# Presentation: 373511

## Production of Gauge Bosons at the Tevatron

- Recent Results
- Harry Melanson
- Fermilab

## A shopping list of W, Z Tevatron topics:

- Pick recent results with a QCD flavor

## p

-  Due to very large pp jj production, need to use leptonic decays
-  W e, W , W   (BR ~ 11% per mode)
-  Z ee, Z (BR ~ 3% per mode)
-  Leptonic decay features:
-  W:  High PT isolated lepton,  Large missing transverse energy
-  Z:  Two high PT isolated leptons

***Introduction to W, Z Production at the Tevatron***

- q

**W(Z)**

***l***

*********(******l ******)***

- O(s0)

## Introduction to W, Z Production at the Tevatron

***Introduction to W, Z Production at the Tevatron***

-  Distinctive event signatures
-  Low backgrounds
-  Large Q2  (Q2 ~ Mass2 ~ 6500 GeV2)
-  Well understood Electroweak Vertex

- D0 W e

- D0 Z ee

**Benefits of studying QCD with W’s and Z’s:**

## QCD Corrections: O(s )

**W**

*g*

*q*

*q’*

*q*

*q*

*q’*

*q’*

**W**

**W**

*g*

**Modifications due to QCD corrections:**

-  Inclusive cross sections larger (K factor ~ 18%)
-  Boson produced with transverse momentum  ( < PT > ~ 10 GeV )
-  Boson + jet events possible  ( W + 1 jet ~ 7%, ETjet > 25 GeV )
-  Boson decay angular distribution modified

- O(s)

## Connections between W,Z Production, QCD and New Physics 

**Inclusive Cross Sections**

- Measure:

- Form ratio:

**Perturbative**
**QCD**

- LEP measurement

- SM EW

**W Width**

## Vertex Corrections:  same for quarks and leptons, so cancel in BR(W  l) 

**Vertex Corrections:**  same for quarks and leptons, so cancel in BR(W  l)

- Rosner, Worah, Takeuchi,
- hep-ph/9309307

- Indirect has no sensitivity to corrections to the coupling of the W to fermions, but is sensitive to possible non-standard model decay modes of the W.

**W decays:**

- Kalinowski and Zerwas
- hep-ph/9702386

- Indirect  vs Direct W Width Measurements

## Inclusive Cross Sections

-  **Measurement errors:**  Stat  Sys ~ 2%,   Luminosity error ~ 4%
-  **Theory error:**  ~ 3%, NNLO, O(s2) (Hamberg, van Neerven, Matsuura)
- Dominated by PDF’s at NLO...(need NNLO)
-  **NB:** **Luminosity determination:** L(D0) = 1.062 x L(CDF)
- D0 uses world avg. ppinel, CDF uses CDF measurement

**NEW**

- Updated

## Inclusive Cross Sections

**Inclusive Cross Sections**

- NNLO theory

- NNLO theory

## R = 10.43 0.15 (stat) 0.20 (sys) 0.10 (theory)

- Luminosity error cancels in the ratio

- R = 10.43 0.15 (stat) 0.20 (sys) 0.10 (theory)
- B(W e) = 0.1066 0.0015 0.0021 0.0016

- New

- D0 preliminary

- 2.6% total
- error

## W Width

**W Width**

**NEW**

- (Preliminary)

## Inclusive Cross Sections

**Inclusive Cross Sections**

- D0 preliminary

## Inclusive Cross Sections

**Inclusive Cross Sections**

## Connections between W,Z Production, QCD and New Physics 

- W boson mass + top quark mass:  Constrain Higgs mass

- Need precise model of W production and decay for Monte Carlos

- NLO QCD

- W mass measurements require low PTW

- Resummation techniques

- Non-perturbative QCD

##  Large PT region (PT 30 GeV): Use pQCD, O(s2) calculations exist

-  **Small P****T**** region **(QCD < PT < 10 GeV): Resum large logs:  ln(Q2/PT2)

- Ellis, Martinelli, Petronzio (83); Arnold & Reno (89);
- Arnold, Ellis, Reno (89); Gonsalves, Pawlowski, Wai (89)

- Altarelli, Ellis, Greco, Martinelli (84);  Collins, Soper, Sterman (85)

- b-space:
- Parisi-Petronzio (79); Davies-Stirling (84); Collins-Soper-Sterman (85); Davies, Webber, Stirling (85); Arnold- Reno-Ellis (89); **AK**: Arnold-Kaufann (91); **LY**: Ladinsky-Yuan (94)
- qt-space:
- Dokshitser-Diaknov-Troian (80); Ellis-Stirling (81); Altarelli-Ellis-Greco-Martinelli (84); Gonsalves-Pawlowksl-Wai (89); **ERV**: Ellis-Ross-Veseli (97); Ellis-Veseli (98)

-  **Large PT region** (PT 30 GeV): Use pQCD, O(s2) calculations exist

-  **Very low P****T**** region **(PT ~ QCD): Non-perturbative parameters extracted from data

