Unsolved problems in particle physics
  I consider selected (most important according to my own choice) unsolved problems in particle theory, both those related to extensions of the Standard Model (neutrino oscillations, which probably do not fit the usual three-generation scheme; indications in favour of new physics from astrophysical observations; electroweak symmetry breaking and hierarchy of parameters) and those which appear in the Standard Model (description of strong interactions at low and intermediate energies). 
Sergey Troitsky
hep-ph