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| Abstract: | Experimental Neutrino Physics is an active area of research in high energy physics. The investigation of the properties of this elusive particles has started since it’s discovery itself. In the standard model of particle physics, neutrinos are massless, the discovery of neutrino oscillation is the first evidence that demands the extensions of standard model. It is well established the existence of three active neutrinos, e, μ and , but recent experiments like LSND and MiniBooNE has found some anomalies in their data. These experimental data could not be explained using three flavour neutrino oscillation physics, but they could explain the anomaly by adding a fourth type neutrino called sterile neutrinos. The evidences obtained from these experiments are not yet conclusive. Search for sterile neutrino is an extensive research area in the field of neutrino physics. The main work presented in this thesis is a sterile neutrino search at MINOS (Main Injector Neutrino Oscillation Search) experiment at Fermilab, USA. MINOS is a two detector experiment at Fermilab, which studies the neutrinos produced at Fermilab Main Injector particle accelerator. MINOS Near Detector is situated at 1 km away from the source and the Far Detector is at Soudan Mine at Minnesota, 735 km away from the neutrino source. The experiment is built to study neutrino oscillation phenomena in the atmospheric sector and has made world class measurements on neutrino oscillation parameters. The MINOS experiment is also capable of looking for small perturbation in the energy spectra caused by any fourth type of neutrino and can extract the oscillation parameters. |
| URI: | http://dyuthi.cusat.ac.in/purl/5135 |
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| Dyuthi-T2169.pdf | (7.459Mb) |
| Abstract: | In the present thesis we have formulated the Dalgarno-Lewis procedure for two-and three-photon processes and an elegant alternate expressions are derived. Starting from a brief review on various multiphoton processes we have discussed the difficulties coming in the perturbative treatment of multiphoton processes. A small discussion on various available methods for studying multiphoton processes are presented in chapter 2. These theoretical treatments mainly concentrate on the evaluation of the higher order matrix elements coming in the perturbation theory. In chapter 3 we have described the use of Dalgarno-Lewis procedure and its implimentation on second order matrix elements. The analytical expressions for twophoton transition amplitude, two-photon ionization cross section, dipole dynamic polarizability and Kramers-Heiseberg are obtained in a unified manner. Fourth chapter is an extension of the implicit summation technique presented in chapter 3. We have clearly mentioned the advantage of our method, especially the analytical continuation of the relevant expressions suited for various values of radiation frequency which is also used for efficient numerical analysis. A possible extension of the work is to study various multiphoton processcs from the stark shifted first excited states of hydrogen atom. We can also extend this procedure for studying multiphoton processes in alkali atoms as well as Rydberg atoms. Also, instead of going for analytical expressions, one can try a complete numerical evaluation of the higher order matrix elements using this procedure. |
| Description: | Department of Physics, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/2847 |
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| Dyuthi-T0856.pdf | (2.863Mb) |
| Abstract: | In this thesis quark-antiquark bound states are considered using a relativistic two-body equation for Dirac particles. The mass spectrum of mesons includes bound states involving two heavy quarks or one heavy and one light quark. In order to analyse these states within a unified formalism, it is desirable to have a two-fermion equation that limits to one body Dirac equation with a static interaction for the light quark when the other particle's mass tends to infinity. A suitable two-body equation has been developed by Mandelzweig and Wallace. This equation is solved in momentum space and is used to describe the complete spectrum of mesons. The potential used in this work contains a short range one-gluon exchange interaction and a long range linear confining and constant potential terms. This model is used to investigate the decay processes of heavy mesons. Semileptonic decays are more tractable since there is no final state interactions between the leptons and hadrons that would otherwise complicate the situation. Studies on B and D meson decays are helpful to understand the nonperturbative strong interactions of heavy mesons, which in turn is useful to extract the details of weak interaction process. Calculation of form factors of these semileptonic decays of pseudo scalar mesons are also presented. |
| Description: | Department of Physics, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/2342 |
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| Dyuthi-T0615.pdf | (2.916Mb) |
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