Search for Compositeness at the Tevatron

Iain A. Bertram

Northwestern University/DØ

Talk Outline

Introduction Direct Search for Composite Quarks Contact Interaction Searches

Quark-Quark Compositeness: Dijet Events Quark-Lepton Compositeness: Drell-Yan Events

Run II Prospects Conclusion

Introduction

Three quark and lepton generations suggests that quark and leptons are composites.

Composed of PREONS. Preons interact via a new strong

interaction (Metacolour). Below a characteristic energy scale

, the preons form metacolour singlets: quarks and leptons.

Strength of interactions related to

Atom

Nucleus

Nucleon

Quark 2ˆ

s

s

Effective Lagrangian

M cos

2ˆ

s

s

Ra

RRa

RRR

La

LRa

RRL

Ra

RLa

LLR

La

LLa

LLL

RRRRRRLLRRRL

RRLLLRLLLLLL

qqqq

qqqq

qqqq

qqqq

qqqqqqqq

qqqqqqqq

L

22

22

22

224

1

1

1

1

00

00

2

A

V

1

0

Axial

:1

Vector

:1

nsinteractio o:

nsinteractiosinglet :

XRL

XLR

XRR

XLL

XRL

XLR

XRR

XLL

XX

XX

ctet

Dijet and Dielectron Variables

Dijet and di-electron Event Measure the following:

massive

massless coscosh2

2/tanln ,, :electron or Jet

221

221

2

21212,1,2

PPEEM

EEM

E

TT

T

Jet, electron 2: ET

2, 2, 2

Jet, electron 1: ET

1, 1, 1

= 0

“Typical DØ Dijet Event”

ET,1 = 475 GeV, 1 = -0.69, x1=0.66ET,2 = 472 GeV, 2 = 0.69, x2=0.66

MJJ = 1.18 TeVQ2 = 2.2x105

“Typical CDF Drell-Yan Event”

Dijet & Drell-Yan Production

1P

2P

1xfi11Px

22Px

1jet e,

2jet e,

sij ̂

2xf j

,,,ˆ

,,

2

2

2

22

2211

22

2121

RFRsij

ijFjFi

QQPxPx

xfxfdxdx

To search for compositeness we need a good prediction for Standard Model production

Dijets: NLO event generator JETRAD, Giele, Glover, Kosower Nucl. Phys. B403, 633.

Drell Yan: NNLO CalculationHamberg, Van Neerven, & Matsuura, Nucl. Phys. B359 343.

Need to choose pdf Choose Renormalization and Factorization

scales (set equal) Jets: Rsep: maximum separation allowed

between two partons to form a jet (mimic exp. algorithm)Rsep=1.3R (Snowmass: Rsep=2.0R)

2R

1.3R

Compositeness Contact Predictions

Compositeness CalulationsEichten et al., Rev. Mod. Phys. 56, 579 (84) Eichten et al., Phys. Rev. Lett 50, 811 (83)Chivukula et al., Phys. Lett. B 380, 92 (96)Lee, Phys. Rev. D 55, 2591 (97)Lane, hep-ph/9605257 (96)

= +1 + destructive interference = 1 - constructive interference Only leading order calculation:

Use to scale highest order QCD calculations.

Dijets: Use NLO Jetrad prediction as basis Drell-Yan

Use Hamburg et al., NNLO calculation as a basis.

TeV TeV

TeV NLO

LO

LO

X

M

Colorons

Colorons

(R.S. Chivukula, A.G. Cohen and

E.H. Simmons, hep-ph/9603311,Phys. Lett. B380 92 (1996)

Produces similar effects to compositeness. Motivated by technicolor Add additional SU(3) QCD type

group. Symmetry breaking between this

and standard QCD SU(3) leads to an additional set of massive gluons called colorons

Can be modeled in a similar way to compositeness:

cot cs M

Search for Excited Quarks

Search for excited quarks in dijet mass spectrum motivated by UA2’s observation of W,Z JJ (Zeit. Phys. C49)In proton anti-proton collisions.

M

Search for Excited Quarks

q qg q u d* ,

PYTHIA, f=f’=fs=1.0, =Mq*, Contact terms only.Smeared with Jet Resolutions, CTEQ3L PDF.Baur et al Phys. Rev. D42, 815 (90)

s

M

ddL

f qqg

ss

2

22

3

Search for Excited Quarks

Select data at central rapidity:

DØ: |jet| < 1.0, |jet| < 1.6

104 pb-1

Use Bayes Theorem to fit Jetrad NLO QCD prediction + q* line shape to data

CDF: |jet| < 2.0, cos < 2/3

106 pb-1

Phys. Rev. D55, 5263 (1997)

Phys. Rev. Lett. 74, 3539 (1995)

Fit data with Ansatz Function + q* line shape.

