443 research outputs found
Experimental identification of non-pointlike dark-matter candidates
We show that direct dark matter detection experiments can distinguish between
pointlike and non-pointlike dark-matter candidates. The shape of the nuclear
recoil energy spectrum from pointlike dark-matter particles, e.g., neutralinos,
is determined by the velocity distribution of dark matter in the galactic halo
and by nuclear form factors. In contrast, typical cross sections of
non-pointlike dark matter, for example, Q-balls, have a new form factor, which
decreases rapidly with the recoil energy. Therefore, a signal from
non-pointlike dark matter is expected to peak near the experimental threshold
and to fall off rapidly at higher energies. Although the width of the signal is
practically independent of the dark matter velocity dispersion, its height is
expected to exhibit an annual modulation due to the changes in the dark matter
flux.Comment: 4 pages; minor changes, references adde
Brane-world dark matter
We show that, in the context of brane-world scenarios with low tension
, massive brane fluctuations are natural dark matter candidates. We
calculate the present abundances for both hot(warm) and cold branons in terms
of the branon mass and the tension scale . The results are compared with
the current experimental bounds on these parameters. We also study the
prospects for their detection in direct search experiments and comment on their
characteristic signals in the indirect ones.Comment: 4 pages, 2 figures, REVTeX 4. Updated figures, new comments and
references included. Final version to appear in Phys. Rev. Let
Constraints on the parity-violating couplings of a new gauge boson
High-energy particle physics experiments allow for the possible existence of
a new light, very weakly coupled, neutral gauge boson (the U boson). This one
permits for light (spin-1/2 or spin-0) particles to be acceptable Dark Matter
candidates, by inducing sufficient (stronger than weak) annihilation cross
sections into e+e-. They could be responsible for the bright 511 keV gamma ray
line observed by INTEGRAL from the galactic bulge.
Such a new interaction may have important consequences, especially at lower
energies. Parity-violation atomic-physics experiments provide strong
constraints on such a U boson, if its couplings to quarks and electrons violate
parity. With the constraints coming from an unobserved axionlike behaviour of
this particle, they privilegiate a pure vector coupling of the U boson to
quarks and leptons, unless the corresponding symmetry is broken sufficiently
above the electroweak scale.Comment: 6 page
Large-Mass Ultra-Low Noise Germanium Detectors: Performance and Applications in Neutrino and Astroparticle Physics
A new type of radiation detector, a p-type modified electrode germanium
diode, is presented. The prototype displays, for the first time, a combination
of features (mass, energy threshold and background expectation) required for a
measurement of coherent neutrino-nucleus scattering in a nuclear reactor
experiment. The device hybridizes the mass and energy resolution of a
conventional HPGe coaxial gamma spectrometer with the low electronic noise and
threshold of a small x-ray semiconductor detector, also displaying an intrinsic
ability to distinguish multiple from single-site particle interactions. The
present performance of the prototype and possible further improvements are
discussed, as well as other applications for this new type of device in
neutrino and astroparticle physics (double-beta decay, neutrino magnetic moment
and WIMP searches).Comment: submitted to Phys. Rev.
Generalized Analysis of Weakly-Interacting Massive Particle Searches
We perform a generalized analysis of data from WIMP search experiments for
point-like WIMPs of arbitrary spin and general Lorenz-invariant WIMP-nucleus
interaction. We show that in the non-relativistic limit only spin-independent
(SI) and spin-dependent (SD) WIMP-nucleon interactions survive, which can be
parameterized by only five independent parameters. We explore this
five-dimensional parameter space to determine whether the annual modulation
observed in the DAMA experiment can be consistent with all other experiments.
The pure SI interaction is ruled out except for very small region of parameter
space with the WIMP mass close to 50 GeV and the ratio of the WIMP-neutron to
WIMP-proton SI couplings . For the predominantly SD
interaction, we find an upper limit to the WIMP mass of about 18 GeV, which can
only be weakened if the constraint stemming from null searches for energetic
neutrinos from WIMP annihilation the Sun is evaded. None of the regions of the
parameter space that can reconcile all WIMP search results can be easily
accommodated in the minimal supersymmetric extension of the standard model.Comment: 27 pages, 3 figure
Standard Model tests with trapped radioactive atoms
We review the use of laser cooling and trapping for Standard Model tests,
focusing on trapping of radioactive isotopes. Experiments with neutral atoms
trapped with modern laser cooling techniques are testing several basic
predictions of electroweak unification. For nuclear decay, demonstrated
trap techniques include neutrino momentum measurements from beta-recoil
coincidences, along with methods to produce highly polarized samples. These
techniques have set the best general constraints on non-Standard Model scalar
interactions in the first generation of particles. They also have the promise
to test whether parity symmetry is maximally violated, to search for tensor
interactions, and to search for new sources of time reversal violation. There
are also possibilites for exotic particle searches. Measurements of the
strength of the weak neutral current can be assisted by precision atomic
experiments using traps of small numbers of radioactive atoms, and sensitivity
to possible time-reversal violating electric dipole moments can be improved.Comment: 45 pages, 17 figures, v3 includes clarifying referee comments,
especially in beta decay section, and updated figure
Determining the Mass of Dark Matter Particles with Direct Detection Experiments
In this article I review two data analysis methods for determining the mass
(and eventually the spin-independent cross section on nucleons) of Weakly
Interacting Massive Particles with positive signals from direct Dark Matter
detection experiments: a maximum likelihood analysis with only one experiment
and a model-independent method requiring at least two experiments.
Uncertainties and caveats of these methods will also be discussed.Comment: 24 pages, 10 figures, 1 reference added, typos fixed, published
version, to appear in the NJP Focus Issue on "Dark Matter and Particle
Physics
Magnetic monopoles revisited: Models and searches at colliders and in the Cosmos
In this review, we discuss recent developments in both the theory and the
experimental searches of magnetic monopoles in past, current and future
colliders and in the Cosmos. The theoretical models include, apart from the
standard Grand Unified Theories, extensions of the Standard Model that admit
magnetic monopole solutions with finite energy and masses that can be as light
as a few TeV. Specifically, we discuss, among other scenarios, modified
Cho-Maison monopoles and magnetic monopoles in (string-inspired, higher
derivative) Born-Infeld extensions of the hypercharge sector of the Standard
Model. We also outline the conditions for which effective field theories
describing the interaction of monopoles with photons are valid and can be used
for result interpretation in monopole production at colliders. The experimental
part of the review focuses on, past and present, cosmic and collider searches,
including the latest bounds on monopole masses and magnetic charges by the
ATLAS and MoEDAL experiments at the LHC, as well as prospects for future
searches.Comment: 82 pages, 21 figures, invited review; more references and discussions
added; to appear in International Journal of Modern Physics
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