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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
Electron IdentificationElectron Identification
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
Electron IdentificationElectron Identification
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
Electron IdentificationElectron Identification
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 Identification
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 Identification
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
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
BB
Forward Electron Tracking Algorithm
1. Form 2 seed tracks,
one of each sign, from calorimeter
& beam spot
Forward Electron Tracking Algorithm
1. Form 2 seed tracks,
one of each sign, from calorimeter
& beam spot
2. Project into silicon and attach hits
using standard silicon
pattern recognition
Forward Electron Tracking Algorithm
1. Form 2 seed tracks,
one of each sign, from calorimeter
& 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?
What else could lead to high pT Z bosons? What else could lead to high pT Z bosons?
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
• 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 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
• 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 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. (I.e., XYZ)
Search 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. (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
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
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.
We can enhance the sensitivity to theproduction asymmetry
We can enhance the sensitivity to theproduction asymmetry
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?