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Searches for Techniparticles at DØ

Lorenzo FeligioniBoston 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

D

U

LL

DU RR ,

0 DDUU RLRL

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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 • Decays

• Our final state is a W and two b-jets– M(T) = 105 GeV M(T)=200 GeV– Cross sections (We), MV=200:

• Wpb

• Wpb

Z WWWWWZf f,g g f f,g gff,ggbb, bc dominate)

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• 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

– WT and T T

– MV = 100

LEP T and T

+ T

- (OPAL)

• MV < 200 T WW, TTW (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

Previous Searches

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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

Technicolor search

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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 > 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

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

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DATA 74

tt 15.8

Single top 4.4

W+ Heavy Flavors

35.9

WZ 0.66

Zee 1.6

Physics Backd

58.4

QCD 6.7

W + light quarks 11.8

Tot Backd 76.9

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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•HTE < 200 GeV

(jj) > 2.2

•pT(jj) > 75 GeV

•ETW > 65 GeV

MTW + ETW + 1 btag3 74 73.4 9.1

MTW + ETW + 1 btag + 28 28.3 7.5

MTW + ETW + 1 btag + + pT(jj)

22 24.7 7.4

MTW + ETW + 1 btag + + pT(jj) + HTE

17 18.3 7.2

MTW + ETW + 1 btag + + pT(jj) + THE + mass window

4 6.6 6.2

data backd sig

Cross section 95% C.L. upper limit 6.4 pb

Cross Section Limit

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summary

• DØ has begun to search for Technicolor particles in the W+2 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