Z

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Z Mediation of Supersymmetry Breaking

• Itay Yavin
• Princeton University

arXiv0710.1632 hep-ph- G. Paz, P. Langacker,
L. Wang and IY arXiv0801.3693 hep-ph- G. Paz,
P. Langacker, L. Wang and IY arXiv0711.3214
hep-th- H. Verlinde , L. Wang, M. Wijnholt and
IY
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Outline

• Motivation
• Connection with String theory
• A model
• Setup
• Experimental signatures
• Extensions

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The Forces of Nature
Electromagnetic force
Strong force
Atoms 10-10 m
Weak force
Protons and Neutrons 10-15 m
Radioactive decay 10-18 m

1. Why is the weak force stronger than gravity?
2. Are there any other forces?

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A Fifth Force (an extra Abelian gauge-boson)
Supersymmetry (an extended spacetime sym.)

• There are many reasons to conjecture that
  supersymmetry exists in nature,
• Consistent theories of quantum gravity predict
  its existence.
• Grand unified theories work better with it.
• Helps to explain, both statically and dynamically
  why the Weak force is stronger than the
  gravitational force.

• There are many reasons to conjecture that a fifth
  force exists in nature,
• Consistent theories of quantum gravity almost
  always include it.
• Grand unified theories have it.
• Certain unexplained global symmetries of the
  Standard Model seem to demand it.

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Supersymmetry Breaking
None of the degrees of freedom associated with
these symmetries are seen at low energies.
Following the paradigm of SUSY breaking in a
hidden sector (see H. P. Nilles talk) we propose
the following scenario
U(1) and EWSB is dynamically generated.
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Z mediation in String theory
An abelian gauge field can mix with the RR-form
in the gravitational multiplet. The RR-form
propagates in the bulk and can act to mix two
U(1)s on remote branes.
?
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Charge assignment and anomaly cancellation
conditions
Assume that only matter on the visible brane
participate in the anomaly cancellation
conditions. Also, allow for the following
coupling of the singlet field,
D, Dc are colored exotics. E, Ec are color
singlet exotics.
Solving for the anomaly cancellation
conditions Two free charges Q2 and QQ and nD
3, nE 2.
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General features and fine-tuning
The gauginos are not charged under the new force
and dont directly interact with it. Nonetheless,
they feel it quantum mechanically,
The scalars are at roughly 100 TeV and so
fine-tuning is inevitable. This is a mini-version
of the split SUSY scenario, N. Arkani-Hamed,
S.Dimopoulos, hep-th/0405159 G. Giudice and
A. Romanino, hep-ph/0406088
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Dynamics
The singlet must break the U(1) gauge-symmetry
in the visible sector, generate a ??term, and
give the exotics a mass.

