Feasibility of Detecting Leptoquarks With the CDF Detector

Althea MoorheadMentor: Darin Acosta

Outline

Background: What is a leptoquark? Leptoquark production and

previous work Results & Calculations Conclusions

The Standard Model Quarks, leptons,

and gauge particles (force carriers)

Arranged into three generations

Why is there a correlation between quarks and leptons?

Leptoquarks

Predicted by grand unified theories, supersymmetry, and string theory

Would be bosons Would have characteristics of both

quarks and leptons

Leptoquark Production

Gauge Coupling Mediated by

gauge bosons

Yukawa Coupling Direct fusion of a

lepton and a quark

The Tevatron Proton-antiproton

collider Energy of 1 TeV

(most energetic in the world)

Run 1: 100 pb-1

Run 2: 2000 pb-1

The CDF Detector Tracking chamber

maps the trajectories of charged particles

Calorimeters measure particle energies

Background: Current Leptoquark Limits

Leptoquarks decay into a lepton and a quark.

Probability of that lepton being charged is the branching ratio .

Interested in region of small .

Procedure Simulate leptoquark and

background events PYTHIA – event simulation cdfSim – detector simulation Production – event reconstruction Stntuple – event analysis

Use cuts to differentiate between signal and background

Missing Transverse Energy

Leptoquark Background

Table of Expected Events

Type Nobs

Leptoquark: 100 GeV 58

150 GeV 14

Background: QCD 195

W 100

W+jets 67

Z 36

Z+jets 20

Top quark 7

Sensitivity vs. Missing Energy

The statistical significance:

Statistical significance not very dependent on the missing energy

SS B

Sensitivity vs. Min. Jet Energy

Statistical significance is dependent on the minimum jet energy

Peak at about 35 GeV

Other CutsMissing Transverse Energy 40 GeV

Number of Jets = 2 or 3 (Energy 35 GeV)No other jets with energy > 7 GeV

0.1 Jet em fraction 0.9(MET, j) > 45

(MET, j1) < 165

45 < (j1, j2) < 165Electron Veto

Jet

Jet

Missing Energy

Cross Section Upper Limits Find upper limits

on leptoquark events, then:

N L

N

LM M

obs

ULobs UL

LL UL

FHG

IKJ

FHG

IKJ

Projected New Limits

Mass Limit vs. Luminosity

Conclusions

Results consistent with previous work

Experimental data will change these results somewhat

Could be improved with heavy flavor tagging