) × (Fragmentation)

+ (initial and final-state radiation: LLA)



Other Sources of Heavy QuarksOther 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

Proton AntiProton

“Flavor Excitation” Q-quark

gluon, quark, or antiquark



Q-quark

“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.

Proton AntiProton

“Gluon Splitting”

Q-quark



Q-quark

“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.

g

g

g

Q

Q Amp (FC)

g

g

g

Q

Q

Amp (FE)

g

g

g

Q

Q

Amp (GS)

Amp(gg→QQg) = + +(gg→QQg) =

2and there are interference terms!



Integrated b-quark Cross Section for PT > PTmin

1.0E-03

1.0E-02

1.0E-01

1.0E+00

1.0E+01

1.0E+02

0 5 10 15 20 25 30 35 40

PTmin (GeV/c)

Cro

ss

Se

cti

on

(b

)

PY 6.158 (67=4) Total

Flavor Creation

Flavor Excitation

Shower/Fragmentation

D0 Data

CDF Data

1.8 TeV|y| < 1

PYTHIA 6.158CTEQ3L PARP(67)=4

Inclusive b-quark Cross SectionInclusive b-quark Cross Section

Data on the integrated b-quark total cross section (PT > PTmin, |y| < 1) for proton-antiproton collisions at 1.8 TeV compared with the QCD Monte-Carlo model predictions of PYTHIA 6.158 (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”


Tevatron Run 1 b-Quark Cross Section



All three sources are important at the Tevatron!

Conclusions from Run 1Conclusions 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).

Proton AntiProton

“Flavor Excitation” b-quark

gluon, quark, or antiquark



b-quark

Proton AntiProton

“Flavor Creation” b-quark

b-quark



MC@NLO!

“Nothing is goofy” Rick Field, Cambridge Workshop,

July 18, 2002

Proton AntiProton


Q-quark



Q-quark



The Run 2 J/The Run 2 J/ Cross Section Cross SectionThe 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)

4.080.02(stat)+0.36(sys)-0.48(sys)

Down to PT = 0!

J/

KB

J/ coming from b-hadrons

will be displaced from primary vertex!

39.7 pb-1

Primary vertex(i.e. interaction point)



Run 2 B-hadron PT distribution compared with FONLL (CTEQ6M).

B-hadron pT

CDF (b) FONLL (b)

(B-hadron) 29.40.6(stat)6.2(sys) 27.5+11-8.2

|Y| < 1.0

Good agreement between theory and experiment!

39.7 pb-1

Cacciari, Frixone, Mangano, Nason, Ridolfi

PRD 71, 032001 (2005)

CDF Run 2 B-hadron Cross SectionCDF Run 2 B-hadron 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 PT distribution (MidPoint, R = 0.7).

Collision point

CDF Run 2 b-Jet Cross SectionCDF Run 2 b-Jet Cross Section



Shows the CDF inclusive b-jet cross section (MidPoint, R = 0.7, fmerge = 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.

CDF Run 2 b-Jet Cross SectionCDF Run 2 b-Jet Cross Section



The bThe b--bbar DiJet Cross-Sectionbbar DiJet Cross-SectionET(b-jet#1) > 30 GeV, ET(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 nbQCD Monte-Carlo Predictions:

PYTHIA Tune A CTEQ5L

38.71 ± 0.62 nb

HERWIG CTEQ5L 21.53 ± 0.66 nb

MC@NLO 28.49 ± 0.58 nb

Proton AntiProton

“Flavor Creation” b-quark

b-quark



Predominately Flavor creation!

SystematicUncertainty

Large Systematic Uncertainty: Jet Energy Scale (~20%). b-tagging Efficiency (~8%)



The b-bbar DiJet Cross-SectionThe b-bbar DiJet Cross-Section ET(b-jet#1) > 30 GeV, ET(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 CTEQ5L 21.5 ± 0.7 nb

MC@NLO 28.5 ± 0.6 nb

MC@NLO + Jimmy 35.7 ± 2.0 nb

Differential Cross Section as a function of the b-bbar DiJet invariant mass!

Proton AntiProton

“Flavor Creation”

b-quark

b-quark



Final-State Radiation

Adding multiple parton interactions (i.e. JIMMY) to enhance the “underlying event” increases the b-bbar jet cross section!

JIMMY: MPIJ. M. Butterworth

J. R. ForshawM. H. Seymour

JIMMYRuns with HERWIG and adds multiple parton interactions!


Rick Field – Florida/CDF Page 19

Top Decay ChannelsTop Decay Channels mt>mW+mb so dominant decay tWb.

