Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Decays $K \to \pi \ell^+ \ell^-$ beyond Leading Order in the Chiral
  Expansion   We present a model-independent analysis of $K^+\to\pi^+\ell^+\ell^-$ and
$K_S\to\pi^0\ell^+\ell^-$ decays, including $K\to 3 \pi$ unitarity corrections
and a general decomposition of the dispersive amplitude. From the existing data
on $K^+\to\pi^+ e^+ e^-$ we predict the ratio $R=
B(K^+\to\pi^+\mu^+\mu^-)/B(K^+\to\pi^+ e^+ e^-)$ to be larger than 0.23, in
slight disagreement with the recent measurement $R = 0.167 \pm 0.036$.
Consequences for the $K^\pm \to\pi^\pm e^+ e^-$ charge asymmetries and for the
$K_L\to\pi^0 e^+ e^-$ mode are also discussed.

17
The categories of this paper are: q-fin
36
The categories of this paper are: cmp-lg
2
The categories of this paper are: math
15
The categories of this paper are: nucl-ex
5
The categories of this paper are: gr-qc
7
The categories of this paper are: hep-th
6
The categories of this paper are: astro-ph
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
10
The categories of this paper are: q-bio
30
The categories of this paper are: q-alg
31
The categories of this paper are: ao-sci
4
The categories of this paper are: cond-mat
22
The categories of this paper are: chao-dyn
16
The categories of this paper are: stat
14
The categories of this paper are: math-ph