The Curious Early History of CKM Matrix -- miracles happen!

TL;DR

This paper reviews the early history of the CKM matrix, highlighting initial skepticism, subsequent discoveries, and its rise to prominence in particle physics research over the past 50 years.

Contribution

It provides a historical perspective on the development and acceptance of the CKM matrix, emphasizing overlooked circumstances and key discoveries that influenced its significance.

Findings

Initial rejection due to quark number assumptions

Discovery of the charmed quark boosted acceptance

CKM became central to flavor physics research

Abstract

The 1973 Kobayashi Maskawa paper proposed a compelling link between Cabibbo's flavor-mixing scheme and CP violation but, since it required the existence of six quarks at a time when the physics community was happy with only three, it received zero attention. However, two years after the paper appeared -- at which time it had received a grand total of two citations -- the charmed quark was discovered and it finally got some notice and acceptance. After this stumbling start, it subsequently emerged as the focal point of an enormous amount of experimental and theoretical research activity. In an invited talk at a KEK symposium to celebrate the 50th anniversary of the KM paper, I reviewed some of the less well known circumstances that occurred in the years preceding and following the paper's appearance.