# Presentation: 180573

## POSTCARDS FROM

**POSTCARDS**** ****FROM**

**John Womersley**
**Fermi National Accelerator Laboratory**

- THE ENERGY FRONTIER

**BATAVIA, ILL.**

## What’s New at DØ

**What’s New at D****Ø**

**Route of this talk:**

**Our Tools**
**   **
**        ****Our Physics**
**                ****Our Future**

**All aboard!**

## DØ

**D****Ø is an international collaboration of ****~ 650 physicists from 19 nations who have designed, built and operate a collider detector at the Tevatron**

**Institutions: 35 US,  41 non-US**

**Collaborators:**

**~ 50% from non-US institutions**
**   ****(note strong European involvement)**
**~ 140 graduate students**

## Fermilab

## Physics goals

**Precise study of the known quanta of the Standard Model**
**Weak bosons, top quark, QCD, B-physics**
**Search for particles and forces beyond those known**
**Higgs, supersymmetry, extra dimensions, other new phenomena**

## protons

**protons**

**antiprotons**

**Electronics**

**Tracker**

**Solenoid Magnet**

**3 Layer****Muon **
**System**

## Slide 7

## Slide 8

## Silicon Microstrip Tracker Status

- 4 barrel layers
- axial + stereo strips

**Detector working very well!**
- ~10% barrel detectors not operational
- – some concern over trend
- Radiation dose and damage match expectations – inner layer lifetime estimated 3.6±1.8 fb-1

## Scintillating Fiber Tracker

**8 axial, 8 stereo layers**
**VLPC readout**
**Performing well **
**good light yield**
**layer ******** > 98%*** **	**(including dead channels)*

- Occupancy matches expectations

- track 

- zero is suppressed

- Light yield

## Photon Conversion “Tomography”

**Photon Conversion “Tomography”**

**6-chip readout HDI**

**Silicon**

**Fiber Tracker**

**x (cm)**

**y (cm)**

**HV cap**

## Calorimeter

**Calorimeter**

- Calorimeter Level 1 triggers for electrons and jets: rates agree with Monte Carlo

- Liquid argon calorimeterwith uranium absorber

- J/ and  from
- EM clusters

## Muon System

- scintillator

**  ****Three layers of scintillator planes for triggering**
**  ****Three layers of drift tubes for muon track measurement**

- shielding

- Z  +-

- Precise momentum measurement

- Identificationand rough momentum measurement

## Tracking Performance

**Tracking Performance**

**Impact Parameter Resolution**

**B****±**** ******** J/******** K****±**

## b-tagging

**b-tagging**

**We have developed two independent tagging algorithms, together with multiple ways of verifying their efficiencies**

**Efficiency ~ 50%**
**Mistag rate **
**(light quark jets) ~ 1-1.5%**

**Top candidate event**tagged by bothalgorithms
- Run 169923 event 16396718Electron pT = 27 GeV , Missing ET = 58 GeV, 4 jets with pT(jet) = 51, 36, 30, 53 GeV ; HT = 207 GeV

## The experiment is operating well and recording physics quality data with high (~ 90%) efficiency 
Data are being reconstructed within a few days 
~200 pb-1 on tape
100-140 pb-1  used for analysis for summer 2003

**The experiment is operating well and recording physics quality data with high (~ 90%) efficiency **
**Data are being reconstructed within a few days **
**~200 pb****-1**** on tape**
**100-140 pb****-1****  used for analysis for summer 2003**

## Fermilab

**Fermilab**
**DØ Experiment**

**Worldwide Data Grid ** Autumn 2003

**Monte Carlo files**

## Remote International Monitoring for the DØ Experiment

**Remote International Monitoring for the D****Ø Experiment**

## Our Physics Goals

**Confront the Standard Model through**
**1. The strong interaction**
**2. The CKM matrix**
**3. Precision electroweak tests**
**4. The top quark **
**5. The Higgs boson**
**And directly search for new phenomena not part of the SM**

