# Presentation: 940942

## Searches for Supersymmetry  inMultileptonic Signatures at CDF

**Searches for Supersymmetry  in****Multileptonic Signatures at CDF**

***Giulia Manca,  ***
***University of Liverpool***

**Wine and Cheese Seminar**
**Fermilab, 12 May 2006**

## Outline

- Supersymmetry
- Searching for SUSY at CDF
- Chargino and Neutralino
- Di/Trileptons
- Adding more leptons...
- Conclusions
- Outlook

- Giulia Manca, University of Liverpool

- 12th May 2006

## Supersymmetry: what ?

**Supersymmetry: what ?**

- Extends the Standard Model (SM) by predicting a _***new symmetry***_***:***
- spin-1/2 matter particles (fermions) <=> spin-1 force carriers (bosons)

- Giulia Manca, University of Liverpool

- 12th May 2006

**Notes:**
Introduce leptons, chargino-neutralino
Sneak in what I want to do (interested in chargino-neutralino)

## Supersymmetry: what ?

**Supersymmetry: what ?**

- Extends the Standard Model (SM) by predicting a _***new symmetry***_***:***
- spin-1/2 matter particles (fermions) <=> spin-1 force carriers (bosons)

- Giulia Manca, University of Liverpool

- 12th May 2006

**Notes:**
Introduce leptons, chargino-neutralino
Sneak in what I want to do (interested in chargino-neutralino)

## Supersymmetry: why ?

** ****Stabilisation of Higgs mass at EW scale**
** ****Couplings don’t unify at one scale**
** ****Dark Matter**
** ****Dark Energy**
** ****Neutrino masses**
** ****Gravity**

** **

**Limitations of  Standard Model****_x0003_**

**SUSY**

- Giulia Manca, University of Liverpool

- 12th May 2006

**Notes:**
Get new plot 

## Supersymmetry: The Challenge

- VERY SMALL cross sections !!

- Giulia Manca, University of Liverpool

- 12th May 2006

## Wide range of signatures: look for SuSy specific signatures or
excess in SM ones; examples:

- Wide range of signatures: look for SuSy specific signatures or
- excess in SM ones; examples:

**Supersymmetry:  how ?**

- Large Missing Energy ET
- AND:
- Isolated leptons
- Multijets
- ...and many more!

- Giulia Manca, University of Liverpool

- 12th May 2006

## mSugra: a working  model

- hep-ph/9311269

**EW scale**

**GUT scale**

**mSugra: a working  model**

- SUSY broken through gravity
- Five parameters:
- m0:common scalar mass at GUT scale
- m1/2:common gaugino mass at GUT scale
- 	(i.e. M1(GUT)=M2(GUT)=M3(GUT)= M1/2 )
- A0: common trilinear scalar interaction at the GUT scale (Higgs-sfermionR-sfermionL)
- tan: ratio of Higgs vacuum expectation values
- Sign(), the higgsino mass parameter
- 	(determined by EWSB)
- Lightest supersymmetric particle(LSP) is the 01, stable

**Tevatron **

**Running masses (GeV/c****2****)**

**log****10****(Q) (GeV)**

- Giulia Manca, University of Liverpool

- 12th May 2006

## mSugra Existing Limits : LEP

**mSugra Existing Limits : LEP**

** ****LSP**** > M****Z****/2**
** ****Chargino**** > ****103****  GeV/c****2**** (heavy sneutrinos); **
** ****Sleptons**** > 90-100 GeV/c****2**** for M(********0****1****)<M(********R****); **

- 103

- Giulia Manca, University of Liverpool

- 12th May 2006

**Notes:**
What are the stars ??

## Searching for Chargino and Neutralino at 

## The signature

-  Low background
-  Easy to trigger
-  LITTLE MODEL DEPENDENCE

- Chargino-Neutralino production :
- Striking signature
**THREE ISOLATED LEPTONS**
- If Rp conserved,
**LARGE MISSING TRANSVERSE ENERGY **
**from the stable LSP+******

**The signature**

- GOLDEN SIGNAL AT THE TEVATRON !!

