IMFP2006 - Day 3 April 5, 2006 Rick Field – Florida/CDF/CMSPage 1 XXXIV International Meeting on Fundamental Physics Rick Field University of Florida (for.

IMFP2006 - Day 3 April 5, 2006

Rick Field – Florida/CDF/CMS Page 1

XXXIV International Meeting on XXXIV International Meeting on Fundamental PhysicsFundamental Physics

Rick FieldUniversity 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

3nd LecturePhotons, Bosons, and Jets at the Tevatron



uud

Antiproton

uud

proton

Photons, Bosons, and JetsPhotons, Bosons, and Jets at the Tevatron at the Tevatron

The Direct Photon Cross-Section.

Beam-Beam Remnants Beam-Beam Remnants

1.96 TeV

The + Cross-Section.

Some Cross Sections Measured at the Tevatron

The + Heavy Quark Cross-Section.

The Z-Boson Cross-Section.

The Inclusive Jet and DiJet Cross-Sections.

The W+Jets, Z+Jets, and Z+b-Jet Cross-Sections.

The W-Boson Cross-Section.

The W+ and Z+ Cross-Sections.

The W+W Cross-Section.

The W+Z and Z+Z Cross-Sections.

The Higgs → W+W Cross-Section. H → W+W with 100 times more data!

+ b

b-quark

photon

+

photon

photon

Z-boson

W-boson

W+jets

W-boson

jet jet

W +

W-boson

photon

W + W

W-boson

W-boson

W + Z

W-boson

Z-boson

Jets

jet jet

jet

and comparisons with theory!



The Direct Photon Cross-SectionThe Direct 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 Cross Sections (CDF) + b/c Cross Sections (CDF)

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

L = 67 pb-1



+ b/c Cross Sections (CDF)+ b/c Cross Sections (CDF)

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!



+ + Cross Section Cross Section (CDF)(CDF)

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 +



Z-boson Cross Section (CDF)Z-boson Cross Section (CDF)

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 Section (CDF)Z-boson Cross Section (CDF)

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 (CDF) Cross Section (CDF)Signalcone

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 (CDF) Cross Section (CDF) 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 (CDF) Search (CDF)

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



W-bosonW-boson Cross Section (CDF) Cross Section (CDF)

(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 ~4.5% background48,144 W candidates ~4.5% background overall efficiency of signal ~7% overall efficiency of signal ~7%

W Acceptance



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



W+Jets Production (CDF)W+Jets Production (CDF)Background to Top and Higgs Physics.

Testing ground for pQCD in multi-jet environment.

Restrict W :

• W → e , |e|< 1.1.

JETCLU jets (R=0.4):

• ETjets>15 GeV, |jet| < 2.

Uncertainties dominated by background subtraction and Jet Energy Scale.

LO predictions normalized to data integrated cross sections:

Shape comparison only!

L = 320 pb-1



W+Jets Production (CDF)W+Jets Production (CDF) Important to study distributions and

topological structure of W + Jets!

More exhaustive comparisons expected soon!!!

di-jet invariant mass distribution in the W+ ≥2 jet

di-jet R distribution in the W+ ≥2 jet

LO predictions normalized to data integrated cross sections:

Shape comparison only!



Z+Jets Production (DZ+Jets Production (DØØ))

MCFM: NLO for Z+1p or Z+2p good description of the measured cross sections.

ME + PS: with MADGRAPH tree level process up to 3 partons reproduce shape of Njet distributions (Pythia used for PS).

Same physics as W + jets (Z) ~ (W)/10, but Z→e+e- cleaner.

Central electrons (||<1.1). MidPoint jets: (R = 0.5, pT > 20 GeV/c, |yjet|<2.5).

)](/[

])(/[*

*

0

eeZ

njetseeZR n

n

Z+j

L = 343 pb-1

PT distribution of the nth jet

Z+2j

Z+3j



Z + b-Jet Production (CDF & DZ + b-Jet Production (CDF & DØ)Ø) 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 (CDF) Cross Sections (CDF)

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 (CDF) Cross Sections (CDF)

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



The W+W Cross-SectionThe W+W Cross-Section

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



The W+W Cross-Section (CDF)The W+W Cross-Section (CDF)

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!



