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,