Praha, Mar 30, 2006
Strong EWSB in Top Quark
Production at ILC
Ivan Melo
M. Gintner, I. Melo, B. Trpišová
(University of Žilina)
Outline
• Motivation for new vector (ρ) resonances:
Strong EW Symmetry Breaking (SEWSB)
• Vector resonance model
• ρ signal at future e+e- colliders
e+e- → νν tt
e+e- → t t
• Beamstrahlung
EWSB:
SU(2)L x U(1)Y → U(1)Q
Weakly interacting models:
- SUSY
- Little Higgs
Strongly interacting models:
- Technicolor
Summary of the DCR Physics Group
Strongly interacting Higgs sector: a priority !!!!
- Summarize/update the scenario with resonances
- See for new studies with the chiral approach
Chiral SB in QCD
SU(2)L x SU(2)R
→ SU(2)V ,
vev ~ 90 MeV
EWSB
SU(2)L x SU(2)R
→ SU(2)V ,
vev ~ 246 GeV
WL WL → WL WL
WL WL → t t
t
π = WL
L = i gπ Mρ /v (π- ∂μ π+ - π+ ∂μ π-) ρ0μ
+ gt t γμ t ρ0μ + gt t γμ γ5 t ρ0μ
tt→tt
t
t
International Linear Collider: e+e- at 1 TeV
ee ―› νν WW
ee ―› νν tt
ee ―› ρtt ―› WW tt
ee ―› ρtt ―› tt tt
ee ―› WW
ee ―› tt
Large Hadron Collider: pp at 14 TeV
pp ―› jj WW
pp ―› jj tt
pp ―› ρtt ―› WW tt
pp ―› ρtt ―› tt tt
pp ―› WW
pp ―› tt
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)
BESS
μ
+
+
+
+ b1 ψL i γ (u ∂μ – u i gv ρμ . τ/2 + u i g’/6 Yμ) u ψL
+ b2 ψR Pb i γμ (u ∂μ – u i gv ρμ . τ/2 + u i g’/6 Yμ) u+ Pb ψR
+ λ1 ψ L i γ μ u + A μ γ 5 u ψ L
Our model
+ λ2 ψR Pλ i γμ u Aμ γ5 u+ Pλ ψR
Standard Model with Higgs replaced with ρ
ωμ = [u+(∂μ + i g’/2 Yμτ3)u + u(∂μ+ i g Wμ . τ/2)u+]/2
gπ- u(∂=+ i M
v +g]/2v)
ρ /(2
Aμ = [u+(∂μ + i g’/2 Yμτ3)u
g
W
.
τ/2)u
μ
μ
t
g
= gv b2 /4 + …
u = exp(i π . τ /2v)
ψL = (tL,bL)
t
Pb = diag(p1,p2)
Mρ ≈ √a v gv /2
Low energy constraints
gv ≥ 10
→ gπ ≤ 0.2 Mρ (TeV)
|b2 – λ2| ≤ 0.04 → gt ≈ gv b2 / 4
|b1 – λ1| ≤ 0.01 → b1 = 0
Unitarity constraints
WL WL → WL WL , WL WL → t t, t t → t t
gπ ≤ 1.75 (Mρ= 700 GeV)
gt ≤ 1.7 (Mρ= 700 GeV)
Partial (Γ―›WW) and
total width Γtot of ρ
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)
Pythia (fb)
CompHEP (fb)
800
0.35
0.66
1000
0.95
1.16
1500
3.27
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)
R=
|N(ρ) – N(no res.)|
√(N(no res.))
≈ S/√B > 5
e- e+ → t t
ρ
different from Higgs !
ρ (M= 700 GeV, b2=0.08, g’’=20)
x+y=560 nm
z=0.40 mm
n=2x1010
Beamstrahlung
Bunch parameters at IP:
TESLA (500 GeV):
SLC (SLAC):
N = 5 x 1010
N = 2 x 1010
σx = 1500 nm
σx = 554 nm
σy = 1500 nm
σy = 5 nm
σz = 1.05 mm
σz = 0.3 mm
δBS = 0.00045
δBS = 0.02 – 0.2
L = N2 Hd f/ 4πσxσy
pinch effect
E(b)= Ne/(2πε0 L R2) b
R = 2 σx = 2 σy
L is bunch length
b
ey
e+ bunch
y(z) = b0 cos[(√3Dy/2)1/2 z/L]
z
x
Dy = 2N reσz/[γσy(σx+σy)]
Disruption
Pinch effect
p
e-
F= eE(b)
r
z
r= p/eE(b)
s
L = N2 Hd f/ 4πσxσy
Dy = 2N reσz/[γσy(σx+σy)]
PW= 2ke2γ4/(3r2), v→c=1
ΔE = PWΔt = PWΔz
δBS = ∫ ΔE /E
= 4N2γ re3/[3√3 σz (σx+σy)2]
= 2 – 20 %
Conclusions
• strong ρ-resonance model (modified BESS)
• e+e- → ννtt
e+e- → tt
R ≤ 26 at CM energy = 1 TeV, L = 200 fb-1
Lscan = 1 fb-1