Download Z` Mediation of Supersymmetry Breaking

Z’ Mediation of Supersymmetry
Breaking
Itay Yavin
Princeton University
arXiv:0710.1632 [hep-ph]- G. Paz, P. Langacker, L. Wang and IY
arXiv:0801.3693 [hep-ph]- G. Paz, P. Langacker, L. Wang and IY
arXiv:0711.3214 [hep-th]- H. Verlinde , L. Wang, M. Wijnholt and IY
SUSY08
Itay Yavin
Outline
• Motivation
• Connection with String theory
• A model
– Setup
– Experimental signatures
• Extensions
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Itay Yavin
The Forces of Nature
Electromagnetic force
Atoms ~ 10-10 m


Strong force
Weak force



e-
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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Supersymmetry (an extended spacetime sym.)
There are many reasons to conjecture that supersymmetry exists in nature,
o
Consistent theories of quantum gravity predict its existence.
o
Grand unified theories work better with it.
o
Helps to explain, both statically and dynamically why the Weak force is
stronger than the gravitational force.
A Fifth Force (an extra Abelian gauge-boson)
There are many reasons to conjecture that a fifth force exists in nature,
o
Consistent theories of quantum gravity almost always include it.
o
Grand unified theories have it.
o
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.
1) No D-terms
2)
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Itay Yavin
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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
Q ui ck Ti m e ™ an d a
T IF F ( Un co m p re ss ed ) d ec om pr e ss or
a re ne ed ed t o s ee th i s pi c tu r e.
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Q ui ck Ti m e ™ an d a
T IF F ( Un co m p re ss ed ) d ec om pr es so r
a re ne ed ed t o s ee th i s pi c tu r e.
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Itay Yavin
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 don’t 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)
V(S)

S
Singlet’s U’(1) charge cannot be too large.
Yukawa coupling to exotics cannot be too small
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EWSB
The two Higgs doublet mass matrix is,
Note:
varyingS we can finetune one against the other
This tuning leads to some amount of accidental tuning:
mS sets the masses of the Z’ gauge-boson and the singlino’s
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Energy Scales
S
E
V(S)

Supersymmetry is broken.
Only the Z’ vector
supermultiplet feels the
breaking directly.
S
MZ’~

Matter scalar partners
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Electroweak Scale
E
V(h)
Matter
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Electroweak
scale
h
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Scanning over parameter space
(charge assignment)
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The red dots represent charge
assignment for which a viable
solution for the Electroweak
scale. The Yukawa were chosen
to be,
= yD = 0.5
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yE = 0.1
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Scanning over parameter space (Exotic Yukawa couplings)
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Z’ gauge-boson
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Gluino
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Wino
Singlino
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Discovery @ LHC
Proton - Proton Collider at 10
14 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
don’t 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 offshell 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 arXiv:hep-ph/0506214
Arvanitaki et al arXiv:hep-ph/0506242.
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Life-time for different benchmark points.
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Similar calculations in the context of split susy were done by
Toharia and Wells arXiv:hep-ph/0503175
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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,
t
t
~
u
g
g
g
d
~
t
~
N1
Hadronic bound state.
Is there any way to experimentally distinguish between
a gluon that decay before or after hadronizing?
Grossman and Nachshon - arXiv:0803.1787 [hep-ph]
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Z’ Production

Cross-section
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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(pb)
mll2
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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
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• Exotic gluino decay
• Higgs mass at 140 GeV
Cross-section
• Z’ production
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mll2
• 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 gauginomediation. How do things change if we were to consider a gaugemediation 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:
6)
.
Grimm and Klemm arXiv; 0805.3361[hep-th]
Any connection with the landscape?
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Itay Yavin
Conclusions
1)
2)
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.
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The resulting model is dynamical, calculable and predictive.

V(S)
S
3)
The general features are quite robust and lead to
distinct signatures. With some luck we’ll be able to
see it at the LHC!!!

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Itay Yavin
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:
1)
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)
2)
Theoretical misunderstanding and prejudices:
“ . . . Prevailing prejudice still strongly favoured a discrete spectrum possibly
due to a monoenergetic primary source.” (Pais)
3)
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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Itay Yavin
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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Itay Yavin
U(1) Mixing
Will be induced at loop level. Consider the superpotential,
By construction k does not have an F-term. It’s lowest component is roughly,
Which will induce kinetic mixing. However, since in the limit that M1 vanishes
there is chiral symmetry protecting it so,
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Itay Yavin