Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Sub-GeV $U(1)_{R}$ gauge boson to address the proton radius discrepancy   We propose a Standard Model extension by a $U(1)_{R}$ gauge symmetry where
only right-handed chiral fermions can carry a non-trivial charge. Here we show
that the simplest anomaly-free solution to accommodate the proton charge radius
discrepancy takes right-handed muons $\mu_R$ and first generation quarks, $u_R$
and $d_R$. Consistency with the latest muon's $(g-2)$ measurements is achieved
through an extra light scalar, which itself must lie in the tens of MeV mass
range to be viable.

33
The categories of this paper are: plasm-ph
7
The categories of this paper are: hep-th
35
The categories of this paper are: mtrl-th
26
The categories of this paper are: bayes-an
29
The categories of this paper are: funct-an
1
The categories of this paper are: cs
22
The categories of this paper are: chao-dyn
23
The categories of this paper are: solv-int
24
The categories of this paper are: dg-ga
30
The categories of this paper are: q-alg
11
The categories of this paper are: hep-lat
36
The categories of this paper are: cmp-lg
4
The categories of this paper are: cond-mat
10
The categories of this paper are: q-bio
17
The categories of this paper are: q-fin
5
The categories of this paper are: gr-qc