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Register a new userA new test of the light dark matter hypothesis
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Detection of a surprisingly high flux of positron annihilation radiation from the inner galaxy has motivated the proposal that dark matter is made of weakly interacting light particles (possibly as light as the electron). This scenario is extremely hard to test in current high energy physics experiments. Here, however, we demonstrate that the current value of the electron anomalous magnetic moment already has the required precision to unambiguously test the light dark matter hypothesis. If confirmed, the implications for astrophysics are far-reaching.
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The EW-$ u_R$ model was constructed in order to provide a seesaw scenario operating at the Electroweak scale $Lambda_{EW} sim 246$ GeV, keeping the same SM gauge structure. In this model, right-handed neutrinos are non-sterile and have masses of the order of $Lambda_{EW}$. They can be searched for at the LHC along with heavy mirror quarks and leptons, the lightest of which have large decay lengths. The seesaw mechanism requires the existence of a complex scalar which is singlet under the SM gauge group. The imaginary part of this complex scalar denoted by $A^{0}_s$ is proposed to be the sub-MeV dark matter candidate in this manuscript. We find that the sub-MeV scalar can serve as a viable non-thermal feebly interacting massive particle (FIMP)-DM candidate. This $A_s^0$ can be a naturally light sub-MeV DM candidate due to its nature as a pseudo-Nambu-Goldstone (PNG) boson in the model. We show that the well-studied freeze out mechanism falls short in this particular framework producing DM overabundance. We identify that the freeze in mechanism produce the correct order of relic density for the sub-MeV DM candidate satisfying all applicable constraints. We then discuss the DM parameter space allowed by the current bounds from the direct and indirect searches for this sub-MeV DM. This model has a very rich scalar sector, consistent with various experimental constraints, predicts a $sim 125$ GeV scalar with the SM Higgs characteristics satisfying the current LHC Higgs boson data.
Dark matter, proposed decades ago as a speculative component of the universe, is now known to be the vital ingredient in the cosmos, eight times more abundant than ordinary matter, one quarter of the total energy density and the component which has controlled the growth of structure in the universe. Its nature remains a mystery, but, assuming it is comprised of weakly interacting sub-atomic particles, is consistent with large scale cosmic structure. However, recent analyses of structure on galactic and sub-galactic scales have suggested discrepancies and stimulated numerous alternative proposals. We discuss how studies of the density, demography, history and environment of smaller scale structures may distinguish among these possibilities and shed new light on the nature of dark matter.
We address the question of gravitino dark matter in the context of gauge mediated supersymmetry breaking models.
We present $psi$MSSM, a model based on a $U(1)_{psi}$ extension of the minimal supersymmetric standard model. The gauge symmetry $U(1)_{psi}$, also known as $U(1)_N$, is a linear combination of the $U(1)_chi$ and $U(1)_psi$ subgroups of $E_6$. The model predicts the existence of three sterile neutrinos with masses $lesssim 0.1~{rm eV}$, if the $U(1)_{psi}$ breaking scale is of order 10 TeV. Their contribution to the effective number of neutrinos at nucleosynthesis is $Delta N_{ u}simeq 0.29$. The model can provide a variety of possible cold dark matter candidates including the lightest sterile sneutrino. If the $U(1)_{psi}$ breaking scale is increased to $10^3~{rm TeV}$, the sterile neutrinos, which are stable on account of a $Z_2$ symmetry, become viable warm dark matter candidates. The observed value of the standard model Higgs boson mass can be obtained with relatively light stop quarks thanks to the D-term contribution from $U(1)_{psi}$. The model predicts diquark and diphoton resonances which may be found at an updated LHC. The well-known $mu$ problem is resolved and the observed baryon asymmetry of the universe can be generated via leptogenesis. The breaking of $U(1)_{psi}$ produces superconducting strings that may be present in our galaxy. A $U(1)$ R symmetry plays a key role in keeping the proton stable and providing the light sterile neutrinos.
We consider the possibility of using dark matter particles mass and its interaction cross section as a smoking gun signal of the existence of a Big Bounce at the early stage in the evolution of our currently observed universe. A study of dark matter production in the pre-bounce contraction and the post bounce expansion epochs of this universe reveals a new venue for achieving the observed relic abundance of our present universe. Specifically, it predicts a characteristic relation governing a dark matter mass and interaction cross section and a factor of $1/2$ in thermally averaged cross section, as compared to the non-thermal production in standard cosmology, is needed for creating enough dark matter particle to satisfy the currently observed relic abundance because dark matter is being created during the pre-bounce contraction, in addition to the post-bounce expansion. As the production rate is lower than the Hubble expansion rate information of the bounce universe evolution is preserved. Therefore once the value of dark matter mass and interaction cross section are obtained by direct detection in laboratories, this alternative route becomes a signature prediction of the bounce universe scenario. This leads us to consider a scalar dark matter candidate, which if it is light, has important implications on dark matter searches.
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