Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The $\epsilon'/\epsilon$-Story: 1976-2021   The ratio $\epsilon'/\epsilon$ measures the size of the direct CP violation
in $K_L\to\pi\pi$ decays $(\epsilon^\prime)$ relative to the indirect one
described by $\epsilon$ and is very sensitive to new sources of CP violation.
As such it played a prominent role in particle physics already for 45 years.
Due to the smallness of $\epsilon'/\epsilon$ its measurement required heroic
efforts in the 1980s and the 1990s on both sides of the Atlantic with final
results presented by NA48 and KTeV collaborations 20 years ago. Unfortunately,
even 45 years after the first calculation of $\epsilon'/\epsilon$ we do not
know to which degree the Standard Model agrees with this data and how large is
the room left for new physics contributions to this ratio. This is due to
significant non-perturbative (hadronic) uncertainties accompanied by partial
cancellation between the QCD penguin contributions and electroweak penguin
contributions. While the significant control over the short distance
perturbative effects has been achieved already in the early 1990s, with several
improvements since then, different views on the non-perturbative contributions
to $\epsilon'/\epsilon$ have been expressed by different authors over last
thirty years. In fact even today the uncertainty in the room left for NP
contributions to $\epsilon'/\epsilon$ is very significant. My own work on
$\epsilon'/\epsilon$ started in 1983 and involved both perturbative and
non-perturbative calculations. This writing is a non-technical recollection of
the steps which led to the present status of $\epsilon'/\epsilon$ including
several historical remarks not known to everybody. The present status of the
$\Delta I=1/2$ rule is also summarized. This story is dedicated to Jean-Marc
Gerard on the occasion of the 35th anniversary of our collaboration and his
64th birthday.

14
The categories of this paper are: math-ph
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
25
The categories of this paper are: patt-sol
13
The categories of this paper are: quant-ph
19
The categories of this paper are: eess
37
The categories of this paper are: supr-con
33
The categories of this paper are: plasm-ph
18
The categories of this paper are: econ
3
The categories of this paper are: physics
30
The categories of this paper are: q-alg
27
The categories of this paper are: comp-gas
29
The categories of this paper are: funct-an
1
The categories of this paper are: cs
36
The categories of this paper are: cmp-lg
9
The categories of this paper are: nlin