Abstract
If there exists the mirror world, a parallel hidden sector of particles with exactly the same microphysics as that of the observable particles, then the primordial nucleosynthesis constraints require that the temperature of the cosmic background of mirror relic photons should be smaller than that of the ordinary relic photons, T′/T<0.5 or so. On the other hand, the present experimental and astrophysical limits allow a rather fast neutron–mirror neutron oscillation in vacuum, with an oscillation time τ∼1 s, much smaller than the neutron lifetime. We show that this could provide a very efficient mechanism for transporting ultra high energy protons at large cosmological distances. The mechanism operates as follows: a super-GZK energy proton scatters a relic photon producing a neutron that oscillates into a mirror neutron which then decays into a mirror proton. The latter undergoes a symmetric process, scattering a mirror relic photon and producing back an ordinary nucleon, but only after traveling a distance (T/T′)3 times larger than ordinary protons. This may relax or completely remove the GZK-cutoff in the cosmic ray spectrum and also explain the correlation between the observed ultra high energy protons and far distant sources as are the BL Lacs.
Highlights
We show that the possibility of such a fast oscillation opens up very intriguing prospects for understanding the problems concerning the cosmic rays at ultra high energies (UHE)
3 Implications for ultra high energy cosmic rays. It was pointed out a long time ago [16] that the cosmic microwave background (CMB) of relic photons makes the universe opaque to the ultra high energy cosmic rays (UHECR)
As for the non-linear scales, such a coherent cancellation cannot be expected because of the segregation between O- and M-matter components and between the respective magnetic fields. The physics of such a familiar and long studied particle as the neutron still contains a big loophole: the experimental data do not exclude that its oscillation time into a mirror partner can be as small as 1 s [14]
Summary
The hypothesis that there may exist a mirror world, a hidden parallel sector of particles which is an exact duplicate of our observable world, has attracted a significant interest over the past years in view of its implications for particle physics and cosmology [1]-[11] (for reviews, see [12, 13].) The basic concept can be formulated as follows: one has a theory given by the product G × G′ of two identical gauge factors with identical particle contents, where the ordinary particles belong to G and are singlets of G′, and vice versa, mirror particles belong to G′ and are singlets of G. ( on all fields and quantities of the mirror (M) sector will be marked with ′ to distinguish from the ones of the ordinary/observable (O) world.) The Lagrangians of both sectors are identical i.e., all coupling constants (gauge, Yukawa, Higgs) have the same pattern in the O- and M-worlds, which means that there is a discrete symmetry, the so called mirror parity, under the interchange of G and G′ gauge and matter fields [3]. There can exist interactions between the O- and M-fields mediated by some messengers, which may be pure gauge singlets or some fields in mixed representations of G×G′, an axion from a common Peccei-Quinn symmetry, as well as extra gauge bosons acting with both sectors, related e.g. with a common flavor or B − L gauge symmetries [8, 13]. Such interactions could induce the mixing of some neutral O-particles, elementary as well as composite, with their M-counterparts. We discuss the implications for the cosmic rays at super-GZK energies (sect. 3) and conclude with section 4
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