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My first
research was neutrino phenomenology and particle detector development in
master’s course. In neutrino physics, I studied massive neutrinos and their mixing
parameters. According to neutrino oscillation experiments, the interaction
eigenstates of neutrinos are not the mass eigenstates as well as neutrinos must
have non-zero masses. This mixing is similar structure to but much larger than
that of quark sector. I assumed a model so called “complex quark-lepton
complementarity” and derived the parameters from the model. The model is
based on two ideas. One of them is that theoretical frame explaining quark
sector, Cabbibo-Kobayashi-Maskawa matrix, is very similar to that of neutrino
sector, Pontecorvo-Maki-Nakagawa-Sakata matrix. The matrices are factorized to
three elementary rotation matrices(Eulerian rotation matrices) and one complex
phase matrix. The other is that each sum of angles corresponding to the same
elementary matrix in two mixing matrices is almost pi/4. This is called
quark-lepton complementarity model. Because two matrices describe rotations in
3-dimensional complex space, the complementarity can be generalized to 3-dimensional
complex space and one of their eigenvectors can be taken as the axis of rotation.
After taking the axis, we can determine rotation angles of two matrices around
the axis. My argument is two angles have relation similar to Pythagorean
theorem. The relation acts as a constraint to mixing angles, so unknown mixing
parameters can be derived.

In particle
detector project, my task was to design detector chamber and to simulate
current signal obtained by detector circuit originated from high energy cosmic
ray. The chamber was type of multiwire proportional chamber. I made the chamber
design with a computer aided design software. The chamber was operated in
vacuum because high voltage was assigned to multi-wire and poor vacuum might
cause to air breakdown. To obtain simulated signal, thanked to a simulation
code developed by a member in my group, which traced pathes of charged
particles induced by cosmic rays in the field, temporal charge signal was
interpreted as current, which was converted to oscilloscope waveform after amplifier
circuit by circuit simulation program.

The second
research was ultra-high power laser experiment. When I was in Advanced
Photonics Research Institute, I participated in extremely intensive laser
application experiments, which were particle acceleration and secondary radiation
generation. In the experiments, my major tasks were to operate detectors and to
analyse obtained signal. When a target is irradiated by extremely intensive and
short laser pulse, charged particles are accelerated and secondary lights like
water window x-ray and x-ray laser are generated by interaction between laser
and plasma. To distinguish particle species, we developed Time-of-flight
spectrometer and Thomson parabola spectrometer. In the development, I did
assemble, examine, calibrate, and operate the detectors and wrote program code
to diagnose characteristics of particles: energy, current, temperature,
divergence, and spectrum. Another part of my tasks was to produce ultra-thin
film of a few nm thickness to use as laser target. I made the film with
spin-coating method from an organic polymer and multi-layer film of the polymer
and metal with plasma enhanced chemical vapor deposition devices. The film was
used as a target to accelerate heavy ions with relativistic kinetic energy. As
a minor part of jobs, I was assistant manager of radiation safety: radioisotope
management and radiation detector monitoring.

As shown above,
I am good at dealing with physical problems by mathematical, computational, and
experimental methods because I have experienced both laboratories of theory and
experiment. Even though portion for me to perform works related to solid state
physics is small, my experience is benefit because when I try to solve a
problem, it will allow me to approach different sight of view to traditional
ways. Hence, I would propose and perform experiments to prove my theories and
arguments.

All in all, I
was a generalist who is experienced in many fields: particle, plasma, optics,
and nuclear physics and in various methodologies: theoretical, computational,
and experimental researches. Now, I want to proceed a specialized physicist
studying solid state material or heavy ion acceleration. Solid state physics Explaining
my academic objectives concretely, I want to find mathematical structure to
understand matters, to compute its physical properties using computational
tools such as density functional theory if there is no analytic solution, and
to prove it from experiments. My experiences will be helpful to research
because broad experiences should give me creative ideas and solutions for the
unsolved