- Giulia Manca, University of Liverpool

- 12th May 2006

## Chargino-Neutralino production... 

**Chargino-Neutralino production... **

- t-channel interferes destructively

-  Low cross section
- 	(weakly produced)

- 

- Giulia Manca, University of Liverpool

- 12th May 2006

## ...and decay

- Leptons of 3rd generation
-  are preferred

**Chargino Decay**** **

**Neutralino Decay**** **

**Leading lepton**

**Next-To-Leading lepton**

**Third lepton**

**M****12****=180, M****0****=100, tan********=5, A****0****=0,********>0**
**M(********1****±****)~113 GeV/c****2**

- Giulia Manca, University of Liverpool

- 12th May 2006

## Finding SUSY at CDF 

- CENTRAL REGION

- Had Calorimeter

- Muon system

- Drift chamber

- Em Calorimeter

******=0**

******=1**

******=2**

- Giulia Manca, University of Liverpool

- 12th May 2006

## The Missing Energy (MET)

***Real MET ***
-  Particles escaping detection
-    *Fake MET** *
- Muon pT or jet ET mismeasurement
- Instrumental effects
- Cosmic ray muons
- Mismeasurement of the vertex

- Giulia Manca, University of Liverpool

- 12th May 2006

## Trileptons Analyses

## The Data

- Mar02-Aug05
- 750 pb-1

*Many thanks to the accelerator division !!*

- Giulia Manca, University of Liverpool

- 12th May 2006

## Leptons to discover SUSY:The SM Calibration Samples 

- Lepton ID efficiencies
- Trigger efficiencies
- Calorimeter Calibration
- Lepton E and P Scale
- Luminosity

- High pT leptons

- Low pT leptons

- Giulia Manca, University of Liverpool

- 12th May 2006

## Analyses Overview

**Analyses Overview**

| CHANNEL | LUM | TRIGGER PATH |
| --- | --- | --- |
| ee,e,  | 710 | High pT Single Lepton |
|  + e/ | 750 | High pT Single Lepton |
| ee + e/ | 350 | High pT Single Lepton |
|  + e/ | 310 | Low pT Dilepton |
| ee + track | 610 | Low pT Dilepton |

- No third lepton requirement
- => Higher acceptance

- Use e/mu only
- =>Very small backgrounds

- Sensitive to taus as 3rd lepton
- => Keeps acceptance at high tan

- Giulia Manca, University of Liverpool

- 12th May 2006

## Like-Sign Dileptons

**Like-Sign Dileptons**

- Sensitive to both chargino-neutralino and squark-gluino production
- Ask for 2 high-pt (20,10) isolated leptons of the same charge
- Main background :
- 	conversions!

- Giulia Manca, University of Liverpool

- 12th May 2006

## Backgrounds 

- HEAVY FLAVOUR PRODUCTION
-  Leptons mainly have low pT
-  Leptons are not isolated
-  MET due to neutrinos

-  DRELL YAN PRODUCTION + additional lepton
-  Leptons have mainly high pT
-  Small MET
-  Low jet activity

- DIBOSON (WZ,ZZ) PRODUCTION_ _
-  Leptons have high pT_x0013_
-  Leptons are isolated and separated
-  MET due to neutrinos
*	**irreducible background*

**Backgrounds: ****how to reduce them****?**

- Giulia Manca, University of Liverpool

- 12th May 2006

## Jets Faking Leptons

**Jets Faking Leptons**

- Inclusive Jet Sample with different trigger thresholds
- used to extract Fake rates and test Jet Energy Scale

- Inclusive Jet Sample
- L= 380 pb-1

- ~10-4

- Electron Fake rate per Jet

**Inclusive Jet Triggers: **
**Et>20**
**Et>50**
**Et>70**
**Et>100**

**Et>20**
**Et>50**
**Et>70**
**Et>100**

- ET (GeV)

- Giulia Manca, University of Liverpool

- 12th May 2006

**Analysis Strategy**

**COUNTING EXPERIMENT**
- Optimise selection criteria** for best signal/background value; **
- Define **the **signal region** and keep it blind**

-  Test** agreement observed vs. expected number of events in orthogonal regions (“**control regions**”)**
-  Look **in the signal region  and **count** number of **SUSY** **events** !! **
**(Or set limit on the model)**

