Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Laboratory limit on the charge of photons by electric field deflection   The deflection of a laser beam traveling through a modulated electric field
is measured using phase-sensitive detection to place an upper bound on photon
charge. An upper limit of $10^{-14}e$ is obtained. The experiment involves a
number of experimental techniques that are commonly encountered in modern
precision measurements and is suitable for both advanced undergraduate and
beginning graduate students in physical science as a laboratory exercise.

23
The categories of this paper are: solv-int
11
The categories of this paper are: hep-lat
33
The categories of this paper are: plasm-ph
25
The categories of this paper are: patt-sol
34
The categories of this paper are: chem-ph
26
The categories of this paper are: bayes-an
14
The categories of this paper are: math-ph
30
The categories of this paper are: q-alg
29
The categories of this paper are: funct-an
10
The categories of this paper are: q-bio
6
The categories of this paper are: astro-ph
15
The categories of this paper are: nucl-ex
1
The categories of this paper are: cs
0
The categories of this paper are: hep-ph
21
The categories of this paper are: adap-org
22
The categories of this paper are: chao-dyn