30 August 04Lorenzo Feligioni1 Searches for Techniparticles at DØ Lorenzo Feligioni Boston University for the DØ collaboration

30 August 04Lorenzo Feligioni2 Outline Technicolor: physics and phenomenology detecor and RunII dataset Data Selection cross section limit Summary

30 August 04Lorenzo Feligioni3 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(N TCD ) 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(N TCD )  SU(N TCD ) symmetry produces -4N 2 TCD - 1 goldstone bosons –Three Goldstone bosons (Technipions) become the longitudinal components of the W and Z which acquire mass

30 August 04Lorenzo Feligioni4 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 (W  e ), M V =200: W     pb W     pb                   Z  W      W        WW  WZ  f f,g g  f f,g g    ff,gg      bb,      bc dominate)

30 August 04Lorenzo Feligioni5 Technicolor Parameters –N TC : number of technifermions –Q D = Q U -1 : technifermion charge –sin  : mixing angle –M V : mass parameter (it controls technifermions coupling and decay mode) Previous searches CDF RunI –W  T and  T  T –M V = 100 LEP –  T and  T +  T - (OPAL) M V < 200 –  T  WW,  T  T W (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

30 August 04Lorenzo Feligioni6 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

30 August 04Lorenzo Feligioni7 Events Selection One reconstructed Primary Vertex (PV) One isolated electron –veto on the presence of another electrons suppress Z contamination Missing E T > 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

30 August 04Lorenzo Feligioni8 DATA 74 tt 15.8 Single top 4.4 W+ H eavy F lavors 35.9 WZ 0.66 Z  ee 1.6 Physics Backd 58.4 QCD 6.7 W + light quarks 11.8 Tot Backd 76.9 Single b-tagged analysis

30 August 04Lorenzo Feligioni9 Technicolor Optimization E T W (electron p T + missing E T ) HTE (electron p T + ∑ jet p T ) p T (jj) = p T of the dijet system  (jj) M(jj) (invariant mass of the dijet system) M(Wjj) (invariant mass of the W + dijet system)

30 August 04Lorenzo Feligioni10 HTE < 200 GeV  (jj) > 2.2 p T (jj) > 75 GeV ETW > 65 GeV MTW + ETW + 1 btag MTW + ETW + 1 btag +  MTW + ETW + 1 btag +  + p T (jj) MTW + ETW + 1 btag +  + p T (jj) + HTE MTW + ETW + 1 btag +  + p T (jj) + THE + mass window data backd sig Cross section 95% C.L. upper limit 6.4 pb Cross Section Limit

30 August 04Lorenzo Feligioni11 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