## QCD

**We need to: resolve some outstanding puzzles**
**understand the backgrounds to new physics**

## Jets in Run II

**Cross sections not updated for Summer 2003 **
**Working to reduce the dominant ****uncertainty: the jet energy scale**
**Energy scale is derived from p****T**** balance in ****photon + jet events **
**EM scale set by Z ******** ee events:**

**Inclusive Run II jet p****T**** spectra**
**Central and forward jets**

- Jet triggers

- Uncorrected Jet pT

## Physics goals for jets

**Physics goals for jets**

******g(x), CTEQ6**

**Much theoretical discussion:**
**choice of Jet Algorithm for Run II**
**and why k****T**** ******** cone**

**D****Ø Run I jet data already used in CTEQ6 and ****MRST2001 parton distribution fits**
**Complement HERA’s kinematic range**

**D****Ø Run I**

**High p****T**** jets constrain the gluon content of the proton**

## Heavy flavour production

**Unanswered questions from Run I**
**B production cross section****	****	**

- Can be made to fit better using resummation and retuned fragmentation

## Run I diffractive W signal:

If a rapidity gap really implies diffraction, how can it be that we can kick a parton out of a proton with Q2 = mW2 and not destroy the proton in the process?
And do this 10% of the time? (1% rate, 10% survival probability)
What does this tell us about the colour content of the proton?
How do we relate gaps to the “normal” underlying event? 
Is a rapidity gap an underlying event as particle/energy flow  0?
Or one possible colour configuration? (or is that the same thing?)

**Run I**** diffractive W signal:**
**If a rapidity gap really implies diffraction, how can it be that we can kick a parton out of a proton with Q****2**** = m****W****2**** and not destroy the proton in the process?**
**And do this 10% of the time?**** ***(1% rate, 10% survival probability)*
**What does this tell us about the colour content of the proton?**
**How do we relate gaps to the “normal” underlying event? **
**Is a rapidity gap an underlying event as particle/energy flow ******** 0?**
**Or one possible colour configuration? (or is that the same thing?)**

**Diffractive W production**

## Forward Proton Detector

**New ****instrumentation for Run II:**
**Roman pots at z = ******** 23, 33, 57, 59m, plus veto counters to cover 2.5 < |********| < 6**

- 

-  t

- Elastic scattering data

- Scintillating fiber detector inside

## Diffraction in Run II

**Some physics goals ***	** for the“Pomeron skeptical”*

**Measure the gap survival probability: relate rapidity gaps to diffractive (anti-)protons seen in Roman Pots**
**Now underway using Run II diffractive Z’s tagged by both rapidity gaps and FPD**
**Measure********pp ********p ****(gap)**** jj ****(gap)**** p**
**Will provide a sanity check for “loose talk of Higgs production”****at the LHC **

**Khoze, Martin & Ryskin predict S/B > 1 for ****m****H**** = 115 GeV **includes gap survival factor 1/50
**BUT other authors say it’s impossible**(e.g. Schlein)
**Published cross section estimates cover 3 orders of magnitude!**

## CKM Physics

**Confront the unitarity triangle in ways that complement  measurements at the e****+****e****– ****B-factories **
**e.g. through the B****0****S**** system . . .**
**[Also, can measure V****tb**** through single top production]**

## B-physics at Hadron Colliders

**CP violation established in the B system through B****d**** ******** J/******** K****S**
**sin********d**** = 0.734 ****± 0.054 **
**Either ********d**** = 47 ******** (2******** in SM) or 133******** (new physics)**
**BaBar and BELLE will do much more with their data e.g.**
**Is B ******** ********K consistent with SM ******** < 90****°?**
**Same mixing asymmetry in B****d**** ******** J/******** K****S ****and B****d**** ******** ******** K****S ****?**
**B****d**** ******** ******** ******** will be an important piece of the puzzle**
**For hadron colliders (first CDF and D****Ø, then BTeV and LHCb) ****the**** B****S**** system  is the “El Dorado”**
**Mixing parameters ********m****s****, ********s**** **
**x****s**** = ********m****s/ ********s ****> 20 (LEP)**
**B****S**** ******** D****S****K: extract ********S**** + ******** ******** ******
**Sizeable CP violation in B****S**** ******** J/******** ********?**
**B****S**** ******** KK complements B****d**** ******** ******** ********; ******** extract ******
**Many other interesting topics e.g.**
**Rare decays e.g. B ******** K*********+********-****, B****s,d**** ******** ********+********-**