**W P****T **
- D0 Run 1b electrons (82 pb-1)
- (Compared to **AK** *O*(s2) b-space)
- CDF Run 1a+1b electrons (110 pb-1)
- (Compared to **ERV** *O*(s) b&qt space)

**Z P****T **
- D0 Run 1b electrons (82 pb-1)
- (Compared to **AK** *O*(s2) & **LY** *O*(s) b-space)
- CDF Run 1a+1b electrons (110 pb-1)
- (Compared to *O*(s) **LY** b-space & **ERV** *O*(s) qt-space)

**Recent W,Z P****T**** measurements**

**NEW**

-    **W’s vs Z’s**
- W: x10 more statistics
- Z: Better PT resolution, lower backgrounds

- Recent

## D0 W PT measurements

**D0 W P****T**** measurements**

- Arnold-Kauffman Nucl. Phys. B349, 381 (91). O(s2), b-space, MRSA’ (after detector simulation)

**Preliminary**

- New

## D0 W PT measurements

**D0 W P****T**** measurements**

- Resolution effects dominate at low PT
- High PT dominated by statistics & backgrounds

- dof=7/19 (pT(W)<120 GeV/c)
-  dof=10/21 (pT(W)<200GeV/c)

**Preliminary**

- Arnold, Kauffman, Nucl. Phys. B349, 381.
- O(s2), b-space, MRSA’ (after detector simulation).

## CDF W PT measurements

**CDF W P****T**** measurements**

- Ellis, Ross, Veseli, NP B503, 309 (97). O(s), qt space, after detector simulation.

## CDF Z PT measurements

- ResBos:  Balasz, Yuan,* PRD 56, 5558 (1997)*, O(s2), b-space.

## CDF Z PT measurements

- ResBos: Balas, Yuan,* *PRD 56, 5558 (1997), O(s2), b-space
- VBP: Ellis, Veseli,* *NP B511,649 (1998), O(s), qt-space

## D0 Z PT measurements

**D0 Z P****T**** measurements**

- 2/dof = 17/16

- 2/dof = 83/16

- Preliminary

- Ladinsky, Yuan, PRD 50, 4239 (94), O(s2), b-space.

- Arnold, Kauffman, NP B349, 381 (91), O(s2), b-space.

## D0 Z PT measurements

**D0 Z P****T**** measurements**

- Arnold, Reno, Nucl. Phys. B319, 37. O(s2), MRSA’, after detector simulation.

- Preliminary

## MW = 10 MeV MH/MH = 14% 

- W boson mass + top quark mass:  Constrain Higgs mass

- W production Monte Carlos tuned to Z data

- NLO QCD

- Resummation techniques

- Non-perturbative QCD

- W, Z PT distributions “confirm” formalism(s)

- Z PT distributions constrain non-pert. parameters

- Current CDF/DØ MW ~ 5-9 MeV from PTW model
- MW = 10 MeV MH/MH = 14%

## sW

**W Decay Distribution**

- Angular distribution of electron in W rest frame:

- Pure V-A:

- NLO QCD corrections to production modify this distribution:

- q

- sq

**s****W**

- q

- g

- sq

**s****W**

- Mirkes, NP B387, 3 (1992) - O(s2).

- Collins-Soper frame

- V-A

- QCD

## V-A: 1 = 1

- V-A: 2 = 1

- V-A: 1 = 1
- D0 only sensitive
- to 2

***Connections between W,Z Production, QCD and New Physics ***

- Including this effect in W mass Monte Carlo: MW ~ 40 MeV (D0)

- 2 vs PTW

## D0 method to measure 2

-  Use correlation between cos* and MTW to infer cos* on a statistical basis

-  Define probability function

-  For each PT (W) bin, plot background subtracted mT (W) and get

-  Compare to ni templates from MC

-  Use log-likelihood to determine best value of 2(PT (W))

- Bayesian

## D0 method to measure 2

- Extracted cos* distributions

## D0 method to measure 2

- PT < 10 GeV

- 10 GeV < PT < 20 GeV

- 20 GeV < PT < 35 GeV

- 35 GeV < PT < 200 GeV

- Log-likelihoods vs 2

## W Decay Distribution - 2

**W Decay Distribution - ********2**

- V-A: 2 = 1

- Prob(V-A + NLO QCD) = 87%
- Prob(V-A only) = 7%

## Conclusions

-  **W, Z** **inclusive cross sections** in good agreement with SM.
- Stat  Sys ~ 2%, Luminosity error ~ 4%, Theory error:  ~ 3%
- Maybe use to *determine* luminosity in Run II.

-  **W width** measurement (direct and indirect) in good agreement with SM.
- Indirect measurement error ~ 3%

-  **W, Z P****T**** distributions** measured.
- CDF & D0 measurements over wide range of PT with errors ~ 10 - 20%
- Testing NLO QCD + resummation + non-perturbative models

-  QCD correction to **W decay distribution** confirmed.
- D0 preliminary measurement of 2 vs PTW