BESS Model Resonance in the pp W+W tt + X Channel

at LHC

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

Herlany, September 2006

Outline

BESS Model Vector Resonance ρ

Cross sections for pp →WWtt + X

reconstruction jjbjjbjjl l

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,

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

052

01

0)(v

ttgttgM

igL tt

VgM

gv2

t t t

π = WL

2

22

21 4 V

Vtt

ggObggg

2,bgV are BESS coupling constantsg is the SU(2)L coupling constant

10Vg

1.02 b

International Linear Collider: e+e- at 1 TeV

ee ―› νν WW ee ―› νν tt ee ―› ρtt ―› WW ttee ―› ρtt ―› tt tt

ee ―› WWee ―› tt

Large Hadron Collider: pp at 14 TeV

pp ―› jj WW pp ―› jj tt pp ―› ρtt ―› WW ttpp ―› ρtt ―› tt tt

pp ―› WWpp ―› tt

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

Analysis of pp XttWW

I. cross-sections and statistical significance (CompHEP calculation) II. reconstruction CompHEP – events generation Pythia – decay and hadronization Atlfast – detector effects and reconstruction of the jets ROOT, C++ -- event reconstruction

For the dominant gg channel:

ttWW -

jjbjjbjjl l

39/8 diagrams in the dominant gg channel

No-resonancebackground

ρ

ρ

ρ

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 (39 diag.)

ρ: Mρ=700 GeV, Γρ=4 GeV, b2=0.08, gv=10

SM: MH = 700 GeV ΓH = 184 GeV

σ(gg) = 11.3 fb ―› 0.20 fbMWW(GeV)

8 diagrams: σ(WWtt) = σ(ρtt) x BR(ρ->WW)

Total cross sections for ρtt and WWtt

|N(ρ) – N(no res.)| √(N(no res.))R = ≈ S/√B > 5

8 diagr.

39 diagr.

Search at LHC: tttt vs WWtt

8 diagrams

l jjbjjbjj ReconstructionOne charged lepton channel:

jjbjjbjjlWbbWWWttWW l

Cuts: Tpelectron > 30 GeVmuon > 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

llW jjW

32 %68 %

num

ber

of e

vent

s/17

GeV

GeV]mWW[nu

mbe

r of

eve

nts/

17 G

eV

GeV]mWW[

8 diagrams 39 diagrams

Lum=100/fb2.4 events

Lum=100/fb

12.2 events

Invariant mass of WW pair (ρ →WW)

8 diagrams 39 diagramsnu

mbe

r of

eve

nts/

0.6

GeV

num

ber

of e

vent

s/0.

6 G

eV

num

ber

of e

vent

s/2.

5 G

eV

num

ber

of e

vent

s/2.

5 G

eV

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/fb2.4 events

2.4 events 12.2 events

12.2 events

Conclusions

I. ttWW in the final state – maximum values of R at around 100

II. jjbjjbjjl l reconstruction

The top quark and the W reconstruction O.K.The ρ reconstruction – 40% of events fall into the ρ peak need to improve the reconstruction algorithm

III. Future work -- -- much larger cross-section compared to , i.e. larger numbers of events

ttttppttWW

tttt versus ttWW

g g