Phenomenology of New Vector Resonances from SEWSB at Future e+e- Colliders
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Transcript of Phenomenology of New Vector Resonances from SEWSB at Future e+e- Colliders
Phenomenology of New Vector Resonances from SEWSB at
Future e+e- Colliders
Ivan Melo
M. Gintner, I. Melo, B. Trpisova (University of Zilina)
IEP SAS, Kosice, May 13, 2005
• Motivation for new vector (ρ) resonances: Strong EW Symmetry Breaking (SEWSB)
• Vector resonance model
• ρ signals in e+ e- → ννtt, e+ e- → tt• ρ signal in pp → ρtt → WWtt
Outline
Higgs bosonHiggs boson
EWSB: SU(2)L x U(1)Y → U(1)Q
Weakly interacting models: - SUSY - Little Higgs
Strongly interacting models: - Technicolor
Chiral SB in QCD SU(2)L x SU(2)R → SU(2)V , vev ~ 90 MeV
EWSBSU(2)L x SU(2)R → SU(2)V , vev ~ 246 GeV
LEP: e+e-, Ecm = 209 GeVTevatron: pp, Ecm = 2 000 GeV, L = 1 fb-1
LHC: pp, Ecm = 14 000 GeV, L = 100 fb-1
ILC: e+e-, Ecm = 1 000 GeV, L = 200 fb-1
CLIC: e+e-, Ecm = 3-5 000 GeV, L = 200 fb-1
WL WL → WL WL WL WL → t t t t → t t
L = i gπ Mρ /v (π- ∂μ π+ - π+ ∂μ π-) ρ0μ
+ gV t γμ t ρ0μ + gA t γμ γ5 t ρ0
μ
International Linear Collider: e+e- at 1 TeV
ee ―› νν WW ee ―› νν tt ee ―› ρtt ―› WW ttee ―› ρtt ―› tt tt
ee ―› WWee ―› tt
Large Hadron Collider: pp at 14 TeV
pp ―› jj WW pp ―› jj tt pp ―› ρtt ―› WW ttpp ―› ρtt ―› tt tt
pp ―› WWpp ―› tt
Chiral effective LagrangianSU(2)L x SU(2)R global, SU(2)L x U(1)Y localL = Lkin - v2 Tr [ Aμ Aμ] - a v2 /4 Tr[(ωμ + i g'' ρμ . τ/2 )2] - ψL u+ u+ M ψR – h.c. + ψL i γμ (∂μ + Wμ + i g’/6 Yμ) ψL
+ ψR i γμ (∂μ + Yμ + i g’/6 Yμ) ψR
+ 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
+ κ2 ψR Pκ i γμ u (ωμ + ρμ) u+ Pκ ψR
Minimal model Standard Model with Higgs replaced with ρ
BESS
Our model
A simple Lagrangian
L = i gπ Mρ /v (π- ∂μ π+ - π+ ∂μ π- )ρ0μ
+ gV t γμ t ρ0μ + gA t γμ γ5 t ρ0
μ
Chiral effective Lagrangian
L = - v2 Tr [ Aμ Aμ] - a v2 /4 Tr[(ωμ + i g'' ρμ . τ/2 )2] + b1 Ib
L + b2 IbR + ...
gπ = Mρ /(2 v g'') gV ≈ g'' b2 /4 = gA (b1 = 0) Mρ ≈ √a v g''/2
Unitarity constraints
WL WL → WL WL , WL WL → t t, t t → t t
Low energy constraints
gπ ≤ 1.75 (Mρ= 700 GeV)gV ≤ 1.7 (Mρ= 700 GeV)
g’’ ≥ 10 → gπ ≤ 0.2 Mρ (TeV)|b2 – λ2| ≤ 0.04 → gV ≈ g’’ b2 / 4
Subset of fusion diagrams + approximations (Pythia)
Full calculation of 66 diagrams at tree level (CompHEP)
Pythia vs CompHEP
ρ (M = 700 GeV, Γ = 12.5 GeV, g’’ = 20, b2 = 0.08)
Before cuts
√s (GeV) 800 1000 1500 Pythia (fb) 0.35 0.95 3.27 CompHEP (fb) 0.66 1.16 3.33
Backgrounds (Pythia)
e+e- → tt γ e+e- → e+e- tt
σ(0.8 TeV) = 300.3 + 1.3 fb → 0.13 fb (0.20 fb) σ(1.0 TeV) = 204.9 + 2.4 fb → 0.035 fb (0.16 fb)
≈ S/√B
e- e+ → t t
different from Higgs !
ρ (M= 700 GeV, b2=0.08, g’’=20)
ρ
Search at Hadron Colliders
Tevatron: p + p ―› t + t σS = 1.2 fb σB = 8 306 fb
LHC: p + p ―› t + t σS = 22.7 fb σB = 752 000 fb
Search at LHC: pp → W W t t
Cuts: 650 < mWW < 750 GeV pT > 100 GeV |y| < 2
g g ―› WW tt 39 diagramsu u ―› WW tt 131 diagramsd d ―› WW tt 131 diagrams
Signal: σ(gg) = 10.2 fb ―› 1.0 fb
Background: σ(gg) = 10.6 fb ―› 0.6 fb σ(uu) = 2.4 fb ―› 0.1 fb
R > 5
Conclusions
• New strong ρ-resonance model
• ρ in e+e- → ννtt R values up to 8
• e+e- → tt – sensitive probe of mt physics,
Lscan = 1 fb-1 (preliminary)
• pp → W W t t R > 5 (preliminary !)