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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
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 2
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!
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 3
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!
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 4
+ 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
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Rick Field – Florida/CDF/CMS Page 5
+ 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!
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 6
+ + 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 +
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 7
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
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Rick Field – Florida/CDF/CMS Page 8
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
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 9
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.
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 10
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
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 11
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
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 12
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
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 13
20 Years of Measuring W & Z20 Years of Measuring W & Z
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 14
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
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 15
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!
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 16
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
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 17
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
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 18
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
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 19
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
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 20
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
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 21
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!
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 22
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!
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 23
Di-Bosons at the TevatronDi-Bosons at the Tevatron
We are getting closer to the Higgs!
W
Z
W+
Z+
W+W
W+Z
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 24
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.
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 25
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?
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 26
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”!
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 27
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.
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 28
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!
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 29
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!
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 30
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
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 31
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!
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 32
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
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 33
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!
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 34
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”!?
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 35
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!
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 36
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
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 37
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!
IMFP2006 - Day 3 April 5, 2006
Rick Field – Florida/CDF/CMS Page 38
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).