higgs phenomenology & new...
TRANSCRIPT
Higgs phenomenology & new physics
Shinya KANEMURA(Univ. of Toyama)
KEKTH07, Dec. 13. 2007
Content of talk• Introduction
– Electroweak Symmetry Breaking– Physics of Higgs self-coupling
• Self-coupling measurement at collider experiments– LHC– ILC
• Possibility of measuring HHH at a γγ colliderγγ→ H*→ HH
Is there any advantage in the HHH determination?Sensitivity study
• Summary
Electroweak Symmetry BreakingSM Gauge structure: SU(3)C×SU(2)I×U(1)Y
EWSB: SU(2)I×U(1)Y → U(1)EM
SM Higgs sectorA Higgs doublet
Light Higgs → Weak couplingHeavy Higgs → Strong coupling
Fields obtain masses from VEV.
Gauge interaction(Higgs mechanism)
Yukawa interaction
Mass-Coupling relation in the SM
All masses are given in proportion to the unique VEV
The SM is tested by usingthis universality
In general, this relation does not hold in extended Higgs models.
Not measured
Measure both the mass and the coupling independently!
LEP Constraint
Indirect constraint via the oblique correction
Direct search
Higgs self-coupling
• SM Higgs potential – Electroweak Symmetry Breaking
– Free parameter of the SM λ
• It is important to measure independently both the mass mh and the coupling hhh (and hhhh)– Test for the SM Higgs potential– Nature of the EWSB, – New physics determination
Hierarchy problem (Λ=1016-19GeV)
– Scenarios for NP• SUSY (boson ⇔ fermion)• Dynamical SB (Higgs = composite)• Little Higgs (Higgs=pseudo NG boson)• ….
New Physics
Radiative correction to the mass of H (spin 0)
~Λ2
H H
Strange!
But mH is O(100)GeV
It is difficult to believe that the SM holds up to very high energy.
New physics is expected to appear at TeV scales.
These models of new physics deduce a special extended Higgs sector in the low energy effective theory
New Physics effect on the HHH coupling
Effective Theory Genuine dim-6 operators
T. Han et al
Quantum Correcitons to HHH(Non-decoupling effect)
The Higgs self-coupling receives large quantum corrections
New Physics effect on the triple Higgs boson coupling
The hhh coupling is sensitive to loop effects.
New particles with similar properties also give large effects in the hhh prediction (2HDM etc)
Large deviations (several 10 % - 100%) can easily appear.
2HDM
SK, Kiyoura,Okada,Senaha,Yuan
Decoupling/Non-decoupling
Non-decoupling effect
Λ: CutoffM: Mass scale
irrelevant to VEV
New Physics Effect
MSSM
Cosmological Connections• Higgs Effective Potential• Electroweak Phase Transition
at Early Universe– SM λHHH A large δλHHH
– 2nd Order ⇔ Strong 1st Order – Electroweak Baryogenesis requires a
strong 1st Order PT (For avoiding sphaleron smearing in broken phase)
– 2HDM – Dim-6 Operator (Grogean, Sevant, Wells,)– MSSM (Nelson et al; Carena et al, …..)
SK, Okada, Senaha
⇒
Measurement of the HHH coupling
• Higgs self-coupling (HHH, HHHH)– Direct information to the Higgs potential– Effect on the New Physics– Cosmological Connection
• Measurement at collider experiments– LHC– ILC
• Alternative possibility: ILC (γγ option)• Sensitivity to anomalous deviations of λ
λ=λSM + δλ = λSM (1+ δκ)
Required accuracy
HHH measurement at LHC• Decays into gauge boson
pairs • Hopeless for a light H• Intermediate masses:
Non-vanishing of λ can be established at the LHC.
Bauer, Plehn, RainwaterPrecision measurement of the HHH coupling is
business of the ILC.
Measurement at the ILC
HH-Strahlung HH-Fusion
Two Production Mechanisms
collision
Measurement at the ILC
HH-strahlung HH-fusion
Anomalous λ dependences
Higgs potential reconstruction• Sensitivity to new physics is large in the triple Higgs
coupling (HHH). • Naively, NP effects on the quartic coupling (HHHH) is
6 times greater than those on the hhh coupling.
– Possible to measure the hhhh coupling ?– Unfortunately very challenging.
(even at a multi TeV collider)– Any idea is required.
hep-ph/0412251CLIC Physics WG
HHH measurement at the γγ collider
• We discuss a possibility to measure the Higgs tri-linear coupling via the process of
γγ→HHat the ILC photon collider option.
– Alternative or better as compared to that in the e+e-collision? Jikia, Jikia and Belusevic
– Can new physics effects on γγ→HH drastically change SM predictions?
– Valuable for a simulation study?• Study is now developing.
– The results are preliminary.
