1. Deep Inelastic Scattering 2006
EWK Results
@ Tevatron
20th April 2006
Jose E. Garcia - INFN PISA
for the CDF and DØ Collaborations

2. Outline W and Z production Motivation W, Z cross section
W and Z asymmetries
Diboson production
WZ and WW
Anomalous couplings
Summary
Measurements shown here use Ldt  0.1 to 0.8 fb-1
The Tevatron Accelerator
Peak luminosity ·1032 cm-2s-1
Recent Integrated luminosity per week  25 pb-1
CDF and DØ  1.2 fb-1
J.E.Garcia - DIS Tsukuba 2

3. CDF and DØ in RUNII CDF DØ 3 Both detectors Silicon vertex tracker
Solenoid
High rate trigger/DAQ
Calorimeter and muons
CDF
Silicon tracking system in 1.4T magnetic field.
Lead (iron) scintillating EM (Had) Calorimeter.
Forward end-plug calorimeter,  =3
Silicon and fiber tracker in 2T magnetic field
Liquid argon/uranium calorimeters
Muon coverage up to || = 2 DØ
J.E.Garcia - DIS Tsukuba 3

4. ElectroWeak Analyses Motivation
Test the Standard Model (precise measurements)
Provide evidence of physics beyond SM
Important input to LHC physics program
Signatures: at hadronic colliders W and Z bosons decaying hadronically are overwhelmed by direct multiple jet production.
Identification through leptonic decays
W/Z
2 isolated leptons with opposite charge
isolated lepton and ET
J.E.Garcia - DIS Tsukuba 4

5. Z   5 Detection through two high pT muons (CDF,DØ): || < 1 (2)
Two muons with pT > 20 (15) GeV
Background dominated by:
QCD jets into semi-leptonic decays of bb and Z
14352 Candidates
Data
337 pb-1
updated
148 pb-1
66 GeV
116 GeV
Narrow peak: high resolution of CDF tracking system
Large number of events due to higher acceptance of muon DØ system
J.E.Garcia - DIS Tsukuba 5

6. W in forward region
 = 1.2 W
END WALL
HADRON
CAL.
END PLUG HADRON
CALORIMETER
END PLUG EM CALORIMETER
COT
SOLENOID
electron
neutrino
Extension of electron ID to forward region of detector  1.2 <|η|< 2.8.
Complementary to central result
Used combined information from forward EM calorimeters and extended tracking system (ISL)
CDF
CDF Run II Preliminary
223 pb-1
updated
48144 W candidates
 4.5 %
0.07
J.E.Garcia - DIS Tsukuba 6

7. Cross Section Summary Tevatron W  l  cross sections
Tevatron Z  l+ l- cross sections
Run II
Run II
Run I
Run I
consistent and in good agreement with NNLO theoretical calculations
uncertainties dominated by luminosity  6%
accuracy limited by systematic effects
lepton-id:  1 - 3% (  3 - 4% for ’s)
PDF:  1 - 2%
J.E.Garcia - DIS Tsukuba 7

8. W Charge Asymmetry Use Ws to probe the proton structure
u quark inside proton carries higher fraction of momentum than d.
W production is sensitive to u and d PDF.
anti-proton
proton
Observable quantity is lepton rapidity
Convolution of W production asymmetry and V-A decay
W charge asymmetry provides new PDF constraints
J.E.Garcia - DIS Tsukuba 8

9. W Charge Asymmetry (II)
New DØ result in W channel
increased acceptance up to  = 2 (forward triggers)
require single isolated muons
Measurement statistically limited
Charge identification is crucial
Misidentification probability is 0.01% for ||  2
CP folding to provide better statistical uncertainties
DØ Run II Preliminary
DØ Run II Preliminary
230 pb-1
new
230 pb-1
new
Asymmetry
Asymmetry
MRST02 PDF central value
CTEQ6.1M PDF uncertainties
J.E.Garcia - DIS Tsukuba 9

10. Consistent with SM  /ndof with respect to SM is 10.9/12
Z / *  ee Asymmetry - AFB
Interference between Z and * exchanges
Vector and Axial-vector gives rise to an angular asymmetry
d / dcos = A(1+cos2) + B cos  B  0 introduces asymmetry
Direct probe of V and A couplings
New particles would change AFB
AFB depends on mass
CDF Run II Preliminary
364 pb-1
new
Consistent with SM  /ndof with respect to SM is 10.9/12
J.E.Garcia - DIS Tsukuba 10

11. Di-boson Studies Diboson production Test Triple Gauge Couplings
Tevatron explores higher ŝ than LEP
New physics probe
Background to different analyses, important knowledge for LHC
Signatures:
High pT leptons
Electron or muon with PT>20-25 GeV
Isolated: ET(R = 0.4) < 0.1 ET(l)
Large missing ET: ET > GeV
Similar cuts in CDF and DØ
H,X
J.E.Garcia - DIS Tsukuba 11

12. WZ Production W W Z 12 Sensitivity to the WWZ vertex coupling
Unavailable at e+e- colliders
Clean tri-lepton signature (no other SM process)
Z selection :
2 high pT leptons and M(ll) = MZ
W selection :
Isolated high pT lepton and Missing ET
Backgrounds : Z / * + jet W W Z
WZ signal MC
backgrounds
data
DØ Run II Preliminary
CDF Run II Preliminary
Dilepton Invariant Mass (GeV/c2)
Missing ET (GeV/c2)
825 pb-1
updated
320 pb-1
J.E.Garcia - DIS Tsukuba 12

