The Physicsof

Generations

Don Lincolnf

Four Fermion General ‘Theory’

Theory consists of all terms of any chiral combinations

)}(

))(())((

))((

))(())((

)2

)(2

())(({ 12

2

HCLedq

eeddeeuu

eeqq

LLddLLuu

LLqqLLqqg

LRRLSC

RRRRdRRRRRR

uRR

RRLLeLR

LLRRdRLLLRR

uRL

La

LLa

LLLLLLLoLL

oDY

L

L

LL

L

LL l

Ld

uq

l

lq

q

Drell-Yan Only

Tevatron R

un I L

imits

Model Λ+ Λ- Λ+ Λ- Λ+ Λ- Λ+ Λ-

LL 3.3 4.2 2.5 3.7 2.9 4.2 3.1 4.2LR 3.4 3.6 2.8 3.3 3.1 6.7 3.3 3.7RL 3.3 3.7 2.9 3.2 3.2 3.5 3.3 3.9RR 3.3 4.0 2.6 3.6 2.9 4.0 3.0 4.3LL+RR 4.2 5.1LR+RL 3.9 4.4LL-LR 3.9 4.5RL-RR 4.0 4.3VV 4.9 6.1 3.5 5.2 4.2 6.0 5.0 6.3AA 4.7 5.5 3.8 4.8 4.2 5.4 4.5 5.6

e+e-

DØ CDF

e+e- +- combineD

rell

-Yan

QC

D

Model Λ+ Λ- Λ+ Λ- Λ+ Λ- Λ+ Λ-

Limit 2.7 2.4 2.1 2.2 1.6 1.4

DØ CDFds/dM ds/d(cos q*)ds/dM ds/d(cos q*)

Units:TeV

Topics Currently Covered

• All pp two particles– pp (p resolution limited)

– pp eevisa problems)

– pp e(MET questions)

– pp bb (two tagging approaches)

– pp jet-jet (most robust)

– ds/dM & ds/d(cos q*)

Run II Projected: Dijet Mass Spectrum

Dramatic increase in high pT cross sectionsLarge gains in statistics

Run II: Drell-Yan

ConstructiveInterference

DestructiveInterference

mass bin Run I Run II Run II

(GeV) 100 pb-1 2 fb-1 30 fb-1

120-160 136 2329 34414160-200 38 610 8970200-240 7 234 3584240-290 2 119 1939290-340 4 65 884340-400 0 35 468400-500 0 24 273500-600 0 6.5 98

600-1000 0 1.4 431000-1500 0 0 2.2

NkDY

Channel -lim

+lim

-lim

+lim

LL 10.1 8.0 18.9 17.8RR 9.3 6.0 17.0 15.1RL 7.8 5.7 13.5 9.1LR 7.3 6.0 12.1 9.2

L = 2 fb-1 L = 30 fb-1

Projected Limits (Bayesian)

PRL 82 4769 (1999)

2VTX Tagging High P b Jets

Don Lincoln

f

Isn’t that two there?

Bee) (Two ! || Bee) Two(

Kapow!

Motivation

Fit to CDFqQCD calculation

CDF: PRL 82 (1999) 2038

• High mass bb pairs can be sign of new physics (compositeness ?)

• Problem– ~100:1 QCD:bb

• Solutions tagging

– 2nd VTX tagging

– Impact parameter

Current Work

DCA

DecayLength

Key

Calorimeter Jet

b hadron

Secondary vertex

Primary vertex

Particles of Interest

Question: Is failure to reconstructsecondary vertex due to tracking efficiency or vertex algorithm?

•Many variables have been tried for 2 VTX tag•Decay length & significance (2D & 3D)•Vertex MassR•etc.

•Only decay length and related quantities works.

•Consider other tags eventually.

R

ImpactParameter

What if ?We know that one can findsecondary vertices by accidentin light quark initiated events

Estimate Eff(right) ~ Eff(found) - Eff(light)

No light statistics at high ptReality could be worse

Eyeball trends and guess.

Eff(found) = Eff(luck) + Eff(right)

Efficiency only that of finding a ‘good’ secondary vertex

Decay Length (found and 2VTX)

Found = found track2VTX = used in secondary vertex

Ptmin(track) = 500 MeV

Efficiency = 2VTX/found

Efficiency ~ Pt and flavor-initiator independent

R (real and found) Found = correct + fake

Ptmin(track) = 500 MeV

Efficiency = found/real

Light quark jets has better tracking efficiency in core.

Pt Eff (b) Eff (light)100-150 ~52% ~58%250-300 ~34% ~42%

Tracking ‘Efficiency’ vs Pt.

Summary• Several different high mass di-object searches

underway

• In bb– Need to understand tracking efficiency in core of jets– Need to look more at muon tagging (but low mass

reach)– Need to better understand b quark content from parton

showers.

• Active effort

• Need more people thinking about it.