Aspects and probes of supersymmetric and extradimensional beyond the standard model theories

The Standard Model (SM) of high energy physics suffers from the gauge hierarchy problem, which is the fine-tuning required to maintain a low Higgs mass given a high fundamental scale. Given this, it appears that the SM should be viewed as a low energy effective theory of an even more fundamental theory. Aspects of this underlying theory, which we wish to find, and might come into evidence in future experiments are termed as "beyond the SM physics".; Supersymmetry, extra dimensions and technicolor have been proposed to address the gauge hierarchy problem. In this thesis we will analyze various aspects of the supersymmetric and extradimensional proposals.; An important way to look for new particles is through virtual quantum effects when the energy available is insufficient to produce them on-shell. We will consider one such indirect means to probe supersymmetry, CP violation in b → sgamma.; The mass of the gravitino, which arises in spontaneously broken supergravity theories, is unknown, since we lack a precise understanding of how supersymmetry is broken. A superlight gravitino having a mass of around 10-4 eV can be interesting in next generation colliders. We consider electron-photon collisions producing a superlight gravitino and compute the reach of a linear collider in probing the supersymmetry breaking scale.; We consider the subtleties associated in interpreting a deviation from the SM in the e+ e - → gamma + E/ channel, where E/ denotes missing energy. We will show that an excess in this channel due to a superlight gravitino looks very similar to the one due to the production of a Kaluza-Klein tower of gravitons in an extradimensional theory.; We consider a scenario of having SU(5) gauge bosons propagating in the extra dimension of the Randall-Sundrum scenario and analyze the constraints due to proton decay. We find that matter can be on the Planck brane but the constraints exclude it from being on the TeV brane.