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 collider γγ H* HH Is there any advantage in the HHH determination? Sensitivity study Summary
Electroweak Symmetry Breaking SM Gauge structure: SU(3)C SU(2)I U(1)Y EWSB: SU(2)I U(1)Y U(1)EM SM Higgs sector A Higgs doublet Fields obtain masses from VEV. Light Higgs Weak coupling Heavy Higgs Strong coupling Gauge interaction (Higgs mechanism) Yukawa interaction
Mass-Coupling relation in the SM All masses are given in proportion to the unique VEV Not measured The SM is tested by using this universality In general, this relation does not hold in extended Higgs models. Measure both the mass and the coupling independently!
LEP Constraint Direct search Indirect constraint via the oblique correction
Higgs self-coupling SM Higgs potential Electroweak Symmetry Breaking Free parameter of the SM λ It is important to measure independently both the mass m h and the coupling hhh (and hhhh) Test for the SM Higgs potential Nature of the EWSB, New physics determination
New Physics Hierarchy problem (Λ=10 16-19 GeV) Radiative correction to the mass of H (spin 0) But m H is O(100)GeV H ~Λ 2 H Strange! It is difficult to believe that the SM holds up to very high energy. New physics is expected to appear at TeV scales. Scenarios for NP SUSY (boson fermion) Dynamical SB (Higgs = composite) Little Higgs (Higgs=pseudo NG boson). 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 2HDM 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. SK, Kiyoura,Okada,Senaha,Yuan
Decoupling/Non-decoupling Λ: Cutoff M: Mass scale irrelevant to VEV Non-decoupling effect
MSSM New Physics Effect
Cosmological Connections Higgs Effective Potential Electroweak Phase Transition at Early Universe SM λ HHH A large δλ HHH 2 nd Order Strong 1 st Order Electroweak Baryogenesis requires a strong 1 st 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 Required accuracy λ=λ SM + δλ = λ SM (1+ δκ)
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. Precision measurement of the HHH coupling is business of the ILC. Bauer, Plehn, Rainwater
Measurement at the ILC collision Two Production Mechanisms HH-Strahlung HH-Fusion
Measurement at the ILC Anomalous λ dependences HH-strahlung HH-fusion
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/0412251 CLIC Physics WG
HHH measurement at the γγ collider Asakawa, Harada, SK, Okada, Tsumura We discuss a possibility to measure the Higgs tri-linear coupling via the process of γγ HH at the ILC photon collider option. Alternative or better as compared to that in the e+ecollision? 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.
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 ~ L e+e- /3 Helicity amplitude
Process SM diagrams G.V.Jikia Helicity amplitudes
Sub-Process
Sub-Process 6.5 ++ Root(s)=1.5 TeV mh=730gev 0.32 0.28 400 σ(γγ HH) (fb) 5.5 4.5 δκ= 1 0.3 σ(γγ HH) (fb) 0.24 0.2 0.16 0.12 450 mh=500gev 3.5 2.5 1 0.5 0 0.5 1 cosθ 0 +0.3 Anomalous coupling parameter δκ +1 0.08 0.04 + Root(s)=1.5TeV 0 1 0.5 0 0.5 1 cosθ δκ does change cross sections, but does not affect angular distribution
Photon structure function Ginzburg, et. al Full Cross Section
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 E ee.
The best E ee for each m H mh=160 GeV Full Cross Section becomes large for Eee=450-500 GeV Photon Structure Funciton 3 dl γγ /dz x=4.8 k 2 L ee ( 1, 1) 2 (0. 1) 1 (0,0) (2λ 1 P c1,2λ 2 P c2 ) (0, 1) 0 0 0.2 0.4 0.6 0.8 1 z=w γγ /2E E ee
The best E ee for each m H mh=200gev Full Cross Section becomes large for Eee=550-600 GeV Photon Structure Funciton 3 dl γγ /dz x=4.8 k 2 L ee ( 1, 1) 2 (0. 1) 1 (0,0) (2λ 1 P c1,2λ 2 P c2 ) (0, 1) 0 0 0.2 0.4 0.6 0.8 1 z=w γγ /2E E ee
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 m H =120GeV WW O(10-100) pb m H =200GeV WWWW O(10-100) fb Reduction by invariant mass kinematic cuts and
Backup Slide 1
Sensitivity Backup Slide 2
HHH, HHHH Measurement at the LHC
Sub-Process 1 10 0 ++ Root(s)=500Ge mt=150gev 10 0 ++ root(s)=1000gev 10 1 ++ Root(s)=2000GeV mt=150gev σ(γγ HH) (fb) 10 1 top loop W loop σ(γγ HH) (fb) 10 1 top loop both σ(γγ HH) (fb) 10 0 10 1 both W loop top loop W loop 10 2 50 100 150 200 250 mh (GeV) 10 2 50 150 250 350 450 mh (GeV) 10 2 0 200 400 600 800 1000 mh (GeV) 10 0 10 0 10 0 both combined combined σ(γγ HH) (fb) 10 1 10 2 + Root(s)=500GeV mt=150gev W loop top loop σ(γγ HH) (fb) 10 1 10 2 + Root(s)=1000GeV mt=150gev W loop top loop σ(γγ HH) (fb) 10 1 10 2 + Root(s)=2TeV mt=150gev W loop top loop 10 3 50 100 150 200 250 mh (GeV) 10 3 50 150 250 350 450 mh (GeV) 10 3 50 250 450 650 850 mh (GeV)
Full Cross Sections (m H, E ee dependences)