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Vector Higgs-Portal Dark Matter and Fermi-LAT Gamma Ray Line. Ki -Young Choi , Hyun Min Lee, Osamu Seto June 2013 Presented by Randy Lafler. Outline. Observation Model Lagrangian Feynman Diagrams Conclusions. Observation.

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vector higgs portal dark matter and fermi lat gamma ray line

Vector Higgs-Portal Dark Matter and Fermi-LAT Gamma Ray Line

Ki-Young Choi, Hyun Min Lee,

Osamu Seto

June 2013

Presented by Randy Lafler

outline
Outline
  • Observation
  • Model
  • Lagrangian
  • Feynman Diagrams
  • Conclusions
observation
Observation
  • In the Fermi-LAT data a Gamma Ray Line Spectrum was found at Eγ=130 GeV
    • Narrow Spectral Lines originating from the Galactic Center
  • Signature independently confirmed by other groups and Officially Investigated By Fermi-LAT Collaboration
    • Peak shifted to 135 GeV
  • Possible Explanations
    • Monoenergetic Pulsar Winds, Fermi Bubble, or Instrument Effects including Earth Limb Signal
proposed explanation
Proposed Explanation
  • Fermi-LAT Collaboration and H.E.S.S Collaboration reported only upper bound on annihilation X-Section of WIMPs
    • Could be DM
  • DM is neutral
    • Cannot annihilate into γ’s at tree level
    • Generation of γ’s must happen via loops of charged particles which DM is directly or indirectly coupled
    • Annihilation X-Section into γ’s is much suppressed compared to other tree level annihilation channels
    • In order for Large Branching Fraction, DM must have Large Coupling to New Charged Particle Running in Loops
model
Model
  • Vector DM couples to SM via Higgs Portal Interactions
  • Gauge Sector: SU(3)C x SU(2)L x U(1)Y x U(1)x
  • Introduce a Complex Scalar Field S1
    • It obtains a Vacuum Expectation Value (VEV) and Spontaneously Breaks the Extra U(1)x Gauge Symmetry
  • To have DM annihilation into a Photon Pair
    • Introduce SU(2) Singlet Charged Scalar S2+
    • Y=1
    • Neutral under U(1)x
  • Higgs Doublet φ and All SM particles are Neutral under U(1)x
slide6

DM is the Gauge Boson of U(1)x after Spontaneously Broken by VEV of Hidden Higgs Field at RenormalizableLevel (S1)

  • Ensure stability of VDM
    • When U(1)x is broken there is a remnant Symmetry Z2 under which S1 S1* and X  -X
  • DM predominately annihilates into W and Z through s-channel exchange of h and H Higgs Bosons in Early Universe
    • Ensure observed Thermal Relic Abundance of DM
model lagrangian
Model Lagrangian
  • Fuv = duXv - dvXu
  • Du S1 = (du – igxXu)S1
    • Covariant Derivatives (CD) with respect to U(1)x and U(1)Y
    • After EW Symmetry Breaking, D2S2 is reduced to CD with respect to U(1)em Symmetry
  • Final term
    • Li is SM lepton doublet with flavor index i = 1,2,3
    • C is Charge Conjugation Operator
    • Dot denotes SU(2) Antisymmetric product
    • Lepton Flavor Violation because fij is Antisymmetric
    • S2+  li+/- +
mass eigenstates h and h
Mass Eigenstates h and H
  • Expand Higgs Doublet φand S1 Fields around EW vacuum
    • <φ>=v/sqrt(2) and <S1> =vs/sqrt(2)
    • v = 246 GeV
  • For small sin(α)
    • h ~ φ; SM Higgs particle
    • H ~ φs ; Singlet
vdm annihilation to w z
VDM Annihilation to W,Z
  • XX  Zγ will produce additional Gamma Ray Line at Eγ=114GeV
    • Flux is reduced by 0.21
  • XXZZ
    • Flux is negligible
explanation of observations
Explanation of Observations
  • When H has small coupling to W and Z but Large (Quartic) Coupling to Charged Scalar S2+
    • Diphoton production from DM annihilation takes larger branching fraction of annihilation X-Section
  • Annihilation into WW or ZZ must now be suppressed to prevent generation of excess Continuum Photons
  • Explains both Relic DM Density and Gamma Ray Line
  • S2+ Lepton Coupling Matrix fij< O(10-2) to be consistent with EW Precision Measurements
predictions
Predictions
  • Mx=MH/2=135 GeV
    • MH = 270 GeV
  • To have Gamma Ray Line Spectrum at Eγ=135Gev
    • <σv>XX γγ = 1.1x10-10 GeV-2
  • Gamma Ray Line at Eγ114 GeV
    • 0.21 reduced flux
  • Lepton Flavor Violation from Charged Scalar S2+ decay
conclusion
Conclusion
  • Renormalizable Model of Vector DM
  • Extra SU(1)x Gauge Boson is DM candidate and interacts with SM particles through Higgs Portal
  • For Quartic Coupling between Singlet Scalar H and Charged Scalar S2+, DM annihilation into photons has sizable Branching Fraction
  • Finding Singlet Scalar H will be hard to find due to small mixing with the Higgs
slide14

S2 would be accessible at LHC due to distinct signature that 2 oppositely signed Leptons of different flavors are equally produced from S2 decay

references
References
  • Choi, Ki-Young, Hyun Hyun Lee, and Osamu Seto. "Vector Higgs-Portal Dark Matter and Fermi-Lat Gamma Ray Line." PHYSICAL REVIEW (2013)
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