Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: First Search for the Flavor Changing Neutral Current Decay D^0 -> gamma
  gamma   Using 13.8 fb^{-1} of data collected at or just below the \Upsilon(4S) with
the CLEO detector, we report the result of a search for the flavor changing
neutral current process D^{0} \to \gamma\gamma.
  We observe no significant signal for this decay mode and determine 90%
confidence level upper limits on the branching fractions Br(D^{0}\to
\gamma\gamma)/Br(D^{0}\to\pi^{0}\pi^{0}) < 0.033 and Br(D^{0}\to\gamma\gamma) <
2.9 \times 10^{-5}.''

20
The categories of this paper are: acc-phys
31
The categories of this paper are: ao-sci
13
The categories of this paper are: quant-ph
15
The categories of this paper are: nucl-ex
9
The categories of this paper are: nlin
10
The categories of this paper are: q-bio
2
The categories of this paper are: math
22
The categories of this paper are: chao-dyn
19
The categories of this paper are: eess
26
The categories of this paper are: bayes-an
36
The categories of this paper are: cmp-lg
7
The categories of this paper are: hep-th
5
The categories of this paper are: gr-qc
37
The categories of this paper are: supr-con
4
The categories of this paper are: cond-mat
12
The categories of this paper are: nucl-th