SUSY

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LHC
SUSY
_at_
The Challenge
Dmitri Kazakov
JINR / ITEP
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What comes beyond the SM?
SUSY main stream and main expectation at TeV
scale
LHC ultimate TeV scale machine to discover new
physics
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What is SUSY?
SUSY is boson-fermion symmetry
Bosons and Fermions come in pairs
Spin 0
Spin 1/2
Spin 1
Spin 1/2
Spin 3/2
Spin 2
scalar
gravitino
chiral fermion
graviton
vector
majorana fermion
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Particle Content of the MSSM
sleptons
leptons
squarks
quarks
higgsinos
Higgses
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The MSSM Lagrangian
The Yukawa Superpotential
Superfields
Yukawa couplings
Higgs mixing term
R-parity
B - Baryon Number L - Lepton Number S - Spin
These terms are forbidden in the SM
The Usual Particle R 1 SUSY Particle
R - 1
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MSSM Parameter Space
Hidden sector
MSSM
SUSY
Five universal soft parameters
versus
and
in the SM
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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
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Constrained MSSM (Choice of constraints)
Experimental lower limits on Higgs and
superparticle masses
Regions excluded by Higgs experimental limits
provided by LEP2
tan ß 35
tan ß 50
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B-gts ? decay rate
MSSM
Standard Model














W, H
SM
MSSM
H
Experiment
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Constrained MSSM (Choice of constraints)
Data on rare processes branching ratios
Regions excluded by experimental limits (for
large tanß)
tan ß 50
tan ß 35
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Rare Decay Bs ? µ µ-
SM
SM Br3.5?10-9
Ex lt4.5? 10-8
Main SYSY contribution
2

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Constrained MSSM (Choice of constraints)
Data on rare processes branching ratios
Regions excluded by experimental limits (for
large tanß)
tan ß 50
tan ß 35
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Anomalous magnetic moment
2710
EW
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Constrained MSSM (Choice of constraints)
Muon anomalous magnetic moment
Regions excluded by muon amm constraint
tan ß 50
tan ß 35
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Constrained MSSM (Choice of constraints)
The lightest supersymmetric particle (LSP) is
neutral.
This constraint is a consequence of R-parity
conservation requirement
Regions excluded by LSP constraint
tan ß 35
tan ß 50
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Favoured regions of parameter space
Pre-WMAP allowed regions in the parameter space.
From the Higgs searches tan ß gt4, from aµ
measurements µ gt0
tan ß 35
tan ß 50
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Favoured regions of parameter space
Pre-WMAP dark matter constraint
0.1lt O h2 lt 0.3
tan ß 35
tan ß 50
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Allowed regions after WMAP
In allowed region one fulfills all the
constraints simultaneously and has the suitable
amount of the dark matter
WMAP
LSP charged
Narrow allowed region enables one to predict the
particle spectra and the main decay patterns
Higgs
EWSB
Phenomenology essentially depends on the region
of parameter space and has direct influence on
the strategy of SUSY searches
tan ß 50
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Favoured regions of parameter space
Bulk region The region is characterized by low
m0 and low m1/2 thus leading to light
superpartners Typical processes
annihilation of neutralinos through t-channel
slepton and/or squark exchange The bulk
region is practically excluded by LEP2
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Favoured regions of parameter space
-coannihilation region The region is
characterized by low m0 but large m1/2 Masses of
tau-slepton and neutralino are almost
degenerate Typical processes neutralino-stau
co-annililation
Possibility of long-lived heavy charged staus
flying through the detector or decaying at a
distance !
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Favoured regions of parameter space
Focus point region The region is characterized
by large m0 and low m1/2 At the boundary of
REWSB excluded region neutralino is almost
higgsino Possible long-lived chrginos Splitting
of heavy squarks and sleptons from light
gauginos Typical processes annihilation of
neutralinos to gauge bosons and/or quarks
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Favoured regions of parameter space
A-annihilation funnel region The region where
Typical processes resonance annihilation of
neutralinos to fermion pairs through exchange of
heavy Higgses A (and/or H) The region requires
large tan ß and leads to heavy sparticles
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Favoured regions of parameter space
EGRET region
The region is compatible with diffuse gamma ray
flux from the DM annihilation It corresponds to
the best fit values of parameters
tan ß 51 m0 1400 GeV
m1/2 180 GeV
SUSY DM
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???????????? ????????????
??????? ?? ??????? ??????? ????? ???? ?????
?????????? ?? ????? ? LSP
WMAP
LSP charged
????????????
????????????
Higgs
????????????
EWSB
????? ????? gt 10-10 ???, ? 100 ??? ?????? ?
???????????? ????????? ??????? ??? ?????? ??????
????????
???????????? ?????????? ????
??????? ?????? ?????????? ??????????
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Search for Superpartners _at_ Colliders
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Superpartners Production at LHC
Annihilation
Quark- gluon Fusion
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SUSY Signatures at LHC
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Cascade Processes (weak ints)
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Cascade Processes (strong ints)
4l 4j
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Creation and decay of superpartners in cascade
processes _at_ LHC
weak int's
Strong int's
2l,6j,ET
l,2j,ET
8j,ET
2l,2j,ET
Typical SUSY signature Missing energy and
transverse momentum
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Background Processes in the SMfor superpartner
production
weak int's
Strong int's
l,2j,ET
2l,6j,ET
2l,2j,ET
4j,4l,ET
The x-section typically are smaller than for SUSY
prodution
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Cross-Sections at LHC
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SUSY PRODUCTION AT LHC
m0 1400 GeV m1/2 180 GeV A
0 sign(µ) 1 tanß 50
s13 pb
SIGNATURE4 b-jets 4 muons Etmiss
LARGE!
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SUSY IN ATLAS
JINR(Dubna) ATLAS Group
V. Bednyakov, Y.Budagov, G. Khoriauli, J.Khubua
Pythia within ATHENA, B-vertex taging
Neutralino Pt
B mesons
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SUSY SIGNAL at ATLAS
Clear end-point behaviour
Important to distinguish true from false events
Invariant mass distribution of OS charged lepton
pair
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SUSY Searches at LHC
Reach limits for various channels at 100 fb
5 s reach in jets
channel
-1
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MSSM versus SM
Global fit to precision EW data

• MSSM is as good as SM
• B-gts?
• aµ
• ODM

MSSM is better than SM
Is NOT described by SM, but is naturally
described by MSSM
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SUSY Pros and Cons

• Provides natural framework for unification with
  gravity
• Leads to gauge coupling unification (GUT)
• Solves the hierarchy problem
• Is a solid quantum field theory
• Provides natural candidate for the WIMP cold DM
• Predicts new particles and thus generates new
  job positions

Pro
Contra

• Does not shed new light on the problem of
• Quark and lepton mass spectrum
• Quark and lepton mixing angles
• the origin of CP violation
• Number of flavours
• Baryon assymetry of the Universe

Doubles the number of particles
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Conclusions

• LHC has potential for major discoveries already
  in the first year of operation (1 day of LHC at
  1033 10 years of previous machines)
• SUSY might be discovered quickly, light Higgs
  more difficult
• Machine luminosity performance is crucial in the
  first year
• However lot of data and time is needed in the
  beginning to -- commission the detectors
• -- reach the performance
• -- understand the SM physics at vs14 TeV