Casting Light on Dark Matter?
John ELLIS,
King’s College London & CERN
The Current Context
• Three major new experimental results
• The discovery of a Higgs boson @ LHC
– Constraints on models of dark matter
– But no evidence of dark matter particles
• Planck satellite data
– Consistent with ΛCDM model
– Constraints on inflationary models
• First data from the AMS-02 experiment
– Rising positron fraction
– Astrophysics or dark matter annihilations?
Unofficial Combination of Higgs Search
Data from March 6th
Is this the
Higgs Boson?
No
Higgs
here!
No Higgs here!
It Walks and Quacks like a Higgs
• Do couplings scale ~ mass? With scale = v?
Global
fit
JE & Tevong You, arXiv:1303.3879
• Red line = SM, dashed line = best fit
What else is there?
Supersymmetry
• Successful prediction for Higgs mass
– Should be < 130 GeV in simple models
• Successful predictions for Higgs couplings
– Should be within few % of SM values
• Naturalness, GUTs, string, …
• Could explain the dark matter
Lightest Sparticle as Dark Matter
• Stable in many models because of conservation of
Fayet
R parity:
R = (-1) 2S –L + 3B
where S = spin, L = lepton #, B = baryon #
• Particles have R = +1, sparticles R = -1:
Sparticles produced in pairs
Heavier sparticles  lighter sparticles
• Lightest supersymmetric particle (LSP) stable
• Present in Universe today as relic from Big Bang
Relic Density Calculation
• Freeze-out from thermal equilibrium
• Typical annihilation cross section ~ 3 ✕ 10-26 cm2
• Lower if coannihilation with related particles
Supersymmetric Signature @ LHC
Look for missing transverse energy
carried away by dark matter particles
Supersymmetry
Searches
LHC
Searches ~ 5/fb
@ 8@
TeV
“Classic” missing-energy search
Multiple searches including b, leptons
Global Fit to Supersymmetric Model
2
5
Scan of CMSSM
Impacts of searches
with full 2012 data
Update of Buchmueller et al: arXiv:1207.3715
p-value of simple models < 10%
Global Fit to Supersymmetric Model
1
Gluino mass
5
CMSSM
Update of Buchmueller, JE et al: arXiv:1207.3715
Favoured values of gluino mass significantly
above pre-LHC, > 1.5 TeV
Cosmological Inflation in Light of Planck
• A scalar in the sky? A Wess-Zumino model?
Inflationary Models in Light of Planck
• Planck CMB observations consistent with inflation
• Tilted scalar perturbation spectrum:
ns = 0.9585 ± 0.070
• BUT strengthen upper limit on tensor
perturbations: r < 0.10
• Challenge for simple
inflationary models
• Starobinsky R2 to rescue?
• Supersymmetry to rescue? Croon, JE & Mavromatos: arXiv:1303.6253
Higgs Inflation: a Single Scalar?
Bezrukov & Shaposhnikov, arXiv:0710.3755
• Standard Model with non-minimal coupling to
gravity:
• Potential similar to Starobinsky, but not identical
BUT: needs MH > 127 GeV ≠ LHC?
Supersymmetric Inflation in Light of Planck
• Supersymmetric Wess-Zumino (WZ) model
consistent with Planck data
ϕ4
ϕ2
WZ
ϕ
ϕ2/3
Croon, JE, Mavromatos: arXiv:1303.6253
No-Scale Supergravity Inflation
•
•
•
•
The only good symmetry is a local symmetry
Early Universe cosmology needs gravity
Supersymmetry + gravity = Supergravity
BUT: potentials in generic supergravity models
have potential ‘holes’ with depths ~ – MP4
• Exception: no-scale supergravity
• Appears in compactifications of string
• Flat directions, scalar potential ~ global model +
controlled corrections JE, Nanopoulos & Olive, arXiv:1305.1247, 1307.3537
No-Scale Supergravity Inflation
• Good inflation for
Looks like R2 model
JE, Nanopoulos & Olive, arXiv:1305.1247, 1307.3537
Strategies for Detecting Supersymmetric
Dark Matter
• Scattering on nucleus in laboratory
χ +Aχ+A
• Annihilation in core of Sun or Earth
χ–χν+…μ+…
• Annihilation in galactic centre, dwarf galaxies
χ – χ  γ + …?
