Leptoquark Searches at the Tevatron

Leptoquark Searches at the Tevatron

April 16th, 2004XIIth Deep Inelastic Scattering Workshop

Štrbské Pleso, Slovakia

For the CDF and DØ Collaborations

Daniel Ryan

Tufts University

Outline● “Re”-introduction to CDF and DØ

● Introduction to Leptoquarks at the TeVatron

● Searches for 1st Generation Leptoquarks

● Searches for 2nd Generation Leptoquarks

● Summary and Comparison to Run I results

● Run II Summary and Future Outlook

2Daniel Ryan Searches for Leptoquarks at the Tevatron

Main Injector & Recycler

Tevatron

Chicago

p source

p

p

p p 1.96 TeV

Booster

CDF

DØ

Muon System

Central Calorimeter

Solenoid

Plug Calorimeter

Drift Chamber

Silicon Microstrip Tracker

Front End ElectronicsPipelined Triggers / DAQOnline & Offline Software

Time-of-Flight

New

Partly New

Old

CDF and DØ Run II upgrades

CDF ~ 200pb-1

Feb, 2002 March, 2004

DØ - 175pb-1

FY '04 Projection:230 - 310 pb-1

FY '04 Projection:230 - 310 pb-1

CDF - 72pb-1DØ - 104pb-1

Run IRun I

200

100

300

400

Leptoquarks

Spin 0 or 1 and both have lepton and baryon numbers

Color triplet

Fractional Electric Charge

Constraints on FCNC, assume LQ's couple uniquely within a lepton/quark generation

Introduction to Leptoquarks


Why study leptoquarks?

Some models beyond the SM (GUT's, Technicolor, composite models) assume additional symmetry between leptons and quarks.

uu

e

e

dd

cc

ss

tt

bb

µ

µ

ee µµ

qu

ark

sle

pto

ns

Leptoquark Production at the TeVatron

Production

qgLQ + LQ*

ggLQ + LQ

qqLQ + LQ

Pair produced

Independent of , coupling between LQ's and lepton/quark.

*Not shown


e e

Leptoquark Production at s = 1.96 TeV


Run IRun II

Leptoquark DecayEach generation can decay into 3 final states:

= 1

= 0.5

= 0


LQ LQ → llqq → 2l+2j BR =

LQ LQ → lqq → l+MET+2j BR = 2(1-LQ LQ → qq→ MET+2j BR = (1-

Exclusive to the Tevatron


1st Generation Leptoquark Searches, = 1, circa 2003

1st Gen. LQ's – ej ej

DØ Search – 175pb-1


Backgrounds Drell-Yan+2jets

Top (We)

QCD/Fakes

Selection 2 EM clusters E

T > 25 GeV

(1 cluster w/ track match)

2 jets ET > 20 GeV

Z veto (80 < Mee

< 102) GeV

First Generation Decay

DØ – ej ej

No. Exp. 0.4 ± 0.1Observed 0

Exclude at 95% CL M

LQ<238 GeV/c2


Selection (cont.)

Scalar Sum ST(eejj) > 450 GeV

Signal Acceptance ~(10 - 30)%


CDF – ej ej

Luminosity 203pb-1

Acceptance (32-42)%Background 6.2+3.1

-2.5

Observed 4

Exclude at 95% CL MLQ<230 GeV/c2

CDF Selection 2 electrons (CC,CE) E

T > 25 GeV

2 jets, ET(j1) > 30 GeV, E

T(j2) > 15 GeV

Z Veto (76 < Mµµ

< 110) GeV

Muon/Jets: ET

j1(e1) + ET

j2(e2) > 85 GeV

Sqrt( (ET(j

1) + E

T(j

2))2 +

(PT(e

1) + P

T(e

2))2 ) > 200 GeV

CDF Selection 1 electron (central) E

T>25 GeV

MET > 35 GeV

2 jets ET > 30 GeV

Phi (MET - jet) > 10o

Sum ET(jet1,jet2) > 80 GeV

MT(e,v) > 120 GeV

MET/Sqrt(ET) > 4.5

Signal Acceptance ~(18 - 37)%13Daniel Ryan Searches for Leptoquarks at the Tevatron

Backgrounds W+2jets Top (We) Top (dilepton + jets)

1st Gen. LQ's – ej j

CDF Search – 72pb-1

Luminosity 72pb-1

Background 1.7 ± 1.5Observed 2

Exclude at 95% CL MLQ < 166 GeV/c2

CDF – ej j


Events Expected in 72pb-1

Update in progress...Update in progress...

