Recent Developments in Little Higgs Searches. at LHC

Transcription

1 SUSY 06, Newport Beach 1 Recent Developments in Little Higgs Searches at LHC presented by: F. Ledroit on behalf of the ATLAS collaboration

2 Outline 2 The model Heavy gauge boson searches Leptonic decays (Eur. Phys. J. C39S2, 13 (2005)) Hadronic decays Higgs decays, m h =200 GeV Higgs decays, m h =120 GeV (Eur. Phys. J. C39S2, 13 (2005)) Summary NEW! NEW!

3 Little Higgs model 3 Effective model adressing hierarchy problem larger symmetry, broken at high scale introduce heavy top T, heavy Higgses φ and heavy gauge bosons Z H,W H, A H Littlest Higgs model [Arkani-Hamed et al., JHEP 207(2002)34] SU(5) SO(5), scale f~tev Gauge sector [SU(2) U(1)] 2 SM Higgs Phenomenology Han et al., Phys.Rev.D67(2003)95004 Gauge sector: parameter θ: mixing angle between W triplets W H, Z H mass degenerate M < 6 TeV 200 m h GeV 2 EW fits strong constraints Little Higgs realized in several models. Similar particle content.

4 Z H,W H production and decays 4 qq anihilation q q Z H,W H Fermionic channels: Bosonic channels: Z H l + l -, qq Z H Zh, W + W - ± W H l ν, qq W H W ± h, W ± Z ± σ(z H ) (fb) σ (cot θ) 2 BR(Z H ) 12% All l + l - or qq Zh+W + W - BR( Z H qq) = 1/8 BR(W H qq ) = 1/4 cot θ = 1 Br(W H tb)=3xbr(w H eν) cot θ σ(w H ) = 2 σ(z H ) Γ W (Wh+WZ) = Γ Z (Zh+WW) H H

5 Outline 5 The model Heavy gauge boson searches Leptonic decays (Eur. Phys. J. C39S2, 13 (2005)) Hadronic decays Higgs decays, m h =200 GeV Higgs decays, m h =120 GeV (Eur. Phys. J. C39S2, 13 (2005)) Summary NEW! NEW!

6 Leptonic V H decays V H = Z H, W H 6 Discovery channel Z H e + e - W H e ν With 300 fb -1 = 3 years of LHC high luminosity: Z H cotθ W H eν 5 σ reach for 300 fb -1 ATLAS W H m(w H ) (GeV) All analyses performed using a parameterized simulation of the ATLAS detector (ATLFAST) ε(lepton tag) = 90% Poisson significance (~S/ B) > 5 + S 10 in the mass window discovery

7 Outline 7 The model Heavy gauge boson searches Leptonic decays (Eur. Phys. J. C39S2, 13 (2005)) Hadronic decays Higgs decays, m h =200 GeV Higgs decays, m h =120 GeV (Eur. Phys. J. C39S2, 13 (2005)) Summary NEW! NEW!

8 Hadronic V H decays NEW! 8 V H = Z H, W H ( R)2 = ( η) 2 + ( φ) 2 Z H t 1 t 2, t 1 blν, t 2 bjj (l=e,µ) η=pseudo-rapidity, φ=azimuthal angle Signature: 2 b-jets + 1 lepton + E T Z H Background: t 2 t 1 W W b b tt,, W+jets j j l ν Cuts: - 1 isol. lepton, p T >25 GeV - E T > 25 GeV - 2 b-jets, p T >25 GeV, R(b 1 l )<2, R(b 2 l )>2 - t 1 = b 1 + l 1 + E T (with ν // l) - t 2 = b 2 + all jets R<2 - p T (b 2 +j) > 0.25 M ZH ε(b tag) = 50 (20)% Ru = 100 (130) M = 1 (2)TeV Z H validated with full simulation ε kine = 27 (21)%, M=1 (2) TeV

9 Hadronic V H decays 9 Z H tt M=1 TeV 30 fb fb -1 Mass reco. bias: <1% Mass resolution: ~12% >> natural width: Γ/M = 2% cotθ Two other modes: Z H bb W H tb b l ν b 300 fb -1 M=2 TeV cotθ = 1

10 Hadronic V H decays 10 The Z H to tt and bb decays are difficult to detect 300 fb -1 The W H to tb decay might yield a signal clearly separable from background Possible improvement by optimizing b-tagging at very high p T

11 Outline 11 The model Heavy gauge boson searches Leptonic decays (Eur. Phys. J. C39S2, 13 (2005)) Hadronic decays Higgs decays, m h =200 GeV Higgs decays, m h =120 GeV (Eur. Phys. J. C39S2, 13 (2005)) Summary NEW! NEW!

