# Presentation: 892143

## Victoria Martin
Northwestern University
La Thuile 2004

- Northwestern University
- La Thuile 2004

- W and Z Physics at CDF

- Contents:
- Electroweak Physics at Run II
- CDF Detector and Reconstruction
- Cross Section Measurements
- Precision Measurements
- Conclusions and Outlook

## Why Electroweak Physics at Run II?

- Large numbers of W bosons
- High mass Z/γ* events
- Sensitive to u & d quarks

- New Forward Detectors

- W mass

- W, Z cross sections

- Lepton Universality

- Z Forward-Backward
- Asymmetry

- Indirect Γ(W)

- Di-boson
- cross sections

- Tri-boson
- couplings

- W asymmetry

- sin2(θW),
- quark couplings

- Beyond SM:
- Di-bosons couplings
- Z’resonance
- anomalous  q couplings

- Higgs Mass Constraint

- Direct Γ(W)

## Run II Luminosity 

- Run II Luminosity

- Tevatron has delivered ~430 pb−1
- We have ~350pb−1 on tape.
- Analyses presented here are using either ~ 72 pb−1,  120 pb−1 or 200 pb−1 of data
- Error on luminosity is ±6%. Limited by knowledge of pp inelastic cross section.

## CDF Run II Detector

- From Run I:
- Solenoid
- Central muon system
- Central calorimeter

- New For Run II:
- Front-end DAQ
- Trigger
- Track (L1) and Displaced Track (L2)
- Silicon Tracker (8 Layers) (η  2.0)
- Central Outer Tracker (η  1.0)
- Plug Calorimeters (1.0  η  3.6)
- Extended Muon Coverage (η  1.5, gaps filled in)

- Polar angle θ

## CDF Run II Detector

- Central tracking
- η  1.0

- Muon Chambers
- η  1.5

- Central+Plug
- Calorimetery
- η  3.6

- Silicon tracking
- η  2.0

## Electron, Muon, Photon & Neutrino Reconstruction

- Electrons

- Central electron:
- A track pointing to an EM
- calorimeter cluster

- Plug electron:
-  EM calorimeter cluster
- (silicon, COT hits may
- be attached)

- Muons

- η  1.0

- 1.0  η  2.8

- ‘Tight’ Muon:
-  An isolated track pointing
- to a muon ‘stub’

- η  1.0

- ‘Loose’ muon:
- An isolated track
- pointing to a gap in
- the muon coverage

- η  1.0

- Neutrinos:
- Large Missing Energy
- (Only Transverse: ET)

- Photons:
- EM Calorimeter
- cluster with no
- associated track

- η  1.1

## Inclusive W and Z Signals

## Inclusive W cross section

| Candidate events in 72pb-1 |  | Estimated
background | Acceptance x efficiency |
| --- | --- | --- | --- |
| W → μν | 31,722 | (10.6 ± 0.4)% | (17.94+0.36−0.33)% |
| W → eν | 37,574 | ( 4.4 ± 0.8)% | (14.39+0.32−0.31)% |

- W→μν signal:
- tight muon plus large ET
- W→eν signal:
- central electron plus large ET
- Backgrounds from QCD, Z→l+l−, W→τν and cosmic (μ channel)

## Inclusive Z cross section

- Z → e+ e− signal:
- 2 central electrons (CC)
- 1 central plus 1 plug electron (CP)
- Z →μ+ μ− signal:
- one tight muon plus one track
- 66 < m(ll)/GeVc-2 < 116
- Small backgrounds from QCD, Z/W→τ, cosmics (μ)  less than 1.5%

| Number of candidates in 72pb-1 |  | acceptance x efficiency |
| --- | --- | --- |
| Z → e+ e− (CC) | 1730 | (22.74 +0.47−0.48)% |
| Z → e+ e− (CP) | 2512 |  |
| Z → μ+ μ− | 1785 | (10.18 +0.24−0.28)% |

- For 66 < m(ll)/GeVc-2 < 116:

