Supersymmetric candidates for dark matter

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Supersymmetric candidates for dark matter

• David G. Cerdeño
• Universidad Autónoma de Madrid

RENATA, Valencia, October 23-25, 2006
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Contents

• Present status
• Dark matter is a necessary ingredient in present
  models for the Universe
• but we have not identified it yet.
• It can be the Lightest Supersymmetric Particle
  (LSP).
• Direct detection experiments will continue
  providing data in the near future.
• It may be detected in running or projected dark
  matter experiments?
• The lightest Neutralino?
• Or maybe not?
• The gravitino (or the axino)?

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Lightest Supersymmetric Particle

• The LSP is stable in SUSY theories with
  R-parity. Thus, it will exist as a remnant from
  the early universe and may account for the
  observed Dark Matter.

In the MSSM, the LSP can be
Lightest squark or slepton charged and therefore
excluded by searches of exotic isotopes
Lightest sneutrino They annihilate very quickly
and the regions where the correct relic density
is obtained are already experimentally excluded
Lightest neutralino WIMP
Gravitino Present in Supergravity theories. Can
also be the LSP and a good dark matter candidate
Axino SUSY partner of the axion. Extremely weak
interactions
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Contents

• Neutralino dark matter (prospects for its direct
  detection)
• General Supergravity theories (MSSM, NMSSM, )
• SUGRA from string theories
• Gravitino dark matter (analysis of the parameter
  space of the CMSSM)
• Big Bang Nucleosynthesis.

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SUSY dark matter

• The lightest Neutralino

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Neutralino dark matter

• The lightest Neutralino is a very well motivated
  dark matter candidate it is a WIMP and could be
  observed in direct detection experiments

Direct detection through the elastic scattering
of a WIMP with nuclei inside a detector.
Many experiments around the world are currently
looking for this signal with increasing
sensitivities
How large can the neutralino detection cross
section be?
Could we explain a hypothetical WIMP detection
with neutralino dark matter?
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Neutralinos in SUGRA theories

• How large can the direct detection cross section
  for neutralinos be in Supergravity theories?

1) The Soft supersymmetry-breaking terms are
taken as inputs at the GUT scale and RGE are used
to evaluate the SUSY spectrum
Gaugino masses
Scalar masses
Trilinear parameters
Radiative Electroweak Symmetry breaking is
imposed, leaving two more inputs
Ratio of Higgses VEVs
Sign of Higgsino mass parameter
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Neutralinos in SUGRA theories

• How large can the direct detection cross section
  for neutralinos be in Supergravity theories?

2) Once the spectrum is calculated, experimental
constraints are applied Masses of
superpartners
Mass of the Higgs boson
Low energy observables that receive SUSY
contributions
Muon anomalous magnetic moment (g-2)m
Rare decays (e.g., b?sg, BS ? mm-)
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Neutralinos in SUGRA theories

• How large can the direct detection cross section
  for neutralinos be in Supergravity theories?

2) Once the spectrum is calculated, experimental
constraints are applied Masses of
superpartners
Mass of the Higgs boson
Low energy observables that receive SUSY
contributions
3) The correct dark matter relic density has to
be reproduced
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General Supergravity

• The number of free parameters in a general SUGRA
  is very large

More than 100 in the MSSM

• One often assumes simplifications

e.g., minimal Supergravity, mSUGRA (a.k.a.
Constrained MSSM)
Universal soft masses
5 free parameters

• Departures from universality are then considered.

• In string theory models the soft terms are
  calculated and the number of free parameters may
  be smaller.

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Constrained MSSM

• In the Constrained MSSM (universal soft terms)
  the allowed parameter space is very limited

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mSUGRA

• For example, in the Constrained MSSM (universal
  soft terms) the allowed parameter space is very
  limited

The resulting neutralino detection cross section
is very small.
Departures of the CMSSM allow an increase of the
cross section
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The lightest Neutralino

• In the MSSM the mechanisms which allow for an
  increase in the detection cross section are well
  known

In the MSSM, the neutralino is a physical
superposition of the B, W, H1, H2
The detection properties of the neutralino depend
on its composition
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Large detection cross sections

• The scalar part of the cross section has two
  contributions

Squark-exchange
Higgs-exchange
Leading contribution. It can increase when

• The Higgsino components of the neutralino
  increase

• The Higgs masses decrease

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Large detection cross sections
Higgs-exchange
Leading contribution. It can increase when

• The Higgsino components of the neutralino
  increase

• The Higgs masses decrease

In terms of the mass parameters in the RGE
mHd2
Non-universal soft terms (e.g., in the Higgs
sector)
MGUT
mHu2
mHu2 ?
mHd2 ?
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Non-universal soft terms

• Example with non-universal Higgs masses at the
  GUT scale

2
(S.Baek, D.G.C., G.Y.Kim, P.Ko, C.Muñoz04)
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Non-universal soft terms

• With non-universalities in both the scalar and
  gaugino sectors neutralinos in the detectable
  range can be obtained with masses of order 10-500
  GeV

Very light Bino-like neutralinos with masses 10
GeV.
Heavy Higgsino-like neutralinos with masses 500
GeV.
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The NMSSM

• Extensions of the MSSM also allow an increase of
  the Higgs-exchange amplitude. For instance, in
  the Next-to-MSSM, where a new singlet (and
  singlino) is included

The lightest neutralino has now a singlino
component
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Large detection cross sections

• Changes on the spin-independent contribution to
  the cross section

Squark-exchange
Formally identical to MSSM new mixings in
Higgs-exchange
New contribution from singlino components
New contribution from extra neutral Higgs
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Large detection cross sections
Higgs-exchange
Leading contribution. It can increase when

• The Higgsino components of the neutralino
  increase

• The Higgs masses decrease

• Very light Higgses (mh 20 GeV) can be obtained
  in the NMSSM. These have a large singlet
  component and thus avoid experimental constraints.

