Precision low energy measurements and search for physics beyond the standard model

Date of Completion

January 2002


Physics, Elementary Particles and High Energy




In the first two parts of this dissertation I present the complete calculation of one-loop contributions to low energy charged and neutral current weak interaction observables in the framework of the Minimal Supersymmetric Standard Model (MSSM). For the former, I perform the first model-independent analysis of charged current data and use it to constrain the MSSM parameter space. I show that the constraints are incompatible with the predictions of the most widely used models of SUSY breaking mediation and discuss possible solutions to this conflict. For neutral current reactions, I study the impact of SUSY corrections on the weak charges of the electron, QeW , and the proton, QpW . I show that the relative signs of the SUSY loop effects on QeW and QpW are correlated and positive, whereas inclusion of R-parity nonconserving interactions can lead to opposite sign relative shifts. Thus, a comparison of QpW and QeW measurements could help distinguish between different SUSY scenarios. ^ In the third part, I construct the relationship between effective, nonrenormalizable, time-reversal violating (TV) parity-conserving (PC) interactions of quarks and gauge bosons and various low-energy TVPC and TV parity-violating (PV) observables. I delineate the scenarios under which experimental limits on electric dipole moments (EDM's) of the electron, neutron, and 199Hg as well as limits on TVPC observables provide the most stringent bounds on new TVPC interactions. If parity invariance is restored at short distances, the one-loop EDM of elementary fermions generate the most severe constraints. If parity remains broken at short distances, direct TVPC limits provide the least ambiguous bounds. ^ In the fourth part I evaluate the one-loop SM radiative corrections to the charged (CC) and neutral (NC) current neutrino-deuterium disintegration cross sections for energies relevant to the Sudbury Neutrino Observatory (SNO) experiment. The correction to the total CC cross section is independent of the bremsstrahlung detection threshold. It slowly decreases with neutrino energy Eν from about 4% at low energies to 3% at the end of the 8B spectrum. The correction to the NC cross section amounts to about 1.5% and is energy-independent. ^