## W→τν and Z→τ+τ− Signals

- Look for hadronic tau decays
- Narrow isolated jet
- Low track multiplicity
- invariant mass of tracks and π0 < m(τ)
- 2345 candidate events in 72pb-1

- Z→τ+τ− signal:
-  1 hadronic tau decay (jet)
-  1 τ→eν or τ→μν decay
- Backgrounds from Z→l+l−, QCD

## Combining e and μ channels

- Assuming lepton universality, combine W and Z results
- correlated systematics effects accounted for

## BR(W→lν) and Γ(W)

- 3.3677±0.024
- NNLO (PDG)

- From LEP:
- (3.366 ± 0.0002)%

- Using NNLO calculation Γ(W→lν)=226.4 ±0.4 MeV (PDG):

- Current World Average: 2092±42 MeV

## Lepton Universality

-  Calculate R separately for e and μ channels:

-  From a measurement of yields from a τ trigger, we extract an value for the ration of τ and e couplings:

## Z→e+e− Forward-Backward Asymmetry

- Z→e+e− Forward-Backward Asymmetry

- Tevatron is uniquely sensitive to Z-γ* interference at high invariant masses.
- Shape of the Afb spectrum can be used to extract values for sin2(θW) and u, d couplings to Z
- Agreement with SM prediction.

- P

- angle between
-  p and e−

## Di-boson Signals

- W γ

- Z γ

- Triple Boson
- Coupling

- Non SM!

## Di-boson production: Wγ

- Di-boson production: Wγ

- pp → Wγ → lνγ
- One tight high-PT lepton (e,μ)
- One Photon with:
- ET>7GeV
- ΔR(γ,l)>0.7
- Large missing-ET
- Backgrounds from QCD, Zγ
- Probes electroweak boson self-coupling, new physics

| Candidate 
Events in 202 pb-1 |  | estimated
background |
| --- | --- | --- |
| Wγ→ eνγ | 131 | (25 ± 6) % |
| Wγ→ μνγ | 128 | (32 ± 5) % |

- NLO prediction (U. Baur)                              (LO + ET(γ) dependent k –factors):

- ET(γ)

- ΔR(γ,l)

## Di-boson production: Zγ

- Di-boson production: Zγ

- pp → Zγ → l+l—γ
- Two oppositely-charged high-pT leptons
- One photon with ET>7GeV, ΔR(γ,l) > 0.7
- Small backgrounds (~10%)

| Candidate events 
in ~200 pb-1 |  |
| --- | --- |
| Zγ→ eeγ  | 34 |
| Zγ→ μμγ | 35 |

- NLO prediction (U. Bahr)                               (LO + ET(γ) dependent k –factors):

## Di-boson production: W+W−

- Di-boson production: W+W−

- pp → W+W— → lνl l’νl’
- Two oppositely-charged high-pT leptons
- Large missing-ET
- Veto events with jets
- Veto Z background:
-             76<mee, mμμ<106 GeV/c2
- 5 candidate events in 126pb-1
- (2.3±0.4) background expected from Drell-Yan, QCD, WZ and tt.

- NLO calculation:            Campbell & Ellis  hep-ph/9905386

## Towards W Mass and Asymmetry

- Sensitivity to u/d fraction PDFs

- Use MC templates to fit to signal + background
- CDF Run I mW = 80,465 ± 100(stat) ± 104(sys) MeV
- CDF Run II for 500/pb (estimated):
-                                 = X ±  40(stat) ±   55(sys) MeV

- Work in progress – no results yet

- High mT tail is sensitive to Γ(W)

## Conclusions

- We have measured the cross section for pp collisions at √s=1.96 TeV
- W→lν for electron, muon, tau channels
- Z→ll for electron and muon channel
- Di-bosons: Wγ, Zγ, WW
- Extracted first results on electroweak parameters:
- Indirect measurement of Γ(W)
- Lepton universality
- All results consistent with Standard Model – no sign of New Physics (yet!)
- Look for CDFII first results on W-mass, W asymmetry, direct Γ(W), sin2(θW) and boson-quark couplings, all coming soon!