DØ Selection 1 electron (w/ em cluster –

track match) ET > 35 GeV

MET > 30 GeV

2 jets ET> 25 GeV

Phi (MET,jet) > 8o

ST(j1,j2,e,MET) > 330 GeV

MT(e,v) > 130 GeV



DØ Search – ej j

Luminosity 175pb-1

Background 4.7 ± 0.8Observed 2

Exclude at 95% CL M

LQ < 194 GeV/c2

MET + JetsCDF Search - 191pb-1


● Flavor Independent● 1st time for CDF● Channel rich with background● Relies heavily on event topology

● Flavor Independent● 1st time for CDF● Channel rich with background● Relies heavily on event topology

MET + Jets


CDF Selection 2-3 jets (1st & 2nd leading jets

in central region) Require central jets w/ 4

tracks (rejects events) Misaligned jets and MET

(rejects QCD, MET from mismeasured jets)

(Signal) MET > 60 GeV 80< Phi (jet1 – jet2) < 165o

Veto e, µ events



Luminosity 191pb-1

Background 118 ± 13 Observed 124

Exclude at 95% CL 78 < M

LQ < 117 GeV/c2

MET + Jets

CDF Combined:CDF Combined:beta = 0.0 MLQ > 117 GeV/c2

beta = 0.1 MLQ > 135 GeV/c2




eejjeejjeejjjjjjjj

Combined Results

DDØ Ø Combined:Combined:beta = 0.0 MLQ > 98 GeV/c2






eejjeejjeejjjj


2nd Gen. -- µj µj

CDF Search – 198pb-1

Second Generation Decay

Backgrounds Drell-Yan+2jets Fakes Top (We)

CDF Selection 2 muons with P

T > 25 GeV

2 jets with ET(j1,j2) > 30,15 GeV

Dimuon Mass Veto:

76 < Mµµ

< 110, Mµµ

< 15 GeV

ET(j

1) + E

T(j

2) > 85 GeV and

PT(µ

1) + P

T(µ

2) > 85 GeV

Sqrt( (ET(j

1) + E

T(j

2))2 + (P

T(µ

1) + P

T(µ

2))2 ) > 200 GeV


Luminosity 198pb-1

Background 3.1 ± 1.2 Observed 2

Exclude at 95% CL M

LQ < 241 GeV/c2

CDF -- µj µj

Luminosity 104pb-1

Background 1.6 ± 0.5 Observed 1

Exclude at 95% CL M

LQ < 186 GeV/c2

DØ -- µj µj

Update in progress...Update in progress...



2nd Gen. -- µj jin progress

CDF Selection Muon P

T>25, MET>60 GeV

2 jets, @ ET>30GeV

Veto aligned (Muon, MET)

and (MET,jets) E

T(jet1)+E

T(jet2) > 80 GeV

MT(MET,Muon) > 110 GeV

MET/Sqrt(ET) > 4.5

Backgrounds W+2jets Top (W) QCD

DØ Run I Limit 180 GeV

CDF Run I Limit 164 GeV

CDF Run II 200pb-1 Sensitivity ~200 GeV

Summary


Beta I II1 225 2001/2 2040 98 98

1 220 2021/2 182 1640 1231

Beta I II1 225 2001/2 2040 98 98

1 220 2021/2 182 1640 1231

Beta I II1.0 238 2000.5 213 in progress

0.0 in progress in progress

1.0 230 2400.5 197 in progress

0.0 117 117

Beta I II1.0 238 2000.5 213 in progress

0.0 in progress in progress

1.0 230 2400.5 197 in progress

0.0 117 117

1 c c3rd generation not shown

Run 1 Run 2

Summary


CDF and DØ have updated their 1st and 2nd generation direct leptoquark searches using Run II data

DØ has combined results for 1st generation (175pb-1)

CDF has combined results for 1st generation (72pb-1)

No Run II updates on vector leptoquarks from either DØ or CDF.

Work to be done:

CDF and DØ investigating jj channel and DØ investigating qq channel.

3rd generation leptoquarks.

Vector leptoquarks for Yang-Mills and Minimal type coupling.

Backup Slides

Run I Vector Leptoquark Searches

1st GenerationMass (GeV/c2)

Beta Yang-Mills Minimal

1.0 345 290

DØ 0.5 337 282

0.0 298 238

1.0 330 280

CDF 0.5 310 265

0.0

1st GenerationMass (GeV/c2)

Beta Yang-Mills Minimal

1.0 345 290

DØ 0.5 337 282

0.0 298 238

1.0 330 280

CDF 0.5 310 265

0.0

Documents

Leptoquark Searches at the Tevatron