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Romain Contant Supervisor: Stéphane Péries Phenomenological study of scalar and pseudo-scalar particle decaying into top-antitop pairs Sommaire 1 Introduction 2 New physics effects 3 Experimental Constrains 4 The Two Higgs Doublets Model 5 The Minimal Supersymetric Standard Model 6 The Next-to-Minimal Supersymetric Standard Model 7 Conclusion Contant Romain 1 Introduction The Standard Model The Standard Model describe the sub-atomic world In excellent agreement with experimental measurements Tested with remarkable accuracy Discovery of the Higgs boson at the LHC in 2012 However the SM ignore many physical observed phenomena The gravitational interaction Matter-antimatter asymmetry No dark matter Neutrinos mass And suffer from theoretical problem in the Higgs sector Introduce an ad hoc potential in the theory The fine-tuning problem Some Beyond Standard Model effects can occur at the electroweak scale 1/19 Contant Romain 1 Introduction Context of the study Search for new spin 0 particle Predicted by Supersymetric models Predicted by model with additional interaction Predicted by models with extra dimension Top quark sector as a window to new physics The top is the heaviest fundamental particle The top has a special position in the SM We focus only on «what can be observable» in the LHC How to produce spin 0 particle in a hadronic collider ? 2/19 Contant Romain 2 New physics effects 3/19 g t g t g t g t ϕ g t g New physics t SM background The existence of interferences between the new physics effects and top quark production mechanisms in the Standard Model induce a «peak-hole» structure BSM top pair invariant mass 20 19 SM top pair invariant mass 18 17 We need to specify what type of production mechanisme we will consider 16 15 14 450 500 550 600 650 700 Contant Romain 2 New physics effects Production mechanisme g 4/19 g t t ϕ ϕ g t t g Parameters : We define : ∼ ∼ The typical «peak-hole» Complex structur we can go further and study the cross section evolution Contant Romain 2 New physics effects Cross section evolution ∼ 5/19 ∼ ∼ ∼ Constrained the fit but need an huge amount of cpu-time It’s necessary to find realistical new physics parameters Contant Romain 3 Experimental constraints The SM Higg coupling and direct search 6/19 Many BSM predict the existence of new scalar fields and modify the standard Higgs coupling to Standard Model particles The standard model Higgs couplings were measured at the LHC by ATLAS and CMS collaboration We introduce a test .... We define : but and depend on the tree level coupling So it’s necessary to define a new parametrisation for the loopinduced processe. This new parametrisation is BSM-dependent We select only values at one σ from the experimental results Direct search for spin 0 particle at LEP / TEVATRON / LHC in VV / ff / γγ Contant Romain 3 Experimental constraints Low energie measurement 7/19 The BSM studied predict the existence of new particles and change the standard Higgs coupling to Standard Model particles The oblique parameters (STU) Measure the effect on new physics through the vacuum polarization The anomalous magnetic dipole moment of the muon has reached a level of precision wich is sensitive to supersymetric contribution Flavor Violation in the bottom quark sector H BSM theory with new scalar multiplets predict new contribution of FV - γ t b H- b s _ s s μ νμ μ H+ Contant Romain 4 The Two Higgs Doublets Model 8/19 The Two Higgs Doublets Model assume the existence of an extra Higgs doublet compared to the Standard Model We limit our study to a potential with a discrete symmetry ℤ2 Predict 5 spin 0 particles Two scalar state. The lightest is the one discovered at the LHC A pseudo-scalar state, unprecedented compared to the Standard Model Two state, electrically charged Change the Higgs coupling to SM particules Through an angle of mixing between the two doublets of scalar field : β Through an angle of mixing between the two scalar state : α Contant Romain 4 The Two Higgs Doublets Model Theoretical results The new scalar particle has strong branching ratio for sin(β-α) = ±1 The pseudo-scalar particle has a wide range of usable parameters 9/19 Contant Romain 4 The Two Higgs Doublets Model Experimental constraints 10/19 Exclude all values of tan(β) < 1 Constraints Promote high masses of electrically charged Higgs for values of tan(β) close to 1 Direct search for new spin 0 particles