Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Softly broken lepton numbers and maximal neutrino mixing   We consider lepton mixing in an extension of the Standard Model with three
right-handed neutrino singlets. We require that the three lepton numbers L_e,
L_\mu, and L_\tau be separately conserved in the Yukawa couplings, and we
assume that they are softly broken only by the Majorana mass matrix M_R of the
neutrino singlets. In this framework, where lepton-number breaking occurs at a
scale much higher than the electroweak scale, deviations from
family-lepton-number conservation are calculable and finite, and lepton mixing
stems exclusively from M_R. We then show that a discrete symmetry exists such
that, in the lepton mixing matrix U, maximal atmospheric neutrino mixing
together with U_{e3}=0 can be obtained naturally. Alternatively, if one assumes
that there are two different scales in M_R and that the lepton number \bar L =
L_e - L_\mu - L_\tau is conserved in between them, then maximal solar neutrino
mixing follows naturally. If both the discrete symmetry and intermediate \bar L
conservation are introduced, bimaximal mixing is achieved.

15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
36
The categories of this paper are: cmp-lg
20
The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph
23
The categories of this paper are: solv-int
6
The categories of this paper are: astro-ph
10
The categories of this paper are: q-bio
29
The categories of this paper are: funct-an
2
The categories of this paper are: math
16
The categories of this paper are: stat
17
The categories of this paper are: q-fin
12
The categories of this paper are: nucl-th
26
The categories of this paper are: bayes-an
22
The categories of this paper are: chao-dyn
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The categories of this paper are: alg-geom