• Annihilation in galactic halo
χ – χ  positrons, antiprotons, …?
Direct Searches for Dark Matter
New CDMS result
Aprile et al.
Best limit: XENON100 with 225 days of data
Confusion at low WIMP masses?
Global Fit to Supersymmetric Model
2
-40
10
-41
10
-42
10
-43
10
-44
10
-45
10
-46
10
-47
10
-48
Spin-independent
Dark matter scattering
Excluded by
XENON100
5 .9 9
0
1
10
2
m χ˜ 01 [GeV]
5 .9 9 0
5 .9 9 0
10
Excluded
by LHC
2.
30
2.3 00
5 .9 9 0
σpSI [cm 2 ]
--- 1/fb
___ 5/fb
10
5
0
10
3
Buchmueller, JE et al: arXiv:1207.3715
Favoured values of dark matter scattering
cross section significantly below XENON100
Strategies for Detecting Supersymmetric
Dark Matter
• Scattering on nucleus in laboratory
χ +Aχ+A
• Annihilation in core of Sun or Earth
χ–χν+…μ+…
• Annihilation in galactic centre, dwarf galaxies
χ – χ  γ + …?
• Annihilation in galactic halo
χ – χ  positrons, antiprotons, …?
Neutralino Annihilation Rates
In some
supersymmetric models
may be much
smaller than
order-of-magnitude
estimate
JE, Olive & Spanos, arXiv:1106.0768
Annihilation Branching Fractions
Vary in different regions of parameter space
JE, Olive & Spanos, arXiv:1106.0768
Must be modelled correctly
Fermi γ line
@ 130 GeV?
Weniger analysis
claimed “4 σ”
(3 σ with look-elsewhere effect)
• BUT: Fermi Collaboration also
sees bump in control sample of
γ’s from Earth’s limb
• Presumably a systematic effect
AMS-02 on International Space Station (ISS)
Positron Fraction Rising with E
Dark Matter? Galactic cosmic rays? Local sources?
Dark Matter Fit to AMS Positron Data
0
+ -
2
t t min c point; E>20 GeV
CR
+ t t
Fermi ’11
AMS-02
Pamela ’10
20
18
2
c /bin
2
c
16
14
12
-1
2
10
c
Je+/(Je-+Je+)
10
10
8
6
4
2
10
-2
10
0
10
1
10
E [GeV]
2
10
3
0
1
10
10
2
E [GeV]
• Can find good fit: χ2 ~ 18 with annihilation to
τ+τ- by modifying cosmic ray parameters
JE, Olive & Spanos, in preparation
Dark Matter Fit to AMS Positron Data
3
<s v> [cm /s]
D c2 (AMS-02) : t+ t- channel
10
-19
10
-20
10
-21
10-22
10
-23
10
-24
102
J=0
J=1
CL=68%
CL=95%
103
104
105
mDM [GeV]
• BUT: very large annihilation cross section
~ 3 ✕ 10-23 cm2 >> required for relic density
• OR: very large boost from halo density
JE, Olive & Spanos, in preparation
fluctuation(s)
Galactic Cosmic Rays Alone?
Blum, Katz& Waxman, arXiv:1305.1324
• Rising positron fraction compatible with
model-independent bound on secondary e+
10
10
Je-, Je+ (cm-2 s-1 sr-1 GeV-1)
Galactic Cosmic
Rays Alone?
0
CR
t t
Fermi ’11
AMS-02
Pamela ’10
10
-2
10
-4
10
-6
10
-8
-
e
+
e
+
e +e
Fermi ’10
10-10
10
-12
10
-14
10
10
0
10
1
2
10
2
10
10
3
E [GeV]
10-1
10
-2
10
0
10
1
10
2
10
E [GeV]
• Can fit positron data with
modified cosmic-ray model
_
• BUT: problems with e , p
3
antiprot/prot
Je+/(Je-+Je+)
+ -
0
-3
CR
Pamela ’10
10-4
10
-5
10
-6
10
0
10
1
10
3
E [GeV]
JE, Olive & Spanos, in preparation
Assume Local Source: Constrain any
extra Dark Matter Contribution
• Dark Matter annihilation could give feature
above otherwise smooth distribution
Bergstrom et al, arXiv::1306.3983
The LHC may cast light on dark matter…
… dark matter experiments may cast light on
fundamental questions in particle physics