SUPERSYMMETRIC EXTENSION OF THE STANDARD MODEL

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SUPERSYMMETRIC EXTENSION OF THE STANDARD MODEL

• DMITRI KAZAKOV
• JINR / ITEP

Outline

• What is SUSY
• Motivation of SUSY
• The MSSM
• SUSY Searches
• SUSY in Astrophysics

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What is SUSY

• Supersymmetry is a boson-fermion symmetry
• that is aimed to unify all forces in Nature
  including
• gravity within a singe framework
• Modern views on supersymmetry in particle
  physics
• are based on string paradigm, though low energy
• manifestations of SUSY can be found (?) at modern
• colliders and in non-accelerator experiments
• The concepts of Quantum Field Theory allow SUSY
• without any restrictions
• There is no direct confirmation of SUSY but
  this does
• not stop theorists due to extreme beauty of
  SUSY models

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Supersymmetry
Local translation general
relativity !
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The Standard Model

• Fits the experimental data very well
• Has too many free parameters and unexplained
  features
• The Higgs boson is still missing

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Comparison with Experiment
Global Fit to Data
Higgs Mass Constraint
Though the values of sin ?w extracted from
different experiments are in good agreement, two
most precise measurements from hadron and lepton
asymmetries disagree by 3?
Remarkable agreement of ALL the data with the SM
predictions - precision tests of radiative
corrections and the SM
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The SM and Beyond
The problems of the SM

• Inconsistency at high energies due to Landau
  pole
• Large number of free parameters
• Formal unification of strong and electroweak
  interactions
• Still unclear mechanism of EW symmetry breaking
• CP-violation is not understood
• Flavour mixing and the number of generations is
  arbitrary
• The origin of the mass spectrum in unclear

The way beyond the SM

• The SAME fields with NEW
• interactions

GUT, SUSY, String

• NEW fields with NEW
• interactions

Compositeness, Technicolour,
preons
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We like elegant solutions
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Motivation of SUSY in Particle Physics

• Unification with Gravity

• Unification with Gravity
• Unification of gauge couplings
• Solution of the hierarchy problem
• Dark matter in the Universe
• Superstrings

Unification of matter (fermions) with forces
(bosons) naturally arises from an attempt to
unify gravity with the other interactions
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Motivation of SUSY in Particle Physics

• Unification of gauge couplings

Running of the strong coupling
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Motivation of SUSY
RG Equations
Input
Output
SUSY yields unification!
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Motivation of SUSY

• Solution of the Hierarchy Problem

Cancellation of quadratic terms
Destruction of the hierarchy by Radiative
corrections
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Motivation of SUSY

• Dark Matter in the Universe

The flat rotation curves of spiral galaxies
provide the most direct evidence for the
existence of large amount of the dark matter.
Spiral galaxies consist of a central bulge and a
very thin disc, and surrounded by an
approximately spherical halo of dark matter
SUSY provides a candidate for the Dark matter
a stable neutral particle
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Particle Content of the MSSM
sleptons
leptons
squarks
quarks
Higgses
higgsinos
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SUSY Shadow World
One half is observed!
One half is NOT observed!
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SUSY Lagrangians
Superfields
Components
Potential
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The MSSM Lagrangian
The Yukawa Superpotential
superfields
Yukawa couplings
Higgs mixing term
R-parity
B-Bartion Number L-Lepton Number S-Spin
The Usual Particle R 1 SUSY Particle
R - 1
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R-parity Conservation
The consequences

• The superpartners are created in pairs
• The lightest superparticle is stable

Physical output
The lightest superparticle (LSP)
should be neutral - the best
candidate is
neutralino (photino or higgsino)
It can survive from the Big Bang
and form the
Dark matter in the Universe
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Interactions in the MSSM
Creation of superpartners
Interaction Vertices
Decay of superpartners
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Soft SUSY Breaking
Hidden Sector Scenario
SUGRA
The Universal Soft Parameters
and
Versus
and
in the SM
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Mass Spectrum
Neutralino
Chargino
Squarks Sleptons
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SUSY Higgs Bosons
SM
MSSM
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The Higgs Potential
Minimization
Solution
At the GUT scale
No SSB in SUSY theory !
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Radiative EW Symmetry Breaking
Due to RG controlled running of the mass terms
from the Higgs potential they may change sign
and trigger the appearance of non-trivial
minimum leading to spontaneous breaking of EW
symmetry - this is called Radiative EWSB
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Constrained MSSM
Requirements

• Unification of the gauge couplings
• Radiative EW Symmetry Breaking
• Heavy quark and lepton masses
• Rare decays (b -gt s?)
• Anomalous magnetic moment of muon
• LSP is neutral
• Amount of the Dark Matter
• Experimental limits from direct search

Allowed region in the parameter space of the MSSM
Parameter space
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SUSY Fits
Minimize
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Low and High tanß Solutions

• Requirements
• EWSB
• bt unification

Low tanß solution
High tanß solution

• bt unification is the
• consequence of GUT
• Non working for the
• light generations

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Allowed Regions in Parameter Space
All the requirements are fulfilled
simultaneously !

• µ is defined
• from the EWSB

- is the best fit value
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Masses of Superpartners
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Mass Spectrum in CMSSM
SUSY Masses in GeV
Fitted SUSY Parameters
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SUSY Searches

• m? ? 100 GeV
• m?0 ? 40 GeV
• mg ? 300 GeV

• mq ? 300 GeV
• ml ? 100 GeV

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SUSY Production at Hadron Colliders
Annihilation channel
Gluon fusion, qq scattering and qg scattering
channels
No new data so far due to insufficient
luminocity at the Tevatron
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The Higgs Mass Limit

• Indirect limit from radiative corrections
• Direct limit from Higgs non-observation
  at LEP II (CERN)

113 lt mH lt 200 GeV
At 95 C.L.
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The Higgs Mass Limit
(Theory)

• The SM Higgs
• mH ? 134 GeV

? SUSY Higgs mH ? 130 GeV
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Higgs Searches

• mH ? 113.4 GeV at 95 C.L.

114 -115 GeV Event
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Allowed Regions Renewed

• from the
• Higgs limit at LEP
• µgt0 from

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Cosmological Constraints
New precise cosmological data

• Supernova Ia explosion
• CMBR thermal fluctuations

(recent news from WMAP )
Hot DM (not favoured by galaxy formation)
Dark Matter in the Universe
Cold DM (rotation curves of Galaxies)
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SUSY Fits to Dark Matter
Results in severe constraints on parameter space
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SUSY Search in Space
Cosmic ray spectrum at high energies
Excess
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Positrons from Neutralinos of the Dark Matter
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AMS Antimatter Search in Space at ISS
Will be able to check SUSY Dark matter predictions
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Superparticles
Discovery of the new world of SUSY
Back to 60s New discoveries every year