- Giulia Manca, University of Liverpool

- 12th May 2006

## The Basic Selection

- Two leptons preselection
- 1st lepton: 20(15,5), 2nd 10(8,5) GeV/c
- Invariant Mass
- reject resonances
- ****** ******** **
- reject Drell-Yan
- Low jet activity
- reject ttbar,W+jets,Z+jets
- High Missing Transverse Energy
- further Drell-Yan rejection

*Minimal number of cuts to keep analysis simple while rejecting the most overwhelming backgrounds*

- Giulia Manca, University of Liverpool

- 12th May 2006

## Selection criteria:  (I) Mass

**Selection criteria:  (I) Mass**

**Dielectron events**

- Rejection of  J/,  and Z

- DiElectron Mass(GeV/c2)

- Asking for the third lepton...

- DiMuon Mass(GeV/c2)

-  M****<76 GeV  &  M****** **>106 GeV
-   M****> 15 (20,25) GeV
-  min M****** **< 60 GeV (dielectron+track analysis)

- Giulia Manca, University of Liverpool

- 12th May 2006

## (II) ( , ) and  Jet  Veto

**(II) ********( ********,******** ****) and  Jet  Veto**

| Analysis | Kinematic Variable | Kinematic Cut |
| --- | --- | --- |
| Trilepton analyses | Jet ET > 20 GeV | n. Jets < 2 |
| Dielectron + track analysis | HT= ∑jetETj | HT < 80 GeV |

- Rejection of DY and high jet multiplicity processes

- Number of Jets Et>20 GeV

- (e,e) (o)

- Sum Et of Jets (GeV)

**Drell-Yan**
**W/********->e******
**ttbar**
**Dibosons**
**Fakes**
**- SUSY**
** ****DATA**

- Number of events

- Number of events

- Giulia Manca, University of Liverpool

- 12th May 2006

## (III) MET selection

**(III) MET selection**

- ...Still BLIND !

- Further reducing DY by asking MET > 15 GeV

- Giulia Manca, University of Liverpool

- 12th May 2006

## Understanding of the Data:The Control Regions

- Each CONTROL REGION is investigated:
-  with different jet multiplicity
*	**check NLO processes*
-  with 2 leptons requirement 	*gain in statistics*
-  with 3 leptons requirement   	*signal like topology*

- Control regions defined as a function of M(****** ******** **) and MET:

- Giulia Manca, University of Liverpool

- 12th May 2006

## Control Regions for Trilepton Analyses

**     ****MET**

- Testing Control Regions with two leptons

- MET (GeV)

- Dielectron Invariant Mass(GeV/c2)

- Drell-Yan
- WZ
- ZZ
- ttbar
- Fakes
- -SUSY
-  DATA

**Drell-Yan**
**Dibosons**
**ZZ**
**bbbar**
**- SUSY**
** ****DATA**

- L=607 pb-1

- Dimuon PT(GeV/c)

- N events/2 GeV/c 2

*LS-dilepton analysis has additional Control Regions to test conversion removal*

- Giulia Manca, University of Liverpool

- 12th May 2006

## LS-Dileptons Control Regions

- Very good agreement between SM prediction and observed data

- -like sign

- L=704 pb-1

- EWK        low DY      Zmass

- ee-like sign

- L=704 pb-1

- Conversion- like control-region

- Signal-like but opposite sign

- Conversions        EWK  low DY  Zmass

- Giulia Manca, University of Liverpool

- 12th May 2006

## Systematic uncertainty

**Systematic uncertainty**

- Major systematic uncertainties affecting the measured number of events
- ee+lepton (high-pt)
-  Signal
-  Lepton ID 5%
-  Muon pT resolution 7%
-  Background
-  Fake lepton estimate method 5%
-  Jet Energy Scale 22%
-  Common to both signal and background
-  Luminosity 6%
-  Theoretical Cross Section 6.5-7%
-  PDFs 7%

- Z->ee  MC

- Missing Et (GeV)

