DIFFICULTIES IN EXPLAING THE COSMIC PHOTON EXCESS WITH COMPACT COMPOSITE OBJECT DARK MATTER

1. DIFFICULTIES IN EXPLAING THE COSMIC PHOTON EXCESS WITH COMPACT COMPOSITE OBJECT DARK MATTER Dan Cumberbatch arXiv:astro-ph/0606429 (accepted by Phys. Rev. D) Daniel Cumberbatch, Glenn Starkman & Joe Silk

2. Compact Composite Objects • Assemblies of colour superconducting pairs of u, d and s (anti)quarks • Phases: Colour Flavour Locked (CFL), 2SC, etc. (e.g. hep-ph/0011333 ) • CFL favoured (nu = nd = ns)  leptons excluded from bulk matter (Rajagopal & Wilcek, PRL (2000) ) • nq~O(1fm-3) (i.e. a few times nuclear densities) • Formed from Axion domain wall collapse during QCD phase transition (A. Zhitnitsky, astro-ph/0204218 ) • CCO Fermi Pressure Vs. Axion Domain Wall Surface Tension • B~1033 , R~6m, M~1 ton (!!!) • B >1020 possible (metastable) • CCO Dark Matter • Formed before light elements  doesn’t contribute to B • Effectively non-radiative (~B-1/3)  contributes to DM • Preferentially forms from antiquarks B asymmetry (Oaknin & Zhitnitsky, PRD (2005))

3. CCO DM and the Photon Excess • CCO DM also postulated to explain several astrophysical observations, including… 511 keV line signal (SPI/INTEGRAL) 1-20 MeV diffuse gamma-ray excess (COMPTEL) (Jean et al., A&A (2006)) 96.7+/-2.2% Positronium (Ahn & Komatsu, PRD (2005) ) How can CCO DM possibly explain these signals???

4. Charged CCOs • Qe = -0.3B2/3e ~ -3x1021e (!) (Madsen, PRL (2001) ) • Finite curvature of CCOs increases thermodynamic potentials •  Deficiency in massive antiquarks (i.e. ) at CCO surface ( z ~ 1fm) • CCO charge neutralized by accumulation of e+ from ISM • `Positronsphere’ surrounding bulk matter • Behaves like a Fermi gas (Thomas-Fermi model): Vc ~ 20 MeV (Alcock et al.)

5. e+ - e- interactions • (non-relativistic) e- from the ISM interact with positronsphere: • Forms positronium (Para- (25%), Ortho- (75%) ) with low energy e+ (resonant process) • Parapositronium decays  511 keV photons • Directly annihilates Continuum spectra 0 < E < PF (z) • Hence if e- penetrate to z = 0 E < Vc ~ 20MeV • Relative Rates (Zhitnitsky (2006) ): • Hence if incident electrons from the ISM can freely penetrate CCO positronspheres, CCO DM may explain the SPI and COMPTEL observations.

6. CCOs and the Photon Excess • But can ISM electrons freely penetrate the positronspheres….NO! Can ISM e- interact quickly enough / penetrate positronsphere deeply enough?

7. Classical Treatment • 2nd Law  • We must also investigate quantum effects…

8. QM Treatment • Quantum Tunnelling will increase time spent by e-’s in positronsphere and reduce effective zmin. • Solve for (non-relativistic)  using Numerov Method… Tunnelling effects are marginal…use classical trajectories

9. CCOs and the 511 keV Excess • Approximate upper limit for P using • Radial e- trajectory (~maximizes e+line density) • (geometrical overestimate) • Using classical trajectories, calculate suppression factor P • For NFW DM/Baryonic profiles, the 511 keV flux from CCO DM is

10. CCOs and the 1-20 MeV Excess • Production of MeV photons requires tunnelling to z~0 • Estimate Probability: • Since potential energy V decreases monotonically with decreasing z, we obtain upper estimate for by extrapolating to using In other words… …no MeV photons!

11. Conclusions • CCO DM is an unlikely explanation of the 511 keV line signal observed by SPI/INTEGRAL owing to insufficient rates of Positronium formation. • CCO DM is an unlikely explanation of the 1-20 MeV excess observed by COMPTEL owing to extremely strong repulsive effects within CCO positronspheres preventing incident ISM electrons from reaching high energy positrons residing at low altitudes. • Possibility of pair-production at low altitudes may result in high energy direct annihilations MeV photons. • Requires detailed knowledge of thermal structure of CCOs. • Photons would be largely attenuated by positronsphere. • CCO DM is still possible, though its motivation is weakened.