3,376 research outputs found
Determining the Flavour Content of the Low-Energy Solar Neutrino Flux
We study the sensitivity of the HELLAZ and Borexino solar neutrino
experiments on discriminating the neutrino species nu_e, anti-nu_e,
nu_{mu,tau}, anti-nu_{mu,tau}, and nu_{sterile} using the difference in the
recoil electron kinetic energy spectra in elastic neutrino-electron scattering.
We find that one can observe a non-vanishing nu_{mu,tau} component in the solar
neutrino flux, especially when the nu_e survival probability is low. Also, if
the data turn out to be consistent with nu_e nu_{mu,tau} oscillations, an
anti-nu_e component can be excluded effectively.Comment: 24 pages, 7 figure
Fake Dark Matter at Colliders
If the dark matter (DM) consists of a weakly interacting massive particle
(WIMP), it can be produced and studied at future collider experiments like
those at the LHC. The production of collider-stable WIMPs is characterized by
hard scattering events with large missing transverse energy. Here we point out
that the discovery of this well-characterized DM signal may turn out to be a
red herring. We explore an alternative explanation -- fake dark matter -- where
the only sources of missing transverse energy are standard model neutrinos. We
present examples of such models, focusing on supersymmetric models with
R-parity violation. We also briefly discuss means of differentiating fake dark
matter from the production of new collider-stable particles.Comment: 11 pages, 3 figures, revtex; references adde
New Chiral Fermions, a New Gauge Interaction, Dirac Neutrinos, and Dark Matter
We propose that all light fermionic degrees of freedom, including the
Standard Model (SM) fermions and all possible light beyond-the-standard-model
fields, are chiral with respect to some spontaneously broken abelian gauge
symmetry. Hypercharge, for example, plays this role for the SM fermions. We
introduce a new symmetry, , for all new light fermionic states.
Anomaly cancellations mandate the existence of several new fermion fields with
nontrivial charges. We develop a concrete model of this type, for
which we show that (i) some fermions remain massless after
breaking -- similar to SM neutrinos -- and (ii) accidental global symmetries
translate into stable massive particles -- similar to SM protons. These
ingredients provide a solution to the dark matter and neutrino mass puzzles
assuming one also postulates the existence of heavy degrees of freedom that act
as "mediators" between the two sectors. The neutrino mass mechanism described
here leads to parametrically small Dirac neutrino masses, and the model also
requires the existence of at least four Dirac sterile neutrinos. Finally, we
describe a general technique to write down chiral-fermions-only models that are
at least anomaly-free under a gauge symmetry
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