- Number of events

- Giulia Manca, University of Liverpool

- 12th May 2006

## Let’s look at the signal region !

##        Results !

- Look at the  “SIGNAL” region

| Analysis | Luminosity
(pb-1) | Total predicted
background | Example SUSY
Signal | Obs-erved data |
| --- | --- | --- | --- | --- |
| ee,e,  | 710 | 6.801.00 | 3.180.33 | 9 |
|   +e/ 
(low-pT) | 310 | 0.130.03 | 0.170.04 | 0 |
| ee+track | 610 | 0.480.07 | 0.90_x0018_0.09 | 1 |
| ee + e/ | 350 | 0.170.05 | 0.490.06 | 0 |
|   +e/ | 750 | 0.640.18 | 1.610.22 | 1 |
|  e +e/ | 750 | 0.780.15 | 1.010.07 | 0 |

*LS dileptons*

*Low-Pt trileptons*

*High-Pt trileptons*

- Giulia Manca, University of Liverpool

- 12th May 2006

##        Results !

| Analysis | Luminosity
(pb-1) | Total predicted
background | Example SUSY
Signal | Obs-erved data |
| --- | --- | --- | --- | --- |
| ee,e,  | 710 | 6.801.00 | 3.180.33 | 9 |
|   +e/ 
(low-pT) | 310 | 0.130.03 | 0.170.04 | 0 |
| ee+track | 610 | 0.480.07 | 0.900.09 | 1 |
| ee + e/ | 350 | 0.170.05 | 0.490.06 | 0 |
|   +e/ | 750 | 0.640.18 | 1.610.22 | 1 |
|  e +e/ | 750 | 0.780.15 | 1.010.07 | 0 |

**       ****Results !**

- Look at the  “SIGNAL” region

- N events/5 GeV/c2

- WZ
- ZZ
- DY+gamma
- Fakes
- -SUSY
-  DATA

- Giulia Manca, University of Liverpool

- 12th May 2006

##        Results !

| Analysis | Luminosity
(pb-1) | Total predicted
background | Example SUSY
Signal | Obs-erved data |
| --- | --- | --- | --- | --- |
| ee,e,  | 710 | 6.801.00 | 3.180.33 | 9 |
|   +e/ 
(low-pT) | 310 | 0.130.03 | 0.170.04 | 0 |
| ee+track | 610 | 0.480.07 | 0.900.09 | 1 |
| ee + e/ | 350 | 0.170.05 | 0.490.06 | 0 |
|   +e/ | 750 | 0.640.18 | 1.610.22 | 1 |
|  e +e/ | 750 | 0.780.15 | 1.010.07 | 0 |

**       ****Results !**

- Look at the  “SIGNAL” region

- Number of events

- Giulia Manca, University of Liverpool

- 12th May 2006

## Trimuon Event

**Trimuon Event**

- Giulia Manca, University of Liverpool

- 12th May 2006

## Highest lepton-pt  event

- e- : 103 GeV

- MET : 25 GeV

-  : 15 GeV

- e- : 107 GeV

- e+ : 5 GeV

*In the ee like-sign analysis, we observe one interesting event*

- Giulia Manca, University of Liverpool

- 12th May 2006

## Limit

**Limit**

- No SUSY :(
- Combined all analyses to obtain a limit on the mass
- of the chargino in mSugra-like scenario
- with no slepton mixing
- slepton masses ~ neutralino masses
-  _Observed limit:_
- 	M(1) ~ 127 GeV/c2
- 	xBR ~ 0.25 pb

- D0 limit in similar scenario:
- 	 M(1) > 116 GeV/c2

*Beyond LEP and Tevatron Run I ! *

- Giulia Manca, University of Liverpool

- 12th May 2006

## Looking at different models...

**Looking at different models...**

- But : the limit we can set
- depends on the model !
- In “standard” mSugra
- Sensitive to chargino masses of ~ 116 GeV/c2

- Not able to exclude _x0004_this particular region of parameter space with these results ...

