Signatures of a new vector resonance from strongly interacting electroweak

symmetry breaking at LHC

M. Gintner, I. Melo, B. TrpišováUniversity of Žilina

Nuclear Seminar, FMFI UK Bratislava May 21, 2008

Outline

• Strong Electroweak Symmetry Breaking

• BESS Model Vector Resonance ρ

• LHC processes sensitive to ρ, cross sections (CompHEP calculation)

• Reconstruction of pp → W+ W- t t + X; pp → b b t t + X

(CompHEP, Pythia, Atlfast, Root)

EWSB - one of Great Mysteries of Particle Physics

• SM ………………………. 1 Higgs

• Strong EWSB …….. no Higgs

• SUSY (MSSM) ..... 5 Higgs

Monotheists

Atheists

Polytheists

Problem !

Classical

Naturalness problem (Fine-tuning problem)

≈ - (200 GeV)2 . 1032 for Λ = 1019 GeV

mH ≈ 100 – 200 GeV - (200 GeV)2 . 1032 + (200 GeV)2 . 1032

SM

SUSY (MSSM)

= 0 → mH = 319 GeV

t1(2)

~

H not elementary, melts into techniquarks above ΛTC ≈ 1-3 TeV

Strong EWSB

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

ttgttg

MigL tt

t t t

π = WL

v is EW scale (v = vev ~ 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

mt = 171 GeV ≈ v/√2

(Equivalence theorem)

Large Hadron Collider: pp at 14 TeV

pp ―› jj WW pp ―› jj ttpp ―› ρtt ―› WW tt +Xpp ―› ρbb ―› WWbbpp ―› ρtt ―› tt ttpp ―› ρtt ―› bb ttpp ―› ρbb ―› bb ttpp ―› ρ+tb ―› tb tbpp ―› ρ+tb ―› W+Z tb

pp ―› WW+Xpp ―› tt+X

Mρ = 1 000 GeVΓρ = 42.3 GeV

Vg

Mg

v2

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

R.Casalbuoni et al. Phys.Lett. B155 (1985) 95; M.Gintner, I.Melo, B.Trpisova, Acta Phys. Slovaca, 56(2006)1

2

21

21 4 V

Vtt

g

gO

bgggt

1,2

(2)

Unitarity constraints

WL WL → WL WL , WL WL → t t, t t → t t unitary up to 3 TeV

Low energy constraints

gπ ≤ 1.4 (Mρ= 1 000 GeV)gt ≤ 2.0 (Mρ= 1 000 GeV)

gv ≥ 10 gπ = Mρ /(2v gv) ≤ 0.2 Mρ (TeV)

|b2 – λ2 | ≤ 0.04 gt ≈ gv b1(2) / 4

|b1 – λ1 | ≤ 0.01

if

Partial (Γ―›WW) andtotal width Γtot of ρ0

Mρ = 1 000 GeVΓρ = 42.3 GeV

gv = 20b1 = 0.08

CompHEP: pp → bb → tt + X

σS = 121 fb Background G G → tt 3 diagrams

σB = 26 617 fb

Signal bb → tt 6 diagrams

Cuts: Mρ-3Γρ < mtt < Mρ +3Γρ (GeV)

pT(t), pT(t) > 350 GeV

σB = 6 353 fb

σS = 47 fb

M±3Γ

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

M±3Γ

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

M±3Γ

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

39/8 diagrams in the dominant gg channel

ttWW -

jjbjjbjjl l

No-resonancebackground

ρ

ρ

ρ

CompHEP: pp → (W+ W-) t t + X pp → (W+ W-) b b + X

signal

Signal + Background: 39 diagrams

CompHEP: pp → (W+ W-) t t + X (continued) pp → (W+ W-) b b + X

Signal: 8 diagrams

b,

b,

,bσS+B = 4 400 fb

σS = 9.4 fb σS+B = 9.4 fb

σS = 6.7 fb

Cuts: Mρ-3Γρ < mWW < Mρ +3Γρ (GeV)

mW+b, mW-b > 200 GeV

Signal + Background: 46 diagrams

CompHEP: pp → (W+ Z) t b + X

Signal: 8 diagramsσS+B = 12.7 fb

σS = 2.9 fb σS+B = 2.9 fb

σS = 2.5 fb

Cuts: Mρ-3Γρ < mWZ < Mρ +3Γρ (GeV)

mW+b > 200 GeV

W+

Z

Signal + Background: 54 diagrams

CompHEP: pp → (tt) tt + X

Signal: 8 diagrams

σS+B = 3.7 fb

σS = 1.3 fb

Cuts: Mρ-3Γρ < mtt < Mρ +3Γρ (GeV)

t

t

1. pp → bb → tt + X

2. pp → bb → W+W- + X

3. pp → (bb) tt + X

4. pp → bb (tt) + X

5. pp → b(bt) t + X

6. pp → (W+W-) t t + X

7. pp → (W+W-) b b + X

8. pp → (W+Z) t b + X

9. pp → (tt) tt + X

σS = 47

σS = 14

σS = 3.7

σS = 134

σS = 86

σS = 0.23

σS = 6.7

σS = 2.5

σS = 1.3

Cross sections in fb + statistical significance (peak region)

S = NS/ √(NB) statistical significance

NS = L σS , NB = L σB , with L = 100 fb-1 integrated luminosity

S = 5.9 *

S = 14.0 *

S = 9.0

S = 46.4

S = 47.2

S = 4.6

S = 40.8 *

S = 39.5 *

S = 8.4

σB = 6 353

σB = 100

σB = 17

σB = 833

σB = 332

σB = 0.25

σB = 2.7

σB = 0.4

σB = 2.4

signal background significance

* More than 1 cut applied

pp → W W t t + X l jjbjjbjj reconstruction (in collaboration with Jonathan Ferland, University of Montreal)

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

(CompHEP, Pythia, Atlfast, Root)

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

CompHEP

Reconstruction

pp → ρ0 tt → bb t t + X → bb lνlb jjb (43.5%) reconstruction

(in collaboration with J. Ferland)

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

Conclusions

• Strong EWSB: an alternative to SUSY

• ρ is a general prediction of Strong EWSB

• (Modified) BESS model preferentially couples ρ with t,b

• Several processes promising at CompHEP level

Backup

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,