1. Strong EWSB in Top Quark Production
Praha, Nov 3, 2005
Strong EWSB in Top Quark Production
Ivan Melo
M. Gintner, I. Melo, B. Trpišová
(University of Žilina)

2. Outline ρtt → tttt + X Motivation for new vector (ρ) resonances:
Strong EW Symmetry Breaking (SEWSB)
Vector resonance model
ρ signal at LHC pp → ρtt → WWtt + X
ρtt → tttt + X
ρ signal at future e+e- colliders
e+e- → ννtt
e+e- → tt

3. EWSB: SU(2)L x U(1)Y → U(1)Q
Weakly interacting models:
- SUSY
- Little Higgs
Strongly interacting models:
- Technicolor

4. Chiral SB in QCD EWSB SU(2)L x SU(2)R → SU(2)V , vev ~ 90 MeV
SU(2)L x SU(2)R → SU(2)V , vev ~ 246 GeV

5. WL WL → WL WL WL WL → t t t t → t t
L = i gπ Mρ /v (π- ∂μ π+ - π+ ∂μ π-) ρ0μ
+ gt t γμ t ρ0μ + gt t γμ γ5 t ρ0μ

6. International Linear Collider: e+e- at 1 TeV
ee ―› ρtt ―› WW tt
ee ―› ρtt ―› tt tt
ee ―› WW
ee ―› tt
ee ―› νν WW
ee ―› νν tt
Large Hadron Collider: pp at 14 TeV
pp ―› ρtt ―› WW tt
pp ―› ρtt ―› tt tt
pp ―› WW
pp ―› tt
pp ―› jj WW
pp ―› jj tt

7. Chiral effective Lagrangian
SU(2)L x SU(2)R global, SU(2)L x U(1)Y local
L = Lkin + Lnon.lin. σ model - a v2 /4 Tr[(ωμ + i gv ρμ . τ/2 )2]
+ Lmass LSM(W,Z)
+ b1 ψL i γμ (u+∂μ – u+ ρμ + u+ i g’/6 Yμ) u ψL
+ b2 ψR Pb i γμ (u ∂μ – u ρμ + u i g’/6 Yμ) u+ Pb ψR
+ λ1 ψL i γμ u+ Aμ γ5 u ψL
+ λ2 ψR Pλ i γμ u Aμ γ5 u+ Pλ ψR
BESS
Our model
Standard Model with Higgs replaced with ρ
gπ = Mρ /(2 v gv)
gt = gv b2 /4 + …
Mρ ≈ √a v gv /2 t

8. Unitarity constraints
Low energy constraints
gv ≥ → gπ ≤ 0.2 Mρ (TeV)
|b2 – λ2| ≤ → gt ≈ gv b2 / 4
|b1 – λ1| ≤ → b1 = 0
Unitarity constraints
WL WL → WL WL , WL WL → t t, t t → t t
gπ ≤ (Mρ= 700 GeV)
gt ≤ (Mρ= 700 GeV)

9. Partial (Γ―›WW) and total width Γtot of ρ

10. Search at LHC: pp → W W t t + X
J. Leveque et al. ATL-PHYS : pp -> Htt -> WWtt
MH =[ ] GeV ρ
BRA: pp → ρtt →WWtt
σ(WWtt) = σ(ρtt) x BR(ρ->WW)
2) Full calculation: pp → WWtt

11. pp → W W t t + X (full calculation)
39 diagrams in gg channel
No resonance
background ρ ρ ρ

12. CompHEP results: pp → W W t t + X
ρ: Mρ=700 GeV,
Γρ=4 GeV,
b2=0.08, gv=10
SM: MH = 700 GeV
ΓH = 184 GeV
MWW(GeV)
MWW(GeV)
σ(gg) = fb ―› fb
σ(gg) = fb ―› fb
No resonance background: σ(gg) = fb
Cuts: Γρ < mWW < Γρ (GeV)
pT > 100 GeV, |y| < 2

13. Total cross sections for ρtt and WWtt
BRA: σ(WWtt) = σ(ρtt) x BR(ρ->WW)

14. |N(ρ) – N(no res.)|
√(N(no res.))
R =
≈ S/√B > 5
BRA
Full calc.

15. Search at LHC: tttt vs WWtt
BRA
BRA

16. Search at Hadron Colliders: p+p(p) ―› t + t
Tevatron: p + p ―› t + t
σS = 1.2 fb σB = fb
LHC: p + p ―› t + t
σS = fb σB = fb
Mρ=700 GeV
Γρ=12.5 GeV
No cuts

18. Subset of fusion diagrams + approximations (Pythia)
Full calculation of 66 diagrams at tree level
(CompHEP)

19. Pythia vs CompHEP Before cuts √s (GeV) 800 1000 1500
ρ (M = 700 GeV, Γ = 12.5 GeV, g’’ = 20, b2 = 0.08)
Before cuts
√s (GeV)
Pythia (fb)
CompHEP (fb)

21. Backgrounds (Pythia) e+e- → e+e- tt e+e- → tt γ
σ(0.8 TeV) = fb → 0.13 fb (0.20 fb)
σ(1.0 TeV) = fb → fb (0.16 fb)

24. e- e+ → t t ρ different from Higgs ! x+y=560 nm z=0.40 mm n=2x1010
ρ (M= 700 GeV, b2=0.08, g’’=20)

25. Conclusions New strong ρ-resonance model
pp → W W t t + X pp → t t t t + X at LHC
R values up to a few 100 (before t,W decays and detector effects), L = 100 fb-1
Backgrounds pp → tt, W + jets, Z + jets, … ?
e+e- → ννtt R ≤ 26 at CM energy = 1 TeV, L = 200 fb-1
e+e- → tt Lscan = 1 fb-1
Similar work on pp → t t t t + X : T.Han et al, hep-ph/

26. WWtt reconstruction WWtt →lν jj jjb jjb b tagging …… 50 %
l detection … %
one trigger lepton pT > 30 (20) GeV e (μ)
jets pT > 30 GeV
kinematical cuts for 6 jets …….. ≈ 20 %
BR: W → e(μ)ν … % … Pl
W → hadrons …68 % …. Ph
ε = εcutsεb2εl 4 Pl Ph = 1.2 %

27. Search at Hadron Colliders
Mρ=700 GeV, Γρ=12.5 GeV
Tevatron: p + p ―› t + t
σS = 1.2 fb σB = fb
LHC: p + p ―› t + t
σS = fb σB = fb

29. pp → ρ t t + X (8 diagrams in gg channel)
BRA: σ(WWtt) = σ(ρtt) x BR(ρ->WW)