CP Violation Group at the University of Chicago

Previous experiments

Before we were able to start E14 at J-PARC, other experiments were carried out. These provided us with a lot of useful information that was necessary to prepare this experiment, and suggested some results. These are:

E799-I (1993), Fermilab

This experiment focused primarily on the decay K_L -> π⁰ e⁺ e^-. However, its results showed that the rate of the decay K_L -> π⁰ ν ν is higher than it should be according to the CKM matrix.

E799-II (1996-97), KTeV

Here, the preceding measurements were repeated with a higher sensitivity.

E832 (1996-1997), KTeV

E832 used the same beamline as E799-II, but in a different configuration. The reason was that this time, it focused on the ratio ε / ε'.
E799-II & E832 summary

E391a (2008), KEK

There were three long running periods in the E391a experiment. Run I took place between the beginning of February and the middle of July of 2004. Run II began in February of 2005 and finished in April of that year. Finally, Run III took place in the fall of 2005, from October through early December.
Thanks to this experiment, the upper bound of the rate of K_L -> π⁰ ν ν was established.
Experiment summary

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