The Wimp Forest Alberto Vallinotto Fermilab In collaboration with: G. Bertone, C. Jackson, G. Shaughnessy, T. Tait ArXiv: 0904.1442, PRD in press
Outline ● Indirect detection of dark matter (DM) through γ -rays ● Comparison between 5D KK model and the chiral square model ● Predictions for the chiral square model ● Conclusions
The hunt for dark matter ● 3 complementary strategies Direct Detection
The hunt for dark matter ● 3 complementary strategies Indirect Detection Direct Detection
The hunt for dark matter ● 3 complementary strategies Indirect Detection Direct Detection Collider Searches
Indirect Detection of γ-rays... ● Dark matter has to be stable ● However, it can pair-annihilate into SM particles ● Annihilation products detected in cosmic rays ( ) ● Here we focus on γ – They travel undeflected (point directly to source) – They travel almost unattenuated (don't require a diffusion model)
… from the ground and from above ● Fermi ● ACT's (Hess, Veritas,...) – Full sky coverage – Smaller fraction of sky – Sensitive to ~300 GeV – Sensitive to TeV's – ΔE/E ~ 10% – ΔE/E ~ 15-20%
Contributions to the γ-rays spectrum ● Continuum spectrum ● Lines Loop-induced processes ● into γ+X Spectral lines at ● Secondary γ's from quark or ● gauge boson fragmentation, or from final state radiation from ● “Smoking gun” ● charged SM particles. signature of Almost featurless, but with dark matter ● sharp cutoff at Wimp mass.
The Kaluza-Klein Zoo (1) ● 5D KK model ● 6D KK (Chiral Square) – UED compactified on a – UED compactified on a square circle with two adjacent sides identified – KK modes identified by one index, i.e. – LKP is the KK partner of – KK modes identified by 2 the hypercharge gauge indeces, i.e. boson – LKP's are the two KK partner – LKP is lepton-friendly of hypercharge gauge boson – LKP mass can reach 1TeV – LKP is lepton-unfriendly – Favors lighter LKP (up to 450 References: GeV) Bertone et al. (PRD 2003), Bergstrom et al. (PRL, 2004), References: Dobrescu and Ponton (JHEP, Bergstrom et al. (JCAP 2004). 2004), Dobrescu et al. (JCAP, 2007)
The Kaluza-Klein Zoo (2) ● 5D KK model ● 6D KK (Chiral Square) – Particles are even (odd) – Particles are even (odd) if (i+j) if i is even (odd) is even (odd) – Particle masses are – Particle masses are
The Kaluza-Klein Zoo (2) ● 5D KK model ● 6D KK (Chiral Square) – Particles are even (odd) – Particles are even (odd) if (i+j) if i is even (odd) is even (odd) – Particle masses are – Particle masses are – LKP's can only pair- LKP's can pair-annihilate annihilate into SM into other KK-particles! particles In models with 2 or more UED the LKP is kinematically allowed to pair- ● annihilate into other KK-particles and γ These lines are well separated from the γγ and Zγ lines and potentially carry ● a wealth of information “Spectroscopy of UED” if the x-section and continuum are favorable. ●
Flux of γ from wimp annihilation ● Differential flux from a source with DM density ρ is Microphysics Astrophysics (Halo profile)
Flux of γ from wimp annihilation ● Differential flux from a source with DM density ρ is Microphysics Astrophysics (Halo profile) ● The largest uncertainties arise from the lack of knowledge of the halo profile near the galactic center.
Flux of γ from wimp annihilation Uncertainties in the halo ● profile are quantified with We consider two benchmark ● models, with : Navarro-Frenk-White – [Bertone et al., JCAP 2009] scenario “Adiabatic compression” – Astrophysical uncertainties ● span three orders of magnitude
Continuum spectrum Chiral square case characterized by pair-annihilation into W's ● (~50%), H's (~25%) and Z's (~25%), which then decay. Spectrum of secondary photons (from FSR and decays) is ● softer than in the 5D (lepton-friendly) case. Calculation carried out with MicrOmegas ● 6D
Continuum spectrum Chiral square case characterized by pair-annihilation into W's ● (~50%), H's (~25%) and Z's (~25%), which then decay. Spectrum of secondary photons (from FSR and decays) is ● softer than in the 5D (lepton-friendly) case. Calculation carried out with MicrOmegas ● 5D 6D
Cross sections for Chiral Square Lines ● couples differently with SM fermions and their KK partners. ● This leads to less cancellations w/ respect to the γγ and Zγ cases. ● The x-section for turns out to be enhanced.
Cross sections for 5D KK Lines ● In stark contrast with the 5D case, where the x-section for is suppressed.
The Chiral Square Spectrum ● Three lines and two distinctive bumps. ● 10% energy resolution is insufficient to resolve and lines. ● The bump is well separated from the other. ● Contributing factors: – Large x-section. – Large – Small continuum.
The Chiral Square Spectrum ● Three lines and two distinctive bumps. ● 10% energy resolution is insufficient to resolve and lines. ● The bump is well separated from the other. ● Contributing factors: – Large x-section. – Large – Small continuum.
The 5D KK Spectrum ● Three lines but only one bump. ● 10% energy resolution is insufficient to resolve and lines and kills the one. ● Contributing factors: – Small x-section. – Higgs mass smaller than – Large continuum.
Conclusions ● KK extensions of the SM with more than one extra dimension exhibit one or more extra lines, well separated from . ● This “forest” of lines may be detectable with the right combination of xsection and continuum and can potentially provide a lot of information. ● However, this is not the only model characterized by a two bump feature. ● Information from colliders could complement the one coming from lines (cf Tait talk). ● Detection of a single bump and no drop off could also hint toward a Wimp forest scenario.
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