Other Particle Searches at the Tevatron

1
Other Particle Searches at the Tevatron
Arnold Pompoš The University of Oklahoma For the
CDF DØ Collaborations
Štrbské Pleso
April 14-18
DIS 2004
Slovakia
2004
2
Outline
In this talk we report on

• Search for Large Extra Dimensions (LED)
• in Monojet MET channel
• in ee combined with ?? channel
• via dedicated search with ee
• in µµ channel
• Search for heavy gauge boson
• in ee channel
• in µµ channel
• Search for excited electrons

For search for Higgs, SUSY and LQ see S.
Beauceron, T. Kurca D. Ryans talks
3
-
Tevatron - pp collider
290 pb-1 on tape per experiment
data for physics
Feb 2002
April 2001

• High data taking efficiency
• in the range 80-90
• So far analyzed
• around 200 pb-1, which is already 2x the total
  Run I data.

Jul 2002
first data for analyses
detector commissioning
4
CDF DZero Experiments

• Extended spatial e, µ coverage
• New plug calorimeter improves also MET
  measurement
• Improved MET triggers
• Added triggers to identify leptons at early
  stage

• New silicon and fiber tracker
• Solenoid (2 Tesla)
• Upgrade of muon system
• Upgrade of Trigger/DAQ

5
New Phenomena Search Strategies
Both CDF DZero start searches with

• signature based strategy
• categorize data into bins of various event
  signatures
• compare bins to SM predictions and search for
  signs of deviations

and then the searches are tuned for best
sensitivity on

• specific models
• show us the signatures of your favorite model
• we tell you if data contains any event with such
  signature

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New Phenomena Search Challenges

• Production cross sections very small
• s(new phenomena) 1 pb
• s(pp inelastic) 5x1010 pb
• Detectors are great, but not perfect
• particle detection efficiency lt 100
• Often hard to distinguish signal from background
• jet based strategies overwhelmed by SM processes
  
• we employ lepton based signatures, but the rates
  are often suppressed

-
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Large Extra Dimensions
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Motivations for Extra Dimensions

• Newtons 1/r2 law needs to be tested on
  submillimeter scales
• Hierarchy puzzle - Why is gravity so weak?
• EWK scale is MEWK1TeV
• Gravity scale is MPL1/vGN 1016 TeV
• Hierarchy solution Extra Dimensions.
• Gravity is localized (Randal Sundrum) on a
  different brane at d?0 from the brane we live
  on
• - Gravity propagation to extra D (us) is
  exponentially damped
• Gravity is not weak! (Arkani-Ahmed,
  Dimopoulos,Dvali) It is diluted into many
  dimensions, 4n, with n of them compactified to
  radius R
• M2PL(4 D) M2nPL(4n D)Rn
• - IF MPL(4n D) MEWK 1TeV then
• if n1 then R 1013 m (excluded by Newtons 1/r2
  law)
• if n2 then R 10-3 m (WORTH OF TESTING!)

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Strong Gravity ( ADD )

• Compactified n dim. implies massive KK towers GKK
  of massless graviton G in each extra dim.
• SM lives in 31D, GKK live in 4n D ? strength of
  gravity diluted
• GKK couple to SM matter proportional 1/MPL (very
  weak coupling)
• Huge number of KK modes sum up and yield to
  measurable effects

V
g
q
g
g
q
g
Gkk
Gkk
Gkk
_
Gkk
Gkk
g
q
_
g
q
V
Possible real graviton emmission
Enable Graviton Mediated Processes
MonojetMET event signature
Dilepton and diphoton event signature
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LED with Monojet MET
After all selection cuts Observe 63, Expect 100
with 60 uncertainty
Search for Real Graviton Emission
q
g
g
g
_
Gkk
Gkk
g
q
Analysis sensitive to jet energy scale (JES)
uncertainty.
Data versus SM
heavy G escapes to extra D large MET recoil
jet very energetic
Limit on Planck Scale Md
DØ ?Ldt 85 pb-1

• Data Selection
• MET gt 150 GeV,
• Jet1 gt 150 GeV
• Jet2 lt 50 (reduce ISR, FSR)
• ?FJ-MET gt 30o (reduce chance that MET comes
  from jet mismeasurement)
• Irreducible Background
• Z-gt ?? 1 or 2 jets (60 of total bckg.)

