# Presentation: 668754

## FNAL in D0 Physics

Herbert Greenlee

DOE Annual Review
Sept. 26, 2007

**Herbert Greenlee**
**DOE Annual Review**
**Sept. 26, 2007**

## Outline

**D0 organization and FNAL D0 group.**
**Physics topics.**
**QCD.**
**B Physics / B****s**** Mixing.**
**Electroweak / diboson.**
**Top.**
**Higgs.**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## The D0 Collaboration

**The current D0 masthead.**
**600 names**
**81 institutions (one of which is FNAL).**
**The FNAL D0 group.**
**54 names (9% of D0 collaboration).**
**42 Particle Physics Division.**
**9 Computing Division.**
**3 other.**
**FNAL group is the largest institutional group in D0 (by far).**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## D0 Physics Organization

- 1/2 outgoing
- 1/2 incoming

- 0/2 outgoing
- 1/2 incoming

- 2/13 outgoing
- 0/14 incoming

- 3/10 outgoing
- 2/12 incoming

- 4/36

- Convener change Aug. 2007

- H. Greenlee, DOE Annual Review

- September 26, 2007

## D0 Luminosity History

**D0 Luminosity History**

**End of Run 2a**

**Summer 2007 Data**

**2007 Shutdown**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## Jet Energy Scale

**Match energy scale of reconstructed data and mc jets to idealized particle jets.**
**JES and JES systematic error are an important component of most D0 physics analyses.**
**Major improvement coming.**
**JES working group convened by Fermilab physicist A. Juste (until recently).**

**JES Uncertainty**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## QCD

**Jets.**
**Inclusive jets.**
**Dijet mass.    ****(D. Lincoln)**
**Dijet angular (********) distributions.    ****(M. Wobisch, V. O’Dell)**
**3-jets.**
**Vector bosons.**
**Photons.**
**W,Z + jets.**
**Heavy flavors.**
**bb dijets.    ****(D. Lincoln)**
**Diffracitve, rapidity gaps.**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## Inclusive Jets

**Probes highest available p****T****.**
**Highly sensitive to JES.**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## D0 B Physics

**Flavor oscillation & CPV.**
**B****s ****mixing     ****(S. Burdin, A. Nomerotski, M. Naimudden).**
**Lifetimes.**
**Branching ratios.**
**Spectroscopy.**
**Rare decays**
** ****B****s********.    ****(B. Casey).****	**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## Bs Mixing

**Four B****s**** decay modes with OS and SS flavor tagging.**

- Bs

- Bse

- Bs

- BsK*0K

- Combined

- 2.4 fb1

- ms = 18.56 ± 0.87 ps1

**M. Naimudden**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## Electroweak Diboson Production

**The Standard Model makes nontrivial and unambiguous predictions for trilinear gauge couplings.**
**TGC couplings probed by diboson production.**
**W********, Z********, WW, WZ, ZZ.**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## D0 Diboson Results

**Tevatron and D0 have an illustrious history of diboson results over the years. **
**D0 Diboson Group has been led by FNAL physicists for many years (T. Diehl, A. Lyon).**
**Recent results:**
**WZ (********, Anomolous Couplings), 1 fb********1****, submitted.**
**ZZ (********), 1 fb********1****, preliminary.**
**Z********, (********, AC), 1 fb********1****, published 2007.**
**W******** (********), 900 pb********1****, preliminary.**
**WW (********, AC), 200 pb********1****, published 2005, 2006 (update soon).**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## WZ Cross Section

**WZ ******** eee, ee********, ********e, ********.**
**Counting experiment results (1 fb********1****).**
**13 events observed, 4.5 ± 0.6 background.**
** ********WZ**** = 2.7 ****+1.7**** pb (3.0 ********significance), ********WZ**** (SM) = 3.7 pb.**

- **1.3**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## WZ Anomalous Couplings

**WZ Anomalous Couplings**

**Three anomalous coupling parameters for WWZ  trilinear coupling.**
** ********g****1****Z****, ********Z****, ********Z**

- Experimental limit

- Unitarity limit

- H. Greenlee, DOE Annual Review

- September 26, 2007

## ZZ Cross Section

**ZZ********eeee, ee********, ********.**
**Counting experiment results (1 fb********1****).**
**1 ee******** event observed, (0.17 ± 0.04 background).**
** ******** ****< 4.3 pb @ 95% CL**
**SM predicts ******** = 1.6 pb  (1.7 events expected).**
**Consistent with SM.**
**AC limits available shortly.**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## Top Quark Mass in Lepton + Jets

**The top quark mass is overconstrained in l+jets channel.**
**With and without b-tagging.**
**Matrix element method.**
**Calculate probability *****P*****(*****m*****top*****,*****JES) for each candidate event.**
**JES=jet energy scale factor.**
**Includes internal (W mass) and external JES constraint.**
**Combine probabilities from all events.**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## Matrix Element Top Mass Results

***     *****m****top****=170.5±2.4(stat+JES)±1.4(syst) GeV.**
**FNAL physicists**
**Gaston Gutierrez (coinventor of ME method).**
**Mike Wang (pioneered use of the grid for analysis).**

**e+jets**

******+jets**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## Top Quark Mass Summary

**Top Quark Mass Summary**

**(M. Weber)**

**(Gutierrez, Wang)**

**(Gutierrez, Wang)**

**(Gutierrez, Wang)**

**(Gutierrez, Wang)**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## Single Top Quark Production

**Directly probe weak couplings of top quark.**
**One of D0’s physics highlights from the past year is first evidence (3.4********) for single top production.**
**Much worse background than top quark pairs.**
**D0 has a large and active single top physics subgroup including FNAL physicists.**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## Single Top Analyses