12 V H decays to Higgs (m h =200 GeV) NEW! 12 Assume Higgs discovered m h =200 GeV BR(h W + W - ) = 74 % SM Higgs usual BR BR(h ZZ) = 26 % V H V 1 h V 1 V 2 V 3 V = Z,W Studied channels: V H 3 leptonic V ( leptons only) V H 2 leptonic V + 1 V jj A modes: (V 1 jj) and isolated leptons B modes: (V 2 or V 3 jj) lepton in jet Branching fractions = (cotθ=0.5)

13 A modes V H decays to Higgs (m h =200 GeV) 13 V H Vh jjzz jj l + l - l + l - (l=e,µ) very clean Signature: 4 leptons + jet(s) V H V h Z Z j j l l l + l - Cuts: - 2 isol. leptons (1,2) M 12 = M Z ±15 GeV - 2 isol. leptons (3,4) R 1,2-3,4 <1.5 - p T ( )>0.25 MV H - 1 or 2 jets, p T > 0.25 M ( R 1-2 <1) V H - m(4l+j)=m ± 15% V H cotθ=0.5 M(Z H ) σ.br (fb) M(W H ) σ.br (fb) Background: ~ none

14 A modes V H decays to Higgs (m h =200 GeV) 14 Z H Zh +W H Wh 1 TeV 300 fb -1 Two other modes: Z H Zh l + l - W + W - l + l - l + νl - ν W H Wh lνw + W - lνl + νl - ν 1 TeV 300 fb -1 S= 28.7 ε S 26% cotθ = 0.5 S= 76.7 ε S 12% Mass reco. bias: 1% Mass resolution: 4% Assume p = p T bias, poor resolution

15 B modes V H decays to Higgs (m h =200 GeV) 15 Z H Zh l + l - WW l + l - jj lν (l=e,µ) Signature: 3 leptons + jet(s) + E T Z j Z H W h W l + l - l ν j Cuts: - 2 isol. leptons (1,2) M 12 = M Z ±15 GeV - 1 isol. lepton, W 1 =l 3 +E T, p T >50 GeV apply M W constraint or assume ν // l 3-1 or 2 jets, M j = M W ±15 GeV -p T (l 1 +l 2 +W 1 +j)>100 GeV cotθ=0.5 M(Z H ) σ.br (fb) Background: tt, Zh, WZ, ZZ, h Lack of statistics on background extrapolated

16 B modes V H decays to Higgs (m h =200 GeV) fb TeV 9.2 σ S= 31 ε S 24% ε B <1% Two other modes: Z H Zh l + l - ZZ l + l - jj l + l - W H Wh lν ZZ lν jj l + l fb -1 1 TeV 18.6 σ S= 92 ε S 21% Mass reco. bias: 1% Mass resolution: 4% ~same all modes cotθ = 0.5 ε B <1%

17 V H decays to Higgs (m h =200 GeV) 17 Ldt = 300 fb -1 BR(Z H ) 12% All l + l - or qq Zh+WW cot θ Mass reach about 2 TeV, except when cotθ ~1 Although ATLFAST lepton isolation criteria were especially tuned (B modes), needs validation with full simulation M < 6 TeV for m h = 200 GeV (avoid fine tuning) V H

18 Outline 18 The model Heavy gauge boson searches Leptonic decays (Eur. Phys. J. C39S2, 13 (2005)) Hadronic decays Higgs decays, m h =200 GeV Higgs decays, m h =120 GeV (Eur. Phys. J. C39S2, 13 (2005)) Summary NEW! NEW!

19 V H decays to Higgs (m h =120 GeV) 19 Earlier results: BR(h bb) = 66 % BR(h γγ) = 0.2 % 300 fb -1 Z H Zh jjγγ, ll bb W H Wh jjγγ, lν bb (l=e,µ) excluded M < 2.2 TeV for m h =120 GeV ε(b tag) = 40-50% Ru = 100 m (GeV) V H

20 Summary 20 The Z H, W H can be discovered up to 5-66 TeV if cotθ large It may be possible to probe the model up to ~ 2 TeV using the V H Vh decay (cot( cotθ [0.8,1.2]) using the W H tb decay (cot( cotθ > 0.25) Fermionic decays Bosonic decays

21 21 References: G. Azuelos et al., Eur. Phys. J. C39S2, 13 (2005) S. Gonzales de la Hoz et al., ATL-PHYS-PUB E. Ros and D. Rousseau, ATL-COM-PHYS Many thanks to the authors of these analyses, and especially David Rousseau and Matthieu Lechowski Eduardo Ros and Jose E. Garcia

22 22 Backup slides

23 Z H,W H production and decays 23 qq anihilation q q Z H,W H Fermionic channels: Bosonic channels: Z H l + l -, qq Z H Zh, W + W - ± W H l ν, qq W H W ± h, W ± Z ± σ(z H ) (fb) σ (cot θ) 2 cot θ = 1 BR(Z H ) 12% e + e - + µ + µ - + τ + τ - Zh+W + W - Γ Z (ll ) ~ (cot θ) 2 H Γ Z (Zh) ~ (cot 2θ) 2 H Γ Z (W + W - ) = Γ Z (Zh) H H cot θ σ(w H ) = 2 σ(z H ) Γ W (Wh+WZ) = Γ Z (Zh+WW) H H

