Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Search for the Decay Kl -> pi0 e+ e-   We report on a search for the decay Kl -> pi0 e+ e- carried out by the
KTeV/E799 experiment at Fermilab. This decay is expected to have a significant
CP violating contribution and the measurement of its branching ratio could
support the CKM mechanism for CP violation or could point to new physics. Two
events were observed in the 1997 data with an expected background of 1.06
+-0.41 events, and we set an upper limit Br(Kl -> pi0 e+ e-) < 5.1 x 10^-10 at
the 90% confidence level.

18
The categories of this paper are: econ
29
The categories of this paper are: funct-an
13
The categories of this paper are: quant-ph
4
The categories of this paper are: cond-mat
10
The categories of this paper are: q-bio
19
The categories of this paper are: eess
3
The categories of this paper are: physics
24
The categories of this paper are: dg-ga
16
The categories of this paper are: stat
6
The categories of this paper are: astro-ph
9
The categories of this paper are: nlin
35
The categories of this paper are: mtrl-th
21
The categories of this paper are: adap-org
36
The categories of this paper are: cmp-lg
30
The categories of this paper are: q-alg
0
The categories of this paper are: hep-ph