July 22nd, 2005 A.Canepa, SUSY 2005, Durham 1

CDF

Search for chargino and neutralino in trilepton final states

Anadi Canepa(Purdue University IN, USA)for the CDF Collaboration

The 13th Annual International Conference

on SUperSYmmetry

and Unification of the

Fundamental Interactions

July 22nd, 2005 A.Canepa, SUSY 2005, Durham 2

CDF Why trilepton ?

Higgsinos and gauginos mix

CHARGINOS NEUTRALINOS

pp

~

1

~02

~01

~01

Low background Easy to trigger

LOW MODEL DEPENDENCE

Striking signature at Hadron Collider,THREE LEPTONS

In mSUGRA Rp conserved scenario,LARGE MISSING TRANSVERSE ENERGY from the stable LSP

July 22nd, 2005 A.Canepa, SUSY 2005, Durham 3

CDF Best reach for the trilepton search

Weakly produced

100 150 200 250 300 350 400 450 500

10-3

1

10-2

10-1

10SUSY (pb) vs

sparticle mass (GeV)

T. Plehn, PROSPINO

~02~

1

W*

q

q

t-channel interferes

destructively

Efficiency and acceptance depend upon the scenario

Scenario Topology

q

'q

~

q

~02~

1

Best scenario for low mass gauginos

Low production cross section

July 22nd, 2005 A.Canepa, SUSY 2005, Durham 4

CDF Event topology

~01

~02

Z*

~02

~

~01

~

1

~

~01

~

1

~

~01

~01~

1

W*

Leptons of 1st, 2nd generation

are preferred

Leptons of 3rd generation

are preferred

Best reach for the Tevatron for low mass sleptons

Ch

arg

ino D

ecay

N

eu

tralin

o D

ecay

July 22nd, 2005 A.Canepa, SUSY 2005, Durham 5

CDF How do we investigate the different scenario ?

Low tan

scenario

High tan

scenario

sensitive to leptonic

decay

sensitive to hadronic

decay

CHANNEL STATUS TRIGGER PATH

+ e/ reported High pT Single Lepton

ee +/e reported High pT Single Lepton

+ e/ Ongoing Low pT Dilepton

e + e/ Ongoing High pT Single Lepton

e + e/ Ongoing Low pT Dilepton

e + track

Ongoing Low pT Dilepton

e + track

Ongoing Low pT Dilepton

ee + track

reported Low pT DileptonLow tan scenario tan=5 , 38%

High tan scenario tan=20, 100%

Acceptanceimprovement

High pT data-sample well understood, it also provides benchmark

for the challenging low pT data-sample

July 22nd, 2005 A.Canepa, SUSY 2005, Durham 6

CDF Event kinematic

Chargino and Neutralino

prompt decay

Leptons

separated in space

EWK rangeTypical SUSY leptons

Leading leptonNext-To-Leading lepton

Third lepton

Lepton pT (GeV)

Asymmetric pT

distribution

)()( 01

02 mm m p T

Lepton pT thresholds

trilepton analyses 20,8,5 GeV

dielectron + track analysis 10,5,4 GeV

July 22nd, 2005 A.Canepa, SUSY 2005, Durham 7

CDF

Missing Transverse Energy(MET)

e

Finding SUSY at CDF

CENTRAL REGION

Had Calorimeter

Muon system

Drift chamber

Em Calorimeter

=0=1

Recover loss in acceptance due

to cracks in the detector if

we accept muons with no

hits in the Muon Chamber

Real MET Particles escaping detection ()

Fake MET Muon pT or jet ET mismeasurementAdditional interactionsCosmic ray muonsMismeasurement of the vertex

July 22nd, 2005 A.Canepa, SUSY 2005, Durham 8

CDF Background

HEAVY FLAVOR 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 real MET from decay

Low jet activity

DIBOSON PRODUCTION

Leptons have high pT

Leptons are isolated and separated

MET due to neutrinos

irreducible background

e

pp

ee

pp

The third lepton originates from

conversion

pp

0 The third lepton is a fake lepton

July 22nd, 2005 A.Canepa, SUSY 2005, Durham 9

CDF Analysis strategy

BLIND ANALYSIS performed as a COUNTING EXPERIMENT

Understand the SM processes yielding the same signature

Increase the Sensitivity to New Physics by identifying

discriminating variables

Verify the SM background in “control regions”

ANALYSIS CUTS

Kinematic regions where New Physics is expected to be small

The kinematic region where we expect New Physics (“signal” region) is NOT investigated

during the whole analysis

Compare the number of predicted events to the number of observed events in the “signal” region

