878 research outputs found
How Magnetic is the Neutrino?
The existence of a neutrino magnetic moment implies contributions to the
neutrino mass via radiative corrections. We derive model-independent
"naturalness" upper bounds on the magnetic moments of Dirac and Majorana
neutrinos, generated by physics above the electroweak scale. For Dirac
neutrinos, the bound is several orders of magnitude more stringent than present
experimental limits. However, for Majorana neutrinos the magnetic moment bounds
are weaker than present experimental limits if is generated by new
physics at ~ 1 TeV, and surpass current experimental sensitivity only for new
physics scales > 10 -- 100 TeV. The discovery of a neutrino magnetic moment
near present limits would thus signify that neutrinos are Majorana particles.Comment: 9 pages, 6 figures. Talk given at Festschrift in honour of B. H. J
McKellar and G. C. Josh
Capture of Leptophilic Dark Matter in Neutron Stars
Dark matter particles will be captured in neutron stars if they undergo
scattering interactions with nucleons or leptons. These collisions transfer the
dark matter kinetic energy to the star, resulting in appreciable heating that
is potentially observable by forthcoming infrared telescopes. While previous
work considered scattering only on nucleons, neutron stars contain small
abundances of other particle species, including electrons and muons. We perform
a detailed analysis of the neutron star kinetic heating constraints on
leptophilic dark matter. We also estimate the size of loop induced couplings to
quarks, arising from the exchange of photons and Z bosons. Despite having
relatively small lepton abundances, we find that an observation of an old,
cold, neutron star would provide very strong limits on dark matter interactions
with leptons, with the greatest reach arising from scattering off muons. The
projected sensitivity is orders of magnitude more powerful than current dark
matter-electron scattering bounds from terrestrial direct detection
experiments.Comment: 26 pages, 8 figures, 3 tables, 2 appendices. Discussion extended,
references added, matches JCAP published versio
Neutrino oscillations and Big Bang Nucleosynthesis
We outline how relic neutrino asymmetries may be generated in the early
universe via active-sterile neutrino oscillations. We discuss possible
consequences for big bang nucleosynthesis, within the context of a particular
4-neutrino model.Comment: 6 pages. Talk given at NuFACT'01 workshop, Tsukuba, Japan (May 2001
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