signatures of a new vector resonance from strongly interacting electroweak symmetry breaking m....
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Signatures of a new vector resonance from strongly interacting electroweak
symmetry breaking
M. Gintner, I. Melo, B. TrpišováUniversity of Žilina
Exotics meeting, CERN Oct 10, 2007
Outline
BESS Model Vector Resonance ρ
pp processes sensitive to ρ, cross sections (CompHEP calculation)
Reconstruction of pp → W+ W- t t + X and pp → b b t t + X
(CompHEP, Pythia, Atlfast, Root)
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
052
01
0)(v
ttgttgM
igL tt
Vg
Mg
v2
t t t
π = WL
2
21
21 4 V
Vtt
g
gO
bggg
1,bgV are BESS coupling constantsg is the SU(2)L coupling constant
10Vg
24/1 bgVv 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
,b
,b ,b
,b
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 scaleR.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 ttpp ―› ρtt ―› WW ttpp ―› ρtt ―› tt ttpp ―› ρtt ―› bb ttpp ―› ρbb ―› bb tt
pp ―› WWpp ―› tt
Mρ = 1 000 GeVΓρ = 42.3 GeV
CompHEP: pp → bb → tt + X
σS = 174 fb
Background G G → t t 3 diagrams
σB = 25 605 fb
Signal 6 diagrams
CompHEP: pp → bb → W+W- + X
uu → W+W-
dd → W+W-
4 diagrams
Signal 4 diagramsσS = 15.4 fb
σB = 450 fb
σS → 14.0 fb
σB → 100 fb
mWW
pTW
Background
CompHEP: pp → ttρ0 + X → bb t t + X
Signal 8 diagrams
σS = 3.7 fb
σB = 17 fb
QCD background 35 diagrams
QCD
Signal
mbb
pTb
QCD bottom
Signal bottom
CompHEP: pp → bbρ0 + X → bb t t + X
Signal 8 diagramsσS = 134 fb
σB = 833 fb
QCD background 35 diagrams
QCD
Signal
mtt
pTt
QCD top
Signal top
Γρ=127 GeV σ = 337 fb
CompHEP: pp → tbρ+ + X → bb t t + X
Signal 8 diagrams
σS = 86 fb
σB = 332 fb
QCD background 35 diagrams
mtb
Signal top
QCD top
QCD
Signal
pTq
bottom
bottom
Cuts: 700-3Γρ < mWW < 700 +3Γρ (GeV) pT (t) > 100 GeV, |y(t)| < 2
σS = 1.0 fbIrreducible background
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
σB = 0.037 fb
39/8 diagrams in the dominant gg channel
ttWW -
jjbjjbjjl l
No-resonancebackground
ρ
ρ
ρ
CompHEP results: pp → W W t t + X (continued)
pp → bb → tt + X
pp → bb → W+W- + X
pp → ttρ0 + X → bb t t + X
pp → bbρ0 + X → bb t t + X
pp → tbρ+ + X → bb t t + X
pp → ρ0 tt → W W t t + X
σS = 174 σB = 25 605
σS = 14 σB = 100
σS = 3.7 σB = 17
σS = 134 σB = 833
σS = 86 σB = 332
σS = 1 σB = 0.037
Cross sections in the peak region in fb
pp → W W t t + X l jjbjjbjj reconstruction (CompHEP, Pythia, Atlfast, Root)
One charged lepton channel:
jjbjjbjjlWbbWWWttWW l
Cuts: Tpelectron > 30 GeV
muon > 20 GeVjets > 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
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
CompHEP
Reconstruction
pp → ρ0 tt → bb t t + X → bb lνlb jjb (43.5%) reconstruction
(CompHEP, Pythia, Atlfast, Root)
NS=0.8
NB=8
L = 100 fb-1Cuts: Tp
25Wm
of
e > 30 GeV
j > 25 GeV
μ > 20 GeV
L = 100 fb-1
GeV
2222 )()()(221121 tbWtbWWjj mmmmmm
pp → bb → tt + X
pp → bb → W+W- + X
pp → ttρ0 + X → bb t t + X
pp → bbρ0 + X → bb t t + X
pp → tbρ+ + X → bb t t + X
pp → ρ0 tt → W W t t + X
σS = 174 σB = 25 605
σS = 14 σB = 100
σS = 3.7 σB = 17
σS = 134 σB = 833
σS = 86 σB = 332
σS = 1 σB = 0.037
Conclusions
Thanks to Jonathan Ferland for his great help with reconstruction !
Backup
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
versus
8 diagrams
ttttttWW
1. Can we improve WWtt reconstruction ?
2.
L = 100/fb2.4 events8 diagrams
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,
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