Asakawa, Harada, SK, Okada, Tsumura
Study HHH at a photon collider
Difference from ZHH and HHνν production at ILC– Loop induced process
• Theoretical interests• Direct new physics loop
contribution to the γγH (loop induced) couplings• Different δλ dependences from the e+e- collision
⇒ different sensitivity property
– Two body final state• There is kinematical advantage, even though a loop
suppression and also even though Lγγ ~ Le+e-/3
– Helicity amplitude
Process
SM diagrams
Helicity amplitudes
G.V.Jikia
Sub-Process
Sub-Process
−1 −0.5 0 0.5 1cosΘ
2.5
3.5
4.5
5.5
6.5
σ(γγ
→H
H)
(fb
)
++ Root(s)=1.5 TeVmH=730GeV
δκ=−1
−0.3
0
+0.3
+1
−1 −0.5 0 0.5 1cosΘ
0
0.04
0.08
0.12
0.16
0.2
0.24
0.28
0.32
σ(γγ
→H
H)
(fb
)
+− Root(s)=1.5TeV
mH=500GeV
450
400
Anomalous coupling parameter δκδκ does change cross sections, but does not affect angular distribution
Full Cross Section Photon structure function
Ginzburg, et. al
Full cross sections (δκ dependences)
Anomalous coupling parameter δκ
In some cases, sensitivity to δκ looks large
Full Cross Section 2
Estimation of HHH sensitivity
Estimation of HHH sensitivity• At the ILC, energies of
initial electron and laser can be changed.
• After H is found, mH is known. Then we can examine the HHH coupling by selecting the best Eee.
The best Eee for each mH
mH=160 GeV
Full Cross Section becomes large for Eee=450-500 GeV
0 0.2 0.4 0.6 0.8 1z=Wγγ/2E
0
1
2
3
dLγγ/dz
k2Lee
x=4.8
(−1,−1)
(0.−1)
(0,0)
(0,−1)
(2λ1Pc1,2λ2Pc2)
↑Eee
Photon Structure Funciton
The best Eee for each mH
mH=200GeV
Full Cross Section becomes large for Eee=550-600 GeV
0 0.2 0.4 0.6 0.8 1z=Wγγ/2E
0
1
2
3
dLγγ/dz
k2Lee
x=4.8
(−1,−1)
(0.−1)
(0,0)
(0,−1)
(2λ1Pc1,2λ2Pc2)
Photon Structure Funciton
↑Eee
New Physics effects on
– New physics loop effect can be large, because the SM contributions are also loop-induced.
– New Physics contribution changes not only the size of the cross section but also (delicate) balance between the pole and the box diagrams.
HHH sensitivity could greatly depend on the model
in new physics models
Extended Higgs models: 2HDM – additional charged scalar loop effect– non-decoupling features
Pure Dim-6 operator effects – Two operators of pure HHH dim6-coupling– Momentum dependences of the effective HHH coupling
Other models: SUSY, …– charged new particle effects
Simulation study
Complementarity with ZHH, ννHH study
Summary• Higgs self-coupling (HHH, HHHH)
– Nature of SSB (Higgs potential)– Probe of new physics
• HHH measurements– LHC: Difficult – ILC studies for ZHH, ννHH
• Possibility of measuring HHH at a γγ collider– Consistent with previous works in the SM Jikia, Belusevic– Sensitivity study for the anomalous λ coupling (Preliminary)– For mH > 150 GeV, can be useful with better sensitivity
than that at the 500 GeV e+e- collider– Backgrounds
mH=120GeV WW O(10-100) pbmH=200GeV WWWW O(10-100) fb
Reduction by invariant mass kinematic cuts and …
Backup Slide 1
Backup Slide 2• Sensitivity
HHH, HHHH Measurement at the LHC
Sub-Process 1
50 100 150 200 250mH (GeV)
10−2
10−1
100
σ(γ
γ→H
H)
(fb
)
++ Root(s)=500Ge
W−loop
mt=150GeV
top−loop
50 150 250 350 450mH (GeV)
10−2
10−1
100
σ(γ
γ→H
H)
(f
b)
W−loop
top−loop
both
++ root(s)=1000GeV
0 200 400 600 800 1000mH (GeV)
10−2
10−1
100
101
σ(γ
γ→H
H)
(f
b)
++ Root(s)=2000GeV
mt=150GeV
top−loop
W−loopboth
50 100 150 200 250mH (GeV)
10−3
10−2
10−1
100
σ(γ
γ→H
H)
(f
b)
+− Root(s)=500GeVmt=150GeV
both
top−loop
W−loop
50 150 250 350 450mH (GeV)
10−3
10−2
10−1
100
σ(γ
γ→H
H)
(f
b)
+− Root(s)=1000GeV
combined
top loop
W loop
mt=150GeV
50 250 450 650 850mH (GeV)
10−3
10−2
10−1
100
σ(γ
γ→H
H)
(f
b)
+− Root(s)=2TeV
mt=150GeV
combined
top loop
W loop
Full Cross Sections (mH, Eee dependences)