# Presentation: 237386

## Search for GMSB SUSY at DØ

**Tim Christiansen**
- Munich University

- SUSY 2003, Tucson, Arizona
- June 5-10, 2003

- Latest Results and Prospects

## GMSB-SUSY

- (GMSB = gauge-mediated supersymmetry breaking)

**New messenger field(s)** introduced to mediate
- SUSY-breaking at low energy scale O*(100 TeV)*
- M(   ) << 1 MeV, almost massless
- small     -coupling (depending on SUSY-breaking scale)
-  NLSP is meta-stable, might/might not decay within detector
- Phenomenology
- driven by NLSP:

- Focus of this presentation

- Outlook

- Tim Christiansen, Munich LMU

- SUSY'03, Tucson AZ June 5-10, 2003

**Notes:**
massless Nambu-Goldstone particle: Goldstino, becoming the 3rd component of the formerly massless Gravitino.

## GMSB SUSY in pp Collisions

**GMSB SUSY ****in pp Collisions**

- In case of Bino-like NLSPs:
- Assuming prompt decay of NLSP  perform an inclusive search for  ****** + E****t**** + X**  (X = jets and/or leptons)

- _Motivation:_

- Tim Christiansen, Munich LMU

- SUSY'03, Tucson AZ June 5-10, 2003

## The TeVatron Run II

**The TeVatron Run II**

- Collisions
- every 396 ns
- (36 x 36)
- First data
- taken in 2001

- The TeVatron Accelerator at the Fermilab

- Tim Christiansen, Munich LMU

- SUSY'03, Tucson AZ June 5-10, 2003

## Tue DØ Detector

- The DØ Detector

**The DØ Run-II Detector:**

**New DAQ & Trigger System**
**Increased lepton acceptance**
**New tracking detectors **
**(Silicon + scintillating fibers)**
**in a magnetic solenoid ...**

- The DØ Calorimeter

- Preshower detectors give a very precise
- position measurement: fit shower axis
-  Photon pointing (not yet used)

*Preshowers are still in commissioning.*
***-pointing no used yet. MC estimates are:*
- Central:  R = 1.4 cm   z = 2.2 cm
- Forward:  R = 1.2 cm   z = 2.8 cm

- Tim Christiansen, Munich LMU

- SUSY'03, Tucson AZ June 5-10, 2003

## Search for GMSB SUSY in +MEt Events

**Search for GMSB SUSY in ********+MEt Events**

_**Event selection:**_
**Trigger**
-  1-EM and 2-EM triggered events, 97% efficient for:
**2 photons in the central calorimeter**: || < 1.1
-  90% of the cluster energy in the EM calorimeters
-  only little energy in hollow-
-   cone around the cluster:
-  -consistent shower shape
-  e-veto: no matching track in central tracking system
-  Et > 20 GeV (allows reliable EM-scale & eff. (Zee);
-   above trigger threshold)
**E****t**** reconstruction**
-   over all cal.cells + correction for jet- and EM-E scales

- ~ 41 pb-1 of data
- (Sept. ’02 - Jan. ‘03)

- Tim Christiansen, Munich LMU

- SUSY'03, Tucson AZ June 5-10, 2003

## EM Reconstruction

- M(ee) [GeV]

**DØ RunII Preliminary**

**EM Reconstruction**

**Reconstruction of *****Z ************ ee***** events**
- (EM selection w/o track-veto) used to verify/study:

-  tracking efficiency
-  trigger efficiency
-  EM scale correction
-  Random overlap of
-   tracks and clusters:
- rotation of *e* by /2 in azimuth
-    prob. for random
- overlap in ***Z ************ ee***
- events: 3·10-3

- ee Data

- Histogram: fake-sample,
- normalized. to sidebands

- From (Z) analysis @ DØ

- Tim Christiansen, Munich LMU

- SUSY'03, Tucson AZ June 5-10, 2003

## Background

**Background**

**Background from wrong E****t**
-  **QCD w/ direct ********‘s **
**  ****or mis-identif. jets**** **
-  Drell-Yan (w/ jets) Z  ee, both
-   electrons mis-identified as photons
**Background with true E****t**
-  ***W********* ******** *****e*******   (dominant)
-  *Wj*  *e*„“
-  *Z*    *ee + X*
-  *tt, WW, WZ,* etc. (small )

- (dominant)

******-sample** for the search
- + fake -sample to estimate QCD contribution
- (failed shower-shape cuts)

***e*********-sample** to estimate true-Et background with *e* mis-identification
- + fake *e*-sample to estimate QCD contribution

- contains the GMSB events?!

