# Presentation: 014183

## Search for SUSY at the Tevatron

- Vishnu V. Zutshi
- Northern Illinois University
- for the
- CDF and D Collaborations

## Outline 

- MSSM
-     Stop search (CDF)
- mSUGRA
-     Single electron channel search (D)
- RPV
-     Decays of stop pair (CDF)
-     di-muon channel, pair & resonant prod. (D)
- GMSB
-      Light gravitino search (CDF)
-      di-photon channel search (D)

- ICHEP02, 25th July 2002

## Run1 CDF and D Detectors

- ICHEP02, 25th July 2002

## Run 2 CDF and D Detectors

- silicon detector, c.o.t., tile plug
- and forward calorimeters......

- sci-fi central tracker,silicon detector
- 2T magnet, preshower detectors.....

- ICHEP02, 25th July 2002

## Stop Search

- Final state: 2 leptons+jets+MET

- Drell-Yan, heavy quark pair prod.,
- QCD fakes, diboson production

- ICHEP02, 25th July 2002

**Notes:**
The charginos are virtual.
Bbar and ccbar also contribute to the bckg.

In addition to the cuts mentioned in the fig. A Met cut of 30 GeV, opening angle cuts between lepton and Met and lepton and jet are applied. A cut on the energy of the dilepton system to cut out top contamination is also applied.

Events observed = 0
Expected = 1.5

## Stop Search (II)

- ICHEP02, 25th July 2002

## (m)SUGRA models

- SUSY breaking is communicated to the physical sector by gravitational interactions
- GUT scale parameters + RGE’s  low-scale phenomenology

- M0 = common scalar mass
- M1/2 = common gaugino mass
- A0 = common trilinear coupling value
- tanratio of the V.E.V. of the two Higgs doublets
- sign of  = Higgsino mass parameter

- ICHEP02, 25th July 2002

## Single Electron Channel

- Sensitive to moderate m0
- Complements dilepton and
- Jets+MET channels

- Bckg: W+jets, qcd multijet,t t
- Cuts: Ete >20 GeV,Etj >14 GeV
-           ( 4), no isolated muons,
-           MET > 25 GeV
- L = 92.7 pb-1

- Observed events = 72
- Expected background = 80 ± 10

- DØ

- ICHEP02, 25th July 2002

**Notes:**
Analysis done in mSugra framework with R-parity assumed conserved.
Lightest neutralino is LSP, A0=0 , mu<0 and tanbeta=3.
Search done in m(1/2)-m0 plane.

W+jets         43
Multijet       19
Ttbar           17
WW+jets     2

## Single Electron Channel  

- DØ

- ICHEP02, 25th July 2002

**Notes:**
NN variables: Et of 3rd jet, Met, Ht, Mt, delta-phi between Met and the electron (those which showed discrimination between signal and bckg.)

Extends exclusion in the range 170-250 GeV for m0. The limit worsens with rising m0 as the electrons and jets get softer due to the mass difference between the LSP and NLSP decreasing (N2 or C1).

Significance can be defined as the no. of standard deviations required for b to fluctuate to n.
N.B. CDF analysis in jets+met channel provides more stringent limit
PRL 88, 041801 (2002)

## R-parity and its violation

- Discrete quantum number
-      R = (-1)3B+2S+L ; is 1 for SM particle,-1 for sparticles
- R-parity violation can be introduced by
-      WL=1 = (1/2)ijkLiLjēk+' ijkLiQjđk+' iLiHu
-      WB=1 = (1/2)'' ijkūiđjđk

- Decay of the LSP
- Signatures maybe very different
- Single sparticle production possible
- Whither dark matter candidate

- mSUGRA with RPV
- One RPV coupling dominates
- If coupling large enough, resonant prod.
- Otherwise pair production

- ICHEP02, 25th July 2002

## Decays of Stop Pair

- Assuming RPV only in 3rd gen.

