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New Vector Resonance as an Alternative to Higgs Boson (Strong EWSB)

Fyzika za Štandardným modelom klope na dvere Svit, 9.-16.9. 2007. New Vector Resonance as an Alternative to Higgs Boson (Strong EWSB). Ivan Melo University of Zilina. EWSB - one of Great Mysteries of Particle Physics. SM ………………………. 1 Higgs Strong EWSB …….. no Higgs

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New Vector Resonance as an Alternative to Higgs Boson (Strong EWSB)

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  1. Fyzika za Štandardným modelom klope na dvere Svit, 9.-16.9. 2007 New Vector Resonance as an Alternative to Higgs Boson(Strong EWSB) Ivan Melo University of Zilina

  2. EWSB - one of Great Mysteries of Particle Physics • SM ………………………. 1 Higgs • Strong EWSB …….. no Higgs • SUSY (MSSM) ..... 5 Higgs • Large Extra Dimensions • Little Higgs Problem ! Monotheists Atheists Polytheists Classical New

  3. Naturalness problem (Fine-tuning, Gauge Hierarchy problem) ≈ - (200 GeV)2 for Λ = 103 GeV ≈ - (200 GeV)2 . 1032for Λ = 1019 GeV mH≈ 100 – 200 GeV ≈ - (200 GeV)2 . 1032 ≈ + (200 GeV)2 . 1032

  4. SM Strong EWSB SUSY (MSSM) Large Extra Dimensions Little Higgs = 0 → mH = 319 GeV H not elementary, it melts into techniquarks at ΛTC ≈ 1-3 TeV ~ t1(2) Λ is not 1019 GeV, Λ is as low as 103 GeV

  5. Fundamental energy scales Greg Anderson, Northwestern University

  6. Every fundamental energy scale should have a dynamical origin K. Lane

  7. Linear sigma model (model of nuclear forces) U(σ,π) σ v= μ/√λ ≈ 90 MeV σ = v + σ (spontaneous chiral symmetry breaking) SU(2)L x SU(2)R→ SU(2)V

  8. Standard model Higgs Lagrangian U(σ,π) σ SU(2)L x SU(2)R→ SU(2)V v= μ/√λ ≈ 246 GeV Higgs Lagrangian ≡ Linear sigma model

  9. Where are EW pions ??? mσ = μ2 mπ = 0 SU(2)L x SU(2)R→ SU(2)V (global) massless GB Higgs mechanism: W,Z become massive by eating GB SU(2)L x U(1)Y→ U(1)Q (local) EW pions Φ1,Φ2,χ become WL, ZL

  10. Where is σ ? … the (linear) σ model, although it has some agreeable features, is quite artificial. A new particle is postulated, for which there is no experimental evidence … M. Gell-Mann, M. Levy, Nuovo Cimento 16 p.705 (1960) … and they decided to get rid of σ particle …

  11. Nonlinear σ model (QCD) v = 90 MeV Effective Lagrangian valid until a few hundred MeV

  12. Where is Higgs boson ? … Higgs Lagrangian, although it has some agreeable features, is quite artificial. A new particle is postulated, for which there is no experimental evidence … … so we get rid of the Higgs boson Higgs boson is not necessary, Higgs mechanism works even without Higgs !

  13. Nonlinear σ model (SM Higgs sector) v = 246 GeV Effective Lagrangian valid until 1-3 TeV

  14. Chiral SB in QCD SU(2)L x SU(2)R → SU(2)V , vev ~ 90 MeV EWSB SU(2)L x SU(2)R → SU(2)V , vev ~ 246 GeV

  15. Technicolor Technicolor of massless U and D techniquarks: SU(2)L x SU(2)R invariant As a result of dynamics, interactions of massless techniquarks, we get - SU(2)L x SU(2)R→ SU(2)V - v = 246 GeV - EW pions = WL, ZL made of U,D techniquarks Best explanation of Naturalness & Hierarchy problems

  16. Extended Technicolor (ETC) ETC was introduced to give masses to fermions … but introduced also large FCNC and conflict with precision EW measurements U D ETC Walking technicolor f f ETC has alsoproblem to explain large top mass (mt = 174 GeV) Topcolor assisted technicolor

  17. WL WL→ WL WLWLWL → t tt t → t t t t t (Equivalence theorem) π = WL L = i gπMρ/v (π- ∂μπ+ - π+ ∂μπ-)ρ0μ + gt t γμ t ρ0μ+ gt t γμ γ5 t ρ0μ

  18. International Linear Collider: e+e- at 1 TeV ee ―› ρtt ―›WW tt ee ―› ρtt ―›tt tt ee ―› WW ee ―› tt ee ―› ννWW ee ―›ννtt Large Hadron Collider: pp at 14 TeV pp ―› ρtt ―›WW tt pp ―› ρtt ―›tt tt pp ―› WW pp ―› tt pp ―› jj WW pp ―› jj tt