******m****s****/********m****d**

****** **

****** **

****** **

## B Physics at DØ in Run II

**B Physics at D****Ø in Run II**

******(B****S****) = 1.19 +0.19/-0.14 ****ps**

**	****D****Ø cannot exploit purely hadronic triggers,  but benefits from large muon acceptance, forward tracking coverage, and ability to make use of J****/******** ******** e****+****e****-**

**Putting the tools in place:**
**  ****B, J/********, ********, K ... reconstruction**
**  ****B tagging**
**   ****muons **
**   ****electrons (!)**
**   ****displaced vertices**
**  ****Flavor tagging **
**  ****B****d**** oscillations**

**B****d****** ******** B**********

- First observation at a hadron collider

## Towards a BS Mixing Measurement

**B****S**** ******** D****S**** l******

**Tagging power estimated from B****±**** ******** J/******** K******
**Opposite side jet charge****tagging power ********D****2****=3.3********1.1%**
**Opposite side soft muon****tagging power ********D****2****= 1.6********0.6%**

## X  J/ +–

**X ******** J/******** ********+********–**

**Not quite officially approved yet**
**–**** ****but too nice not to show**

## Electroweak Physics

**Indirectly constrain new physics through precision measurements of electroweak parameters **
**Especially m****W**

## W and Z cross sections

**Z ******** ******

**p****T****(Z)**

- Indirect W width
- First resultfrom new Tevatron EWWG

## Prospects for electroweak measurements

**Prospects for electroweak measurements**

**Current knowledge of m****W**
**D****Ø: **
**80 483 ± 84 MeV**
**hadron colliders:**
**80 454 ****± 59 MeV**
**world:**
**80 451 ****± 33 MeV**
**Run II prospects **(per experiment)
**	****	********m****W**
**2 fb****-1****	****±27 MeV**
**15 fb****-1**** **** ****	****±15 MeV**
- To improve on LEP wil require ~ fb-1 datasets
- Clearly not a short term goal
**We will also measure forward-backward asymmetry in Z production, multiboson production, boson + jets, ...**

## The Top Quark

**Measure its properties with greatly increased statistics**

## The Top Quark

**Why, alone among the elementary fermions, does the top quark couple strongly to the Higgs field?**
**Is nature giving us a hint here?**
**Is the mechanism of fermion mass generation indeed the ****same as that of EW symmetry breaking?**
**The top is a window to the origin of **_**fermion**_** masses**
**The Tevatron Collider is the world’s **_**only source of top quarks**_
**We are measuring its**
**Mass**
**Production cross section **
**Spin **
**Through top-antitop ****spin correlations**
**Electroweak properties**
**Through single top ****production**
**Any surprises, anomalies?**

**X ******** t+jet**

- E. Simmons

**The Run II Top Physics Program has begun**

## Run II top candidate

**Run II top candidate**

## Top Production Cross Section

**Top Production Cross Section**

**Is it as expected from QCD?**

**QCD calculations**

**1.8 TeV**

**2.0 TeV**

**D0 Run II****Preliminary**

**97.7 pb****-1**

**Is it consistent across all ****the various decay modes **
**of the top quark?**

**We measure**

## Top mass

**Top mass**

**We can look forward to improved precision on m****t**** in the future**
**Expect ~ 500 b-tagged lepton+jets events per experiment per fb****-1**
**cf. World total at end of Run I ~ 50**
**Improved techniques**
**e.g. new DØ Run I mass****measurement is equivalent****to a factor 2.4 increase****in statistics:**
**m****top**** = 180.1 ± 5.4 GeV**
**Improved top mass measurements help to constrain the Higgs mass**
**	****	********m****t ****	*****l *****+ jets****   ****	****       ****dilepton ****              **
**	****	****2 fb****-1****	****± 2.7 GeV   ± 2.8 GeV**
**	****	****5 fb****-1****	****± 2.2 GeV   ± 2.2 GeV**
**	****	**

