Searches for Extra Dimensions and Heavy dilepton Resonances at D0

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Searches for Extra Dimensions and Heavy
di-lepton Resonances at D0
Elizabeth Gallas Fermi National Accelerator
Laboratory Computing Division
12th International Conferenceon
Supersymmetryand Unification of Fundamental
InteractionsJune 17-23, 2004Epochal Tsukuba,
Tsukuba, Japan.
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Outline

• 3-Space / Time
• Fermilab Tevatron with Experiment DØ / mid Run 2
• What can Extra Dimensions (ED) do for you ?
• Phenomenology (of interest for pp colliders)
• 2 particular ED models
• Large Extra Dimensions
• ADD (Arkani-Hamed, Dimopoulos, Dvali)
• TeV-1 longitudinal Extra Dimensions
• DDG (Dienes, Dudas, Gherghetta)
• DØ A window into Extra Dimensions (ED)
• DØ Lepton/Photon Final state searches for
• Large Extra Dimensions (ED)
• TeV-1 longitudinal Extra Dimensions
• Z boson
• Summary and Conclusions

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TEVATRON Run 2 Upgrade

• New Main Injector 150 GeV
• Store protons, shoot to target for anti-proton
  production
• New recycler
• Magnet storage ring for anti-proton
• Higher energy
• 1.96 TeV vs 1.8 TeV
• Higher cross sections
• (30 for the SUSY)
• Higher antiproton intensity
• 6x6 ? 36x36 bunches
• (3.5 µs ? 396 ns)
• Higher luminosity
• Run 1 2x1031 cm-2s-1
• Run 2 2x1032 cm-2s-1

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DØ Run 2a Upgrade

• Solenoid (2T)
• 4-layer Silicon Vertex and 16-layer Fiber
  Trackers
• Muon forward chamber (hlt2 ), shielding
• New preshower, upgrade Calorimeter electronics
• Upgrade to Trigger and DAQ system

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What can Extra Dimensions do for you ?

• proposals dating at least back to 1920s
• Recent renaissance in the theory proposes
• unite all known forces (including gravity)
• known particles, electroweak and strong
  interactions
• confined to a brane - a hypersurface in the
  bulk of 4n Dim
• gravity appears weak diluted in extra
  dimensions.

• There is no desert
• Offers alternative to the hierarchy problem
• only one important scale in nature -- may be
  accessible
  at Tevatron and LHC energies
• Lends practical aspects to string theory
• its not just a beautiful idea we can test it !

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Large Extra Dimensions (LED)in the ADD Model

• ADD (Arkani-Hamed, Dimopoulos, Dvali) model
  assumes
• n Extra Dimensions of size R
• SM particles and interactions are confined to
  4D-world (brane)
• Gravity propagates in 4n Dimensional space
• Gravity appears weak diluted in extra
  dimensions
• In this formulation
• where MPl (apparent 4D Planck Scale)
• Ms (fundamental Planck Scale) is brought
  to the TeV
  range
• Constraints (cosmology, tabletop expts)
• Extra dimensions compactified (RC lt 1 mm)
• require ngt1 (g forces at large distances)
• Collider experiments only probe for ED for n?3 !

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LED Tevatron Search Modes

• Direct Searches (graviton escapes the brane)
• look for JET recoiling against missing ET (next
  talk)
• Indirect Searches (this talk)
• virtual graviton - contributions to ll-, ??
  production

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Virtual Graviton Exchange

• The predicted cross section is described by
• where hg F/MS4 (in TeV-4)
• describes strength of gravity in the presence of
  LED
• and F is a dimensionless parameter 1 which
  depends on the formalism (for the effective
  Lagrangian)
• GRW F 1
• HLZ F log(Ms2/M2), n 2
• F 2/(n-2), n gt 2
• Hewett F 2l/p, l1
• Experimentally, the process is defined by the
• invariant mass of the di-boson or di-leptons (M)
• cosine of the scattering angle, ? (cos ?).

• SM term
• interference term
• direct gravity term

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Search for ED in ee/?? channel

• Dataset 200 pb-1
• Use di-EM objects
• both ee and ??
• Selections
• Two EM with Et gt 25 GeV with tight quality cuts
• Fiducial requirements
• central EM objects
• eta lt 1.1
• central/forward objects
• 1.5 lt eta lt 2.4

Bkg
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Highest mass Drell-Yan event

• Invariant mass 475 GeV/c2, cos ? 0.01

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di-EM Mass,Cos ? distributions
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Uncertainties in ?G for di-EM sample

• Uncertainties

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LED ??

• Luminosity 100 pb-1
• Select events with
• ?2 muons
• PTgt 15 GeV
• M?? gt 50 GeV

MS gt 880 GeV (95 CL) Run 2 Preliminary
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Summary Limits on LED MS for various formalisms
F

• No evidence for signatures in excess of high-mass
  dielectron, diphoton or dimuon events over SM
  expectation, from coupling to Kaluza-Klein
  gravitons
• Fit (di-EM Mass,Cos ?) distribution
• Single parameter for ED effects ?G F/M4S
• Translate ?G limits to 95 CL lower limits on
  Planck scale MS , in TeV, using different
  formalisms for F
• DiEM limits - combine Run I Run 2 best
  limits on LED to date
• Di? limits for Run 2 with more statistics -- in
  preparation

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Dedicated ee Search for longitudinal Extra
Dimensions

• Another ED model (TeV-1 longitudinal EDs)
• proposed by Dienes, Dudas, and Gherghetta (DDG)
• Fermions confined to 4D
• but SM gauge bosons propagate in TeV-1 ED of
  size
• R 1/MC
• Predicts Kaluza-Klein states of gauge bosons
  (?KK, WKK, ZKK, gKK)
• produced directly (with sufficient energy)
• produced indirectly (virtual exchange of KK
  modes)
• Lepton pair production cross section depends on
• ?C ?2 / 3 MC2, where MC compactification
  scale of TeV-1 ED
• This analysis
• look for virtual exchanges of KK excitations of
  the Z and ??

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Dedicated ee Search for TeV-1 Dimensions (DDG)

• Predicts strong negative interference effects
• unlike LED discussed before
• Use di-EM dataset (200 pb-1)
• adding track match
• fiducial requirements same as for LED
  analysis
• Find upper limit on
• ?C lt 2.63 TeV
• and thereby (lower limit)
• Mc gt 1.12 TeV (95 CL)
• First search of this type

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Z? Limits from ee SM, E6

• Various models propose new neutral gauge bosons
• SM couplings
• variety of E6 GUT inspired
• Dataset 200 pb-1 same as in ED analysis
• Limits on Z mass in GeV/c2
• SM couplings
• Run I Run II
• 670 780
• E6 couplings
• ZI Z? Z? Z?
• 575 640 650 680

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Z ??
This is a previous result under revision with
increased statistics We used the same dimuon
sample as used for LED ?? search to look for
heavy Z-like resonances
No evidence Set limits M(Z) gt 610 GeV Run 2
Preliminary
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Summary

• No signal for new physics observed so far
• but some interesting events !
• New Limits from DØ Extra Dimensions and Z
• 
  limits under revision with increased statistics
• improved limits on additional gauge bosons !
• most sensitive collider search for EDs to date!
• higher efficiency in widest acceptance
• di-EM channels using 200 pb-1 integrated
  luminosity (now 300 pb-1 on tape)
• first collider search for TeV-1 longitudinal
  Extra Dimensions