Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A measurement of the branching fraction of the exclusive decay B^0 -->
  K^{*0}gamma   The b --> s gamma transition proceeds by a loop ``penguin'' diagram. It may
be used to measure precisely the couplings of the top quark and to search for
the effects of any new particles appearing in the loop. We present a
preliminary measurement of the branching fraction of the exclusive decay, B^0
--> K^{*0}gamma. We use 8.6 x 10^6 B-anti-B decays to measure B(B^0 -->
K^{*0}gamma) = (5.4+/-0.8+/-0.5) x 10^{-5}.

2
The categories of this paper are: math
33
The categories of this paper are: plasm-ph
27
The categories of this paper are: comp-gas
4
The categories of this paper are: cond-mat
35
The categories of this paper are: mtrl-th
36
The categories of this paper are: cmp-lg
17
The categories of this paper are: q-fin
23
The categories of this paper are: solv-int
15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
10
The categories of this paper are: q-bio
28
The categories of this paper are: alg-geom
13
The categories of this paper are: quant-ph
29
The categories of this paper are: funct-an
21
The categories of this paper are: adap-org