Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Muon decays with lepton--number violation via vector leptoquark   The decays $\mu \rightarrow e \gamma$, $\mu \rightarrow e \gamma \gamma$, and
$\mu \rightarrow e e \bar e$ are analysed in the framework of the Pati-Salam
type quark-lepton symmetry $SU(4)_V \otimes SU(2)_L \otimes G_R$ where the
effects of mixing in the quark-lepton currents are taken into account. It is
shown that the $\mu \rightarrow e \gamma \gamma$ and $\mu \rightarrow e e \bar
e$ decays via the vector leptoquark have not a GIM--type suppression, while the
$\mu \rightarrow e \gamma$ decay has. So, the specific hierarchy of the decay
probabilities could take place $\Gamma(\mu \rightarrow e e \bar e) \gg
\Gamma(\mu \rightarrow e \gamma \gamma) \gg \Gamma(\mu \rightarrow e \gamma)$.
The existing bounds on the vector leptoquark mass and on the mixing matrix
elements, based on the data for the $\mu e$ conversion in nuclei and for the
ratio of the $K_{e 2}$ and $K_{\mu 2}$ decays allow to set the upper limits on
the branching ratios at a level of $10^{-18}$ for the $\mu \rightarrow e \gamma
\gamma$ decay and at a level of $10^{-15}$ for the $\mu \rightarrow e e \bar e$
decay.

36
The categories of this paper are: cmp-lg
5
The categories of this paper are: gr-qc
29
The categories of this paper are: funct-an
31
The categories of this paper are: ao-sci
18
The categories of this paper are: econ
9
The categories of this paper are: nlin
34
The categories of this paper are: chem-ph
1
The categories of this paper are: cs
19
The categories of this paper are: eess
8
The categories of this paper are: hep-ex
12
The categories of this paper are: nucl-th
13
The categories of this paper are: quant-ph
2
The categories of this paper are: math
30
The categories of this paper are: q-alg
24
The categories of this paper are: dg-ga
32
The categories of this paper are: atom-ph