Kashiwa Symposium Lars Bergström, [email protected]Lars Lars Bergstr Bergström Department of Physics Department of Physics Stockholm University Stockholm University Kashiwa Symposium Lars Bergström, [email protected]1 1 0 3 29 2 2 2 0 100 / 10 88 . 1 8 3 − − − ≡ ⋅ = = ≡ Ω Mpc s km H h cm g h m H Pl crit crit i i π ρ ρ ρ Basic facts: Observations give 0.6 < h < 0.8 Big Bang nucleosynthesis and cosmic microwave background determine baryon contribution Ω B h 2 ≈ 0.02. Ω lum ≈ (4 ± 2) . 10 -3 (stars, gas, dust) => baryonic dark matter has to exist (maybe as warm intergalactic gas?) But, if Ω M > 0.06, there has to exist non- baryonic dark matter! K.M. Nollet, 2002
31
Embed
Lars Bergström Department of Physics Stockholm University · Kashiwa Symposium Lars Bergström, [email protected] Lars Bergström Department of Physics Stockholm University Kashiwa Symposium
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
New results from DASI (September 19, 2002): Polarisation detected at > 5σ. TE cross-correlation (2-3σ) agrees perfectly with prediction of Concordance Model, ΛCDM (ΩM = 0.3, ΩΛ = 0.7)
DASI team, J. Carlstrom et al. DASI team, J. Carlstrom et al.
• May or may not describe small-scale structure in galaxies: Controversial issue, but alternatives (self-interacting DM, warm DM, self-annihilating DM) seem worse.
CHANDRA LIMITS ON NATURE OF DARK MATTER. Dark matter distribution seems highly concentrated, in agreement with CDM. Self-interacting dark matter ruled out? (Loewenstein andMushotzky, astro-ph/0205359)
New Chandra results on cluster A2029: perfect fit to CDM, cored model ruled out (astro-ph/0209205).
ΩM ~ 0.3 in Concordance Model instead of ΩM ~ 1 in the ”Standard CDM” of the 1980’s→ Good news for dark matter searches!Explanation: ΩDM ~ 1/(σannv)Crossing symmetry ⇒ σscatt ~ σannThus, low ΩDM (if enough to make up galaxy halos) means higher annihilation & scattering rates
Supersymmetry• Invented in the 1970’s• Necessary in most string theories• Restores unification of couplings• Solves hierarchy problem• Gives right scale for neutrino masses• Predicts light Higgs ( < 130 GeV)• May be detected at Fermilab/LHC• Gives an excellent dark matter candidate (If R-parity is
conserved)• Useful as a template for generic “WIMP” (Weakly
• Allow most general soft SUSY-breaking terms, preserving R-parity:
The most general R-parity conserving lagrangian has 124 free parameters!We reduce to 7 parameters:µ: Higgsino mass parameterΜ2: Gaugino mass parametertanβ: ratio of Higgs vevsM3: Mass of pseudoscalar Higgs bosonM0 : scalar mass parameterAb, At: Soft trilinear parameters
• Major code reorganization to make it user-friendly.• Tested on RedHat Linux 7.3, LinuxPPC, MacOS X and Alphas.• Released now as a fully working beta-version.• Full release in autumn of 2002 with manual and long paper.• Download at http://www.physto.se/~edsjo/darksusy/• If you use it, please sign up on the DarkSUSY mailing list on that
DAMA seems completely ruled out! (However, if the halo has a more complicated DM structure with clumps and streams, this need not be so. See A.M. Green, 2002.)
Advantage of gamma rays: point back to the source. Enhanced flux possible thanks to substructure (as predicted by CDM)
Indirect detectionthrough γ-rays. Two types of signal: continuous (large rate but at lower energies, difficult signature) and monoenergetic line(small rate but at highest energy Eγ = mχ; ”smoking gun”).
• The flux in a given direction (averaged or not averaged over detector resolution ∆Ω) can be obtained for– continuum gamma rays– monochromatic gamma lines from γγ– monochromatic gamma lines from Zγ
• Both differential and integrated fluxes can be obtained.
Galactic center source – interesting but highly uncertain
Bergström, Ullio, Buckley 1998
Binney and Evans 2001: Microlensing data towards bulge indicate low DM density near center. NFW does not fit ⇒ <J> ≤ 100. However, clumps may enhance by at least factor 10 (also maybe spike from black hole; see later)
Simultaneous fit to radio emission (408 MHz) and EGRET γ-ray spectrum possible if halo is mildlysingular ρ(r) ∝ 1/r0.1, enhanced by formation of spike.
Many uncertainties: • spectral index & redshift distribution• intrinsic absorption & energy cut-off• cascading not included• has EGRET isolated the true extragalactic signal?
Indirect detection through neutralino capture and annihilation at the centre of the Earth or the Sun. However, Earth rates and direct detection rates are strongly correlated ⇒neutrinos not competitive with new DM direct detection experiments
Other indirect detection methods(often complementary to γ-rays)