Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: First experimental determination of the charge radius of $^{74}$Rb and
  its application in tests of the unitarity of the CKM matrix   Collinear-laser spectroscopy with bunched-beams technique was used for the
study of neutron deficient Rb isotopes, out to $^{74}$Rb ($N=Z=37$) at TRIUMF.
The measured hyperfine coupling constants of $^{76,78m}$Rb were in agreement
with literature values. The nuclear spin of $^{75}$Rb was confirmed to be
$I=3/2$, and its hyperfine coupling constants were measured for the first time.
The mean-square charge radius of $^{74}$Rb was determined for the first time.
This result has improved the isospin symmetry breaking correction term used to
calculate the $\mathcal{F}t$ value, with implications for tests of the
unitarity of the Cabibbo-Kobayashi-Maskawa matrix.

7
The categories of this paper are: hep-th
21
The categories of this paper are: adap-org
2
The categories of this paper are: math
32
The categories of this paper are: atom-ph
0
The categories of this paper are: hep-ph
35
The categories of this paper are: mtrl-th
3
The categories of this paper are: physics
16
The categories of this paper are: stat
24
The categories of this paper are: dg-ga
4
The categories of this paper are: cond-mat
37
The categories of this paper are: supr-con
28
The categories of this paper are: alg-geom
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
17
The categories of this paper are: q-fin
33
The categories of this paper are: plasm-ph