# Presentation: 474766

## QCD and EW Results at the Tevatron Collider

_**THEN**_**                                               **_**NOW**_
**QCD**
**&               @ Run I           Prospects for Run II**
**EW Physics**

- Personal overview: short change of many analyses!

**DØ**

**CDF**

**Bob Hirosky        University of Virginia         La Thuile        March 6, 2001**

**Notes:**
Thanks to organizers for such a splendid workshop!
Brief overview of CDF and D0 results from RunI w/ an eye to RunII - starting up NOW!!! 
Personal overview, many fine efforts could not be included...

## QCD in Run I

** **Inclusive cross sections and ratios:
-       pfd, pQCD, ...
- Dijet Angular Correlations/Mass:
-       compositeness, pQCD
- Shapes&Fragmentation:
-        hard emission/shower development

- Inclusive cross sections
- Exclusive: +,  +charm, etc

**Jets:**

**Photons:**

**Hard Diffraction/DPE/Color Singlet Exchange:**

- Models vs event characteristics and fits to diffractive pdfs

- Soft Radiation/KT effects!

**Notes:**
QCD studies can be combined into three basic branches
4 counting QCD + W/Z!

## Jet Cross Sections vs Pseudorapidity

**Q****2 ****(GeV****2****)**

*******d******2************ dE******T ******d*************** (fb/GeV)**

**x**

***E******T***** (GeV)**

**D****Ø**

- DØ/CDF central jets

- DØ ||<3 jets

**Notes:**
Run1 was really the dawn of precision jet physics.
D0 result for jet cs as a function of pseudorapidity – probes extensive region of  x – Q^2 space 

## DØ Jet CS vs.  : Quantitative comparisons to predictions

**D****Ø ****Jet CS vs. ******** : Quantitative comparisons to predictions**

**Variations of correlation (ET & ********) coefficients within the range **
**of their uncertainties give a similar ordering of the ********2****,**
**hence a similar relative preference of PDFs.**

**Notes:**
Improvements in jet systematics is a legacy of the RunI era.
Multiple pseudorapidity ranges greatly increases sensitivity to pdfs....

## RunII:High PT reach

_**Run II: (2fb-1)**_
**~100 events ET > 490 GeV**
**~1K events  ET > 400 GeV**
_**Run I:**_** ****16 Events E****T****> 410 GeV**
**Greater reach at **
**large x and Q****2****, **
**to look for **
**new physics and**
**Improved systematics**

**Notes:**
Reduce stat errors in our highest Et bin by ~ 

## CTEQ5 pdfs

- Tevatron jet data serves as strong
- constraint in medium x region

- x-Q region spanned by
- experimental data in CTEQ5
- Tevatron jets in blue

**In RunII scale errors reduce w/**
**Gamma+jet stats.  for **
**moderate to high PT jets offering**
**significant constraints on *****g’*****s**

- G(x,Q)

**Notes:**
Jets at moderate X errors dominated by systematics, largely scaling w/ g+jet luminosity...

## Diphotons

- Resummed calc. in good agreement with data

**Measure of soft emission effects**

- Photon Scaling

- CDF Photons

- DØ DiPhotons

**Notes:**
Important particularly to understand direct photon data at fixed target – this data is MUCH more sensitive to gluon distributions at larger values of x

## Hard Diffraction at Run I

*a.k.a. Hard CSE*

- Hard Diffraction = Hard Scattering + Rapidity Gap / Leading p (p-bar)

- New observation in RunI

- Hardest/Largest PT observations of these classes of events

## CDF: Diffractive W, dijet and b-bbar at sqrt(s)=1800 GeV

- P fraction of pomeron

**Notes:**
CDF has done a number studies of diffractive kinematics and generally find the production rates at the tevatron to be low compared to expectations from HERA measurements.  
Breakdown of Factorization between single and double gap processes – hard to understand w/o understanding survival probability

## Double Pomeron@RunII w/  DØ/CDF upgrades

- Double Pomeron@RunII w/  DØ/CDF upgrades

**                       ****CDF**
- Pots on anti-proton side +
- Beam shower counters
- + mini-plug
- +double spectrometer proposal on the table...

**D****Ø** Roman Pot
- Spectrometer
- complete w/
- p/p-bar arms – now installed

- DoublePom in RunII: Valuable measure for understanding structure/nature of
- diffractive processes

**Notes:**
Double arm spectrometers give fully constrained measurements for system!

## ElectroWeak (W/Z) Physics at the Tevatron

- Top is discussed in the talk by E. Barberis at this conference

**General Features of Production **
**Inclusive Cross Section**
**W Boson Width **
**W Boson Mass**
**Trilinear Gauge Boson Couplings**

- W Bosons Detected:

**Notes:**
1 order of magnitude increase in RunII (initial)
Another order in RunII (prolonged)!

## General Features of W&Z Production

- q

**Notes:**
 Production dominated by qq annihilation
 Due to very large pp jj production, need to use leptonic decays
 W  l (BR ~ 11% per mode)	
 Z  ll (BR ~ 3% per mode)
 Distinctive event signatures 
 High PT isolated leptons (e or )
 One high PT lepton + Missing  ET (W)
 Two high PT leptons (Z)
 Low backgrounds
 Large samples
 Well understood EW vertex 
 Test QCD 

##  W Boson Mass

**Input from theorist’s calculations tuned by our measurements.**

- PT(W) Ladinsky-Yuan

- W Spin Orientation
- E. Mirkes.  (1992)

