P.hd in Belle ExperimentTata Institute of Fundamental Research
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P.hd in Belle Experiment
Our universe is composed mostly of matter particles such as protons, neutrons (that make up nucleus), and electrons rather than their antimatter partners: antiprotons, antineutrons, and positrons. This is in stark contrast with the prediction of the so-called big bang theory, which tells us that equal amounts of matter and antimatter were produced at the time of creation of the universe. So now the question is "What happened to the antimatter?". It is clear that a tiny imbalance between (matter) particles and antiparticles must have developed early in the evolution of the universe, or it all would have annihilated, leaving behind only photons. The Belle experiment at the KEK B-factory in Tsukuba (about 100km north of Tokyo), Japan is built to study that phenomenon called charge-parity (CP) violation in the decays of B mesons that are copiously produced in e+e- collisions. The main goal of the experiment is to look for differences in decays of the B mesons compared to their antimatter partners, the B-bar mesons, in the hope of understanding better the prevailing matter-antimatter asymmetry in the universe.
Belle recorded its first e+e- collision data in May 1999 and continues to take data till date, accumulating nearly 800 million BB-bar events. In this process it has broken its own luminosity record several times! Belle presented its first physics results at the Osaka conference in July 2000, and shortly afterward followed that up with the journal publication: Observation of Large CP Violation in the Neutral B Meson System. This was the first clear and unambiguous verification of the complex phase introduced by Makoto Kobayashi and Toshihide Maskawa in order to explain CP violation in the Standard Model of elementary particles. The highest laurel to the two B factories (the other one is the BaBar experiment at SLAC, Stanford, USA) has come as half of the 2008 Nobel Prize in physics being awarded to Kobayashi and Maskawa, for providing the experimental confirmation of their theory of CP violation.
The TIFR group has a vigorous research program with the Belle experiment. The major focus of our efforts has been on analyzing the high-quality experimental data and on producing physics results. Group members at past have made first observations of several B-meson decay channels mostly involving the b -> c quark-level transitions. We are now expanding the strategy to search for more rarer processes, including those dominated by the b -> s and b -> d quantum-loop diagrams. We are also involved in the R&D of silicon strip detectors for the proposed upgrade of the Belle experiment. Both Ph.D. and M.Sc. students are strongly encouraged to get in touch with either Prof. Tariq Aziz or Dr. Gagan Mohanty in order to explore various interesting topics for their theses and projects.