the self-annihilation cross section
DESCRIPTION
Upper Bound on the Dark Matter Annihilation Cross Section Gregory Mack CCAPP/The Ohio State University. The self-annihilation cross section. How large can the self-annihilation cross section be? That’s the question to ask Most often assumed – “natural scale” 3 x 10 -26 cm 3 /s. - PowerPoint PPT PresentationTRANSCRIPT
Upper Bound on the Dark Matter Annihilation Cross
Section
Gregory MackCCAPP/The Ohio State University
The self-annihilation cross section
How large can the self-annihilation cross section be?
That’s the question to ask
Most often assumed – “natural scale” 3 x 10-26 cm3/s
Early playing field First: Unitarity Limit from Q.M.
The probabilities for elastic and inelastic scattering must sum to 1
Unitarity of the scattering matrix
Early playing field Second: KKT Take a cuspy profile
and turn it into a core
KKT would need a BR of about 10-10 to not be seen in monoenergetic photons
Say it must be “invisible particles”
No invisible products: essentially two classes of annihilation products PhotonsPhotons (direct or eventual)
Hadrons pions photons Charged leptons radiative loss/internal
brehmsstrahlung Gauge bosons charged leptons Monoenergetic Photons
NeutrinosNeutrinos Sum of probabilities = 100%
Compare background fluxes to theoretical signals
Depends on if you’re looking at: diffuse contribution from all galaxies
Need to integrate over redshift and include the fact that dark matter is clumped in
galaxies
Galactic halo (at some angle from GC) External galaxy (M 31)
DM halo line-of-sight int.
DEPENDS ON PROFILE
Theoretical Signals
Neutrinos
Atmospheric neutrino background.
PhotonsINTEGRAL, COMPTEL, EGRET,
CELESTE, HESS, HEGRA
Regardless, divide background into energy bins to look
Combined constraint for 2 photons
Results for Kravtsov profile (NFW = lighter)
Wide range of masses
Limit takes the most stringent value at each mass
TOTAL cross section limits Wide-ranging
model-indep. limit
Conservative, comprehensive
Gamma limit is comparable to Neutrino
Mack, Beacom, Bell, Jacques, YükselAstro-ph/0803.0157v2 (PRD)
More cross section limits New limits on
photons coming from internal brehmsstrahlung from charged leptons
Bell and Jacques Astro-ph/
0811.0821v1
More cross section limits
We have the capability to make statements about the amount of annihilation dark matter experiences
General, comprehensive limits
Better data means tighter constraints
Conclusions
Extra Slides
Distribution
Different profiles different inner behavior
Moore ρ ~ 1/r1.5
NFW 1/r1.0
Kravtsov 1/r0.4
Moore
NFW
Kravtsov
n2Integral over redshift.The spectrum of neutrinosdepends on the redshift
Theoretical flux calculations – Analysis Methods
Line of sight integral – angular radius ψ
Average over a cone of half-angle ψ
Note: This was done by Yüksel, Horiuchi, Beacom, and Ando to modify our neutrino bound for the Milky Way
AMANDA and SK data support the non-existence of a signal from DM annih.
Atmospheric Neutrino Background
Munich (AMANDA), astro-ph/0509330
Ashie, et al (Super-K)PRD 71, 112005 (2005),Fully-contained events
J dependence on profile
YHBA figure Moore
NFW
Kravtsov
Background subtraction J delta’s minus specific J(psi)
HESS
INTEGRAL