Abstract
We recap the main features of minimal dark matter (MDM) and assess its status in the light of recent experimental data. The theory selects an electroweak 5-plet with hypercharge Y=0 as a fully successful DM candidate, automatically stable against decay and with no free parameters: DM is a fermion with a 9.6 TeV mass. The direct detection cross-section, predicted to be 10−44 cm2, is within reach of next-generation experiments. DM is accompanied by a charged fermion 166 MeV heavier: we discuss how it might manifest. Thanks to an electroweak Sommerfeld enhancement of more than 2 orders of magnitude, DM annihilations into W+W− give, in the presence of a modest astrophysical boost factor, an e+ flux compatible with the PAMELA excess (but not with the ATIC hint for a peak: MDM instead predicts a quasi-power-law spectrum), a flux concentrated at energies above 100 GeV, and photon fluxes comparable with present limits, depending on the DM density profile.
Highlights
Recover many good properties of the SM that are lost in these extensions
We follow a constructive approach by scanning all the possible choices of quantum numbers and selecting the successful DM candidates: insisting on full minimality we will see that consistency and phenomenological constraints reject most of the candidates and individuate only one (the fermionic SU (2) quintuplet with hypercharge Y = 0), of which we will study the phenomenology
The minimal dark matter (MDM) model is constructed by adding on top of the SM a single fermionic or scalar multiplet X charged under the usual SM SUL(2) × UY (1) EW interactions (that is: a WIMP; it is assumed not to be charged under SUc(3) strong interactions as the bounds are strong on this possibility6)
Summary
The MDM model is constructed by adding on top of the SM a single fermionic or scalar multiplet X charged under the usual SM SUL(2) × UY (1) EW interactions (that is: a WIMP; it is assumed not to be charged under SUc(3) strong interactions as the bounds are strong on this possibility). The fermionic 3-plet with hypercharge Y = 0 would couple through a Yukawa operator X L H with an SM lepton doublet L and a Higgs field H and decay in a very short time This is not a viable DM candidate, unless the operator is eliminated by some ad hoc symmetries (see again appendix B). The ‘MDM’ construction singles out a fermionic SU (2)L 5-plet with hypercharge Y = 0 as providing a fully viable, automatically stable DM particle It is called ‘MDM’ since it is described by the minimal gauge-covariant Lagrangian that one obtains adding the minimal amount of new physics to the SM in order to explain the DM problem
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