# Presentation: 182096

## Search for Squarks and Gluinos with the D0 detector

- Gérard Sajot
- LPSC-Grenoble

- SUSY 2005  July 18-23 Durham

- G. Sajot

##  New Main Injector : 150 GeV

-             (stores protons , shoots to target
-              for antiproton production)
-  Recycler
-             (magnet storage ring for
-              antiproton)
-  Higher energy
-             (1.96 TeV vs 1.8 TeV)
-         => Higher cross sections
-                  (~30% for SUSY)
-  Higher antiproton** **intensity
-             6x6  36x36 bunches
-             (3.5 s  396 ns)
-            antiproton “recycler”
-        => Higher luminosity
-                 Run I  : 2x1031 cm-2 s-1
-                 Run II : 2x1032 cm-2 s-1
-                Record  1.6 x1032 cm-2 s-1

- The Tevatron at Run II

- SUSY 2005  July 18-23 Durham

- G. Sajot

-  Weekly delivered:
-    8 - 16 pb-1
-  Peak luminosity:
-    6 - 12 1031 cm-2 s-1
-  Data taking efficiency:
-    ~ 90%
-   Physics quality data:
-        ~ 800 pb-1

- In 2005:

- 1032

- Luminosity performance

- SUSY 2005  July 18-23 Durham

- G. Sajot

##  pb   

- Squarks /Gluinos Production at Tevatron

**Dominant process is function of the Susy parameters**

-  ******pb**

**Strong production**

- SUSY 2005  July 18-23 Durham

- G. Sajot

## Squarks /Gluinos decay

**Mgluino < Msquark**

**Msquark < Mgluino**

- SUSY 2005  July 18-23 Durham

- G. Sajot

## Run I and LEP heritage 

**LEP : search for acoplanar jets**
- _[http](http://lepsusy.web.cern.ch/lepsusy/)__[://](http://lepsusy.web.cern.ch/lepsusy/)__[lepsusy.web.cern.ch/lepsusy](http://lepsusy.web.cern.ch/lepsusy/)__[/](http://lepsusy.web.cern.ch/lepsusy/)_

**D0 RunII search : **
**- mSUGRA parameters selected to allow comparison with ****CDF and D0 RunI results ****: **
**tan******** = 3, A0 = 0, ******** ******** 0**
**-  1st and 2nd squark    generations + sbottoms  production (no stops)**

*Msquark = mean  mass of the 10  squarks*

- Run I and LEP heritage

- → **Sbottom and Stop search in D0**
**     ****Talk :  P. Ratoff   July 20th**

**Run I :**
** ****- CDF      MET+multijets **
** ****- D0         Jets + large imbalance in P_T**

- SUSY 2005  July 18-23 Durham

- G. Sajot

##  Low  m0 (~ 25 GeV)

-  Low  m0 (~ 25 GeV)
- Msquark<Mgluino
-   squark antisquark
-   acoplanar dijet events

-   High m0
- (~500 GeV)
- Msquark>Mgluino
-         4 jets

- Intermediate m0
-     (~200 GeV)
- MsquarkMgluino
-         3 jets

**“****3 jets”** analysis

-  **“****gluino”** analysis

**“****dijet”** analysis

- mSUGRA : Event Topology

- SUSY 2005  July 18-23 Durham

- G. Sajot

##  Standard Model 

-  **Standard Model **
** ****(Alpgen, pythia)**
** ****CTEQ5L**
** ****Cross section MCFM**

**Signal :**
**Isajet 7.58 (masses)**
**Pythia 6.202 (generation+sigma LO)**
**PROSPINO (NLO K factors)**

- Signal and Standard Model background

- SUSY 2005  July 18-23 Durham

- G. Sajot

## After pre-selection

- Trigger :
-         L1 : 3 calorimeter trigger towers (E_T > 5 GeV)
-         L2  and L3 Missing Tranverse energy to the reconstructed jets
-          (MHT=|        | >20 GeV (L1) and > 30 GeV (L2) )
-  + after June 2004 :
-      acoplanarity (azimuthal angle between the 2 leading jets)
-                      <170 degrees at L3
-      - H_T =           > 50 GeV at L3
-  Data pre-selction
-        MET > 40 GeV
-        MHT > 40 GeV
-        at least 2 hadonic jets (EMF<0.95)
-  in Central region (|| <0.8)
-        P_T 1st leading jet > 60 GeV/c
-        P_T 2nd leading jet > 40 GeV/c
-          delta phi < 165

-     dijet analysis
-   (m0=25,m1/2=145)

- Trigger and Data pre-selection

- SUSY 2005  July 18-23 Durham

- G. Sajot

## 
Jets reconstructed from calorimetry 
     ->   important to monitor 
      “ quality of calorimeter data” 
    Understanding/curing noise (electronic and external)
     ->  have the best possible JES 

Misvertexing produces 
      fake MET

**Jets reconstructed from calorimetry **
**     ****->   important to monitor **
**      “ ****quality of calorimeter data” **
**    ****Understanding/curing noise (electronic and external)**
**     ****->  have the best possible JES **
**Misvertexing produces **
**      ****fake MET**

**Pt**

**Pt'**

- z

**True vertex**

**Chosen vertex**

- Jets are confirmed with charged
- Particles from primary vertex.