July 22nd, 2005 A.Canepa, SUSY 2005, Durham 10

CDF Mass selection

SM background totally overwhelms New Physics

Cuts in common to the 3 analyses:

Mll<76 GeV & Mll>106 GeV

Mll> 15 GeV

min Mll< 60 GeV (dielectron+track analysis)

Rejection of J/, and Z

# d

imu

on

pai

rs

103

10-1

Dimuon events

July 22nd, 2005 A.Canepa, SUSY 2005, Durham 11

CDF Jet veto

AnalysisKinematic Variable

Kinematic Cut

Trilepton analyses

Jet ET > 20 GeV n. Jets < 2

Dielectron + track analysis

HT= ∑jetETj HT < 80 GeV

Drell Yan production is reduced further in the electron analyses by

• angular cut ee

• min MT(MET,lepton) > 10 GeV

(dilelectron + track analysis)

Rejection of high jet multiplicity processes

July 22nd, 2005 A.Canepa, SUSY 2005, Durham 12

CDF MET selection

Still BLIND

Can we look at the “signal” region ?

Kinematic CutExample

SUSY Signal

TOT BACKGROUN

D

Number of trilepton events

0.480.02

2.850.27

Invariant Mass0.420.0

21.060.18

Jet Multiplicity0.420.0

2 1.040.18

MET0.370.0

20.090.03

Trilepton Analysis (muon based) L=346 pb-1

In Rp conserved searches, key quantity is METDistinguish SUSY from SM by MET > 15 GeV

July 22nd, 2005 A.Canepa, SUSY 2005, Durham 13

CDF Data understanding

Each control region is investigated with different jet multiplicity to check NLO processes with 2 leptons requirement (gain in statistical power) with 3 leptons requirement (signal like topology)

Control Region with

2

Total predicted

background

Observed data

Z veto, high MET, n. Jets < 2

522 79 538

Z mass, high MET, n. Jets > 1

1.9 0.9 2

Z mass window

3178 541 3168

Trilepton Analysis (muon based) L=346 pb-1

Invariant Mass 15 76 106

10

15

??

Z + fakeDY +

Diboson M

ET

July 22nd, 2005 A.Canepa, SUSY 2005, Durham 14

CDF Control regions

Very good agreement between

SM prediction and observed data

Tri

lepto

n a

naly

sis

ee +

e/

Tri

lepto

n a

naly

sis

ee +

e/

Tri

lepto

n a

naly

sis

+

e/

July 22nd, 2005 A.Canepa, SUSY 2005, Durham 15

CDF Systematic uncertainty

Major systematic uncertainties affecting the measured number of events

Signal

Lepton ID 5%

Muon pT resolution 7%

Background

Fake rate 5%

Jet Energy Scale 22%

Common to both signal and background Luminosity 6% Theoretical Cross Section 6.5-7%

July 22nd, 2005 A.Canepa, SUSY 2005, Durham 16

CDF ResultsLook at the “SIGNAL” region

AnalysisTotal

predictedbackground

Example SUSYSignal

Observed data

Trilepton (+l)

0.090.03 0.370.05 0

Trilepton(ee+l)

0.170.05 0.490.06 0

Dielectron+track

0.480.07 0.360.27 2

DY WW/ZZ WZ/* t-tbar

0.250.17

0.062 0.024

0.0320.005

0.0100.00

7

Details about the

dielectron + track analysis

July 22nd, 2005 A.Canepa, SUSY 2005, Durham 17

CDF

Leading electrone+, pT = 41 GeV

Next-to-leadinge-, pT = 12 GeV

MET, 45 GeVIsolated track, pT = 4 GeV Muon?

Candidate event ?

Mass OS141.6 GeV

Mass OS227.0 GeV

In the dielectron + track analysis, we observe one interesting event

July 22nd, 2005 A.Canepa, SUSY 2005, Durham 18

CDF Summary

Sensitive to CHARGINO & NEUTRALINO associated production

8 analyses are ongoing and 3 have being shown in this talk

Data agree with the SM background No excess

Not sensitive in mSUGRA yet …

Acceptance and luminosity are the key for this search

The acceptance will be greatly improved by

adding the additional channels

loosing the lepton identification criteria very low background

….

Tevatron recently delivered 1 fb-1 (analyses presented used 220-350 pb-1)

July 22nd, 2005 A.Canepa, SUSY 2005, Durham 19

CDF Outlook

We hope chargino and neutralino

are light enough for us to find them !

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

CMSSM

The results of 2 fits based on the current experimental results for the

precision observables

MW, sin2eff, (g-2), BR(bs).