The Wimp Forest Alberto Vallinotto Fermilab In collaboration with: - - PowerPoint PPT Presentation

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

Direct Detection Indirect Detection

The hunt for dark matter

• 3 complementary strategies

Direct Detection Indirect 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

– Full sky coverage – Sensitive to ~300 GeV – ΔE/E ~ 10%

• ACT's (Hess, Veritas,...)

– Smaller fraction of sky – Sensitive to TeV's

– ΔE/E ~ 15-20%

Contributions to the γ-rays spectrum

• Continuum spectrum
• Secondary γ's from quark or

gauge boson fragmentation, or

• from final state radiation from

charged SM particles.

• Almost featurless, but with

sharp cutoff at Wimp mass.

• Lines
• Loop-induced processes

into γ+X

• Spectral lines at
• “Smoking gun”

signature of dark matter

The Kaluza-Klein Zoo (1)

• 5D KK model

– UED compactified on a

circle

– KK modes identified by

• ne index, i.e.

– LKP is the KK partner of

the hypercharge gauge boson

– LKP is lepton-friendly – LKP mass can reach

1TeV

References: Bertone et al. (PRD 2003), Bergstrom et al. (PRL, 2004), Bergstrom et al. (JCAP 2004).

• 6D KK (Chiral Square)

– UED compactified on a square

with two adjacent sides identified

– KK modes identified by 2

indeces, i.e.

– LKP's are the two KK partner

• f hypercharge gauge boson

– LKP is lepton-unfriendly – Favors lighter LKP (up to 450

GeV)

References: Dobrescu and Ponton (JHEP, 2004), Dobrescu et al. (JCAP, 2007)

The Kaluza-Klein Zoo (2)

• 5D KK model

– Particles are even (odd)

if i is even (odd)

– Particle masses are

• 6D KK (Chiral Square)

– Particles are even (odd) if (i+j)

is even (odd)

– Particle masses are

The Kaluza-Klein Zoo (2)

• 5D KK model

– Particles are even (odd)

if i is even (odd)

– Particle masses are – LKP's can only pair-

annihilate into SM particles

• 6D KK (Chiral Square)

– Particles are even (odd) if (i+j)

is even (odd)

– Particle masses are

LKP's can pair-annihilate into other KK-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

• The largest uncertainties arise from the

lack of knowledge of the halo profile near the galactic center.

Microphysics Astrophysics (Halo profile)

Flux of γ from wimp annihilation

• Uncertainties in the halo

profile are quantified with

• We consider two benchmark

models, with :

–

Navarro-Frenk-White scenario

–

“Adiabatic compression”

• Astrophysical uncertainties

span three orders of magnitude

[Bertone et al., JCAP 2009]

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

• ne.
• 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
• ne coming from lines (cf Tait talk).
• Detection of a single bump and no drop off could

also hint toward a Wimp forest scenario.