- Giulia Manca, University of Liverpool

- 12th May 2006

## The differences in the models

**The differences in the models**

- In Standard
- mSugra the
- BR into taus
- is enhanced
- smaller
- acceptance

- Giulia Manca, University of Liverpool

- 12th May 2006

## From trileptons to  multileptons... 

## R-Parity Violating SuperSymmetry

- If R-Parity violated sparticles :
- Do not need to be pair-produced
- Can decay into SM particles
- Extra terms in the Super-Potential of the type :
- 	              violates Lepton               violates Baryon
- 	           number conservtion      number conservation
- ’”couplings of the RPV vertex;

*1        2        1 *

- Giulia Manca, University of Liverpool

- 12th May 2006

## R Parity Violation 

**R Parity Violation **

- RPV can be tested in Production and Decay of SUSY particles

_**RPV decay of LSP**_**(********0****1****)**
***At least four leptons in final state !***
******121 ****->(eeee,eee********,ee********+******
******122 ****->(********,********e,********ee) +******

- LSP assumed to decay within the detector ( |d0|<0.02 cm )

*Only one  **λ**ijk **≠ 0:** at the time *

- Giulia Manca, University of Liverpool

- 12th May 2006

## Backgrounds

**Backgrounds**

- Similar backgrounds to trileptons analyses
- Challenge: conversions
- Sensitive to all new physics with >4 leptons in the final state!!

- Luminosity = 346 pb-1

**Fake leptons**

- Giulia Manca, University of Liverpool

- 12th May 2006

## Control Regions

**Control Regions**

- Dielectron events

- Trilepton events

- Chosen changing the requirements on the lepton selection criteria, delta-phi,  invariant mass

- Giulia Manca, University of Liverpool

- 12th May 2006

## Control Region Overview

- 26 total control regions
- By lepton type
- Inside & outside Z window
- Number of leptons
- Fail cut
- Plot shows relative agreement of all control regions.
- Error bars = ±1σ
- Line = perfect  	 	        agreement

- Giulia Manca, University of Liverpool

- 12th May 2006

## Signal Regions

| Trilepton Signal Regions |  |  |
| --- | --- | --- |
| Dataset | ee()+e/
(_x0017_λ121)  | ee (λ122)  |
| Z/ +  | 2.1 ± 0.8 | 1.2 ± 1.0 |
| W Z/  | 0.2 ± 0.1 | 0.1 ± 0.1 |
| Fakes | 0.5 ± 0.3 | 0.3 ± 0.2 |
| Total Background | 2.9 ± 0.8 | 1.8 ± 1.0 |
| RpV SUSY (121) | 3.8 ± 0.4 | ----- |
| RpV SUSY (122) | ----- | 4.0 ± 0.4 |
| Data | 5 | 1 |

| ≥ 4 Signal Region |  |
| --- | --- |
| Dataset | Signal |
| Z/ +  | 0.001 ± 0.001 |
| Z/+Z/ | 0.004 ± 0.002 |
| Fakes | 0.004 ± 0.003 |
| Total Background | 0.008 ± 0.004 |
| RpV SUSY (121) | 1.5 ± 0.2 |
| RpV SUSY (122) | 1.5 ± 0.3 |
| Data | 0 |

- Signal regions are consistent with background and no signal

- Giulia Manca, University of Liverpool

- 12th May 2006

## Event Display

**Event Display**

- Giulia Manca, University of Liverpool

- 12th May 2006

## Limits !

**Limits !**

- 122>0

- 121>0

- D0 Limits :
- 122 >0 : m(+1) >229 GeV/c2
- 121 >0 : m(+1) >231 GeV/c2

- Giulia Manca, University of Liverpool

- 12th May 2006

## Summary and Outlook: Chargino and Neutralino in mSugra

**Summary and Outlook: ****Chargino and Neutralino in mSugra**

- Multileptons signatures:
-  CDF analysed first bunch of data and observed no excess
-  Set limit already beyond LEP results ! (although model dependent )
-  1.5 fb-1 of data  collected and ready to be analysed
-  With 4-8 fb-1 by the end of RunII we should be sensitive to Chargino masses up to ~250 GeV  and xBR ~ 0.05-0.01 pb !!

- Ellis, Heinemeyer, Olive, Weiglein,
- hep-ph\0411216

***Favoured by EW  precision data***

*One e**** like sign event...*

- Giulia Manca, University of Liverpool

- 12th May 2006