• This induces an increase in of
  several orders of magnitude.

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Next-to-MSSM

• Very large detection cross sections can be
  obtained

This is due to the Higgs masses being very small.
These results correspond to Higgses lighter than
70 GeV and mostly singlet-like
(D.G.C., E. Gabrielli, D.López-Fogliani,
A.Teixeira, C.Muñoz in preparation)

• Very light, singlet-like Higgses

• Neutralinos with a mixed Higgsino-singlino
  composition

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SUSY dark matter

• The lightest Neutralino
• General SUGRA
• SUGRA from Heterotic string theory

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SUGRA from string theories

• How large can the direct detection cross section
  for neutralinos be in Supergravity theories?

1) The Soft supersymmetry-breaking terms are
taken as inputs at the GUT scale and RGE are used
to evaluate the SUSY spectrum
2) Experimental constraints masses of
superpartners Low energy observables (
(g-2)m , b?sg, BS ? mm-, )

• String scenarios provide explicit examples of
  SUGRA theories at the low-energy limit.
• The soft terms are given in terms of the moduli
  fields, which characterise the size and shape of
  the compactified space.
• The number of free parameters is greatly reduced
• Are large neutralino detection cross sections
  still possible?

3) Constraint on relic density
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Heterotic Orbifolds

• As a function of the gravitino mass, , the
  Goldstino angle, , and the modular weights,
  , the soft masses read

• Few free parameters,
• Non-universal scalar masses, in general, due to
  the effect of the modular weights
• Gaugino masses larger than scalar masses, Mgtmi

(D.G.C., T.Kobayashi, C.Muñoz , in preparation)
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D-term contribution

• An anomalous U(1) is usually present in
  Heterotic string compactifications.

Although its anomaly is cancelled by the
Green-Schwartz mechanism, it generates a
Fayet-Ilioupoulos contribution to the D-term.
Some scalar fields develop large VEVs in order to
cancel the FI term.
This generates and additional non-universality
among the scalar masses, which depends on their
U(1) charges (qi)
The non-universality can be large, even in the
dilaton limit

• Increase m? and help avoiding UFB constraints

It can even be positive if

• Increase mHu and help increasing the neutralino
  detection cross section

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D-term contribution
The non-universality

• Increase m? and help avoiding UFB constraints

Can even be positive if

• Increase mHu and help increasing the neutralino
  detection cross section

For example, assuming now

• Thanks to the increase in , the Higgsino
  components of the neutralino increase.
• Large detection cross sections become possible,
  fulfilling all the experimental and astrophysical
  constraints.

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D-term contribution
The non-universality

• Increase m? and help avoiding UFB constraints

Can even be positive if

• Increase mHu and help increasing the neutralino
  detection cross section

• Decrease mHd (and therefore the Higgs masses),
  thus increasing the neutralino detection cross
  section

Or more negative with

• Further decreasing leads to a decrease of
  the Higgs masses and implies an extra increase of

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SUSY dark matter

• The lightest Neutralino
• The Gravitino

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Gravitino dark matter

• The gravitino can be the LSP in Supergravity

The relation between the gravitino mass and the
rest of the soft masses depends on the
SUSY-breaking mechanism
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Gravitino dark matter

• Gravitino production mechanisms

Thermal Production
Non-Thermal Production
NLSP freezes out
Photons, charged leptons
Nucleosynthesis 3He, 4He, D, Li
?
Reheating
time
TR
1s
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Gravitino dark matter

• In the CMSSM

Regions of the parameter space appear where the
gravitino is a good dark matter candidate
Correct relic density from only NTP
Correct relic density with TP
(D.G.C., K.Choi, K.Jedamzik, L.Roszkowski, R.Ruiz
de Austri 05)
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Gravitino dark matter

• In the CMSSM

Neutralino NLSP areas excluded by BBN
constraints. Only part of those with stau NLSP
are left.
Non-thermal production alone not sufficient.
Large contributions from thermal prod. are
necessary.
As long as TR109 GeV sizable regions are found
with correct O
(D.G.C., K.Choi, K.Jedamzik, L.Roszkowski, R.Ruiz
de Austri 05)
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Gravitino dark matter

• In the CMSSM

Neutralino NLSP areas excluded by BBN
constraints. Only part of those with stau NLSP
are left.
Non-thermal production alone not sufficient.
Large contributions from thermal prod. are
necessary.
UFB
UFB
In the remaining regions the Fermi vacuum is
metastable. The global minimum breaks charge
and/or colour.
(D.G.C., K.Choi, K.Jedamzik, L.Roszkowski, R.Ruiz
de Austri 05)
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Gravitino dark matter

• Phenomenology

Dark matter experiments would not detect anything
(gravitinos are extremely weakly-interacting)
In particle accelerators (LHC) detection of a
(meta)-stable and electrically charged LSP
(stau). (notice that this could also be true for
axino dark matter)
Valuable information could be obtained about the
vacuum structure (are we living in a false
vacuum?) and early Universe cosmology (value of
TR)
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Summary

• The identification of dark matter is still an
  open problem pointing towards physics beyond the
  SM. Supersymmetric dark matter is one of the most
  attractive possibilities with an interesting
  future

• The lightest neutralino could explain a
  hypothetical detection of WIMP dark matter in the
  next generation experiments

• Gravitino dark matter would lead to an
  interesting phenomenology
• Charged observable LSP (stau)
• No detection in dark matter experiments
• The Fermi vacuum may be metastable
• Information on the reheating temperature

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