celine bœhm, moriond electroweak 2005
DESCRIPTION
Light Dark Matter particles. Possible detection in particle physics experiments?. Celine Bœhm, Moriond ElectroWeak 2005. New physics by INTEGRAL/SPI?. 1. Detection of a 511 keV emission line in the centre of the Milky Way. Explanation: electron-positron annihilation. - PowerPoint PPT PresentationTRANSCRIPT
Celine Bœhm, Moriond ElectroWeak 2005
Light Dark Matter particles
Possible detection in particle physics experiments?
Celine Bœhm, Moriond ElectroWeak 2005
New physics by INTEGRAL/SPI?
1. Detection of a 511 keV emission line in the centre of the Milky Way
2. Possible explanations:
Explanation:electron-positron
annihilation
Supernovae, Wolf-Rayet stars, Low Mass Binaries, …, Dark Matter
Celine Bœhm, Moriond ElectroWeak 2005
r~33deg
Large exposure data but: the Bulge is where most of the signal comes from
Problem faced by SN, Wolf Rayet stars etc (except LMB, DM):
the ratio bulge-to-disk is generally not large enough
Celine Bœhm, Moriond ElectroWeak 2005
1. Results from a model fitting analysis (modelling the source)
FWHM ~ 8.5deg
1e-3 ph/cm2/s
2. DM must fit both the FWHM, the flux and the ratio bulge-to-disk
Celine Bœhm, Moriond ElectroWeak 2005
DM has a ratio bulge/disk compatible with observations
DM annihilations into e+ e- can produce the galactic positrons
• The positrons must be almost at rest
• They must lose their energy through ionization
• Once at rest, they form positronium and produce 2 or 3 photons
This requires mDM < 100 MeV (i.e. very light DM particles).
Celine Bœhm, Moriond ElectroWeak 2005
A. How light DM can be ? (Astrophysics)
Annihilations in the centre produce too much low energy gamma rays.
Solution:
The annihilation cross section must vary with time for mdm< 100 MeV.
Particle Physics requirement:
The annihilation cross section must be dominated by a velocity-dependent
(Boehm, Ensslin, Silk, 2002)
Celine Bœhm, Moriond ElectroWeak 2005
If DM is a fermion and coupled to heavy particles (Z, W) then it should be heavier than a few GeV.
Lee-Weinberg:
B. How light DM can be ? (Particle Physics)
Boehm-Fayet:
If DM is a fermion and coupled to light particles then it can be lighter than a few GeV.
If DM is a scalar and coupled to light or heavy particles then it can be lighter than a few GeV.
Celine Bœhm, Moriond ElectroWeak 2005
Interpretation:
Light scalars (Boehm&Fayet, 2003):
coupled to heavy particles (F): v-independent cross section
coupled to light particles (Z’): v-dependent cross section
Light fermions (Fayet 2004):
coupled to light particles (Z’): v-dependent cross section
Z’ are required to escape the Gamma ray constraints
22 2 2 2dm
dm U Ul Ur4U
m v v C (f + f )
m
Celine Bœhm, Moriond ElectroWeak 2005
First Results
Flux OK with observations: the cross section must be about five order of magnitude lower than the annihilation cross section for the relic density
Z’ favoured!
Halo density profile:
Assumptions: 1/r
as MW halo profile is still unknown
Celine Bœhm, Moriond ElectroWeak 2005
New Results:
taking into account more data (16 deg)
Boehm&Ascasibar, 2004
Implementation of the right velocity dispersion profile
Celine Bœhm, Moriond ElectroWeak 2005
New and Preliminary Results:
Implementation of the e+ distribution for realistic halo profiles (NFW, Moore, Binney-Evans, Isothermal) in INTEGRAL analysis
(the source!)
Implementation of the right velocity dispersion profile
More data, including Dec 2004
New results obtained in collaboration with INTEGRAL
Celine Bœhm, Moriond ElectroWeak 2005
Celine Bœhm, Moriond ElectroWeak 2005
Consequences:
Exchange of heavy particles is needed to fit the 511 keV line
NFW profile is THE profile that fits the data!
For mF ~100 GeV For mF ~1 TeV
Celine Bœhm, Moriond ElectroWeak 2005
Fermionic DM seems to be excluded:
Decaying DM is excluded (unless ??? the profile is extremely cuspy):
Consequences for Particle Physics
NuTeV
Alpha value (anomalous magnetic moment of the electron)
Celine Bœhm, Moriond ElectroWeak 2005
S. Davidson et al
Celine Bœhm, Moriond ElectroWeak 2005
Note on Beacom et al, 2004
But they do not compute the process. They use the result of e+ e- into mu+ mu- valid for gamma exchange which is factorizable.
However, the F exchange is not factorizable.
The final result could change!
Mdm < 20 MeV because of the Final State Radiation
Celine Bœhm, Moriond ElectroWeak 2005
Conclusions
Heavy fermions are required but Z’ exchange possible too
NFW profile (consequences for the MW profile if LDM exists)
Scalar DM
Fermionic and decaying DM are ruled out
Look like SUSY but relationship between the couplings and MF,
Possible implication for NuTeV and the alpha value
J. Kn¨odlseder et al.: SPI/INTEGRAL constraints on the morphology of the galactic 511 keV line emission