Download Phenomenological study of scalar and pseudo

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
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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
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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
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New physics effects
3/19
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t
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t
ϕ
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t
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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
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SM top pair invariant mass
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We need to specify what
type of production
mechanisme we will
consider
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450
500
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700
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New physics effects
Production mechanisme
g
4/19
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t
t
ϕ
ϕ
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Parameters :
We define :
∼
∼
The typical «peak-hole»
Complex structur
we can go further and study
the cross section evolution
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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
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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
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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+
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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
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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
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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
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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
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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
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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
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The Minimal Supersymetric Standard Model
Theoretical Result for Split-SUSY
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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
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The Minimal Supersymetric Standard Model
Experimental constraints for Split-SUSY
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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
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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
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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
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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
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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