Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Measurement of the Branching Fraction For the Semi-Leptonic Decays
  $D^{0(+)}\to \pi^{-(0)}\mu^+\nu_\mu$ and Test of Lepton Flavor Universality   Using a data sample corresponding to an integrated luminosity of $2.93\,\rm
fb^{-1}$ taken at a center-of-mass energy of 3.773\,GeV with the BESIII
detector operated at the BEPCII collider, we perform an analysis of the
semi-leptonic decays $D^{0(+)}\to \pi^{-(0)}\mu^+\nu_\mu$. The branching
fractions of $D^0\to \pi^-\mu^+\nu_\mu$ and $D^+\to \pi^0\mu^+\nu_\mu$ are
measured to be $(0.272 \pm 0.008_{\rm stat.} \pm 0.006_{\rm syst.})\%$ and
$(0.350 \pm 0.011_{\rm stat.} \pm 0.010_{\rm syst.})\%$, respectively, where
the former is of much improved precision compared to previous results and the
latter is determined for the first time. Using these results along with
previous BESIII measurements of $D^{0(+)}\to \pi^{-(0)}e^+\nu_e$, we calculate
the branching fraction ratios to be ${\mathcal R}^0\equiv {\mathcal
B}_{D^{0}\to \pi^{-}\mu^+\nu_\mu}/{\mathcal B}_{D^{0}\to
\pi^{-}e^+\nu_e}=0.922\pm 0.030_{\rm stat.}\pm0.022_{\rm syst.}$ and ${\mathcal
R}^+\equiv {\mathcal B}_{D^{+}\to \pi^{0}\mu^+\nu_\mu}/{\mathcal B}_{D^{+}\to
\pi^{0}e^+\nu_e}=0.964\pm 0.037_{\rm stat.}\pm0.026_{\rm syst.}$, which are
compatible with the theoretical expectation of lepton flavor universality
within $1.7\sigma$ and $0.5\sigma$, respectively. We also examine the branching
fraction ratios in different four-momentum transfer square regions, and find no
significant deviations from the standard model predictions.

22
The categories of this paper are: chao-dyn
12
The categories of this paper are: nucl-th
7
The categories of this paper are: hep-th
1
The categories of this paper are: cs
35
The categories of this paper are: mtrl-th
26
The categories of this paper are: bayes-an
0
The categories of this paper are: hep-ph
29
The categories of this paper are: funct-an
31
The categories of this paper are: ao-sci
17
The categories of this paper are: q-fin
9
The categories of this paper are: nlin
10
The categories of this paper are: q-bio
21
The categories of this paper are: adap-org
6
The categories of this paper are: astro-ph
3
The categories of this paper are: physics
34
The categories of this paper are: chem-ph