The Z+W, Z+Z Cross Sections The Z+W, Z+Z Cross Sections

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!



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 and Gluino SearchGeneric Squark and Gluino Search

Selection: 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.

PYTHIA Tune A

Observe: 3, Expect: 4.1±1.5.



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 currewnt 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.

If Tevatron finds no new physics it will provide further important constraints: And hopefully LHC will then do the job!

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



Jets at TevatronJets at Tevatron

Experimental Jets: The study of “real” jets requires a “jet algorithm” and the different algorithms correspond to different observables and give different results!

“Theory Jets”

Next-to-leading order parton level calculation

0, 1, 2, or 3 partons!

“Tevatron Jets”

Experimental Jets: The study of “real” jets requires a good understanding of the calorimeter response!

Experimental Jets: To compare with NLO parton level (and measure structure functions) requires a good understanding of the “underlying event”!



Jet CorrectionsJet CorrectionsCalorimeter Jets:

We measure “jets” at the “hadron level” in the calorimeter. We certainly want to correct the “jets” for the detector resolution and

effieciency. Also, we must correct the “jets” for “pile-up”. Must correct what we measure back to the true “particle level” jets!

Proton AntiProton

PT(hard)

Outgoing Parton

Outgoing Parton

Underlying Event Underlying Event

Initial-State Radiation

Final-State Radiation

Particle Level Jets: Do we want to make further model dependent corrections? Do we want to try and subtract the “underlying event” from the

“particle level” jets. This cannot really be done, but if you trust the Monte-Carlo

models modeling of the “underlying event” you can try and do it by using the Monte-Carlo models (use PYTHIA Tune A).

Parton Level Jets: Do we want to use our data to try and extrapolate back to the parton

level? This also cannot really be done, but again if you trust the Monte-

Carlo models you can try and do it by using the Monte-Carlo models.

The “underlying event” consists of hard initial & final-state radiation

plus the “beam-beam remnants” and possible multiple parton interactions.



Inclusive Jet Cross Section (DInclusive Jet Cross Section (DØØ ) ) MidPoint Cone Algorithm

(R = 0.7, fmerge = 0.5)

L = 378 pb-1

Two rapidity bins Highest PT jet is 630 GeV/c

Compared with NLO QCD (JetRad, No Rsep)

Log-Log Scale!

Note that DØ does not make any corrections for hadronizationand the “underlying event”!?

They compare the NLO parton leveldirectly to their hadron level data!



Di-Jet Cross Section (DDi-Jet Cross Section (DØØ)) MidPoint Cone Algorithm (R

= 0.7, fmerge = 0.5)

L = 143 pb-1

|yjet| < 0.5

Compared with NLO QCD (JetRad, Rsep = 1.3)

Update expected soon!



Inclusive Jet Cross Section (CDF)Inclusive Jet Cross Section (CDF)

Run I CDF Inclusive Jet Data(Statistical Errors Only)JetClu RCONE=0.7 0.1<||<0.7R=F=ET /2 RSEP=1.3

CTEQ4M PDFsCTEQ4HJ PDFs

Run 1 showed a possible excess at large jet ET (see below).

This resulted in new PDF’s with more gluons at large x.

The Run 2 data are consistent with the new structure functions (CTEQ6.1M).

CTEQ4M

CTEQ4HJ



Inclusive Jet Cross Section (CDF)Inclusive Jet Cross Section (CDF) MidPoint Cone Algorithm (R

= 0.7, fmerge = 0.75)

Data corrected to the hadron level L = 1.04 fb-1

0.1 < |yjet| < 0.7

Compared with NLO QCD (JetRad, Rsep = 1.3)

Sensitive to UE + hadronization effects for PT < 200 GeV/c!