(positive contribution)
(negative contribution)
Singlets U(1) charge cannot be too large.
Yukawa coupling to exotics cannot be too small
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EWSB
?? varying??S we can fine-tune one against the
other
The two Higgs doublet mass matrix is,
Note This tuning leads to some amount of
accidental tuning
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Energy Scales
Supersymmetry is broken. Only the Z vector
supermultiplet feels the breaking directly.
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Electroweak Scale
Electroweak scale
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Scanning over parameter space(charge assignment)
The red dots represent charge assignment for
which a viable solution for the Electroweak
scale. The Yukawa were chosen to be, ????????
yD 0.5 yE 0.1
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Scanning over parameter space (Exotic Yukawa
couplings)
Z gauge-boson Gluino Wino Singlino
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Discovery _at_ LHC
Proton - Proton Collider at 14 TeV
Proton - Proton Collider at 10 TeV
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Higgs Mass
The physical Higgs mass is determined by the
quartic,
But, the quartic is determined by the boundary
condition and the RGE, which dont change
appreciably in the model we consider,
So the Higgs mass is almost entirely determined
by the running from 1000 TeV down to the
Electroweak scale,
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Exotic Gluino Decay
Since all the scalar partners are heavy, the
gluino must decay through an off-shell
intermediate scalar,
?
?
We may never be able to resolve the intermediate
particle, but we may observe the long life-time
of the gluino!
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Exotic Gluino Decay - Continued
The parametric dependence of the two processes is
very different.
Gambino, Giudice and Slavich arXivhep-ph/0506214
Arvanitaki et al arXivhep-ph/0506242.
Life-time for different benchmark points.
Similar calculations in the context of split susy
were done by Toharia and Wells arXivhep-ph/050317
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Glueballino and other exotic Hadrons
The gluino is long lived, but not long enough to
leave a displaced vertex. It will first hadronize
and then decay,
g
u
d
g
Hadronic bound state.
Is there any way to experimentally distinguish
between a gluon that decay before or after
hadronizing? Grossman and Nachshon -
arXiv0803.1787 hep-ph
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Z Production
If a new force is indeed waiting to be
discovered, then we may just observe its carrier
directly at the LHC,
Too many refs. . .
?
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Other Signatures
After its discovery it will be easier to explore
the other decay modes of the heavy vector-boson.
The collider signatures have not been thoroughly
investigated yet, hopefully in the near future .
. .
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Predictions

• Split-SUSY spectrum
• Exotic gluino decay
• Z production
• Higgs mass at 140 GeV
• Light singlino

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Extensions

1. Dark matter remains a problem in this type of
   scenario. When the wino is the LSP the density is
   too low. If either the singlino or gravitino are
   the LSP it is usually a disaster. Any way out?
2. Unification not present in the current model.
   Work in progress. . . seems difficult (Axions).
3. In this setup we assumed UV boundary conditions
   analogues to gaugino-mediation. How do things
   change if we were to consider a gauge-mediation
   type setup?
4. Including more details of the hidden sector.
5. A more extensive study of realizations of such a
   setup in the context of string theory. But see
   Grimm and Klemm arXiv 0805.3361hep-th.
6. Any connection with the landscape?

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Conclusions

1. Our current best speculations about the UV almost
   always lead to the existence of additional U(1)
   gauge fields at low energies. This may fit
   nicely as a (bulk) mediator of SUSY breaking.

1. The resulting model is dynamical, calculable and
   predictive.

3) The general features are quite robust and lead
to distinct signatures. With some luck well be
able to see it at the LHC!!!
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Beta decay

• Radioactivity was observed before the discovery
  of the electron. We are still trying to uncover
  the nature of the weak force. It may be
  instructive to recall that it took about 30 years
  before scientists figured out what Beta decay was
  all about
• Experimental difficulties and confusion . . .
  The ignorance at the time about the relation
  between the blackening of a photographic plate
  and the intensity of the irradiation. (Pais,
  Inward Bound)
• Theoretical misunderstanding and prejudices .
  . . Prevailing prejudice still strongly favoured
  a discrete spectrum possibly due to a
  monoenergetic primary source. (Pais)
• Real physics discrete lines in the spectrum due
  to (the yet undiscovered) nuclear structure.

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Fermi on the problem of the meson
Of course, it may be that someone will come up
soon with a solution to the problem of the meson,
and that experimental results will confirm so
many detailed features of the theory that it will
be clear to everybody that it is the correct one.
Such things have happened in the past. They may
happen again. However, I do not believe that we
can count on it, and I believe that we must be
prepared for a long, hard pull. (E. Fermi,
Collected works, paper 247)
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Gravitino mass
The gravitino mass is given as usual,
But, the SUSY breaking scale is very sensitive to
the precise details of the model,
Hard to predict. Need more details about the
hidden sector and the precise mechanism of SUSY
breaking.
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U(1) Mixing
Will be induced at loop level. Consider the
superpotential,
By construction k does not have an F-term. Its
lowest component is roughly,
Which will induce kinetic mixing. However, since
in the limit that M1 vanishes there is chiral
symmetry protecting it so,