Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Unsterile-Active Neutrino Mixing: Consequences on Radiative Decay and
  Bounds from the X-ray Background   We consider a sterile neutrino to be an unparticle, namely an \emph{unsterile
neutrino}, with anomalous dimension $\eta$ and study its mixing with a
canonical active neutrino via a see-saw mass matrix. We show that there is
\emph{no unitary} transformation that diagonalizes the mixed propagator and a
field redefinition is required. The propagating or ``mass'' states correspond
to an unsterile-like and active-like mode. The unsterile mode features a
complex pole or resonance for $0 \leq \eta < 1/3$ with an ``invisible width''
which is the result of the decay of the unsterile mode into the active mode and
the massless particles of the hidden conformal sector. For $\eta \geq 1/3$, the
complex pole disappears, merging with the unparticle threshold. The active mode
is described by a stable pole, but ``inherits'' a non-vanishing spectral
density above the unparticle threshold as a consequence of the mixing. We find
that the \emph{radiative} decay width of the unsterile neutrino into the active
neutrino (and a photon) via charged current loops, is \emph{suppressed} by a
factor $\sim \Big[2 \sin^2(\theta_0)
\frac{M^2}{\Lambda^2}\Big]^\frac{\eta}{1-\eta}$, where $\theta_0$ is the mixing
angle for $\eta=0$, $M$ is approximately the mass of the unsterile neutrino and
$\Lambda \gg M$ is the unparticle-scale. The suppression of the radiative
(visible) decay width of the sterile neutrino weakens the bound on the mass and
mixing angle from the X-ray or soft gamma-ray background.

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The categories of this paper are: ao-sci
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The categories of this paper are: hep-lat
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The categories of this paper are: stat
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The categories of this paper are: alg-geom
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The categories of this paper are: math-ph
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The categories of this paper are: q-fin
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The categories of this paper are: funct-an
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The categories of this paper are: eess
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The categories of this paper are: bayes-an
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The categories of this paper are: quant-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-th
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The categories of this paper are: adap-org
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The categories of this paper are: physics
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The categories of this paper are: mtrl-th