some recent results from cdf david stuart u.c. santa barbara october 24, 2005

Some recent results from CDFSome recent results from CDF

David Stuart

U.C. Santa Barbara

October 24, 2005

TevatronTevatron

1 mile

pppp+ppEff ~ 107/1012

Repeat at 1Hz

36 “bunches” each1011 protons/bunch1010 antiprotons/bunch40m beam spot

.

Integrated LuminosityIntegrated Luminosity

CDF is pursuing a broad physics programCDF is pursuing a broad physics program

• QCDQCD

• TopTop

• BB

• EWKEWK

• New physicsNew physics

• QCDQCD

• TopTop

• BB

• EWKEWK

• New physicsNew physics

My interest is (mostly) in searches for new physicsMy interest is (mostly) in searches for new physics

Searching for new phenomenaSearching for new phenomena

Why?• SM is incomplete

What?• Higgs• Supersymmetry• Extra generations• Extra forces• Extra dimensions

How?• SM++

Why?• SM is incomplete

What?• Higgs• Supersymmetry• Extra generations• Extra forces• Extra dimensions

How?• SM++

Searching for a Z’

Electron IdentificationElectron Identification

Atypical Zee eventAtypical Zee event A typical di-jet eventA typical di-jet event


Tra

cking

Dete

ctor

Ele

ctrom

agnetic

calo

rimete

r

Hadro

nic

Calo

rimete

r

electron

photon

+

0 2 photons

Require little energy in hadron calorimeterRequire little energy in hadron calorimeter


Tra

cking

Dete

ctor

Ele

ctrom

agnetic

calo

rimete

r

Hadro

nic

Calo

rimete

r

electron

photon

+

0 2 photons

Require little energy around the EM clusterRequire little energy around the EM cluster


Tra

cking

Dete

ctor

Ele

ctrom

agnetic

calo

rimete

r

Hadro

nic

Calo

rimete

r

electron

photon

+

0 2 photons

Require a matching trackRequire a matching track

Electron IdentificationElectron Identificationusing a likelihoodusing a likelihood

In fact, the electron id differs between“central” and “forward” electrons.In fact, the electron id differs between“central” and “forward” electrons.

Reduced trackingin the forward regioncalls for new techniques.

Reduced trackingin the forward regioncalls for new techniques.

Particle Tracking Coverage

e+

e-

antiproton proton

e+

e-

e-

e+

Intermediate Silicon LayersIntermediate Silicon Layers

Forward Electron Tracking Algorithm

1. Form 2 seed tracks,

one of each sign, from calorimeter

& beam spot




& beam spot

2. Project into silicon and attach hits

using standard silicon

pattern recognition




& beam spot

2. Project into silicon and attach hits

using standard silicon

pattern recognition

3. Select best 2 match

Plug Alignment

COTPlug

Align plug to COT using the subset of COTtracks which match plug electrons just above||=1. Then align silicon to the COT.

Plug Calorimeter AlignmentPlug Calorimeter Alignment

GlobalGlobal

InternalInternal

Obtain ≈1mm resolutionObtain ≈1mm resolution

Results from central electronsResults from central electrons

Results from central muonsResults from central muons

LimitsLimits

hep-ex/0507104hep-ex/0507104

More recent resultsMore recent results

M [GeV/c2]e+e-

Forw

ard

-Back

ward

Asy

mm

etr

y

Angular Distribution: sensitive to interference

+

2

1+cos2 cos

pp

e+

e-

Forward Backward

+ +

2

Limits of about 845 GeV/c2 for Z’ with SM couplingsLimits of about 845 GeV/c2 for Z’ with SM couplings

Next, we could • look for other modes

• Z’ • Z’ t t

• exclude other models

Next, we could • look for other modes

• Z’ • Z’ t t

• exclude other models

Strong GravityStrong Gravity

Geometrical factor generates TeV massesmm0ekR

where k is a scale of order the Planck scale.kR≈12 generates the observed hierarchy.Similarly, the graviton mass becomes

PlekR≈ 1 TeV

Geometrical factor generates TeV massesmm0ekR

where k is a scale of order the Planck scale.kR≈12 generates the observed hierarchy.Similarly, the graviton mass becomes

PlekR≈ 1 TeV

Strong GravityStrong Gravity

Coupling k/MPlCoupling k/MPl

Also tt, WW, HH, ZZ Also tt, WW, HH, ZZ

High Mass Diphoton SearchHigh Mass Diphoton Search

Background is

2/3 dijets,

1/3 .

Background is

2/3 dijets,

1/3 .

Other di-boson modes in progressOther di-boson modes in progress

Several modes (eeee, ee, eejj) withpotentially very low backgrounds;Z mass constraint rejects background,and SM Z bosons are low pT.

