Martin zur Nedden, HU Berlin 1 WS 2007/08: Physik am LHC 5. Higgs Searches The Higgs-mechanism in...

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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: Searches at TEVATRON Higgs decay channels Coupling constants Branching ratios Higgs search at the LHC

Transcript of Martin zur Nedden, HU Berlin 1 WS 2007/08: Physik am LHC 5. Higgs Searches The Higgs-mechanism in...

Page 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:

Martin zur Nedden, HU Berlin 1WS 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

Page 2: 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:

Martin zur Nedden, HU Berlin 2WS 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+ , Φ0

4 real components Φ1, …Φ4, produce mass in symmetry breaking due to self-interaction

• Goldstone/Higgs-mechanism: 3 components absorbed in the longitudinal

polarization of the massive 3 Wi-bosons• 1 physical state H remains • coupling to mass with gffH

• No prediction of Higgs mass by SM

00

2

1H

HgHff

Page 3: 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:

Martin zur Nedden, HU Berlin 3WS 2007/08: Physik am LHC

Yukava coupling, Mass of Fermions

),,( 0

0L

eRRLe eeeeGL

)(22)(

0

2

1xheeee

Geeeev

GL

xhv LRRLe

LRRLe

)(2

xheev

meemL

vGm e

ee

e

mnew term in Lagrangien needed: excluded due to gauge invariance

eR(T=0, Y=-2)

eL(T=1/2, Y=-1)

h0 (T=1/2, Y=1)

igme/(2MW)igMW

W

W

(Singlet in I,Y)

choose:

Coupling to the higgs field

h0

Page 4: 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:

Martin zur Nedden, HU Berlin 4WS 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 Φc

Page 5: 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:

Martin zur Nedden, HU Berlin 5WS 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)

Page 6: 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:

Martin zur Nedden, HU Berlin 6WS 2007/08: Physik am LHC

Higgs – Decay Channels

(H VV) ~ GF M3H

(H γγ) ~ α2 GF M3H

(H ff) ~ GF m2f MH

Page 7: 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:

Martin zur Nedden, HU Berlin 7WS 2007/08: Physik am LHC

Possible Higgs Decays / coupling constants

ffH 0

WWH 0

/0 ggH

WW

f

Hff M

emg

sin2

W

WWWH

eMg

sin

WW

ZZZH

eMg

cossin

22

1

2

2

)2(228 WFWWHF

W

MGgG

M

g

Page 8: 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:

Martin zur Nedden, HU Berlin 8WS 2007/08: Physik am LHC

Decay Width of Different Higgs Channels

2

3

2

22

)4

1(24

)(H

fHfFc M

mMmGNffH

)124

1()41(28

)(4

4

2

22

1

2

23

H

W

H

W

H

WHF

M

M

M

M

M

MMGWWH

)124

1()4

1(216

)(4

4

2

22

1

2

2

2

2300

H

Z

H

Z

H

Z

Z

WHF

M

M

M

M

M

M

M

MMGZZH

2

2

2

2

22

3

32

)()(32128

)(H

WW

H

qqq

q

HF

M

MI

M

mIe

MGH

Calculations in the standard model:

Page 9: 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:

Martin zur Nedden, HU Berlin 9WS 2007/08: Physik am LHC

Higgs Decay Channels: Branching Ratios

Page 10: 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:

Martin zur Nedden, HU Berlin 10WS 2007/08: Physik am LHC

Higgs Decay in the Standard Modell

fermions

bosons

decay width branching ratio

Page 11: 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:

Martin zur Nedden, HU Berlin 11WS 2007/08: Physik am LHC

Higgs Search Strategies

bbHZpp *

Good channel for TEVATRON:

M(H) > 135 GeV: H WWM(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

Page 12: 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:

Martin zur Nedden, HU Berlin 12WS 2007/08: Physik am LHC

Cross Sections at TEVATRON

Page 13: 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:

Martin zur Nedden, HU Berlin 13WS 2007/08: Physik am LHC

Higgs Search at TEVATRON, upper Limit

signal: 2 b-Jet + MET + 2 leptons

if M(H) > 135 GeV

Page 14: 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:

Martin zur Nedden, HU Berlin 14WS 2007/08: Physik am LHC

Upper Limit for Higgs production at TEVATRON

if M(H) < 135 GeV

Page 15: 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:

Martin zur Nedden, HU Berlin 15WS 2007/08: Physik am LHC

Higgs Cross Sections at LHC

gluon-gluon fusion

vector boson fusion

Page 16: 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:

Martin zur Nedden, HU Berlin 16WS 2007/08: Physik am LHC

Higgs: Signal to background ratio at LHC

for M(Higgs) = 150 GeV:

S/B < 10-10

Page 17: 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:

Martin zur Nedden, HU Berlin 17WS 2007/08: Physik am LHC

Higgs to 2 Z and 4 Leptons

CMS TDR

Very clean an good measurabe event signature:4 high pT leptons, 2 invariant masses at MZ

Page 18: 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:

Martin zur Nedden, HU Berlin 18WS 2007/08: Physik am LHC

Gluon-Gluon Fusion to 4 Leptonen (Atlas/LHC)

Atlas TDR

invariant masse (ZZ 4 l)

Background, not todistinguish from Higgs-Signal:qq ZZ 4 leptons

Page 19: 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:

Martin zur Nedden, HU Berlin 19WS 2007/08: Physik am LHC

Higgs to 2 Gamma

CMS

also very clean signature, but small cross section:2 high pT isolated EMC-clusters

Page 20: 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:

Martin zur Nedden, HU Berlin 20WS 2007/08: Physik am LHC

Gluon/Gluon Fusion to 2 Gamma (Atlas/LHC)

ATLAS TDR

Background:Not reducable: pp γγXReducable: pp γJγJ

Page 21: 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:

Martin zur Nedden, HU Berlin 21WS 2007/08: Physik am LHC

Vector-Boson Fusion: Decay to 2 W-Bosons

H WW e

Atlas TDRH WW l l υ υ (l υ qq )

Signature:Jets + 2 high pT leptons + MET

No mass peak (MET from neutrino), calculate the transverse mass

Background:tt, Wt, WWJJ production

Page 22: 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:

Martin zur Nedden, HU Berlin 22WS 2007/08: Physik am LHC

Higgs to 2 Tau

H ττ e :

H ττ l l + 4ν (l +J +3ν)

Atlas TDR

2 high pT leptons, big MET

Mass reconstruction possible, even with high MET

Background:Zjj , tt

Page 23: 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:

Martin zur Nedden, HU Berlin 23WS 2007/08: Physik am LHC

Higgs Discovery potential of LHC/ATLAS

Dependency on Higgs mass and decay channel

Page 24: 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:

Martin zur Nedden, HU Berlin 24WS 2007/08: Physik am LHC

Discovery potential of ATLAS/LHC

Dependency of Higgs-mass and Luminosity

LEP2 excluded