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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. Observation Model Lagrangian Feynman Diagrams Conclusions. Observation.

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

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  1. 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

  2. Outline • Observation • Model • Lagrangian • Feynman Diagrams • Conclusions

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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+/- +

  8. 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

  9. 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

  10. Annihilation of VDM to Photon Pair at loop level VDM Annihilation Diagram to Photons

  11. 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

  12. 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

  13. 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

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

  15. 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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