- Tim Christiansen, Munich LMU

- SUSY'03, Tucson AZ June 5-10, 2003

## Background Estimation

**Background ****Estimation**

***W**********e********* & *****Wj ************ e**********j ***
- (1 EM cluster has matching track)
-  Subtraction of QCD
-   contribution (fake *e*-sample)
-  Normalization by means of the
-   known tracking efficiency for *e*

- Tim Christiansen, Munich LMU

- SUSY'03, Tucson AZ June 5-10, 2003

## Missing-Et Distribution of  Events

- Background normalized at MET < 20 GeV

**Missing-E****t**** Distribution of ******** Events**

- Tim Christiansen, Munich LMU

- SUSY'03, Tucson AZ June 5-10, 2003

## Event Numbers and Signal Acceptance

**Event Numbers and Signal Acceptance**

**No excess of data over background was found**
-  limits on the cross section for GMSB-SUSY processes have been calculated for several points of the Snowmass slope.

**GMSB Snowmass slope:**
- messenger mass scale M=2, no. of messengers N=1, tan=15, >0

- 0.66  0.09

- Tim Christiansen, Munich LMU

- SUSY'03, Tucson AZ June 5-10, 2003

## Results from GMSB Search at DØ Run II

**Results from GMSB Search at DØ Run II**

- Comparing the 95% C.L. limits on  with
- theor. calculations:

- _95% C.L. Limits_
-  > 51 TeV
- m(10) > 66 GeV
- m(1) > 116 GeV

- Results from Run I using _similar_ models at DØ (CDF): m(10) > 75 (65) GeV with  more than double the luminosity than shown here. LEP2: m(10) > 95 GeV.

- Tim Christiansen, Munich LMU

- SUSY'03, Tucson AZ June 5-10, 2003

## Highest Et Candidate Event

**Highest E****t**** ****Candidate Event**

- Tim Christiansen, Munich LMU

- SUSY'03, Tucson AZ June 5-10, 2003

## Prospects: Displaced Photons

**Prospects: ****Displaced Photons**

-   -coupling depends on scale of SUSY breaking
- If     lifetime is long, the 2 ‘s don‘t come from interaction point

- {

- ~ inner radius of DØ calorimeter

- use preshower detector with calorimeter for photon pointing:
-  projective geometry
-  high segmentation

- from hep-ph/0008070

- 2 fb-1

- Tim Christiansen, Munich LMU

- SUSY'03, Tucson AZ June 5-10, 2003

## Prospects: Quasi-stable Stau as NLSP

- Missing-Et [GeV]

**Prospects: ****Quasi-stable Stau as NLSP**

- Sleptons are lighter than other sparticles, and
- Stau life-time depends on scale of SUSY-breaking: Stau could be _quasi-stable_

**Stau: ********-like with high dE/dx**

- hep-ph/0008070

- Stau-NLSP model line: N=2, >0, M/=3, tan=15

- Di-“Muon“ Mass [GeV]

- Tim Christiansen, Munich LMU

- SUSY'03, Tucson AZ June 5-10, 2003

**Notes:**
M : Messenger sector mass scale

## Stau NLSP with Prompt Stau Decay

**Stau NLSP ****with Prompt Stau Decay**

- from hep-ph/0008070:

- For sufficiently low SUSY-breaking scale: prompt decay

- for leptonic -decays, together with *W**/*Z** decays from the cascade decays:
- 2 or more leptons + jets +Et

- tri-lepton search

- same-sign-lepton search

- Tim Christiansen, Munich LMU

- SUSY'03, Tucson AZ June 5-10, 2003

## Summary

**Summary**

- Tim Christiansen, Munich LMU

- SUSY'03, Tucson AZ June 5-10, 2003