# Presentation: 149792

## Searches for New Phenomena at the Tevatron

- At the Frontiers of Particle Physics
- January 19-25, 2003

- Richard Partridge
- Brown University
- (for the CDF and DØ Collaborations)

## Searching for New Phenomena 

- New Phenomena at the Tevatron can take many forms:
- Observation of unseen particles predicted by SM (Higgs)
- Discovery of particles not in the SM (SUSY, leptoquarks)
- Identification of new gauge interactions (W’/Z’, technicolor)
- Unexpected complexities beyond the SM (compositeness)
- Fundamental changes to modern physics (extra dimensions)

- A thorough discussion of the possibilities for discovering new phenomena at the Tevatron is a logical impossibility

- A thorough discussion of the CDF and DØ searches for new phenomena in 25’ is merely a human impossibility

- This talk will utilize CDF and DØ Run II results to illustrate the progress and prospects in searches for new phenomena

- Richard Partridge

## The Upgraded CDF Detector

- New central drift chamber and silicon tracker
- New forward calorimeters ("plug")  (1<||<3)
- New TOF, extended muon coverage, improved triggers, ...

- Richard Partridge

## The Upgraded DØ Detector

- First time charged particle tracking added to a major “non-magnetic” detector!
- 2T solenoid
- >100K scintillating fibers
- >700K silicon strips
- Major improvements to muon spectrometer, trigger/DAQ, ...

- Richard Partridge

## Searching for SUSY at the Tevatron

- One of the major features of SUSY it “protects” the SM against large radiative corrections from a high mass scale
- Fermion/Boson symmetry cancels loop divergences
- “The Case for a 500 GeV e+e- Linear Collider* ” argues that the lightest chargino is likely to have a mass below 250 GeV

- Basic idea: if SUSY particles are heavy, radiative corrections again become large and require fine-tuning of parameters
- Chargino limits at right from ALCWG report*

- *American Linear Collider Working Group, prepared for Snowmass 2001.

- Richard Partridge

## Searching for SUSY at the Tevatron

- Some Caveats:
- “Naturalness” approach to estimating SUSY mass scales is neither rigorous nor unique in its predictions
- Even if the lightest chargino mass is below 250 GeV, there is no guarantee that it will be visible at the Tevatron

- LEP constraints already exclude SUGRA at the “95% CL”
*e.g*. Strumia, Hep/PH9904247.
- Tevatron can also search for squark, gluino, and slepton production

- Allowed Region

- Richard Partridge

## DØ Tri-lepton Search in eee, ee

- Sensitive to chargino+neutralino production
- SM backgrounds are small, one of the cleanest SUSY signatures

|  | eee | ee |
| --- | --- | --- |
| SM Background | 0.9 +- 0.2 | 0.13 +- 0.08 |
| EM Fakes | 1.0 +- 0.3 | 0.6 +- 0.2 |
| Cosmics | --- | 0.145 +- 0.014 |
| Total | 1.9 +- 0.4 | 0.9 +- 0.2 |
| Data | 2 | 1 |

- eee Events

- DØ Run II Preliminary (5.2 pb-1)

- Richard Partridge

## Prospects for SUSY Tri-lepton Search

- Run II will allow exploration of new regions in SUSY parameter space

- SUGRA Report, SUSY/Higgs Working Group, hep/ph0003154

- Richard Partridge

## DØ Search for GM SUSY in 

- GM SUSY
- Light Gravitino (<<eV) is LSP, NLSP can be neutralino or slepton
- If neutralino NLSP:
-  Search for ET + X

- DØ Run II Preliminary

- 

- QCD+DY

- 8.7 pb-1

- Richard Partridge

## CDF Search for “CHAMPS”

- CHArged Massive Particles that are sufficiently long-lived to leave the detector (*e.g.* sleptons)
- Makes use of new CDF TOF detectors to identify slow particles at high pT

- Low pT samples used to estimate BG for high pT signal region
- Test method: 20 <pT <30 sample used to predict BG for 30 < pT < 40 sample

- Richard Partridge

## Did CDF Catch a Slepton Decay?

- CDF recorded one event in Run I in the “e”e++MET channel
- All we can say with certainty is that searches for related signatures have all been negative
- CDF and DØ  + missing ET
- DØ  + jets + missing ET
- LEP

- Feynman: “On the way over here, I saw a car with license plate 7203234! What’s the probability of that?”
- Random coincidence, unlikely to happen again?
- Someone was following Feynman, likely to be seen repeatedly?
- Feynman wrote down the wrong number, license plate doesn’t exist ?

