Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Branching Ratio and CP Asymmetry of $B^0 \to \eta^{(\prime)}
  \eta^{(\prime)}$ Decays in the Perturbative QCD Approach   We calculate the CP averaged branching ratios and CP-violating asymmetries
for $B^0 \to \eta \eta, \eta \eta^\prime$ and $\eta^\prime \eta^\prime$ decays
by employing the perturbative QCD (pQCD) factorization approach. The pQCD
predictions for the CP-averaged branching ratios are $Br(B^0 \to \eta \eta)
\approx 0.67 \times 10^{-7}$, $Br(B^0 \to \eta \eta^\prime) \approx 0.18 \times
10^{-7}$, and $Br(B^0 \to \eta^{\prime} \eta^{\prime}) \approx 0.11 \times
10^{-7}$, which are consistent with currently available experimental upper
limits. We also predict large CP-violating asymmetries for the considered three
decay modes, which can be tested by the future B meson experiments.

5
The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
30
The categories of this paper are: q-alg
2
The categories of this paper are: math
9
The categories of this paper are: nlin
22
The categories of this paper are: chao-dyn
15
The categories of this paper are: nucl-ex
23
The categories of this paper are: solv-int
17
The categories of this paper are: q-fin
26
The categories of this paper are: bayes-an
36
The categories of this paper are: cmp-lg
29
The categories of this paper are: funct-an
1
The categories of this paper are: cs
24
The categories of this paper are: dg-ga
18
The categories of this paper are: econ
16
The categories of this paper are: stat