# Presentation: 325716

## New Tevatron Results

- Cecilia Gerber
- University of Illinois at Chicago
*gerber@uic.edu*
- Outline:
- Improved determination of the W mass (D0)
-  Direct measurement of the W width (D0)
-  High Mass Drell Yan pair production (CDF)
- International Europhysics Conference on High Energy Physics
- July 12-18, 2001, Budapest, HUNGARY

- New

- New

- New

## mWmt2

- determined at tree level by *m*Z or sin2w, *G*F, 
- dominant radiative corrections
- important test of the Standard Model
- constrain Higgs boson mass

**Measurement of the W Boson Mass **

*W*

*W*

*t*

*b*

*W*

*W*

*H**0*

*W*

- *m**W**m**t*2

- *m**W*ln *m**H*

-   W mass determined by likelihood fit to Monte Carlo distributions
- including backgrounds, efficiencies and detector resolutions

**Notes:**
I'll now preset the direct measurement of the W mass by CDF and D0. In the SM, EW symmetry breaking gives mass to the W boson. At tree level, the W mass is determined by Mz or sinsq(thetaW0), the Fermi constant G_F and the electromagnetic  coupling constant evaluated at Q^2=MZ^2. Radiative corrections introduce a relationship between mW, mtop and mHiggs. Measuring the W mass therefore represents a stringent test of the SM and together with the top mass measurement can be used to constrain the Higgs mass. At CDF and D0, the W mass is determined by a likelihood fit from the data to a Monte Carlo simulation that includes backgrounds, efficiencies and detector resolutions.

## W mass: strategy for improved analysis 

-  Use same method to measure the W mass than our published results
-  Parameterize detector response using Z        ee events
-  Obtain W mass from maximum likelihood fit to MT(W), PT(e) & PT()
-  BUT use W and Z samples with “edge” electrons
-  W      eevents with edge electrons used in the fits (3853 events)
-  Z      ee events with 1 or 2 edge electrons for calibration (671 events)
- New D0 W mass measurement using “edge” electrons
-  Z      ee events with only one edge electron used to additionally constrain the calibration of non-edge electrons, improving our previous measurements using central and forward electrons by 1% (central) and 8% (forward).
- Improved W mass measurement from non-edge electrons

## What is the “edge” region? 

**What is the “edge” region? **

- Central Calorimeter

- Forward Calorimeter

- Central Calorimeter 32 EM modules

- Boundary between modules: “edge”

## 80.5740.405 GeV

**W Boson Mass from edge electrons **

- 80.730.26 GeV (stat)

- 80.600.23 GeV (stat)

- pT(e)

- mT

- 80.510.31GeV (stat)

- 80.5740.405 GeV

**Preliminary**

- pT()

**Preliminary**

**Preliminary**

**Preliminary**

- Dominant Uncertainties:
-  Statistics (234 MeV)
-  EM scale (270 MeV)
-  EM resolution (267 MeV)
-  Theory (17 MeV)
-  Exp systematics (55 MeV)

**Notes:**
Shown here are resuts from the D0 collaboration using W events  that decay to electrons both in the central and forward calorimeters. The results for central Ws have been published in 1998. The results for forward Ws are very new and represent the first precision measurement that uses electrons detected in forward regions where the backgrounds from dijet events are more important.
The various fits show the results for the W mass as measured from a fit to the electron transverse momentum and W transverse momentum in central and forward regions. 
Major sources of uncertainty are shown in this table and the combined D0 result for the W mass is 80.47+-0.09GeV. 

## Improved W Mass measurements (hep-ex/0106018)

- Updated D0 measurement with additionally constrained calibration and edge electron fits
- (8% improvement)

- New World Average
- direct measurements
- 80.451     0.033 GeV

## Direct Measurement of the W Width

**Direct Measurement of the W Width**

-  Direct Measurement avoids using theoretical inputs.
-  Explores the region above W pole where new physics could appear
-  Direct measurement has  sensitivity to corrections to the coupling of the W to fermions
-  Lineshape shown from Monte Carlo including Detector response
-  The tail region of MT(W) is sensitive to (W) and can be used to extract (W)

## Direct Measurement of the W Width

-  MT(e,) lineshape modeled with W mass fast Monte Carlo
-  W mass from momentum dependent Breit-Wigner x PLF
-  *y *and pT distribution from Ladinsky-Yuan and NLO pQCD
-  W decay from Mirkes (e) and Berends-Klein (e)
-  Detector Modeling tuned to Z to ee distributions
-  Fit MT(W) data distribution in 90 < MT(W) < 200 GeV window to signal MC + background prediction for different values of (W).
-  Dominant Uncertainties:
-  Recoil modeling (60 MeV)
-  EM modeling (50 MeV)
-  Backgrounds (22 MeV)
-  W mass and pT (20 MeV)

## Direct Measurement of the W Width

**Direct Measurement of the W Width**

- (W) = 2.231 + 0.145-0.138 (stat)  0.092 (syst) GeV
- CDF direct (W)=2.055 0.100 0.075 GeV (e + )
- SM prediction: (W)=2.0937 0.0025 GeV

## Drell-Yan Continuum Production

-  Measurements of the mass dependence of the production cross section     ppbar ****e+ e- + X  (d/dM) and the forward-backwards asymmetry (AFB)
-  Improve published results by
-  Using electrons in the plug (1.1<||<2.4) and forward (2.2<|****|<4.2) calorimeters.
-  Reduced backgrounds in the forward region (tighter tracking cuts)
-  QED radiative corrections for the change in mass from the emission of the final state photons allows measurement of AFB in small bins over a large range of mass.
-  Compare to Standard Model Drell-Yan predictions and search for evidence of new interactions
- additional gauge bosons
-  quark-lepton compositeness
-  exchange of R-parity violating SUSY particles
-  leptoquarks
-  extra dimensions

## Mass dependence of the production cross section

**Mass dependence of the production cross section**
**(FERMILAB-PUB-01/116-E)**

- Good agreement with SM prediction

**Preliminary**

## Mass dependence AFB

-  +/- correspond to hemispheres of e wrt proton in Collins-Soper frame
-  Good agreement with SM
-  The highest bin  (4 events -          300<Mee<600GeV) is 2.2below the SM prediction (probability of 2.5%)
-  Negative asymmetry in this region could result from new interactions

**(FERMILAB-PUB-01/116-E)**

**Preliminary**

## Implication of a 300-500GeV Z’ to Tevatron data

**	****	****(Bodek & Baur)**

**Preliminary**

**Preliminary**

- Full line: SM predictions
-  **Good agreement**
- Additional E6 Z’ prediction shown
-  Assume couplings to third generation is large, width~10%M(Z’)
-  Tevatron Z’ limits (~600GeV) assumed Z couplings and 1% width
-  Data compatible with an extra Z’ (350/500GeV, width=10% mass) with enhanced couplings to third generation quarks
-  CDF data can be included in global EW fits to search for physics beyond the SM (hep-ph/0102160)

## Conclusions

-  Improved measurement of the W mass using “edge” electrons
-  8% improvement in combined D0 result.
-  Direct measurement of the W width from D0
-  Good agreement with previous measurements and SM predictions.
-  Mass dependence of the e+e- production cross section and forward-backwards asymmetry from CDF
-  Agrees with SM predictions
-  2.2  below SM prediction for AFB in the (300,600) GeV mass bin compatible with new interaction
-  Data can be used in combined EW fits to look for interactions beyond the SM