The top decays before it hadronizes. B(W qq) ~ 67%. B(W l) ~ 11% l = e,

BR backgrounddilepton ~5% lowlepton + jets ~30% moderateall hadronic ~65% high



Dilepton ChannelDilepton ChannelBackgrounds:

• Physics: Drell-Yan, WW/WZ/ZZ, Z

• Instrumental: fake lepton

Selection:• 2 leptons ET > 20 GeV with opposite sign.• >=2 jets ET > 15 GeV.• Missing ET > 25 GeV (and away from any jet).• HT=pTlep+ETjet+MET > 200 GeV.• Z rejection.

(tt) = 8.3 ± 1.5 (stat) ± 1.0 (syst) + 0.5 (lumi) pb

65 events

20 eventsbackground



Lepton+Jets Channel Lepton+Jets Channel KinematicsKinematics

Selection:• 1 lepton with pT > 20 GeV/c.• >= 3 jets with pT > 15GeV/c.• Missing ET > 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!



Lepton+Jets ChannelLepton+Jets Channel

HT>200GeV

2 b tags

(tt ) 8.8 1.11.2 (stat) 1.3

2.0 (syst)pb

b-Taggingb-TaggingRequire 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



Tevatron Top-Pair Tevatron Top-Pair Cross-SectionCross-Section

(tt ) 6.7 0.90.7 pb

Bonciani et al., Nucl. Phys. B529, 424 (1998)Kidonakis and Vogt, Phys. Rev. D68, 114014 (2003)

Theory

CDF Run 2 Preliminary



CDF MCDF Mtoptop Results Results

CDF Lepton+jets: Mtop (template) = 173.4 ± 2.5 (stat. + jet E) ± 1.3 (syst.) GeVMtop (matrix element) = 174.1 ± 2.5 (stat. + jet E) ± 1.4 (syst.) GeV

Mtop (Lxy) = 183.9 +15.7-13.9 (stat.) ± 5.6 (syst.) GeV

CDF Dilepton: Mtop (matrix element) = 164.5 ± 4.5 (stat.) ± 3.1 (jet E. + syst.) GeV

Transverse decay length!



Top Quark MassTop Quark MassSummer 2005

Dilepton: CDF-II Mtop

ME = 164.5 ± 5.5 GeV

Lepton+Jets: CDF-II Mtop

Temp = 174.1 ± 2.8 GeV CDF-II Mtop

ME = 173.4 ± 2.9 GeV

CDF Combined: Mtop

CDF = 172.0 ± 1.6 ± 2.2 GeV = 172.0 ± 2.7 GeV

New since Summer 2005



Top Cross-Section vs MassTop Cross-Section vs MassTevatron Summer 2005 CDF Winter 2006

Updated CDF+DØ combined result is coming soon!

CDF combined



Is Anything “Goofy”?Is Anything “Goofy”? Possible discrepancy between

l + jets and the dilepton channel measurements of the top mass??

Is it statistical?

• Unlikely! Is there a missing systematic? This is probably nothing, but

we should keep an eye on it!



Future Top Mass MeasurementsFuture Top Mass Measurements

Expect significant reduction in jet energy scale uncertainty with more data. Today we have CDF-II Mtop(Temp) = 174.1 ± 2.8 GeV (~0.7 fb-1).

CDF should be able to achieve 1.5 GeV uncertainty on top mass!

Systematic Source

Uncertainty

(GeV/c2)

ISR/FSR 0.7

Model 0.7

b-jet 0.6

Method 0.6

PDF 0.3

Total 1.3

Jet Energy 2.5

CDF



Constraining the Higgs MassConstraining 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

Spring 2006

Summer 05

Light Higgs very interesting for the Tevatron!



DØ Prelim.365 pb-1

Top Charge

top< 1.75x10-13sctop< 52.5m

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/0603002

CDF Prelim.318 pb-1

Top Lifetime

Impact Parameter (m)

Everything consistent with the Standard Model (so far)!

Top: Charge, Branching, Top: Charge, Branching, Lifetime, W HelicityLifetime, W Helicity



Other Sources of Top QuarksOther Sources of Top Quarks

q

q

t

t ~85%

g

g

Strongly Produced tt PairsStrongly Produced tt PairsDominant production mode

NLO+NLL = 6.7 1.2 pb

Relatively clean signatureDiscovery in 1995

ElectroWeak Production: ElectroWeak Production: Single TopSingle Top

Larger backgroundSmaller cross section ≈ 2 pbNot yet observed!

~15%



Single Top ProductionSingle Top ProductionbtWqq * tqqb ' tWbg

s-channel t-channel Associated tW

Combine

(s+t)

Tevatron NLO 0.88 0.11 pb 1.98 0.25 pb ~ 0.1 pb

LHC NLO 10.6 1.1 pb 247 25 pb 62+17 -4 pb

CDF < 18 pb < 13 pb < 14 pb

D0 < 17 pb < 22 pb

B.W. Harris et al.:Phys.Rev.D66,054024 T.Tait: hep-ph/9909352

Z.Sullivan Phys.Rev.D70:114012 Belyaev,Boos: hep-ph/0003260

Run I

95% C.L.

