Pomita Ghoshal

Research Summary:

During the last one year, I started my research work with Prof. Raj Gandhi in the field of neutrino physics.

• Currently I am working on studies of neutrino oscillations, especially in long-baseline experiments (e.g. MINOS, CERN to Gran-Sasso, Fermilab to SLAC). This involves an understanding of matter effects on neutrino oscillations.

  The evolution equation for neutrinos in matter can be solved analytically in the constant density approximation. We have tried to obtain analytic expressions for oscillation probabilities in constant density matter using certain approximations, and compared them with the results of a full numerical integration of the evolution equation.

  The PREM profile is used to obtain density profiles along the baseline as the neutrino beam passes through the earth, as well as to compute the relevant average density for a given baseline.

  The oscillation probabilities are useful in determining the neutrino mixing parameters, after accounting for certain degeneracies in the measurements. Recently we have focussed on muon neutrino survival probabilities as a probe for the determination of oscillation parameters.

• I have also been involved in calculations involving decay rates of polarized muons yielding muon neutrinos in neutrino factories. The standard expressions for energy and angular distribution of the emitted leptons include the muon mass and polarization, but neglect electron and neutrino masses and average over their polarizations. We have been trying to determine the distribution as a function of electron and finally neutrino masses and helicities. The object is to get some idea of the probability of obtaining wrong helicity neutrinos in such decays. This study may be expected to provide some insight into the Dirac/Majorana nature of neutrinos.

Conference/Workshops Attended:

• 19th Main SERC School on Theoretical High Energy Physics, University of Rajasthan, Jaipur (9th-28th February, 2004)

• International Conference on Perspectives in Particle Physics, Gravitation and Cosmology, Physical Research Laboratory, Ahmedabad (30th March-3rd April, 2004)

Other Activities:

Worked as a tutor for the course taken by Raj Gandhi in Quantum Mechanics for first year students in H.R.I (August - December, 2003).