Several modes (eeee, ee, eejj) withpotentially very low backgrounds;Z mass constraint rejects background,and SM Z bosons are low pT.

What else could lead to high pT Z bosons? What else could lead to high pT Z bosons?

Z bosons from GMSBZ bosons from GMSB

Weak coupling could lead to long life.Weak coupling could lead to long life.

Z bosons from a 4th generation quarkZ bosons from a 4th generation quark

Weak coupling, Vtb’<<1, could lead to long life.Weak coupling, Vtb’<<1, could lead to long life.

Search for displaced Z’sSearch for displaced Z’sSearch strategy

• Select dimuons from a Z

• Require a good vertex measurement (verify efficiency with J/’s)

• Opening angle cut

• Require pT>30 for Z

Aim for simple selection to limitmodel dependence. (aka, XYZ)

Search strategy





Aim for simple selection to limitmodel dependence. (aka, XYZ)

Search for displaced Z’sSearch for displaced Z’sSearch strategy





Aim for simple selection to limitmodel dependence. (I.e., XYZ)

Search strategy





Aim for simple selection to limitmodel dependence. (I.e., XYZ)

Search for displaced Z’sSearch for displaced Z’s

Expect 1.10.8, observe 3A posteriori inspection consistent with background hypothesis.

Expect 1.10.8, observe 3A posteriori inspection consistent with background hypothesis.

And now for something completely different…And now for something completely different…

While the prospect of a discovery that can lead us to the theory beyond the SM is exciting, the most probable answer in each such measurement is

Data - Background = 0.

It is appealing to better measure the SM propertiesalong the way....

So, let me tell you about a measurement where wedon’t already know the answer.

While the prospect of a discovery that can lead us to the theory beyond the SM is exciting, the most probable answer in each such measurement is

Data - Background = 0.

It is appealing to better measure the SM propertiesalong the way....

So, let me tell you about a measurement where wedon’t already know the answer.

We can calculate thisWe can calculate this

But what we measure is thisBut what we measure is this

pp

pp

Parton distribution functionsParton distribution functions

u

d

uu

u

d

p

qq

p

u ≈ 2d, plus much going on in the seathat is incalculable. But, we can measure it.u ≈ 2d, plus much going on in the seathat is incalculable. But, we can measure it.

u/d ratio causes an asymmetry in W productionu/d ratio causes an asymmetry in W production

Asymmetry in W production complicated by unknown pz

Use lepton asymmetry

Which convolves production asymmetry with V-A decay.

Production asymmetry largest in forward direction, but so is decay asymmetry

Production asymmetry largest in forward direction, but so is decay asymmetry

We use our forward tracking algorithm to probe the ||>1 region.We use our forward tracking algorithm to probe the ||>1 region.

• Electron with ET > 25 GeV

• Missing ET > 25 GeV

• 50 < MT < 100 GeV/c2

• No other EMO with ET > 25 GeV to suppress DY and QCD

• Calorimeter seeded silicon track:

We are less worried about acceptance/purity here

and more worried about charge identification:• # hits >= 4• 2 < 8• 2 > 0.5•

W Event Selection

Observed asymmetry(before any corrections)Observed asymmetry

(before any corrections)

Charge mis-identificationCharge mis-identification

Measured withsame vs oppositesign electrons from Zee

Large uncertainty in the forward direction, due to poisson fluctuations,Is the dominant systematic uncertainty

Measured withsame vs oppositesign electrons from Zee

Large uncertainty in the forward direction, due to poisson fluctuations,Is the dominant systematic uncertainty

BackgroundsBackgrounds

Correct for

• Z ee (lost leg)

• W e

• QCD fakes

Correct for

• Z ee (lost leg)

• W e

• QCD fakes

Fully corrected asymmetryFully corrected asymmetry

A(-) = -A(), with 2 = 9.5/11 dofA(-) = -A(), with 2 = 9.5/11 dof

We can enhance the sensitivity to theproduction asymmetry


Ideally, we’dreconstruct theW’s direction toavoid the decaysmearing…

Since we can’t, weinstead use the electron’s kinematics:

For e=1.8, e.g.,look at yW

and x of u quark.

Different ET

electrons probedifferent x regions.

Ideally, we’dreconstruct theW’s direction toavoid the decaysmearing…

Since we can’t, weinstead use the electron’s kinematics:

For e=1.8, e.g.,look at yW

and x of u quark.

Different ET

electrons probedifferent x regions.

Compare to existing pdf fitsCompare to existing pdf fits

CTEQ6.1mCTEQ6.1m

MRST02MRST02

PRD 71, 051104PRD 71, 051104

The End…The End…

…but more to come.…but more to come.

Auxiliary slidesAuxiliary slides

What else could lead to high pT Z bosons? What else could lead to high pT Z bosons?

some recent results from cdf david stuart u.c. santa barbara october 24, 2005

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