  19. Chiral effective Lagrangian 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 gvρμ . τ/2 )2] + Lmass+ LSM(W,Z) +b1ψL i γμ (u+∂μ – u+i gvρμ . τ/2+ u+ i g’/6 Yμ) u ψL + b2ψRPb i γμ (u ∂μ – u i gvρμ . τ/2 + u i g’/6 Yμ) u+PbψR + λ1ψL i γμ u+ Aμγ5 u ψL +λ2ψR Pλ i γμ u Aμγ5 u+PλψR BESS Our model Standard Model with Higgs replaced with ρ ωμ = [u+(∂μ + i g’/2 Yμτ3)u + u(∂μ+ i g Wμ . τ/2)u+]/2 Aμ = [u+(∂μ + i g’/2 Yμτ3)u - u(∂μ+ i g Wμ . τ/2)u+]/2 u = exp(i π . τ/2v) ψL = (tL,bL) Pb = diag(p1,p2) gπ= Mρ /(2 v gv) gt=gv b2/4+ … Mρ≈ √a v gv/2 t

  20. Low energy constraints Unitarity constraints WLWL → WLWL , WLWL → t t,t t → t t gv≥ 10 → gπ ≤ 0.2 Mρ(TeV) |b2 – λ2| ≤ 0.04 → gt≈ gv b2 / 4 |b1 – λ1| ≤ 0.01 → b1 = 0 gπ ≤ 1.75 (Mρ= 700 GeV) gt ≤ 1.7 (Mρ= 700 GeV)

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

  22. Subset of fusion diagrams + approximations (Pythia) Full calculation of 66 diagrams at tree level (CompHEP)

  23. Pythia vs CompHEP ρ (M = 700 GeV, Γ = 12.5 GeV, gv = 20, b2 = 0.08) Before cuts √s (GeV) 800 1000 1500 Pythia (fb) 0.35 0.95 3.27 CompHEP (fb) 0.66 1.16 3.33

  24. Backgrounds (Pythia) e+e- → tt γ e+e- → e+e- tt σ(0.8 TeV) = 300.3 + 1.3 fb → 0.13 fb(0.20 fb) σ(1.0 TeV) = 204.9 + 2.4 fb → 0.035 fb (0.16 fb)

  25. |N(ρ) – N(no res.)| √N(ttγ+eett)+(N(no res.)) R = ≈ S/√B > 5 = gv = gv

  26. e- e+→ t t ρ different from Higgs ! x+y=560 nm z=0.40 mm n=2x1010 ρ (M= 700 GeV, b2=0.08, gv=20)

  27. 39/8 diagrams in the dominant gg channel ρ No-resonance background ρ ρ

  28. CompHEP results: pp → W W t t + X ρ: Mρ=700 GeV, Γρ=4 GeV, b2=0.08, gv=10 39 diagrams 8 diagrams MWW(GeV) gπ=Mρ/2vgv gt1,2= gv b2/4 σ(gg) = 10.2 fb ―› 1.0 fb Cuts: 700-3Γρ < mWW < 700 +3Γρ (GeV) pT (t) > 100 GeV, |y(t)| < 2 No resonance background: σ(gg) = 0.037 fb

  29. l jjbjjbjj reconstruction (CompHEP, Pythia, Atlfast, Root) Athena 9.0.3 One charged lepton channel: 40% of events electron > 30 GeV muon > 20 GeV of Cuts: GeV mass of the W: jets > 25 GeV 50% b-tagging efficiency Reconstruction criterion

  30. 8 diagrams 39 diagrams Lum=100/fb Lum=100/fb 12.2 events 2.4 events number of events/17 GeV Distribution in invariant mass of WW pair (ρ →WW) ρ: Mρ=700 GeV, Γρ=4 GeV, b2=0.08, gv=10 Pz(ν) chosen correctly in 61.5 % of events number of events/17 GeV

  31. 39 diagrams 8 diagrams Mass of the W boson Lum=100/fb Lum=100/fb 12.2 events 2.4 events number of events/0.6 GeV number of events/0.6 GeV Mass of the top quark Lum=100/fb Lum=100/fb 12.2 events 2.4 events number of events/2.5 GeV number of events/2.5 GeV

  32. ρ: Mρ=1000 GeV Γρ=26 GeV Lum = 100 fb-1 12.8 events number of events/32 GeV

  33. 1. Can we improve WWtt reconstruction ? L = 100/fb 2.4 events 8 diagrams versus 2. 8 diagrams

  34. Conclusions • New vector resonance as an alternative to Higgs Boson • Modified BESS model motivated by technicolor • Rich e+e- and pp phenomenology

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