Page for Belle
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
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
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
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.