# Presentation: 821448

## Recent Results in Search for New Physics at Tevatron (Run I)

- SUSY
- RPV mSUGRA stop search in tau channels (CDF)
- RPV mSUGRA search in muon channels (D****)
- mSUGRA in single electron channel (D****)
- Large Extra Dimensions
- Diphoton channel (CDF)
- Jets + ET channel (DØ)
- Leptoquark (DØ)
- Model Independent searches
-  + ET (CDF)
- Quaero (DØ)

- John Zhou
- Rutgers University
- on behalf of
- CDF and D**** collaborations

- La Thuile 3-9 March 2002

- John Zhou

## Tevatron (Run I) Introduction 

- Tevatron (Run **I**) Introduction

- Run I   (Oct. 92  Feb. 96)
- total integrated luminosity
- 	~ 120-1 pb / detector

- 	_Tevatron _
- proton-antiproton collision @ s = 1.8 TeV

- Expected  ~ 2 fb-1 in Run IIa !

**CDF**

**DØ**

- La Thuile 3-9 March 2002

- John Zhou

## CDF RPV mSUGRA Search in Decays of Stop Pair (I)

- Stop pair are produced thru RPC
- Assuming RPV only in the 3rd
-      generation:
-                          in the superpotential

-  h selection (106 pb-1):
- h: cluster PT>15 GeV/c, ||<1.0
-     h ID: number of tracks and o in a narrow cone, isolation energy, etc.

-     Major SM Backgrounds:
- Z, * () + jets
- W (e,) + jets
- W () + jets
- Diboson
- Multijet

- La Thuile 3-9 March 2002

- John Zhou

## CDF RPV mSUGRA Search in Decays of Stop Pair (II)

-     Additional Selections:

-  2 jets: ET > 15 GeV

- MT(lepton,ET) < 35 GeV/c2

- HT(lepton, h, ET) > 70 GeV

- Conclusion:
- No signal found; limit is set.
- (ALEPH:                        )

- limit

- La Thuile 3-9 March 2002

- John Zhou

## DØ Search for Resonant Slepton in RPV mSUGRA (’211)

- Assuming dominant ****’211 coupling
- Search for 2 ’s and 2 jets final state

- u

- d

- d

- u

- Initial selections (94 pb-1):
-   cosmic ray rejection

- NN variables:

- 95% CL limit contour

- After NN selection,
- expect 1.01±0.02 SM
- events. Observed: 2.
- Signal: ~ 6 at contour

- DØ preliminary

- La Thuile 3-9 March 2002

- John Zhou

## DØ Search for RPV mSUGRA in Dimuon and Four-jets channel

- Assumptions:
- SUSY particles pair produced
- only one coupling dominates, e.g. ’222
- only the LSP (    ) goes RPV decay
- Selections:

-       Conclusions     (tan=2):

- 2 muons
- 4 jets

- 77.5 pb-1

- tan=2, <0, A0=0

- Limits

- tan=2, <0, A0=0

- tan=2, <0, A0=0

- La Thuile 3-9 March 2002

- John Zhou

## DØ Search for RPC mSUGRA in Single Electron Channel (I)

- Sensitive to moderate m0 region; complements dilepton, jets+ET searches.
- Selections (92.7 pb-1):

- t t : 16.8  5.2
- WW +  2 jets : 1.4  0.3
- Multijet: 19.1  4.7
- W +  4 jets : 43.0  7.6
- Total background: 80  10

- Observed:
- 72 events

- We use Neural Network to
- further optimize signal significance

- La Thuile 3-9 March 2002

- John Zhou

## DØ Search for RPC mSUGRA in Single Electron Channel (II) 

- NN variable to optimize

-   Limit contour

- NN training:
- m0=170 GeV/c2
- m1/2=58 GeV/c2
- Nsignal=10.4
- Nbkgd=4.4
- Nobs=4

- DØ preliminary

- DØ preliminary

- tan=3, <0, A0=0

- DØ preliminary

- Best limit: LEP, www.cern.ch/LEPSUSY
- Best Tevatron limit: CDF jets+ET, PRL 88, 041801