exclude all values of sin(β-α) not close to ±1 The With all the constrains, we obtain : test exclude all values of tan(β) too far to 1 Contant Romain 5 The Minimal Supersymetric Standard Model 11/19 Supersymmetrie is an ambitious theory that provide : An unification of the running gauge couplings at the GUT scale A possibility to explain the dark matter relic density A solution of the hierarchy problem The MSSM for the higgs sector is special case of 2HDM We consider two special parametrization of the MSSM spectrum Split-SuSy High-Scale SuSy h0 H0 / A0 / Hp M1 M2 M3 h0 H0 / A0 / Hp stop M1 M2 M3 This two parametrization allow : A lighter higg boson state at (125±3) GeV Sufficently heavy first neutralinos state to not participate to the decaying of the new Higgs particle A low tan(β) regime Contant Romain 5 The Minimal Supersymetric Standard Model Theoretical Result for High scale SUSY 12/19 Diffculty to obtain a (125±3)GeV Higgs bosons Existence of an huge gap in the mass of the lightest Higgs boson distribution Difficulty to obtain large tan(β) values And there is a significant correlation between the particles masses (quasi-degenerated state) The theoritical results is equivalent to the 2HDM results with sin(β-α) close to 1 Contant Romain 5 The Minimal Supersymetric Standard Model Experimental constraints for High scale SUSY 13/19 Experimental values : (3.43±0.9) 10^(-4) The FV become less important if : mh+ is really heavy In this case : mH and mA will be too heavy tan(β) is important In this case, the relative coupling to the top will be too small to be observable The theoretical results do not pass the experimental constraints Split-SUSY Contant Romain 5 The Minimal Supersymetric Standard Model Theoretical Result for Split-SUSY 14/19 The results are similar to High Scale SuSy The gap is less important We can easily obtain large tan(β) values The correlation between the Higgs masses are less important Contant Romain 5 The Minimal Supersymetric Standard Model Experimental constraints for Split-SUSY 15/19 Experimental values : (3.43±0.9) 10^(-4) Same results as before FV in the MSSM are too important for the low tan(β) regime As before : the theoretical results do not pass the experimental constraints A low tan(β) regime and a (125±3)GeV Higgs boson is difficult to reconcile with the experimental constraints We need a more «flexible» theory We will consider the Next-to-Minimal Supersymetric Model Contant Romain 6 The Next-to-Minimal Supersymetric Standard Model Présentation du modèle With an additional singlet in the Higgs sector, the MSSM become the NMSSM Predict 7 spin 0 state Three scalar state Two pseudo-scalar state Two electrically charged state That mean 4 mixing angles Between the doublet of scalar fields Two to diagonalize the scalar sector Between the pseudo-scalar sector We consider the parametrization «Split-SuSy» h1 h2 / h3 / a1 / a2 stop M1 M2 M3 16/19 Contant Romain 6 The Next-to-Minimal Supersymetric Standard Model The lightest new spin 0 states The study of the new lighter state give : The branching ratio of the pseudo-scalar particule is really close to 1 The couplings are too small to be observable The branching ratio of the scalar particle are too small to be observable 17/19 Contant Romain 6 The Next-to-Minimal Supersymetric Standard Model Heaviest spin 0 state 18/19 The study of the heaviest spin 0 particles give : For heavy particle ( > 900 GeV) we can see a wide range of hight coupling and branching ratio for scalar and pseudo-scalar This new parameters space remains after the implementation of the experimental constrains Contant Romain 7 Conclusion 19/19 We notice a realistical and interesting range of parameters for the 2HDM and NMSSM The search for new spin 0 particle in the top channel is necessary to constrain Supersymetrical theory (and new multiplets scalar fields ...) The top channel is able to see the decoupling limits of new scalar multiplets theory The top channel is able to see new pseudo-scalar state The same study can be made for : More complex parametrization of these model Consider other Yukawa-type for the 2HDM Take into account a more complex supersymetric spectrum Other BSM theory : Higgs Composite Little Higgs Randall Sundrum 2HDM couplings NMSSM couplings 2HDM Software: 2HDMC SuperIso NMSSM Software: NMSSMTools Fine-tunnig Correlation of mass in the 2HDM NMSSM Direct search of new particles for the 2HDM(II) Low energie direct constraints