Rare B meson decays - mathieu trocmé

I- Introduction 5
I- INTRODUCTION
We live in a matter universe. However, from the ‘Hot Big Bang’ model – the current
model explaining the beginning of the universe (Gamow, 1946, [1]) – this universe began
with an equal amount of matter and antimatter. This model being widely accepted – especially
after the random discovery of the Cosmologic Microwave Background by Penzias and Wilson
in 1965 [2] – , one question comes to mind: Where has all the antimatter gone ? Many
theories generating a matter asymmetry have been proposed, even some antigravity ones. But
the current one is due to Sakharov (1967, [3]) and based on the ‘Sakharov’ conditions, one of
which is CP violation.
Basically, to turn the properties of a particle into the ones of its antiparticle, one just
needs to process a symmetry operation called CP. If this CP operation can be successfully
observed in a decay, matter and antimatter are absolutely symmetric. Otherwise, it proves
there is an asymmetry between matter and antimatter, which could be one explanation of the
matter asymmetry in the universe.
From the middle of the sixties, it has been known that CP violation is a real
phenomenon that occurs in weak decays. Since then, a quantification work has been
undertaken to determine whether or not CP violation processes alone can lead to an
explanation of the universe matter asymmetry.
Having successfully studied K meson systems first, physicists currently track CP
violation in B meson systems. Two major recent collaboration are involved in that study: the
BELLE collaboration at the KEK-B collider in Japan and the BABAR one at SLAC in
California. These both collaborations have already observed CP violation in B mesons [4].
But there is still a lot to do…