Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A neutrino mass matrix with seesaw mechanism and two-loop mass splitting   We propose a model which uses the seesaw mechanism and the lepton number
$\bar L = L_e - L_\mu - L_\tau$ to achieve the neutrino mass spectrum $m_1 =
m_2$ and $m_3 = 0$, together with a lepton mixing matrix $U$ with $U_{e3} = 0$.
In this way, we accommodate atmospheric neutrino oscillations. A small mass
splitting $m_1 > m_2$ is generated by breaking $\bar L$ spontaneously and using
Babu's two-loop mechanism. This allows us to incorporate ``just so''
solar-neutrino oscillations with maximal mixing into the model. The resulting
mass matrix has three parameters only, since $\bar L$ breaking leads
exclusively to a non-zero $ee$ matrix element.

12
The categories of this paper are: nucl-th
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
29
The categories of this paper are: funct-an
19
The categories of this paper are: eess
16
The categories of this paper are: stat
8
The categories of this paper are: hep-ex
14
The categories of this paper are: math-ph
6
The categories of this paper are: astro-ph
7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
26
The categories of this paper are: bayes-an
25
The categories of this paper are: patt-sol
10
The categories of this paper are: q-bio