- Richard Partridge

## DØ Extra Dimensions, Leptoquark Hunts

- Limits on ED in pp  ee
- M**s**(GRW) > 0.92 TeV(ee****, 10 pb-1)
- Run 1: 1.2 TeV (ee****)
- M**s**(GRW)>0.50 TeV(****, 4.5 pb-1)

- Limits on 1st generation LQ from ppeejj (8.0 pb-1)
- MLQ > 113 GeV for B(LQ****ej)=1
- Run 1: 225 GeV

- Plot Mee vs cos(*)

- DØ Run II Preliminary

- Richard Partridge

## CDF Z’ Search

- CDF has studied Drell-Yan events to look for new gauge bosons or evidence of extra dimensions
- Limits on Z’
- MZ’ > 450 GeV (ee)
- MZ’ > 270 GeV ()
- Run 1: MZ’ > 690 GeV (ee + )
- Run 2 Expectation: MZ’ > 1 TeV
- Limits on mass scale for extra dimensions (Randall-Sundrum, k/MPl > 0.1)
- MG > 340 GeV (ee)
- MG > 255 GeV ()

- Richard Partridge

## High ET Jet Production

- Deviations from QCD predictions are potential signal for new physics (*e.g.* quark compositeness)
- Run II’s increased energy, luminosity will increase sensitivity to new physics
- CDF Run II event has the largest jet ET recorded!

- Dijet Mass = 1146 GeV (corr)

- Richard Partridge

## Standard Model Higgs

- Higgs mass constrained by direct and indirect measurements
- MH > 114.4 GeV @ 95% CL (LEP direct search)
- MH < 193 GeV @ 95% CL (Electroweak fits)
- Primary Tevatron channels: WH  bb, ZH  bb, H  WW()

- Richard Partridge

## SM Higgs Prospects

- SUSY/Higgs WG demonstrated Tevatron Higgs sensitivity
- Current focus is on putting together the essential ingredients
- Good jet energy resolution
- Efficient b tagging, lepton identification, and triggering
- Optimization of S/B

- Richard Partridge

## SUSY Higgs Production at the Tevatron

- bb(h/H/A) couplings are enhanced at large tan 
-  ~ 1 pb for tan  = 30 and mh = 130 GeV

**bb(h/A) ******** 4b**

- one
- expt

- Richard Partridge

## The “Luminosity Lift”

- New physics panoramas open up each time we take the “Luminosity Lift”

- Richard Partridge

## CDF and DØ Run IIb Projects

- CDF and DØ detectors were designed to withstand ~2-4 fb-1 with an average of ~2-3 interactions per crossing
- Integrated luminosity limited by radiation damage to silicon tracker
- Instantaneous luminosity limited by trigger rejection
- Tevatron goals for Run II are to accumulate 10-15 fb-1 with an average of ~5 interactions per crossing
- CDF and DØ have developed further detector upgrades needed to meet these goals
- Both experiments will replace silicon trackers, upgrade parts of the trigger
- CDF will replace central preshower detector, add EM calorimeter timing
- Projects have received DOE CD-3(a) approval, major procurements will begin in early 2003
- Run IIb to begin in 2006 following ~7 month shutdown

- Richard Partridge

## Run IIb Silicon Tracker Upgrade

- Overall geometry/capabilities similar for CDF and DØ designs
- 6 layers, good coverage for || < 2
- Rad-hard sensors and readout will survive > 15 fb-1
- All critical elements have been prototyped, sensor procurement will begin in early 2003

- CDF

- DØ

- DØ simulation studies show ~67% increase in double b-tag efficiency for Run IIb silicon tracker

- Richard Partridge

## Conclusions

- Run II at the Tevatron has outstanding opportunities to discover new phenomena
- CDF and DØ detectors have undergone significant upgrades that enhance their ability to make sensitive searches for new phenomena
- The detectors are working well and are beginning to produce physics results
- For many analyses, Run I results are currently the “competition” we are trying to beat – that will change soon!
- Recorded data samples are much larger than the 5-10 pb-1 presented here, expect many new results in the near future
- Run IIb upgrades needed to achieve full potential of the Tevatron collider are well underway

- Richard Partridge