- La Thuile 3-9 March 2002

- John Zhou

## CDF Search for Large Extra Dimension in Diphoton Events

- Cross section of                 :
-             is the variable to fit

- Ms>1.01 TeV
- in GRW
- convention
- (100 pb-1)
- DØ, adding
- cos* in the
- fit, and with
- an extended
- data set
- (incl. elecs),
- obtained
- Ms>1.21 TeV
- (GRW,127 pb-1)
- PRL 86(1156)

- La Thuile 3-9 March 2002

- John Zhou

## Luminosity: 78.8 pb-1
W/Z background: 38.0±8.2
    (including NQCD/Cosmics events: 7.8±7.1)
Observed: 38

**W/Z background: 38.0±8.2**
**    ****(including N****QCD/Cosmics**** events: 7.8±7.1)**
**Observed: 38**

**jet E****T****(1)/MET > 150GeV in central calorimeter**
**jet E****T****(2) < 50 GeV**** **

**D******** Run I preliminary Limits Complement LEP results at high n**

- DØ Search for Large Extra Dimension in Jet(s)+ET Channel

- Limit

- La Thuile 3-9 March 2002

- John Zhou

## DØ Search for Leptoquark in2 jets+ET Channel

- Sensitive to exclusive LQ     q decay; involves all three generations
- Dominant Backgrounds:
- W+jets, Z+jets, tt
- multijet
- NN optimization on:
- ET, (j1,j2), ET(j2)
- Result:

- mSLQ>98 GeV
- mVLQ>200, 238, 298 GeV for min, MV, and YM couplings

- La Thuile 3-9 March 2002

- John Zhou

## CDF +ET Analysis (I)

- Motivation:
- Photon tagging invisible
- particles such as gravitino in
- SUSY and graviton in LED

- Selections:
-                                     .
-                    .
- Reject cosmic ray events
- No jets with ET > 15 GeV
- No tracks with PT > 5 GeV/c

- 11 events observed in 87 pb-1 of data

- Backgrounds:
-  Cosmic Rays:           6.3 ± 2.0
-  Z       :              3.2 **** 1.0
-  W      e:                 0.9** ****** 0.1
-  prompt diphoton:    0.4 **** 0.1
-  W:                         0.3 **** 0.1
-  Total:                     11.0 ****** **2.2

- La Thuile 3-9 March 2002

- John Zhou

## CDF +ET Analysis (II)

- Search for superlight gravitino
- Model: hep-ph/9801329, Brignole, etc.
-   derive an absolute lower limit on the
-   gravitino mass m3/2 and scale
-   F=3m3/2Mplanck of SUSY breaking
- Process:
- Result:
- Past best limit: 217 GeV (CDF jet + ET, DELPHI +ET)

- Search for Large Extra Dimention
- Model: Arkani-Hamed, Dimopoulos, Dvali, PLB 429
- Process:
- Result:

- N = 4, MD > 549 GeV  (680 GeV, DELPHI)
- N = 6, MD > 581 GeV   (510 GeV, DELPHI)
- N = 8, MD > 602 GeV  (411 GeV, L3)

- Generalized acc. And eff. To allow new models to be tested:

- La Thuile 3-9 March 2002

- John Zhou

## Quaero – DØ Makes its Data Public!

- Quaero: Latin for “to seek”

- http://quaero.fnal.gov/quaero/

- QUAERO automatically optimizes an analysis for a particular signature provided by the user, using DØ data sets and SM backgrounds. QUAERO was demonstrated in eleven separate searches: SM WW, ZZ, and tt production; resonant hWW,ZZ; W’WZ, and Z’  tt production; associated Higgs production; and pair production of first generation scalar leptoquarks. Search for W’WZ is the first of its kind.

- Wh ejj, w/
- kinematic fit to W

- Bckgr

- Signal

- Bckgr

- Signal

- Region of max sensitivity

- Data

- Data

- LQLQ eejj

- La Thuile 3-9 March 2002

- John Zhou

## Conclusions  

- Searches for New Physics in Run I data are still actively being pursued. During the past years, better limits have been achieved in
- RPV, RPC mSUGRA parameters
- Large Extra Dimensions
- Leptoquark masses
- New tools and techniques have been developed, e.g. model independent search strategies.
- With these new tools, better detectors, and higher luminosity, Run 2 will be an exciting period for New Physics searches and discoveries.

- La Thuile 3-9 March 2002

- John Zhou