(mtop=175 GeV/c2)

s-channel t-channel tW associated production



Single Top Results from CDFSingle 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:

(syst)pb(stat)0.6σ 0.10.1

1.90.6cht

t-channel:

< 3.1 pb @ 95% C.L.

s-channel:

< 3.2 pb @ 95% C.L.

pb (syst)(stat)0.3σ 0.50.3-

2.20.3chs

The CDF limits!



Single Top at the TevatronSingle 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

We should see single top soon !!!We should see single top soon !!!

ChannelChannel CDF (696 pbCDF (696 pb-1-1)) DØ (370 pbDØ (370 pb-1-1))

Combined 3.4 pb

s-channel 3.2 pb 5.0 pb

t-channel 3.1 pb 4.4 pb(2 pb)(2 pb)

(0.9 pb)(0.9 pb)

(2.9 pb)(2.9 pb)

Theory!



Top-AntiTop ResonancesTop-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!



Direct Photon Cross-SectionDirect Photon Cross-Section DØ uses a neural network (NN) with track

isolation and calorimeter shower shape variables to separate direct photons from background photons and 0’s!

g

q

q

Highest pT() is 442 GeV/c (3 events above 300 GeV/c

not displayed)!

Note rise at low pT!



b/c-quark tag based on displaced vertices. Secondary vertex mass discriminates flavor.

L = 67 pb-1

+ b/c Cross Sections+ b/c Cross Sections



PYTHIA Tune A correctly predicts the relative amount of u, d, s, c, b quarks within the photon events.

CDF (pb)

(b+ 40.619.5(stat)+7.4(sys)-7.8(sys)

(c+ 486.2152.9(stat)+86.5(sys)-90.9(sys)

+ c + b

T() > 25 GeV

L = 67 pb-1PYTHIA Tune A!

+ b/c Cross Sections+ b/c Cross Sections



Di-Photon cross section with 207 pb-1 of Run 2 data compared with next-to-leading order QCD predictions from DIPHOX and ResBos.

+ mass

+

L = 207 pb-1

QCD +

+ + Cross Section Cross Section



Impressive agreement between experiment and NNLO theory (Stirling, van Neerven)!

CDF (pb) NNLO (pb)

(Z→e+e-) 254.93.3(stat)4.6(sys)15.2(lum) 252.35.0

L = 72 pb-1

QCDDrell-Yan

Z-boson Cross SectionZ-boson Cross Section



Z-boson Cross SectionZ-boson Cross Section

Impressive agreement between experiment and NNLO theory (Stirling, van Neerven)!

CDF (pb) NNLO (pb)

(Z→+-) 261.22.7(stat)6.9(sys)15.1(lum) 252.35.0

L = 337 pb-1



The ZThe Z→→ Cross Section Cross SectionSignalcone

Isolationcone

Taus are difficult to reconstruct at hadron colliders• Exploit event topology to suppress backgrounds (QCD & W+jet).

• Measurement of cross section important for Higgs and SUSY analyses.

CDF strategy of hadronic τ reconstruction: • Study charged tracks define signal and isolation cone (isolation = require no

tracks in isolation cone).

• Use hadronic calorimeter clusters (to suppress electron background).

• π0 detected by the CES detector and required to be in the signal cone.

CES: resolution 2-3mm, proportional strip/wire drift chamber at 6X0 of

EM calorimeter.

Channel for Z→ττ: electron + isolated track• One decays to an electron: τ→e+X (ET(e) > 10 GeV) .

• One decays to hadrons: τ → h+X (pT > 15GeV/c).

Remove Drell-Yan e+e- and apply event topology cuts for non-Z background.



The ZThe Z→→ Cross Section Cross Section CDF Z→ττ (350 pb-1): 316 Z→ττ candidates. Novel method for background estimation: main contribution QCD. τ identification efficiency ~60% with uncertainty about 3%!

1 and 3 tracks,

opposite signsame sign,

opposite sign

CDF (pb) NNLO (pb)

(Z→+-) 26520(stat)21(sys)15(lum) 252.35.0



Higgs Higgs → → Search Search

Data mass distribution agrees with SM expectation:

• MH > 120 GeV: 8.4±0.9 expected, 11 observed.

Fit mass distribution for Higgs Signal (MSSM scenario):

• Exclude 140 GeV Higgs at 95% C.L.

• Upper limit on cross section times branching ratio.

140 GeV Higgs Signal!

events

1 event

Let’s find the Higgs!