LEP
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LED with ee ?? - Theory
Search for enhanced dilepton production
Gravity effect parametrized by hG
ee, ?? invariant mass
scatter. angle
Functions of M cosq determined by theory

• DØ Search Strategy
• Combine dielectron and diphoton to diEM signature
• Fit distribution of M vs cosq of Data SM
• Extract ?G from the fit
• Translate ?G into Ms limit

• ?G F/MS4
• F is a model dependent dimensionless parameter
  1
• GRW F 1
• HLZ F log(Ms2/M2), n 2
• F 2/(n-2), n gt 2
• Hewett F 2 ?/p, ? 1
• Ms is the UV cutoff MPL(4n dim)

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LED with ee ?? - Event Selection

• LED search focuses on very high mass Drell-Yan
  region (graviton is heavy)
• We are not searching for dilepton mass peaks
  (will do so in Z searches)
• Region of interest is way above the Z mass ? very
  energetic e ?
• Triggers
• high pT single or dielectron triggers
• diphoton triggers

Unprescaled, gt99 efficient due to high pT of EM
objects

• Event Selection
• Two fiducial, central-central or central-forward,
  isolated EM objects
• ET gt 25 GeV for both EM objects
• No track selection. Treat dielectron and diphoton
  samples together

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LED with ee ?? - Data vs Background

• Background estimation
• Drell-Yan and direct diphoton production
  estimated from MC
• Instrumental backgrounds estimated from data that
  fail electron quality cuts
• Normalize backgrounds by fitting to the low di-em
  mass spectrum, where no LED signal is expected

Data
Data vs MC
Signal prediction
QCD
SM prediction
DØ ?Ldt 200 pb-1
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LED with ee ?? - DØ Limits

• Data agrees with SM prediction
• Extract ?g parameter from fit

• Translate hG95 limits to 95 CL lower limits on
  Planck scale MS, in TeV, using different
  formalisms for F

NLO k1.3 scale applied to signal MC
GRW HLZ for n Hewett
2 3 4 5 6 7 ? 1/-1
1.36 1.56 1.61 1.36 1.23 1.14 1.08 1.22/1.10
1.43 1.67 1.70 1.43 1.29 1.20 1.14 1.28/NA
DØ RunII
DØ RunI Run II
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LED with ee - CDF Limits

• Data agrees with SM prediction
• Extract parameter from M(ee) fit
• Use cosq as a cross check

hG95 1.17 TeV-4
hG95 1.05 TeV-4
? -1
? 1

• Translate hG95 limits to 95 CL lower limits on
  Planck scale MS, in TeV, using different
  formalisms for F

GRW HLZ for n Hewett
2 3 4 5 6 7 ? 1/-1
1.11 1.11 1.17 0.99 0.89 0.83 0.79 0.99/0.96
No NLO k factor applied to signal MC
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LED with µµ - DØ

• Event selection
• pT gt 15 GeV for both muon objects
• Isolated tracks
• M(mumu) gt 50 GeV
• Cosmics removed

DØ ?Ldt 100 pb-1
Observed events 3,000 events
No deviation from SM in data
Soon see results from 200pb-1
GRW HLZ for n Hewett
2 3 4 5 6 7 ? 1
0.88 0.75 1.05 0.88 0.80 0.74 0.70 0.79
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LED with µµ - CDF

• Data agrees very well with SM predictions
• New LED results are around the corner _at_ CDF from
  µµ channel

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LED with KK modes of Z Photon

• Model
• compactified n extra dimensions
• chiral matter lives on 3D
• gauge bosons live in all dimensions -gt existence
  Z ? KK modes
• Task
• measure the effect of KK modes of Z and ? on ee
  production

is bilinearly in
? same tools as LED
?C p2/3M2PL(4n dim)
and depends on dilepton mass and scattering angle

• Note
• at high masses the dilepton production is
  enhanced
• at intermediate masses M(Z) ? MC the negative
  interference causes event deficit.