- tt+X = l + b + h + b + X
- Final state: lepton + hadronic 
-                    + 2 jets

- Bckg: W/Z + jets, multijet, diboson
- Cuts: pTlepton >10 GeV,h cluster>15,
-          MT(lepton,Met)<35GeV/c2,HT>70,
-           2jets (ET >15 GeV)
- L = 106 pb-1

- ICHEP02, 25th July 2002

## Decays of Stop Pair

- CDF

- Run IIa proj. ~ mt

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## Pair Production: di-muon channel

- Final state: 2 + 4jets

- Bckg: Drell-Yan, t t, Z+jets, Z
- Cuts: pt >15(10) GeV,ptjets >15 GeV,
- St > 150 GeV,M >5 GeV,Acoplanarity>0.03
- Run1 L = 77.5 ± 4 pb-1

- Events observed = 0
- Expected bckg. = 0.18 ± 0.03 ±0.02

- DØ

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## Pair Production: di-muon channel

- DØ

- Run IIa projection

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## Resonant Production:di-muon channel

- u

- 1o

- ~

- 

- L

- ~

- d

- _

-    u d

-   u d

- d

- +

- l -

- l

- W -

- _

- _

- Resonant prod. and decay
- of LSP via RPV
- Final state: 2+ 2jets

- Bckg: t t, Z+2jets, WW+jets
- Cuts: pT >20 GeV, pTjets >20 GeV,
-          ST >50 GeV, R(-jet) > 0.5
- L = 94 ± 5 pb-1

- Observed events = 5
- Expected bckg = 5.34 ± 0.07

- D

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## Resonant Production:di-muon channel

- Run IIa projection

- ICHEP02, 25th July 2002

## GMSB models

- ‘Messenger’ sector couples to source of SUSY-breaking and physical sector of MSSM (through gauge interactions)
- The identity of the NLSP and its lifetime determine the phenomenology

- ICHEP02, 25th July 2002

## Light Gravitino Search

- Final state: MET+jet

- Bckg: mismeasured multi-jets
-           W/Z + jets, tt, diboson
- Cuts: MET >50 GeV, removal
- of events w/ isolated tracks,
- (MET,jet) >90o, Etlead-jet >80
- GeV, 0.1 < EMFlead-jet < 0.95
- L = 87 pb-1

- CDF

- ICHEP02, 25th July 2002

**Notes:**
In SUSY models with GMSB the goldstino (massless, neutral, spin1/2) is introduced.When gravity is added and SUSY is realized locally the gauge particle graviton has a spin3/2 partner, gravitino which acquires mass while the goldstino is absorbed. Production processes at Tevatron:
qqbarGGg ; qgGGq; gqbarGGqbar; ggGGg or qqbarGggamma

The resulting data sample is dominated by mismeasurement of QCD multijet bckg. 

## Light Gravitino Search (II)

- For MET >175 GeV:
- Events observed = 19
- Expected bckg = 21.6

- (PTĞĞ >100GeV) < 3.1pb
- F > 217 GeV
- mĞ > 1.1 x 10-5 eV/c2

- CDF

- Run IIa proj. ~ 270 GeV

- ICHEP02, 25th July 2002

**Notes:**
For RunIIa the limit will be extended to sqrt(F)>260 GeV.

95% CL upper limit on the cross section is 3.1 pb for the production of
GG+jets events with pT(GG)>100GeV
The production of gravitinos was simulated in Herwig

## Di-photon Channel 

- Final state: 2 photons + MET

- Bckg: multijet, direct photons,W,
-           W+jets, Zee
- Cuts: ET >20 GeV,ET >12 GeV,
-          recon. Vertex, MET>25 GeV
- L = 106.3 ± 5.6 pb-1

- Events observed = 2
- Expected bckg = 2.3 ± 0.9

- D

- ICHEP02, 25th July 2002

## Di-photon Channel (II)

- D

- Run IIa proj. ~ 300 GeV

- ICHEP02, 25th July 2002

**Notes:**
The chargino mass limit will be extended to 300 GeV for RunIIa.

## Di-photon Channel (III)

- Run II

- MET

- D Run II
- preliminary

- ICHEP02, 25th July 2002

## Summary

- Comprehensive searches for SUSY have been carried out at the Tevatron exploiting the Run 1 data to the fullest.
- A new era is beginning .......

- ICHEP02, 25th July 2002