Chapter 5

Dark matter and particle physics

Antonio Masiero and Silvia Pascoli

SISSA, Trieste, Italy

Dark matter constitutes a key problem at the interface between particle physics,
astrophysics and cosmology. Indeed, the observational facts which have been
accumulated in the last years on dark matter point to the existence of an amount
of non-baryonic dark matter. Since the Standard Model (SM) of particle physics
does not possess any candidate for such non-baryonic dark matter, this problem
constitutes a major indication for new physics beyond the SM.
We analyse the most important candidates for non-baryonic dark matter
in the context of extensions of the SM (in particular supersymmetric models).
Recent hints of the presence of a large amount of unclustered ‘vacuum’ energy
(cosmological constant?) are discussed from the astrophysical and particle
physics perspective.

5.1 Introduction

The electroweak SM is now approximately 30 years old and it enjoys a full
maturity with an extraordinary success in reproducing the many electroweak tests
which have been going on since its birth. Not only have its characteristic gauge
bosons, W and Z, been discovered but also the top quark has been found in
the mass range expected by the electroweak radiative corrections, but the SM
has been able to account for an impressively long and very accurate series of
measurements. Indeed, in particular at LEP, some of the electroweak observables
have been tested with precisions reaching the per mille level without finding any
discrepancy with the SM predictions. At the same time, the SM has successfully
passed another very challenging class of exams, namely it has so far accounted
for all the very suppressed or forbidden processes where flavour-changing neutral
currents (FCNC) are present.

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