**D0 has used three different methods to search for single top production.**
**Decision Trees.**
**Matrix Element.     ****(A. Juste)**
**Bayesian Neural Network.**
**Each method is a different way of constructing a multivariate discriminant.**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## Single Top Matrix Element

**Matrix element uses analytic multivariate discriminant of the form:**
**Eight channels: e,******** + 2,3 jets + 1,2 b-tags.**
**Separate discriminants for s-channel and t-channel.**
**Cross section obtained by fitting distribution of discriminants in the different channels to a combination of signal and background.**
**Assume ********s****/********t****=0.44 (SM prediction).**

- where

- H. Greenlee, DOE Annual Review

- September 26, 2007

## Single Top Results

**Single Top Results**

**ME method:                   *********t***** = 4.8****+1.6**** pb (3.2 ********).**
**Combined (3 methods): *********t***** = 4.7±1.3 pb (3.6 ********).**
**SM prediction (s+t):        *********t***** = 2.9 pb. **

**s-channel**

**t-channel**

******1.4**

**Matrix Element Results**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## Higgs Physics

**Higgs Channels.**
**SM Higgs.**
**WH, ZH.   ****(W. Fisher, A. Juste, S. Fu, T. Yasuda)**** **
**H********WW.**
**Combination.   ****(W. Fisher)**
**Non-SM Higgs.**
**SUSY/high tan ********.**
**H****+ ****/ H****++**
**Bosonic Higgs.**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## D0 SM Higgs Results

**WH ******** ebb, ********bb (1.7 fb********1****).    ****(W. Fisher, A. Juste)**
**ZH ******** eebb, ********bb, ********bb (1.1 fb********1****).     ****(S. Fu, T. Yasuda)**** **
**WH ******** WWW************+********+**** + X (1.0 fb********1****).**
**H ******** WW ******** ee, e********, ******** (1.7 fb********1****).**
**H ******** WW ******** ******** (1.0 fb********1****).**
**D0 Combined limit.     ****(W. Fisher)**
**Tevatron Combined limit.     ****(W. Fisher)**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## ZH bb

**Select events with two e,********, two jets, and 1 or 2 b-tags.**
**Next step is 10-variable neural network.**
**Most important variable is m****bb****.**

**1 b-tag**

**2 b-tags**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## ZH bb Result

***ZH **************bb***** Result**

**Limit on Higgs cross section obtained from fit of entire NN histogram.**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## Higgs Combination

**Best limit or discovery potential for Higgs will require combining all available information from all possible Higgs channels.**
**Current D0 combination includes information from 23 channels and subchannels.**
**Integrated luminosity 0.9 – 1.7 fb********1****.**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## Combination Method

**Input from each channel consists of a “final histogram” (often a NN histogram).**
**In effect, each bin of the final histogram is a separate counting experiment.**
**For each bin, calculate “log-likelihood-ratio” (LLR) of Poisson probability of signal+background compared to background.**
**Find global LLR as sum over all channels and bins.**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## CLs Method

**For any given experimental outcome, calculate CL from expected LLR distribution.**
**CL****b**** = P****b****(LLR < LLR****obs****).**
**CL****s+b****(********H****, m****H****) = P****s+b****(LLR < LLR****obs****|********H****, m****H****).**
**P(LLR) takes into account statistical and (correlated) systematic error fluctuations.**
**CLs (modified frequentist) method.**
**Define CL****s****(********H****, m****H****) = CL****s+b****(********H****, m****H****) / CL****b****.**
**95% CL limit obtained by requiring CL****s**** > 0.05.**
**For comparison, pure frequentist result would maximize or limit CL****s+b**** only.**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## Higgs Combined Limit

**Higgs Limit (SM ratio)**

**LLR Plot**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## Editorial Boards

**Each physics analysis is assigned to an editorial board.**
**EBs review physics analyses and papers.**
**An unglamorous task that improves the quality of the final product.**
**EBs chaired by FNAL scientists.**
**EB 010 (D. Lincoln)**
**Top quark pairs to all jets.**
**EB 023 / EB 028 (G. Fisk)**
**B spectroscopy.**
**EB 027 (R. Lipton)**
**B lifetimes.**
**EB 034 (D. Elvira)**
**Jet energy scale.**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## Summary

**D0 is running well and collecting data with ever higher integrated luminosity.**
**Fermilab scientists play significant and leading roles in D0 physics management and individual physics topics.**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## Backup Slides

- H. Greenlee, DOE Annual Review

- September 26, 2007

## Z Cross Section and AC

**Z********ee********, ******** (E****T******** > 7 GeV).**
**Counting experiment ( fb********1****).**
** *********Z********* = 4.96 ± 0.30 ± 0.30 pb**
**    ****(SM predicts *********Z********* = 4.7 pb).**

- Photon *E**T*

- H. Greenlee, DOE Annual Review

- September 26, 2007

## W Radiation Zero

**W******** Radiation Zero**

**W******** ******** e********, ********.**
**The W******** differential cross section exhibits a “radiation zero” – a dip in the ******** distribution between the photon and the lepton – due to interference effects.**
**The radiation zero can be obscured by resolution smearing and background, as well as by anomalous couplings.**

- H. Greenlee, DOE Annual Review

- September 26, 2007

## W Results

** ****Consistent with SM**
** ****Bimodal hypothesis**
**  ****favored over unimodal**
**  ****hypothesis at 2******** level.**

- H. Greenlee, DOE Annual Review

- September 26, 2007