(W) L CDF (pb) NNLO(pb)

Central

electrons72 pb-1 277510(stat)53(sys)167(lum) 268754

Forward

electrons223 pb-1 281513(stat)94(sys)169(lum) 268754

CDF NNLO

(W)/(Z) 10.920.15(stat)0.14(sys)

10.690.08

Extend electron coverage to the forward region (1.2 < || < 2.8)!

48,144 W candidates 48,144 W candidates ~4.5% background~4.5% background

overall efficiency of signal ~7% overall efficiency of signal ~7%

W-bosonW-boson Cross Section Cross SectionW

Acceptance



20 Years of Measuring W & Z20 Years of Measuring W & Z



Z + b-Jet ProductionZ + b-Jet Production Important background for new physics!

)(0033.0)(0078.00237.0][

][

14.032.096.0)(

syststatjetZ

bjetZR

pbbjetZ

)()(004.0021.0

][

][ 002.0003.0 syststat

jetZ

bjetZR

pbbjetZ 52.0)(

Extract fraction of b-tagged jets from secondary vertex mass distribution: NO assumption on the charm content.

L = 335 pb-1

CDF

Assumption on the charm content from theoretical prediction: Nc=1.69Nb.

DØ

Agreement with NLO prediction: 004.0018.0 R

Leptonic decays for the Z. Z associated with jets. CDF: JETCLU, D0: MidPoint: R = 0.7, |jet| < 1.5, ET >20 GeV

Look for tagged jets in Z events.

L = 180 pb-1



W + W + Cross Sections Cross Sections

CDF (pb) NLO (pb)

(W+)*BR(W->l) 19.71.7(stat)2.0(sys)1.1(lum) 19.31.4

ET() > 7 GeVR(l) > 0.7



Z + Z + Cross Sections Cross Sections

CDF (pb) NLO (pb)

(Z+)*BR(Z->ll) 5.30.6(stat)0.3(sys)0.3(lum) 5.40.3

ET() > 7 GeVR(l) > 0.7

Note: (W)/(Z) ≈ 4

while (W)/(Z) ≈ 11



pb-1 CDF (pb) NLO (pb)

(WW) CDF 184 14.6+5.8(stat)-5.1(stat)1.8(sys)0.9(lum) 12.40.8

(WW) DØ 240 13.8+4.3(stat)-3.8(stat)1.2(sys)0.9(lum) 12.40.8

Campbell & Ellis 1999

W+W Cross-SectionW+W Cross-Section



W+W Cross-SectionW+W Cross-Section

L CDF (pb) NLO (pb)

(WW) 825 pb-1 13.72.3(stat)1.6(sys)1.2(lum) 12.40.8

WW→dileptons + MET Two leptons pT > 20 GeV/c.

Z veto. MET > 20 GeV. Zero jets with ET>15 GeV

and ||<2.5.Observe 95 events with

37.2 background!

L = 825 pb-1

Missing ET! Lepton-Pair Mass! ET Sum!

We are beginning to study the details ofDi-Boson production at the Tevatron!



W+Z, Z+Z Limit (pb) NLO (pb)

CDF (194 pb-1) sum < 15.2 (95% CL) 5.00.4

DØ (300 pb-1) W+Z < 13.3 (95% CL) 3.70.1

Upper Limits

CDF (825 pb-1) W+Z < 6.34 (95% CL) 3.70.1

W+Z → trileptons + METObserve 2 events with a background of 0.9±0.2!

Z+W, Z+Z Cross SectionsZ+W, Z+Z Cross Sections



Di-Bosons at the TevatronDi-Bosons at the Tevatron

We are getting closer to the Higgs!

W

Z

W+

Z+

W+W

W+Z



Generic Squark & Gluino SearchGeneric Squark & Gluino SearchSelection:

3 jets with ET>125 GeV, 75 GeV and 25 GeV.

Missing ET>165 GeV.

HT=∑ jet ET > 350 GeV.

Missing ET not along a jet direction:

• Avoid jet mismeasurements.

Background: W/Z+jets with Wl or Z. Top. QCD multijets:

• Mismeasured jet energies lead to missing ET.

Observe: 3, Expect: 4.1±1.5.

PYTHIA Tune A

It will be a long time before ATLAS & CMS understand their missing

ET spectrum this well!



Future Higgs & SUSY SearchesFuture Higgs & SUSY SearchesCDF and Tevatron running great!

Often world’s best constraints. Many searches on SUSY, Higgs and other

new particles.

Most current analyses based on up to 350 pb-1: We will analyze 1 fb-1 by summer 2006. Anticipate 4.4 - 8.6 fb-1 by 2009.

The Tevatron has a chance of finding new physics before the ATLAS and CMS understand their dectors! We may be able to tell the LHC where to

look!

If we find something the real fun starts: What Is It?

Let’s find the Higgs!

lecture 2: university of chicago july 10, 2006 rick field – florida/cdfpage 1 university of...

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