Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Prospects of In-Flight Hyperfine Spectroscopy of (Anti)Hydrogen for
  Tests of CPT Symmetry   The ground-state hyperfine splitting of antihydrogen promises one of the most
sensitive tests of CPT symmetry. The ASACUSA collaboration is pursuing a
measurement of this splitting in a Rabi-type experiment using a polarized beam
from a CUSP magnet at the Antiproton Decelerator of CERN. With the initial
intention of characterizing the Rabi apparatus, a polarized source of cold
hydrogen was built and the $\sigma_1$ transition of hydrogen was measured to a
few ppb precision. A measurement of the $\pi_1$ transition is being prepared.
The availability of this beam opens the possibility to perform first
measurements of some coefficients within the nonminimal Standard-Model
Extension.

23
The categories of this paper are: solv-int
12
The categories of this paper are: nucl-th
2
The categories of this paper are: math
34
The categories of this paper are: chem-ph
32
The categories of this paper are: atom-ph
19
The categories of this paper are: eess
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
15
The categories of this paper are: nucl-ex
24
The categories of this paper are: dg-ga
7
The categories of this paper are: hep-th
35
The categories of this paper are: mtrl-th
10
The categories of this paper are: q-bio
4
The categories of this paper are: cond-mat
9
The categories of this paper are: nlin
33
The categories of this paper are: plasm-ph