24 Deductions for A H 24 theorical uncertainties (strong model-dependency dependency) ) for A H can deduce limits on σ.br(a H Z h) from results for Z H (same decays) hypothesis : favorable cases where M(W H /Z H ) and M(A H ) are distant for each M(A H ) (resolution of M(W H /Z H ) being GeV) W H /Z H not background for A H A H e + e -

25 A modes : Signal : no background considered hypothesis: all leptons are well isolated and at very high p T, so the final state should be distinguished from eventual backgrounds Reconstruction: Z H Zh l + l - W + W - l + l - l + νl - ν Z H l 1 and l 2 same type, opposite charge, M(l 1 l 2 ) = M Z ± 15 GeV l 3 and l 4 opposite charge p(h) ) = p(l 3 ) + p(l 4 ) + p(miss.) with p(miss.) // p(l 3 ) + p(l 4 ) Z H reconstructed with h and Z Z h l 1 l 2 W W in all the following : l 3 ν l 4 ν M(Z H ) cotθ= σ.br (fb) η l <2.5 (Calo's acceptance) ε (lepton lepton-tagging) = ) = 90%

26 A modes : Z H Zh l + l - W + W - l + l - l + νl - ν 26 Cuts: p T (Z) ) > 250 GeV p T (h) ) > 250 GeV M(Z H ) in the range 1000± GeV E T (miss.) > 50 GeV p T (Z) ) > 500 GeV p T (h) ) > 500 GeV M(Z H ) in the range 2000± GeV 1 TeV 2 TeV cotθ=0.5 cotθ=0.5 S= 32.4 ε S 34% S= 1.1 ε S 23%

27 A modes : W H Wh lνw + W - lνl + νl - ν W l 3 ν 27 cotθ=0.5 M(W H ) σ.br (fb) Signal : W H h W W l 2 ν l 1 ν Reconstruction: l 1 and l 2 opposite charge, R(l 1,l 2 ) < 1.5, p("h without miss.") = p(l 1 ) + p(l 2 ) l 3, R(l 3, "h without miss.") > 1.5 p(w H ) = p("h without miss.") + p(l 3 ) + p(miss.) with p(miss.) =p= T (miss.) only partial reconstruction!

28 A modes : Cuts: no jet with p T > 100 GeV p T (l 3 ) > 100 GeV p T ("h without miss.") > 100 M(Z H ) in the range 800±300 W H Wh lνw + W - lνl + νl - ν 100 GeV 300 GeV E T (miss.) > 100 GeV no jet with p T > 200 GeV p T (l 3 ) > 200 GeV p T ("h without miss.") > 200 M(Z H ) in the range 1600± GeV 600 GeV 1 TeV 2 TeV cotθ=0.5 cotθ=0.5 S= 76.7 S= 2.6 ε S 12% ε S 8%

29 B modes : Signal : Z H Zh l + l - ZZ l + l - jj l + l - Z H Z h l l Z Z 1 or 2 jets q q l l 29 cotθ=0.5 M(Z H ) σ.br (fb) Background : tt WbWb lνb lνb big cross-section section : 3376 fb Zh llzz llqqll same final state : fb h, fh, qqh, tth,, ZZ, Wh with b B l X

30 B modes : Reconstruction 30 necessary condition: to have 4 leptons ll Pairs of Leptons ll M ll M Z ll ll jj jj jj jj Pairs of Jets jj jj jj jj jj M jj M Z jj j Jets j j j j p T max p T ZH p T min p T max (since secondary decay) p T max h Higgs h h h h h M h 200

31 B modes : Z H Zh l + l - ZZ l + l - jj l + l - 31 η l <2.5 (Calorimeter's acceptance) ε(identification of lepton) = 90% p T 1 lepton > 30 GeV and p T 2 leptons > 20 GeV (LVL1 trigger) M h - <M h > gaussian fit < 2σ gaussian M V H gaussian fit - <M V H> gaussian fit < 2σ gaussian p T pair of jets or big jet > 50 GeV p T h > 100 GeV gaussian fit

32 B modes : 1 TeV cotθ=0.5 Z H Zh l + l - ZZ l + l - jj l + l σ S= 18 ε S 17% ε B <1% NB: significance S/ S/ B (due to small number of events and big uncertainties) use " "PoissonSig" (Wisconsin's tool) 2 TeV cotθ= not def. S< 1 ε S 9% ε B <1% 1.5 TeV cotθ= σ S= 3 ε S 13% ε B <1%

33 B modes : Signal : W H Wh lν ZZ lν jj l + l - W H W h l ν Z Z 1 or 2 jets q q l l 33 cotθ=0.5 M(W H ) σ.br (fb) Background : tt 3376 fb Zh llww llqqlν same final state : fb h, fh, qqh, tth,, ZZ, Wh, WZ

34 B modes : W H Wh lν ZZ lν jj l + l - 1 TeV cotθ= σ S= 92 ε S 15% ε B <1% 2 TeV cotθ= σ S= 2.4 ε S 7% ε B <1% 1.5 TeV cotθ= σ S= 16 ε S 12% ε B <1%

35 The littlest Higgs Model 35