- PDF’s

- W Boson Production
- & Decay Model

**Sampling of **
**our published**
** ****results:**

- D0 very recent

**Notes:**
Data- based corrections to W model
Resummation corrections to lower W PT spectrum – hight PT is given by pQCD
Decay asymmetry – constraint on pdf’s 
Angular distribution of W decays - higher order QCD corrections to production model

## W Boson Mass

**W Mass measurements from**
_**M**__**T**__**(W) @ CDF+D0**_
**P****T****(lepton) @ D0**
**E****T****(********) @ D0**
**Using **
**electron channels @ CDF+D0**
**muon channels @ CDF**

**CDF (e+********) combined (2000)**
**D0 Run 1 (e) Result (2000)**

- D0 CC electron channel

**Notes:**
Including fwd electrons reduces pdf uncertainties – more acceptance is the key here...

##  Scaling of uncertainties – example from CDF

-  Scaling of uncertainties – example from CDF

- Systematics to attack

- WGRAD

- NLO Showering, etc

- Uncertainties that scale
- w/ statistics

**Notes:**
Move workshop ref to earlier...

##  W/Z Mass Ratio

- DØ Run 1a W Mass
- M_T:   80.350 +- 0.140 +- 0.165 +- 0.160
- Ratio:  80.160 +- 0.360 +- 0.075

- Stat

- Extraction of W Mass from W/Z MT ratio

- Sys

**Alternate Measurement of M_W**

- Ratio of W and Z distributions
- That are correlated to IVB mass.

-  Treat Z  ee as W  e by discarding one of the two Z electrons
-  The scale factor between equivalent Z and W distributions gives M_W / M_Z
- Possible Distributions:
- MT
- PTe
- Pe

## W Boson Width

**Indirect Method**

**Direct Method (CDF)**
**Model independent**
**Study high-end tail of M****T****(l********).**

**Precisely predicted in SM:2.093 ********0.002 (GeV)**

- Form ratio:

**LEP**

**Perturbative**
**QCD**

**SM EW**

- CDF+D0 combined

**(LEP combined:2.12 ********0.11)**

- Final RunII (10 fb-1) sensitivity
- ~ 10MeV

**Notes:**
Precisely determined in Standard Model
Direct and indirect measurements possible – steep fall of MT peak very sensitive to resolution, recoil knowledge
Prospects for run II

## Hadronic Decays of W/Z

- Bbbar useful for improving mass resol studies,
-  Higgs!!!

- CDF studies of
- b b-bar mass resolution

- 200K W/Z  jj could offer a 1% check on jet escale (as seen in toy MC studies)
- But of particular interest is Zb-bbar...

- Good stats for absolute b-jet scale in the energy range we need for **top**!

- 2E6 events  588 after cuts
- Vertex tagging + event energy profile
- Mz = 90+-2.4
- 20x the data  1% accuracy on b-scale

## Gauge Boson Self-Interactions

- We study gauge boson couplings by investigating properties of  vector boson pair production: W, WW, WZ, Zin various final states
- non standard couplings  increased cross section and harder pT spectrum

**Self-interactions are a direct consequence of the non-Abelian SU(2)****L ****x U(1)****Y**** gauge symmetry.**
**SM makes specific predictions for the strength of the couplings.**

**Notes:**
Measured in terms of changes to SM prediction for W electric quadropole moment and magnetic dipole moment

## WW and WWZ Couplings

**In Run 1: **
**Established the EW coupling of  W to ******** and W to Z.**
**The W******** and WW processes were observed. Candidate WZ events observed.**
**Anomalous Coupling Limits     ****W********, WW, and combined WZ results from D****Ø**** (equal ********+Z couplings):**

**In 2 fb****-1****: **
**2000 e********+******** events per  exp.**
**Observe “radiation zero”**
**Sensitivity to anomalous couplings ~2-3X better.**

- e+ 

**Notes:**
Just one shown!
Radiation zero = vanishing amplitudes for cos_theta= 1/3 betweem W and photon!

##          Inclusive Cross Sections

**Luminosity: **
**L(D0) = 1.062 x L(CDF)**
**D0 uses world avg.**** ********(pp)****inel****, **
**CDF uses CDF measurement**

** **B(W****l )  ~ 2.2 nb
-  B(Z****l+ l-) ~ 0.22 nb
- Cross section measurement uncertainty:
- Stat  Sys ~ 2%,
- Luminosity error ~ 4%
- Theory prediction uncertainty:
-  ~ 3%, NNLO, O(s2)
- Dominated by PDF’s at NLO...

-          Inclusive Cross Sections

##  Another prospect for RunII

- The W cross section as a luminosity monitor

- Exp. uncertainties dominated by background fraction and background uncertainty
- Calculated Sigma_w most important, dominated by pdf uncertainties

## }As of two weeks ago

- 	There are currently many great postdoc opportunities to explore fundamental physics at the world's highest energy collider with DØ collaborating institutions !!!
- Fermilab
- Lawrence Berkeley Lab
- Lancaster University
- Manchester University
- Swedish Consortium
- Many located full time at Fermilab at DØ.

**The higher energy (1.96 TeV) and ********L**** (2fb****-1****)+ of Run 2 will make  the Tevatron  a very exciting place to be for the next many years!**

**Summary of results will be increasingly more work!**

- }*As of two weeks ago*

**Notes:**
Personal overview, many fine efforts could not be included – this problem will be much worse after RunII!