*m**top*

- per experiment, using the “classic” technique

**dm****H****/dm****t**** ~ 50 GeV/4 GeV**

*[from M. Grunewald et al., hep-ph/0111217 (2001)]*

*cf  174.3 **** 5.1 GeV (all previous measurements combined)*

## Top mass and Higgs mass

**Top mass and Higgs mass**

**New D****Ø**** top mass will shift the preferred Higgs mass in electroweak fits:**

- Using new DØ mt

## Top decays

**Top decays**

**Because its mass is so large, the top quark is expected to decay very rapidly (~ ys) **
**If this is true, there is no time to form a hadron before it decays**
**Top ******** Wb decay should then preserve the spin information**
**Helicity of the W is predicted in the Standard Model**
**Reflected in several kinematic variables **
**W, ****l**** momenta, mass (b****l****)**
**Can extract fraction of****longitudinally polarized W’s****from top quark sample**
**SM predicts ****F****0**** = 0.70**
**We measure**
**	****F****0**** = 0.56 ******** 0.31 **(68% CL, stat  sys)

**D****Ø**** preliminary**

**F****0**

**M****top**** (GeV/c****2)**

## The Higgs Boson

**Discover (or exclude)**
**Constrain its properties**
**The latest Tevatron luminosity plan will make it hard to cover the whole mass range of interest, but we will do what we can ****— and the lowest masses are the most interesting**** **

## We don’t give up so easily!

**We don’t give up so easily!**

## Update on Higgs sensitivity

**A CDF + D****Ø joint study has now ****updated the “famous” Higgs reach plot:**
**Concentrated on low mass region (favored both in SM and SUSY)**
**The Higgs reach at the Tevatron appears to be at least as good as was projected four years ago**
**Our understanding will continue to improve**

**5******** ****discovery**
**3******** ****evidence**
**95% ****CL exclusion**

- Statistical power onlySystematics not included

## What if we see nothing?

**	****Exclusion of a Higgs would itself be a very important result for the Tevatron**
**In the SM, can exclude the LEP “hint” (115 GeV) with ~ 2 fb****-1**
**The most interesting mass range with ~ 5 fb-1**
**Almost all the allowed mass range with ~ 10 fb****-1**

## Higgs searches

**With our current dataset, we don’t expect to see a standard model Higgs signal**
**We’re looking for nonstandard variants and developing our tools, our understanding, and ability to model backgrounds**

**H ******** WW search**

## Searches

**Find evidence for phenomena outside the SM**
**Improve constraints on such theories**

## Supersymmetry signatures

**Squarks and gluinos are the most copiously produced SUSY particles**
**As long as R-parity is conserved, cannot decay to normal particles **
**missing transverse energy from escaping neutralinos (lightest supersymmetric particle or LSP)**

**Missing E****T**
**SUSY ****	****        backgrounds**

**Make dark matter at the Tevatron!**

**Search region typically > 75 GeV**

**Detect its escape from the detector**

- Possible decay chains always end in the LSP

## Searching for squarks and gluinos

**Searching for squarks and gluinos**

**Run I**

**With 2 fb****-1****:**
**Reach in gluino mass ~ 400 GeV**

- CDF

## Chargino/neutralino production

**“****Golden” signature**
**Three leptons**
**very low standard ****model backgrounds**
**Increasingly important as ****squark/gluino production ****reaches its kinematic limits ****(masses ~ 400-500 GeV)**
**Reach on ************ mass****	**** ****~ 180 GeV (tan ******** = 2, μ< 0)****~ 150 GeV (large tan ********) **
**	**

**Run II Trilepton candidate event**

**We have entered unexplored territory in terms of sensitivity to new physics**

## Indirect searches for new particles

**Indirect searches for new particles**

**Measure the rate of the rare decay B****s**** ******** ******************** **
**In the Standard Model, cancellations lead to a very small branching ratio**
**SM BR= 3.7 ******** 10****-9**** **
**New particles (e.g. SUSY)  contribute additional Feynman diagrams, increase BR **
**up to 10****-6**

