Puzzles of Dark Matter Searches - a signature for Composite Dark Matter?
Casting Light on Dark Matter?
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Transcript of Casting Light on Dark Matter?
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 theHiggs Boson?
No Higgs here!NoHiggshere!
It Walks and Quacks like a Higgs
• Do couplings scale ~ mass? With scale = v?
• Red line = SM, dashed line = best fitJE & Tevong You, arXiv:1303.3879
Globalfit
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 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
Fayet
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
“Classic” missing-energy search
Searches ~ 5/fb @ 8 TeVSupersymmetry Searches @ LHC
Multiple searches including b, leptons
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p-value of simple models < 10%
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Scan of CMSSM
Impacts of searcheswith full 2012 data
Update of Buchmueller et al: arXiv:1207.3715
Global Fit to Supersymmetric Model
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Favoured values of gluino mass significantlyabove pre-LHC, > 1.5 TeV
Gluino mass
Update of Buchmueller, JE et al: arXiv:1207.3715
CMSSM
Global Fit to Supersymmetric Model
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?
• Standard Model with non-minimal coupling to gravity:
• Potential similar to Starobinsky, but not identical
Bezrukov & Shaposhnikov, arXiv:0710.3755
BUT: needs MH > 127 GeV ≠ LHC?
Supersymmetric Inflation in Light of Planck
• Supersymmetric Wess-Zumino (WZ) model consistent with Planck data
ϕ4
ϕ2
ϕϕ2/3
Croon, JE, Mavromatos: arXiv:1303.6253
WZ
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 ~ – MP
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• 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 laboratoryχ + A χ + A
• Annihilation in core of Sun or Earthχ – χ ν + … μ + …
• Annihilation in galactic centre, dwarf galaxiesχ – χ γ + …?
• Annihilation in galactic haloχ – χ positrons, antiprotons, …?
Best limit: XENON100 with 225 days of data
Confusion at low WIMP masses?Aprile et al.
Direct Searches for Dark MatterNew CDMS result
Favoured values of dark matter scatteringcross section significantly below XENON100
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--- 1/fb___ 5/fb
Buchmueller, JE et al: arXiv:1207.3715
Spin-independentDark matter scattering
Excluded byXENON100
Excluded by LHC
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Global Fit to Supersymmetric Model
Strategies for Detecting Supersymmetric Dark Matter
• Scattering on nucleus in laboratoryχ + A χ + A
• Annihilation in core of Sun or Earthχ – χ ν + … μ + …
• Annihilation in galactic centre, dwarf galaxiesχ – χ γ + …?
• Annihilation in galactic haloχ – χ positrons, antiprotons, …?
Neutralino Annihilation Rates
In somesupersymmetric models
may be much smaller than
order-of-magnitudeestimate
JE, Olive & Spanos, arXiv:1106.0768
Annihilation Branching FractionsVary in different regions of parameter space
JE, Olive & Spanos, arXiv:1106.0768 Must be modelled correctly
• BUT: Fermi Collaboration also sees bump in control sample of γ’s from Earth’s limb
• Presumably a systematic effect
Fermi γ line@ 130 GeV?
Weniger analysisclaimed “4 σ”
(3 σ with look-elsewhere 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
• 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
• BUT: very large annihilation cross section
~ 3 ✕ 10-23 cm2 >> required for relic density• OR: very large boost from halo density
fluctuation(s) JE, Olive & Spanos, in preparation
Galactic Cosmic Rays Alone?
• Rising positron fraction compatible with model-independent bound on secondary e+
Blum, Katz& Waxman, arXiv:1305.1324
Galactic Cosmic Rays Alone?
• Can fit positron data with modified cosmic-ray model
• BUT: problems with e-, p_
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