• Search strategy same as in LED
• extract ?C from fit and translate into a limit on
  Mc

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LED with KK modes of Z Photon- Limit

• Event Selection
• same as in diEM search, but
• gt1 e must have track
• no electron isolation required

Data
SM prediction
QCD
Signal prediction
Observed 14200 events
DØ ?Ldt 200 pb-1
Data vs MC
No deviation from SM in data
MCgt1.12 TeV
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Localized Gravity ( RS ) with ee

• Gravity Propagates in Compactified 5th dim. -gt
  Towers of Kaluza-Klein modes of the graviton
• Coupling of GKK to Standard Model is of the order
  of TeV (determined by parameter k/MPL)
• Graviton mediated ee production searched
• CDF searched its high pT ee µµ sample

First direct constraints on RS
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Localized Gravity ( RS ) with µµ
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Heavy Extra Gauge Boson
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Z Search Motivation

• Extra U(1) gauge boson is predicted by BSM
  theories (SO(10),E6)
• SSM Z couplings to fermions considered
  identical to the SM Z
• E6 inspired models E6 ? SU(3) x SU(2) x U(1)y x
  U(1)? x U(1)?, Z Z? sin? Z? cos?

Z? if ? 0 Z? if ? tan-1v(3/5) Z? if ?
p/2 ZI if ? tan-1(-v(3/5))
Z

• We search for leptonic Z decays. (Br 4 but
  very small bckg.)
• Same high pT ee µµ datasets searched as in LED
  analysis
• Looking for a mass peak in M(dilepton)
  distribution, located beyond the Z peak
  (different from LED searches, where we fit the
  high mass continuum).

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Z in ee channel
DØ ?Ldt 200 pb-1

• Same event selection as for the search for LED in
  ee channel (KK modes of gauge bosons) .
• Different data interpretation

Data
SM prediction
Signal prediction
QCD
Limits (in GeV)

• SM Couplings
• CDF 750
• DØ 780
• E6 ZI Z? Z? Z?
• CDF 570 610 625 650
• DØ 575 640 650 680

SM coupling
ZI Z? Z? Z?
95 CL limit
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Z in µµ channel Limits
DØ ?Ldt 100 pb-1
DØ result with 200 pb-1 is coming soon.
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Excited Electron
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Electron compositeness?
Contact Interaction

• CDF has searched for excited electrons (e),
  whose existence would indicate compositeness of
  electrons
• At Tevatron, e can be produced via contact
  interactions or gauge mediated interactions
• We select events with eeg in the final state
• Look for resonances in M(eg)
• Region of interest lies beyond the Z mass
• ET(e1)gt25 GeV, ET(e2)gt25 GeV, ET(g)gt25 GeV
• 81 GeV lt M(ee) lt 101 GeV (veto SM Z)
• SM background Zg events

M(e)/?, ? is the compositness scale
Gauge Mediated Interaction
f/?, f is the coupling to Z
In CDF ?Ldt 200 pb-1 we observed 3 events and
expected 3 events
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Excited Electron Limits
Contact Interaction Limit
Gauge Mediated Interaction Limit
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Spectacular eeee Event

• We are not only excluding, we are also measuring ?

• ZZ candidate in eeee channel
• sxBr 9x10-4

Calorimeter eta-phi lego plot
Et(e1)44 GeV
Et(e2)42 GeV
Et(p1)46 GeV
Et(p2)26 GeV
MET13 GeV
Central tracker
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Conclusion
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Conclusion

• Tevatron keeps breaking peak luminosity records
  and is steadily delivering collisions
• CDF and DØ detectors are recording high quality
  data
• We searched CDFs and DØs high energy electron,
  muon and photon samples for signs of new
  phenomena
• We set world leading limits on parameters of
  theories which consider the existence of extra
  dimensions, extra gauge boson or composite
  electron
• We are still in only a fraction of the expected
  total luminosity of 8fb-1 (2009)? MORE GREAT
  PHYSICS RESULTS are coming soon and even more in
  few years ?.