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Martin zur Nedden, HU Berlin 1 WS 2007/08: Physik am LHC 5. Higgs Searches The Higgs-mechanism in the SM Yukava-coupling, masses of fermions Higgs Production:

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Presentation on theme: "Martin zur Nedden, HU Berlin 1 WS 2007/08: Physik am LHC 5. Higgs Searches The Higgs-mechanism in the SM Yukava-coupling, masses of fermions Higgs Production:"— Presentation transcript:

1 Martin zur Nedden, HU Berlin 1 WS 2007/08: Physik am LHC 5. Higgs Searches The Higgs-mechanism in the SM Yukava-coupling, masses of fermions Higgs Production: Searches at TEVATRON Higgs decay channels Coupling constants Branching ratios Higgs search at the LHC

2 Martin zur Nedden, HU Berlin 2 WS 2007/08: Physik am LHC Higgs Mechanism in the Standard Model Doublet Φ of scalar Higgs fields H(x) exists due to the massive gauge field W,Z and the massless γ Complex fields Φ +, Φ 0 4 real components Φ 1, …Φ 4, produce mass in symmetry breaking due to self-interaction Goldstone/Higgs-mechanism: 3 components absorbed in the longitudinal polarization of the massive 3 W i -bosons 1 physical state H remains coupling to mass with g ffH No prediction of Higgs mass by SM

3 Martin zur Nedden, HU Berlin 3 WS 2007/08: Physik am LHC Yukava coupling, Mass of Fermions new term in Lagrangien needed: excluded due to gauge invariance e R (T=0, Y=-2) e L (T=1/2, Y=-1) h 0 (T=1/2, Y=1) igm e /(2M W ) igM W W W (Singlet in I,Y) choose: Coupling to the higgs field h0h0

4 Martin zur Nedden, HU Berlin 4 WS 2007/08: Physik am LHC Consequences from Yukava-Coupling electron gets mass neutrino rest massles strength of coupling proportional to the mass of the fermion mass is not predicted by the theory masses for quarks: same formalism as for leptons difference: both quarks within the doublet have mass new Higgs Doublet Φ c

5 Martin zur Nedden, HU Berlin 5 WS 2007/08: Physik am LHC Higgs-Production in Hadron-Hadron Interactions gluon-gluon interaction (LHC/TEVATRON): big production cross section, decay in 2 gammas gluon-gluon interaction (LHC/TEVATRON): production cross section very small quark-antiquark interaction (TEVATRON): big production cross section at 2TeV (TEVATRON) decay: W,Z leptons quark-quark interaction (LHC): big production cross section at 14TeV (LHC) decay: W,Z 2 γ (or leptons)

6 Martin zur Nedden, HU Berlin 6 WS 2007/08: Physik am LHC Higgs – Decay Channels (H VV) ~ G F M 3 H (H γγ) ~ α 2 G F M 3 H (H ff) ~ G F m 2 f M H

7 Martin zur Nedden, HU Berlin 7 WS 2007/08: Physik am LHC Possible Higgs Decays / coupling constants

8 Martin zur Nedden, HU Berlin 8 WS 2007/08: Physik am LHC Decay Width of Different Higgs Channels Calculations in the standard model:

9 Martin zur Nedden, HU Berlin 9 WS 2007/08: Physik am LHC Higgs Decay Channels: Branching Ratios

10 Martin zur Nedden, HU Berlin 10 WS 2007/08: Physik am LHC Higgs Decay in the Standard Modell fermions bosons decay width branching ratio

11 Martin zur Nedden, HU Berlin 11 WS 2007/08: Physik am LHC Higgs Search Strategies Good channel for TEVATRON: M(H) > 135 GeV: H WW M(H) < 135 GeV: H bb gg-fusion dominant at all Higgs masses, not to separate from BG at M < 135 GeV qq: Higgs-Strahlung: small contribution, but god to separate from BG

12 Martin zur Nedden, HU Berlin 12 WS 2007/08: Physik am LHC Cross Sections at TEVATRON

13 Martin zur Nedden, HU Berlin 13 WS 2007/08: Physik am LHC Higgs Search at TEVATRON, upper Limit signal: 2 b-Jet + MET + 2 leptons if M(H) > 135 GeV

14 Martin zur Nedden, HU Berlin 14 WS 2007/08: Physik am LHC Upper Limit for Higgs production at TEVATRON if M(H) < 135 GeV

15 Martin zur Nedden, HU Berlin 15 WS 2007/08: Physik am LHC Higgs Cross Sections at LHC gluon-gluon fusion vector boson fusion

16 Martin zur Nedden, HU Berlin 16 WS 2007/08: Physik am LHC Higgs: Signal to background ratio at LHC for M(Higgs) = 150 GeV: S/B <

17 Martin zur Nedden, HU Berlin 17 WS 2007/08: Physik am LHC Higgs to 2 Z and 4 Leptons CMS TDR Very clean an good measurabe event signature: 4 high p T leptons, 2 invariant masses at M Z

18 Martin zur Nedden, HU Berlin 18 WS 2007/08: Physik am LHC Gluon-Gluon Fusion to 4 Leptonen (Atlas/LHC) Atlas TDR invariant masse (ZZ 4 l) Background, not to distinguish from Higgs-Signal: qq ZZ 4 leptons

19 Martin zur Nedden, HU Berlin 19 WS 2007/08: Physik am LHC Higgs to 2 Gamma CMS also very clean signature, but small cross section: 2 high p T isolated EMC-clusters

20 Martin zur Nedden, HU Berlin 20 WS 2007/08: Physik am LHC Gluon/Gluon Fusion to 2 Gamma (Atlas/LHC) ATLAS TDR Background: Not reducable: pp γγX Reducable: pp γJγJ

21 Martin zur Nedden, HU Berlin 21 WS 2007/08: Physik am LHC Vector-Boson Fusion: Decay to 2 W-Bosons H WW e Atlas TDR H WW l l υ υ (l υ qq ) Signature: Jets + 2 high p T leptons + MET No mass peak (MET from neutrino), calculate the transverse mass Background: tt, Wt, WWJJ production

22 Martin zur Nedden, HU Berlin 22 WS 2007/08: Physik am LHC Higgs to 2 Tau H ττ e : H ττ l l + 4ν (l +J +3ν) Atlas TDR 2 high p T leptons, big MET Mass reconstruction possible, even with high MET Background: Zjj, tt

23 Martin zur Nedden, HU Berlin 23 WS 2007/08: Physik am LHC Higgs Discovery potential of LHC/ATLAS Dependency on Higgs mass and decay channel

24 Martin zur Nedden, HU Berlin 24 WS 2007/08: Physik am LHC Discovery potential of ATLAS/LHC Dependency of Higgs-mass and Luminosity LEP2 excluded


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