**In 100pb****-1**** of data, after all cuts, in B****s**** mass region **
**Observe 3 events **
**Expect 3.4 ****± 0.8 background**
**BR (B****s**** ******** ********************) < 1.6 ******** 10****-6****(90% CL) **cf. 2.0  10-6 (PDG)

**Mass of muon pairs**

**J****PC**** = 1******** (all quarkonia)**

## Searching for Extra Dimensions

**Searching for Extra Dimensions**

- Standard Model

- ExtraDimensions

- DATA

- background  (from data)

******pp ******** ee and ******

**D****Ø**** limits from********pp ******** ee, ********, ******** **
**(Summer 2003)**
**M****S****(GRW) > 1.28 TeV **(128 pb-1, 95% CL)
**	****        ****	****  ****> 1.37 TeV **(Run I + Run II combined)
**	****	****  ****most stringent limit to date on large extra dimensions**** **

**Signal would be an excess of ee, ********, ******** events at large mass and large angle, due to virtual graviton exchange**

**High-mass electron pair event**

**mass**** ****= 406 GeV**
**cos ********* = 0.67**

## Our future

## Current status

**Current status**

**The accelerator has just come out of a long shutdown**
**Tevatron realignment**
**Significant work on the recycler ring**
**General feeling of optimism over shutdown work**
**Recycler commissioning will take most of FY 2004**
**D****Ø is reprocessing all of the data recorded so far to take advantage of improvements in our reconstruction software**
**Next round of new results for the 2004 Spring Conferences **

**D****Ø is back up and recording physics data:**
**Post-shutdown Z ******** e****+****e******** ****signal**
**(Thanksgiving week)**

## Tevatron plan

**Luminosity per week**

## Tevatron plan 

**Integrated luminosity**

**Now**

**May 06**

**October 08**

## Run IIb Upgrades

**The present detector was designed for ~ 2fb****-1**** and 2 ******** 10****32**** cm****-2**** s****-1**
**The Director originally set the goal of accumulating ~15 fb****-1**** before LHC physics**
**Exceeds radiation tolerance of existing silicon detector**
**Requires higher luminosities, ~ 5 ******** 10****32**** cm****-2**** s****-1****, trigger upgrades**

- Replace Silicon Detector with a more radiation-hard version
- Improve impact-parameter resolution (b-tagging) through additional layers and smaller beampipe
- Maintain good pattern recognition over || < 2

- Upgrade Trigger
- Shift functionality upstream and increase overall Level 1 trigger capability – contain rates, dead time
- - Calorimeter clustering & digital filtering
- - Enhance track trigger to respond to      increased occupancies
- - Calorimeter cluster match with track
- Incremental Upgrades to Level 2, Level 3 Triggers and online system

- Upgrades were approved for construction in fall 2002

## Descoped Silicon Upgrade

**Descoped Silicon Upgrade**

**In light of the financial and luminosity situation, the Fermilab director decided not to proceed with the CDF and D****Ø ****silicon detector upgrades**
**In order to mitigate concerns over radiation damage and pattern recognition in D****Ø, we are constructing a new Silicon Layer 0 **
**Fits inside the existing detector **
**Adds an additional radiation-hard tracking layer**
**Makes use of Run IIb R&D and technology **** **

## Conclusions

**Rumors of the Tevatron’s downfall are much exaggerated!**
**The Run II physics program is unmatched in breadth and importance**
**This physics program is based on the detailed understanding of Standard Model particles and forces that we have obtained over the last few decades **
**Based on that understanding we can address some very big questions about the universe**
**For example**
**What is the cosmic dark matter? (Supersymmetry?)**
**Is the universe filled with energy? (Higgs?)**
**What is the structure of spacetime? (Extra dimensions?)**
**	****The Tevatron is in the only facility in operation that can do this**
**Run II has now entered unexplored territory****—****who knows what we will find! **