Primordial He' abundance implied by the mirror dark matter interpretation of the DAMA/Libra signal

We compute the primordial mirror helium He' mass fraction emerging from Big Bang nucleosynthesis in the mirror sector of particles in the presence of kinetic mixing between photons and mirror photons. We explore the kinetic mixing parameter (epsilon) values relevant for cosmology and which are also currently probed by the dark matter direct detection experiments. In particular, we find that for epsilon \sim 10^{-9}, as suggested by the DAMA/Libra and other experiments, a large He' mass fraction (Y_{He'} \approx 90%) is produced. Such a large value of the primordial He' mass fraction will have important implications for the mirror dark matter interpretation of the direct detection experiments, as well as for the study of mirror star formation and evolution.Comment: 8 pages, 1 figur

Big Bang nucleosynthesis in visible and hidden-mirror sectors

One of the still viable candidates for the dark matter is the so-called mirror matter. Its cosmological and astrophysical implications were widely studied in many aspects, pointing out the importance to go further with research and refine the studies. In particular, the Big Bang nucleosynthesis provides a strong test for every dark matter candidate, since it is well studied and involves relatively few free parameters. The necessity of accurate studies of primordial nucleosynthesis with mirror matter has then emerged. In order to fill this lack, I present here the results of accurate numerical simulations of the primordial production of both ordinary nuclides and nuclides made of mirror baryons, in presence of a hidden mirror sector with unbroken parity symmetry and with gravitational interactions only. These elements are the building blocks of all the structures forming in the Universe, therefore their chemical composition is a key ingredient for astrophysics with mirror dark matter. The production of ordinary nuclides show differences from the standard model for a ratio of the temperatures between mirror and ordinary sectors x = T'/T > 0.3, and they present an interesting decrease of the abundance of 7Li. For the mirror nuclides, instead, one observes an enhanced production of 4He, that becomes the dominant element for x < 0.5, and much larger abundances of heavier elements.Comment: 6 pages, 3 figure

Early Universe cosmology with mirror dark matter

Mirror matter is a stable self-collisional dark matter candidate. If exact mirror parity is a conserved symmetry of nature, there could exist a parallel hidden (mirror) sector of the Universe which has the same kind of particles and the same physical laws of our (visible) sector. The two sectors interact each other predominantly via gravity, therefore mirror matter is naturally "dark". Here I briefly review the cosmological signatures of mirror dark matter, as Big Bang nucleosynthesis, primordial structure formation and evolution, cosmic microwave background and large scale structure power spectra, together with its compatibility with the interpretation of the DAMA annual modulation signal in terms of photon--mirror-photon kinetic mixing. Summarizing the present status of research and comparing theoretical results with observations/experiments, it emerges that mirror matter is not just a viable, but a promising dark matter candidate.Comment: 10 pages, 2 figures; contributed to "Invisible Universe International Conference", Paris, June 29 - July 3 2009; to be published in AIP proceeding

Have neutron stars a dark matter core?

Recent observational results for the masses and radii of some neutron stars are in contrast with typical observations and theoretical predictions for "normal" neutron stars. We propose that their unusual properties can be interpreted as the signature of a dark matter core inside them. This interpretation requires that the dark matter is made of some form of stable, long-living or in general non-annihilating particles, that can accumulate in the star. In the proposed scenario all mass-radius measurements can be explained with one nuclear matter equation of state and a dark core of varying relative size. This hypothesis will be challenged by forthcoming observations and could eventually be a useful tool for the determination of dark matter.Comment: 3 pages, 1 figur

Early Universe cosmology in the light of the mirror dark matter interpretation of the DAMA/Libra signal

Mirror dark matter provides a simple framework for which to explain the DAMA/Libra annual modulation signal consistently with the null results of the other direct detection experiments. The simplest possibility involves ordinary matter interacting with mirror dark matter via photon-mirror photon kinetic mixing of strength epsilon ~ 10^(-9). We confirm that photon-mirror photon mixing of this magnitude is consistent with constraints from ordinary Big Bang nucleosynthesis as well as the more stringent constraints from cosmic microwave background measurements and large scale structure considerations.Comment: 9 pages, 1 figure; updated computations for T'(T), removed computation of Y

A CoGeNT confirmation of the DAMA signal

The CoGeNT collaboration has recently reported a rising low energy spectrum in their ultra low noise germanium detector. This is particularly interesting as the energy range probed by CoGeNT overlaps with the energy region in which DAMA has observed their annual modulation signal. We show that the mirror dark matter candidate can simultaneously explain both the DAMA annual modulation signal and the rising low energy spectrum observed by CoGeNT. This constitutes a model dependent confirmation of the DAMA signal and adds weight to the mirror dark matter paradigm.Comment: About 8 pages, expanded and update

Thermodynamics of the early Universe with mirror dark matter

Mirror matter is a promising self-collisional dark matter candidate. Here we study the evolution of thermodynamical quantities in the early Universe for temperatures below ~100 MeV in presence of a hidden mirror sector with unbroken parity symmetry and with gravitational interactions only. This range of temperatures is interesting for primordial nucleosynthesis analyses, therefore we focus on the temporal evolution of number of degrees of freedom in both sectors. Numerically solving the equations, we obtain the interesting prediction that the effective number of extra-neutrino families raises for decreasing temperatures before and after Big Bang nucleosynthesis; this could help solving the discrepancy in this number computed at nucleosynthesis and cosmic microwave background formation epochs.Comment: 7 pages, 4 figures, 3 tables; changed values in Table I + minor change

Mirror and hidden sector dark matter in the light of new CoGeNT data

The CoGeNT collaboration has recently made available new data collected over a period of 15 months. In addition to more accurately measuring the spectrum of nuclear recoil candidate events they have announced evidence for an annual modulation signal. We examine the implications of these new results within the context of mirror/hidden sector dark matter models. We find that the new CoGeNT data can be explained within this framework with parameter space consistent with the DAMA annual modulation signal, and the null results of the other experiments. We also point out that the CoGeNT spectrum at low energies is observed to obey $dR/dE_R \propto 1/E_R^2$ which suggests that dark matter interacts via Rutherford scattering rather than the more commonly assumed contact (four-fermion) interaction.Comment: About 12 pages, matches published versio