Search for Excited Quarks

DØ: Mq* > 725 GeVCDF: Exclude Mq*

up to 570 GeVbetween 580 & 760 GeV

Search for Excited Quarks

Combined LimitsMq* > 760 GeV

cos1

cos1exp

1 Measure

d

dN

N

Search for Quark-Quark Compositeness

Dijet Angular DistributionCompositeness produces excess ofevents at small and large mass

Search for Quark-Quark Compositeness

Define: Optimize for compositeness:DØ: X=4 CDF: X=2.5X

XR

events #

events #

DØ: Phys. Rev. Lett. 80, 666,1998.CDF: Phys. Rev. Lett.77, 5336, 1996,

Erratum-ibid.78, 4307, 1997

Dijet Angular Limits

DØ CDF

LL=1 2.1 TeV 1.8 TeV

LL 1 2.2 TeV 1.6 TeV

Compositeness Limits

DØ Coloron Mass LimitsMc/cot > 759 GeVV8 > 2.1 TeV

Dijet Mass Spectrum at DØ

Calculate Ratio of Cross Sections.

Analgous to R

DØ Dijet Mass Spectrum

Accepted by PRL: hep-ex/9807014

pdf Limit on

Limit on -

CTEQ3M 0.25ETmax 3.53 2.87

CTEQ3M 0.50ETmax 2.93 2.56

CTEQ3M 0.75ETmax 2.88 2.52

CTEQ3M 1.00ETmax 2.73 2.49

CTEQ3M 2.00ETmax 2.84 2.48

CTEQ4M 0.50ETmax 2.92 2.55

MRSA 0.50ETmax 2.97 2.59

LL LL1 TeV 4 TeV

Quark-Quark Compositeness Limits

Model + -

LL 2.7 TeV 2.4 TeVVVAA

3.2 TeV 3.1 TeV

V8V8 2.0 TeV 2.3 TeVA8A8 2.1 TeV 2.1 TeV

Coloron Limit: Mc/cot > 837 GeV(hep-ph/9809472)

Drell-Yan Production DØ measures the Drell-Yan Cross

section at high dielectron mass. 120 pb-1 data || < 1.1, 1.5 < || < 2.5 Submitted to PRL hep-ex/9812010

CDF measures the Drell-Yan Cross section at high dielectron and dimuon mass. 110 pb-1 data || < 1.0 Phys. Rev. Lett. 79, 2198, 1997.

High Mass Drell-Yan: Compositeness

DØ DataCDF Data

ee Mass(GeV) Events Back. Events Back.

M > 150 89 8717 17 16.50.5M > 200 26 285 7 6.240.19M > 300 6 64 2 1.450.04M > 400 1 0.90.1 0 0.430.01M > 500 0 0.20.0 0 0.140.00

Quark-Electron Compositeness Limits

CDF DØModel +

qe-

qe+

q-

q+

ql-

ql+

qe-

qe

LL 2.5 3.7 2.9 4.2 3.1 4.3 3.3 4.2LR 2.8 3.3 3.1 3.7 3.3 3.9 3.4 3.6RL 2.9 3.2 3.2 3.5 3.3 3.7 3.3 3.7RR 2.6 3.6 2.9 4.0 3.0 4.2 3.3 4.0VV 3.5 5.2 4.2 6.0 5.0 6.3 4.9 6.1AA 3.8 4.8 4.2 5.4 4.5 5.6 4.7 5.5

Run II Expectations

Assume that we will collect 2 fb-1 of data at 2 TeV M >510 GeV 2 fb-1 M >390 GeV 1 fb-1

M >300 GeV 0.25 fb-1

M >200 GeV 0.05 fb-1

Limits: V8 > 3 TeV(cf 2.3)

No Optimization

Assume Run 1 Systematics (~5%) Place limits using coloron model No optimization of bins

(M > 500 GeV>550 events < 0.5, >800 events 0.5 < < 1.0)

Conclusions

No evidence for Compositeness found at the Tevatron

QCD in excellent agreement with the data Quark-Quark Compositeness

> 2 to 3 TeV depending on modelsColorons: Mc/cot > 837 GeV

Quark-Electron Compositeness > ~ 3 to 6 TeV depending on model

Very Large Data Set in Run II: A Good Opportunity to find New Physics....