13. WW Production X 13 Important for Higgs searches
Test self interaction of heavy bosons
Probe for new heavy bosons
Selection :
2 high pT leptons and Missing ET
Backgrounds :
Drell-Yan, Z / * + jet, tt and Heavy bosons (WW,ZZ) X
DØ Run II Preliminary
CDF Run II Preliminary
Missing ET (GeV)
Events / 8 GeV
825 pb-1
updated
252 pb-1
Events / 2 GeV
Missing ET (GeV)
J.E.Garcia - DIS Tsukuba 13

14. W W/Z W(lep) W/Z(had) Larger yield than fully leptonic decays
Lepton gives trigger to events
Selection:
Lepton ET > 25 GeV, || < 1
ET > 25 GeV
At least 2 jets ET > 15 GeV and 32 < M(jj) < 184 GeV W
W / Z l  q W
W / Z l  q
J.E.Garcia - DIS Tsukuba 14

15. WW/Z W(lep) W/Z(had) 15 Main systematic contributions:
W + 2 jets cross section (20 % uncertainty)
W + 2 jets LO is sensitive to renormalization scale
Jet energy scale (10% uncertainty)
Several methods checked to perform the measurement
Fit signal + background shape to data
Use sidebands in data to check MC
Expectations
Fit to data
350 pb-1
new
J.E.Garcia - DIS Tsukuba 15

16. WW/WZ Anomalous couplings
Anomalous Couplings (AC) can be tested in the WW/WZ production
W transverse momentum is found to be the best observable to test AC
AC parameterized considering:
with = 0 and  = 0 SM is obtained.
pT(W) spectrum fitted for each AC hypothesis  Set limits to  and 
95% CL
J.E.Garcia - DIS Tsukuba 16

17. Some of the latest analyses have been shown
Tevatron EWK measurements increase their precision up to few %
New values for W/Z production using more statistics
Results agree with the SM predictions
Di-boson analyses
Better limits have been established to di-boson production
New decay channels are studied: WW/WZ with jets in the final state.
Limits obtained for AC already better than in RUN I
J.E.Garcia - DIS Tsukuba 17

18. Deep Inelastic Scattering 2006
BACKUP
20th April 2006

19. Tevatron Accelerator Tevatron Collider is operating successfully
Tevatron delivered Ldt  1.6 fb-1
 1.2 fb-1 in tape per experiment
Peak luminosity ·1032 cm-2s-1
Integrated luminosity per week  25 pb-1
CDF and DØ  1.2 fb-1
J.E.Garcia - DIS Tsukuba 19

20. Z  e h 20 Use channel 1  e + 2  had
detect hadronic ’s as narrow, isolated calorimeter clusters matched to tracks
Invariant mass of the system (0 + track-calorimetric cluster) should be consistent with  mass
Requirements
isolated electrons (ET(e) > 10 GeV)
hadronic  (ET() > 10 GeV) and || < 1.0
impose event topology cuts to suppress QCD and W+jets backgrounds
CDF Run II Preliminary
CDF Run II Preliminary
504 events
504 events
350 pb-1
new
350 pb-1
new
J.E.Garcia - DIS Tsukuba 20

21. W Mass Measurement
W propagator includes H, tb and hypothetical new particle loops.
ΔMW= 34 MeV
Precise knowledge of MW constrains SM MH, as well as hypothetical new particles.
Tevatron Run II has now 6 times Run I CDF, DØ data sets. CDF has analyzed first 200 pb-1 of data and determined uncertainties. Run II goal is to reduce uncertainty to less than 40 MeV.
LEP: 80,447  42 MeV
Tevatron: 80,454  59 MeV (Run I)
J.E.Garcia - DIS Tsukuba 21

22. W Mass templates + Backgrounds
W Mass Measurement
W mass is obtained from transverse mass (MT)
Detector Calibration
Calorimeter energy scale
Tracking momentum scale
Simulation
NLO event generator
Model detector effects
W Mass templates + Backgrounds
DATA
Binned likelihood fit
W Mass
J.E.Garcia - DIS Tsukuba 22

23. W Mass Measurement
Z events are used for tuning and cross-checks  model recoil energy and to calibrate the lepton resolution
Muon momentum scale is determined to 3 parts in 10,000 using J /  and (1s) decays.
PRELIMINARY
CDF RUN II
Use calibrated tracks to set calorimeter electromagnetic energy scale: E/p peak in W events.
CDF RUN II
PRELIMINARY
J.E.Garcia - DIS Tsukuba 23

24. W Mass Measurement
Using 200 pb-1 of Run II data CDF estimated the uncertainty on MW
CDF RUN II
PRELIMINARY
mT fit
mT(eν)(GeV)
CDF RUN II
PRELIMINARY
mT fit
mT(μν)(GeV)
Total uncertainty: 76 MeV (e+ combined) already lower than CDF Run I (79 MeV)
J.E.Garcia - DIS Tsukuba 24