Searches for Techniparticles at D

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Searches for Techniparticles at DØ

• Lorenzo Feligioni
• Boston University
• for the DØ collaboration

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Outline

• Technicolor physics and phenomenology
• detecor and RunII dataset
• Data Selection
• cross section limit
• Summary

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Technicolor physics

• Mechanism of electroweak symmetry breaking
• Standard Model and Supersymmetry
• Higgs field ? Higgs boson
• Weakly coupled, light fundamental scalar
• could be observed at Tevatron or LHC
• Technicolor
• New strong dynamics SU(NTCD) gauge theory.
• Technifermions
• fundamental
• representation
• exchange of technigluons In the spin 0, isospin 0
  
• is attractive ? formation of condensates
• The spontaneous breaking of the SU(NTCD) ?
  SU(NTCD) symmetry produces -4N2TCD- 1 goldstone
  bosons
• Three Goldstone bosons (Technipions) become the
  longitudinal components of the W and Z which
  acquire mass

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Technicolor phenomenology

• Technicolor Models requiring large number of
  technifermion doublets
• Topcolor-assisted Technicolor
• Walking Technicolor
• Low Scale Technicolor Phenomenology
• color singlet vectors (200 400 GeV)
• produced in pp collisions
• Decays
• color-singlet scalars
• lightest technihadrons pT0 pT/-
• Decays
• Our final state is a W and two b-jets
• M(?T) 105 GeV M(?T)200 GeV
• Cross sections (W?e?), MV200
• WpT/- 3.66 pb

• wT ? gpT rT ?pT pT rT ? pT pT
• ? gZ ?WpT , ZpT ?
  WpT,ZpT
• ? 3pT ?WW ? WZ
• ? f f,g g ? f f,g g

pT ? ff,gg (pT0 ? bb, pT/- ? bc dominate)
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Previous Searches

• Technicolor Parameters
• NTC number of technifermions
• QD QU -1 technifermion charge
• sin? mixing angle
• MV mass parameter (it controls technifermions
  coupling and decay mode)
• Previous searches
• CDF RunI
• W?T and ?T ???T
• MV 100
• LEP
• ??T and ?T ?T- (OPAL)
• MV lt 200
• ?T ?WW, ?T??TW (DELPHI)
• DELPHI has the mass point considered in the
  current analysis at the edge of the exclusion
  region
• M(?T) 105 GeV M(?T)200 GeV is excluded for
  some value of the parameters of the Technicolor
  model

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DØ RunII dataset

• Data collected with the D? detector at the
  Fermilab Tevatron operating at 1.96 c.o.m. energy
  from April 2002 to April 2004
• Total ? L dt 238 pb-1

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Events Selection

• One reconstructed Primary Vertex (PV)
• One isolated electron
• veto on the presence of another electrons
  suppress Z contamination
• Missing ET gt 20 GeV
• eliminates QCD
• Two calorimeter jets
• Veto on a third jet, suppresses tt background
• At least one jet has to be associated with a
  Secondary Vertex of interaction
• (b-tagging)

B Decay Products
Flight Length few mm
Decay (Secondary) Vertex
Collision
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Single b-tagged analysis
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Technicolor Optimization

• ETW (electron pT missing ET)
• HTE (electron pT ? jet pT)
• pT(jj) pT of the dijet system
• ??(jj)

• M(jj) (invariant mass of the dijet system)
• M(Wjj) (invariant mass of the W dijet system)

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Cross Section Limit

• HTE lt 200 GeV
• ??(jj) gt 2.2
• pT(jj) gt 75 GeV
• ETW gt 65 GeV

data backd sig
Cross section 95 C.L. upper limit 6.4 pb
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summary

• DØ has begun to search for Technicolor particles
  in the W2 jets channel
• New b-tagging capability respect to RunI
• No evidence were found for the ?T, ?T mass
  combination considered
• not yet considering not ruled out mass values
• Outlook
• Almost twice more luminosity for this analysis
• Add ? channel soon
• Different Analysis are also in preparation
• ?T/?T ? 2 leptons