BESS Model Resonance in the pp W+W tt + X Channel
at LHC
M. Gintner, I. Melo, B. Trpišová
University of Žilina
CERN, Nov 1, 2006
Outline
BESS Model Vector Resonance ρ
Cross sections for pp →WWtt + X (CompHEP calculation)
reconstruction
(CompHEP, Pythia, Atlfast, Root)
jjbjjbjjl l
052
01
0)(v
ttgttgM
igL tt
Vg
Mg
v2
t t t
π = WL
2
22
21 4 V
Vtt
g
gO
bggg
2,bgV are BESS coupling constantsg is the SU(2)L coupling constant
10Vg
1.02 bv is EW scale (246 GeV)
1,2 1,2 1,2
R.Casalbuoni et al. Phys.Lett. B155 (1985) 95; M.Gintner, I.Melo, B.Trpisova, Acta Phys. Slovaca, 56(2006)1
Large Hadron Collider: pp at 14 TeV
pp ―› jj WW pp ―› jj tt pp ―› ρtt ―› WW ttpp ―› ρtt ―› tt tt
pp ―› WWpp ―› tt
39/8 diagrams in the dominant gg channel
ttWW -
jjbjjbjjl l
No-resonancebackground
ρ
ρ
ρ
XttWW
Cuts: 700-3Γρ < mWW < 700 +3Γρ (GeV) pT (t) > 100 GeV, |y(t)| < 2
σ(gg) = 10.2 fb ―› 1.0 fb
No resonance background: σ(gg) = 0.037 fb
MWW(GeV)
CompHEP results: pp → W W t t + X
ρ: Mρ=700 GeV, Γρ=4 GeV, b2=0.08, gv=10 39 diagrams 8 diagrams
gt1,2
= gv b2/4gπ=Mρ/2vgv
l jjbjjbjj reconstruction (CompHEP, Pythia, Atlfast, Root)
One charged lepton channel:
jjbjjbjjlWbbWWWttWW l
Cuts: Tpelectron > 30 GeV
muon > 20 GeV
jets > 25 GeV
Reconstruction criterion
22
2222
)()(
)()()(
2211
654321
tbWtbW
WjjWjjWjj
mmmm
mmmmmm
l
40% of events
mass of the W: 25Wm GeV
b-tagging efficiency 50%
of
Athena 9.0.3
nu
mb
er o
f ev
ents
/17
GeV
GeV]mWW[
nu
mb
er o
f ev
ents
/17
GeV
GeV]mWW[
39 diagrams 8 diagrams
Lum=100/fb
12.2 events
Lum=100/fb
2.4 events
Distribution in invariant mass of WW pair (ρ →WW)
GeV]mWW[ GeV]mWW[
ρ: Mρ=700 GeV, Γρ=4 GeV, b2=0.08, gv=10
Pz(ν) chosen correctly in 61.5 % of events
8 diagrams 39 diagramsn
um
ber
of
even
ts/0
.6 G
eV
nu
mb
er o
f ev
ents
/0.6
GeV
nu
mb
er o
f ev
ents
/2.5
GeV
nu
mb
er o
f ev
ents
/2.5
GeV
GeV]m jj[ GeV]m jj[
GeV]mWb[ GeV]mWb[
Mass of the W boson
Mass of the top quark
Lum=100/fbLum=100/fb
Lum=100/fbLum=100/fb
2.4 events
2.4 events 12.2 events
12.2 events
GeV]mWW[
GeV]mWW[
nu
mb
er o
f ev
ents
/32
GeV
Lum = 100 fb-1
12.8 events
ρ: Mρ=1000 GeV Γρ=26 GeV
versus
8 diagrams
ttttttWW
1. Can we improve WWtt reconstruction ?
2.
L = 100/fb2.4 events8 diagrams
Appendix
BESS (Breaking EW Symmetry Strongly) Model 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+ 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 ψL i γμ u+ Aμ γ5 u ψL
+ λ2 ψR Pb i γμ u Aμ γ5 u+ Pb ψR
Standard Model with Higgs replaced with ρ
Our model
ωμ = [u+(∂μ + i g’/2 Yμτ3)u + u(∂μ+ i g Wμ . τ/2)u+]/2Aμ = [u+(∂μ + i g’/2 Yμτ3)u - u(∂μ+ i g Wμ . τ/2)u+]/2u = exp(i π . τ /2v)ψL = (tL,bL)
Pb = diag(1,p)
Mρ ≈ √a v gv /2
v ≈ 246 GeV … EW scale
Total width Γtot of ρ
Vg
Mg
v2
2
22
21 4 V
Vtt
g
gO
bggg
EWSB: SU(2)L x U(1)Y → U(1)Q
Weakly interacting models: - SUSY - SM (light) Higgs
Strongly interacting models: - Technicolor
A new strong vector resonance ρ as an isospin triplet ( ) → BESS0,