- Selection of high quality data

- SUSY 2005  July 18-23 Durham

- G. Sajot

##  Isolation MET vs jets

- >= 2 jets (60,50)
- MET > 175, HT > 250

-  Isolation MET vs jets
-  Veto EM/muon

- “dijet” analysis : event selection

**marginal distributions*

- SUSY 2005  July 18-23 Durham

- G. Sajot

## Isolation MET vs jets

- Veto EM/muon

**>= 4 jets (60/40/30/20) **
**MET > 75, HT > 250**

- gluino” analysis : event selection

- SUSY 2005  July 18-23 Durham

- G. Sajot

## Isolation jets vs MET

- >= 3 jets (60/40/30)
- MET > 100 HT > 325

- Veto EM/muon

- “3 jets” analysis : event selection

- SUSY 2005  July 18-23 Durham

- G. Sajot

## Results : Data/Background

|  | Dijet | 3 jets | Gluino |
| --- | --- | --- | --- |
| QCD | - | - | 1.60.2 |
| Total Bkg | 12.85.4 | 6.13.1 | 7.10.9 |
| Data  | 12 | 5 | 10 |

_**Systematic uncertainties **_
- JES in Data and MC : 8% to 31%
- Luminosity: ± 6.5%
- SM background Cross Section : ± 7.5%

- SUSY 2005  July 18-23 Durham

- G. Sajot

## Upper limits at 95% C.L. on squarks and gluinos

**Yellow band : **
**renormalization and**
**factorization scale :**
** ****higher   → ********=Q/2**
** ****central  → ********= Q**
** ****lower    → ********=2 * Q**

*“****dijet”***
***m0 = 25 GeV/c2***
***Q=m_squark***

***“******Gluino”***
***m0=500 GeV/c2***
***Q=m_gluino***

***“******3jets”***
***m_squark=m_gluino***
***Q=(m_gluino+m_squark)/2***

- SUSY 2005  July 18-23 Durham

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## Green line : expected

| dijet | m_squark 
> 318 GeV/c2 | m0= 25 GeV/c2
 |
| --- | --- | --- |
| gluino | m_gluino
 > 233 GeV/c2
 | m0=500 GeV/c2
 |
| 3jets | m_squark
> 333 GeV/c2

m_gluino
> 333 GeV/c2
 | m_squark=m_gluino |

- Excluded region at 95 % C.L

- SUSY 2005  July 18-23 Durham

- G. Sajot

## MET = 354 GeV et 

- MET = 354 GeV et
- HT = 431 GeV
- 2 High Pt jets:
- jet 1 : 264 GeV/c
- jet 2 : 106 GeV/c

- “dijet” analysis : Highest MET candidate

- SUSY 2005  July 18-23 Durham

- G. Sajot

## With a data sample at least 20 to 40 times larger than at Run I, 

- collected at higher energy with improved detectors,
- Exploration of a new SUSY territory can be done
- and already a massive improvement of existing
-   Run I limits has been achieved

- Conclusions

-  Squarks and gluinos have been searched  in the Jet + MET topology
- on 310 pb-1 of data recorded by D0
-   The observed limits are :
-     -  dijet : for  m0 = 25 GeV/c2            m_squark > 318 GeV/c2
-     -  gluino : for  m0 = 500 GeV/c2       m_gluino > 233 GeV/c2
-     -  3 jets : for m_squark=m_gluino    m_squark and m_gluino > 333 GeV/c2

- Entering into a domain not yet excluded by LEP2 (charginos and sleptons searches)

- SUSY 2005  July 18-23 Durham

- G. Sajot

## Back-up Slides

- SUSY 2005  July 18-23 Durham

- G. Sajot

## Solenoid (2T)
Central tracker
Silicon Vertex Detector

**Solenoid (2T)**
**Central tracker**
**Silicon Vertex Detector**

**Preshower**
**Calorimeter electronic**
**Muon forward chamber**

**DAQ system**
**Trigger system**

- D0  upgrade

- SUSY 2005  July 18-23 Durham

- G. Sajot

## QCD in gluino search 

- QCD in gluino search

- SUSY 2005  July 18-23 Durham

- G. Sajot

## Selection of  generated points

- SUSY 2005  July 18-23 Durham

- G. Sajot

## LEP heritage

- 1:Yellow: no Minimal SUGRA solution: no EWSB or tachyonic particles;
- 2:Light blue: regions inconsistent with the measurement of the electroweak parameters at LEP1;
- 3:Green: regions excluded by chargino searches;
- 4:Red: regions excluded by selectron or stau standard searches;
- 5:Dark Blue: regions excluded by the search for hZ;
- 6:Brown: regions excluded by the neutralino stau cascade searches.
- 7:Magenta: regions excluded by the search for  heavy stable charged particles applied to staus.

- Mu,<0

- SUSY 2005  July 18-23 Durham

- G. Sajot