Below lists some of the unsolve problems facing particle physics. Some of these topics have already been discuss briefly elsewhere.
Higgs boson - According to the Standard Model, there is a class of carrier particle called Higgs boson, H0. It is though to responsible for the mass. It is thought that Higgs boson exerts a 'force field' so that when a particle is subjected under the field it experiences a 'drag'. It is this drag that causes the particle to have a mass. Since different particles will experience different drag, the mass of
different particles is therefore different. Higgs boson is predicted to have 0 spin, zero charge and very heavy, about 200 GeV/c2. The next generation particle accelerator such as the Large Hadron Collider (LHC), still under construction, will be able to detect this particle.
Proton decay - Proton is stable, at least well beyond the current age of the universe. Nevertheless, it is predicted by the Grand Unified Theories that protons have a lifetime in the order of 1031 years. The predicted force carrier have a mass in the order of 1014 GeV/c2, way beyond the energy of the existing particle accelerators. The alternative way is to detect for any spontaneous natural decay.
There are some ongoing experiments to probe the decay but none has yet been detected.
Why matter exist ? - When particle and antiparticle meet a spontaneous burst of pure energy is produced. This is called annihilation. Experiments show that matter and antimatter are created in equal amount. This indicates that way back to the 'era' when the universe was created (which should have the similar energetic conditions as in particle accelerators) the amount of matter should be equal to that of antimatter. If this is the case why did the antimatter not completely annihilate
the matter, leaving only energy (photons) in the universe? It is believed that there is a break down in the symmetry called the charge-parity, CP-violation. It is because of this violation that causes the amount of matter to be slightly more than antimatter. For this reason we, and the universe can exist. The origin of this violation is still poorly understood. It is hoped that the next generation accelerators will provide the answer to the effect.
There are many other mysteries. The above just mentioned a few which are (possibly) solvable in the near future. Other unsolved problems are such as the prediction of grand unified theories, a viable form of quantum theory of gravity and of course the still-sketchy theory of everything.