KKTT Algorithm Algorithm

Proton AntiProton

PT(hard)

Outgoing Parton

Outgoing Parton

Underlying Event Underlying Event

Initial-State Radiation

Final-State Radiation

kT Algorithm: Cluster together calorimeter towers by their kT proximity. Infrared and collinear safe at all orders of pQCD. No splitting and merging. No ad hoc Rsep parameter necessary to compare with parton level. Every parton, particle, or tower is assigned to a “jet”. No biases from seed towers. Favored algorithm in e+e- annihilations!

For each precluster, calculate 2

,iTi pd

For each pair of preculsters, calculate

2

222

,2

,

)()(),min(

D

yyppd jiji

jTiTij

Find the minimum of all di and dij.

Move i to list of jets

no

yes

Begin

End

Minumum is dij?

Any Preclusters

left?

no

Merge i and j

yes

KT Algorithm

Only towers with ET > 0.5 GeV are shown

Raw Jet ET = 533 GeVRaw Jet ET = 618 GeV

Will the KT algorithm be effective in the collider

environment where there is an “underlying event”?

CDF Run 2



KKTT Inclusive Jet Cross Section (CDF) Inclusive Jet Cross Section (CDF)

KT Algorithm (D = 0.7) Data corrected to the hadron level L = 385 pb-1

0.1 < |yjet| < 0.7 Compared with NLO QCD (JetRad)

corrected to the hadron level.

Sensitive to UE + hadronization effects for PT < 300 GeV/c!



Hadronization and Hadronization and “Underlying Event” Corrections“Underlying Event” Corrections

Compare the hadronization and “underlying event” corrections for th KT algorithm (D = 0.7) and the MidPoint algorithm (R = 0.7)!

MidPoint Cone Algorithm (R = 0.7)

The KT algorithm is slightly more sensitive to the “underlying event”!

We see that the KT algorithm (D = 0.7) is slightly more sensitive to the underlying event than the cone algorithm (R = 0.7), but with a good model of the “underlying event” both cross sections can be measured at the Tevatrun!

Note that DØ does not make any corrections for hadronizationand the “underlying event”!?



KKTT Inclusive Jet Cross Section (CDF) Inclusive Jet Cross Section (CDF)Data at the “particle level”!

NLO parton level theory corrected to the “particle level”!

Correction factorsapplied to NLO theory!

7 7 8

D = 0.5 D = 1.0

Corrections increase as D increases!



High x Gluon PDFHigh x Gluon PDF Forward jets measurements put

constraints on the high x gluon distribution!

Uncertainty on gluon PDF (from CTEQ6)

x

Big uncertainty for high-x gluon PDF!

from Run I



KKTT Inclusive Jet Cross Section (CDF) Inclusive Jet Cross Section (CDF)

KT Algorithm (D = 0.7).Data corrected to the hadron

level.L = 385 pb-1.

Five rapidity regions: |yjet| < 0.1 0.1 < |yjet| < 0.7 0.7 < |yjet| < 1.1 1.1 < |yjet| < 1.6 1.6 < |yjet| < 2.1

Compared with NLO QCD (JetRad) with CTEQ6.1

Excellent agreement over all rapidity ranges!



JetJet--Jet Correlations (DJet Correlations (DØ)Ø)

Jet#1-Jet#2 Distribution Jet#1-Jet#2

MidPoint Cone Algorithm (R = 0.7, fmerge = 0.5)

L = 150 pb-1 (Phys. Rev. Lett. 94 221801 (2005)) Data/NLO agreement good. Data/HERWIG

agreement good. Data/PYTHIA agreement good provided PARP(67)

= 1.0→4.0 (i.e. like Tune A, best fit 2.5).

IMFP2006 - Day 3 April 5, 2006 Rick Field – Florida/CDF/CMSPage 1 XXXIV International Meeting on Fundamental Physics Rick Field University of Florida (for.

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higgs w w crosssection

zboson crosssection

wboson crosssection

z jets