1,304 research outputs found
New results from DAMA/LIBRA
DAMA/LIBRA is running at the Gran Sasso National Laboratory of the I.N.F.N..
Here the results obtained with a further exposure of 0.34 ton x yr are
presented. They refer to two further annual cycles collected one before and one
after the first DAMA/LIBRA upgrade occurred on September/October 2008. The
cumulative exposure with those previously released by the former DAMA/NaI and
by DAMA/LIBRA is now 1.17 ton x yr, corresponding to 13 annual cycles. The data
further confirm the model independent evidence of the presence of Dark Matter
(DM) particles in the galactic halo on the basis of the DM annual modulation
signature (8.9 sigma C.L. for the cumulative exposure). In particular, with the
cumulative exposure the modulation amplitude of the single-hit events in the (2
-- 6) keV energy interval measured in NaI(Tl) target is (0.0116 +- 0.0013)
cpd/kg/keV; the measured phase is (146 +- 7) days and the measured period is
(0.999 +- 0.002) yr, values well in agreement with those expected for the DM
particles.Comment: presented at the Int. Conf. Beyond the Standard Models of Particle
Physics, Cosmology and Astrophysics (BEYOND 2010), 1-6 February 2010, Cape
Town, South Afric
Direct Detection of Non-Chiral Dark Matter
Direct detection experiments rule out fermion dark matter that is a chiral
representation of the electroweak gauge group. Non-chiral real, complex and
singlet representations, however, provide viable fermion dark matter
candidates. Although any one of these candidates will be virtually impossible
to detect at the LHC, it is shown that they may be detected at future planned
direct detection experiments. For the real case, an irreducible radiative
coupling to quarks may allow a detection. The complex case in general has an
experimentally ruled out tree-level coupling to quarks via Z-boson exchange.
However, in the case of two SU(2)_L doublets, a higher dimensional coupling to
the Higgs can suppress this coupling, and a remaining irreducible radiative
coupling may allow a detection. Singlet dark matter could be detected through a
coupling to quarks via Higgs exchange. Since all non-chiral dark matter can
have a coupling to the Higgs, at least some of its mass can be obtained from
electroweak symmetry breaking, and this mass is a useful characterization of
its direct detection cross-section.Comment: 22 pages, 3 figures. References added. Minor corrections to match
published versio
Technical aspects in dark matter investigations
Some theoretical and experimental aspects regarding the direct dark matter
field are mentioned. In particular some arguments, which play a relevant role
in the evaluation of model dependent interpretations of experimental results
and in comparisons, are shortly addressed.Comment: Proceedings of TAUP 2011 Conferenc
GENIUS-TF: a test facility for the GENIUS project
GENIUS is a proposal for a large scale detector of rare events. As a first
step of the experiment, a small test version, the GENIUS test facility, will be
build up at the Laboratorio Nazionale del Gran Sasso (LNGS). With about 40 kg
of natural Ge detectors operated in liquid nitrogen, GENIUS-TF could exclude
(or directly confirm) the DAMA annual modulation signature within about two
years of measurement.Comment: 14 pages, latex, 5 figures, 3 tables; submitted to Astroparticle
Physic
Interpreting the bounds on Solar Dark Matter induced muons at Super-Kamiokande in the light of CDMS results
We consider the recent limits on dark matter - nucleon elastic scattering
cross section from the analysis of CDMS II collaboration using the two signal
events observed in CDMS experiment. With these limits we try to interpret the
Super-Kamiokande (SK) bounds on the detection rates of up-going muons induced
by the neutrinos that are produced in the sun from the decay of annihilation
products of dark matter (WIMPs) captured in the solar core. Calculated rates of
up-going muons for different annihilation channels at SK using CDMS bounds are
found to be orders below the predicted upper limits of such up-going muon rates
at SK. Thus there exists room for enhancement (boost) of the calculated rates
using CDMS limits for interpreting SK bounds. Such a feature is expected to
represent the PAMELA data with the current CDMS limits. We also show the
dependence of such a possible enhancement factor (boost) on WIMP mass for
different WIMP annihilation channels.Comment: 7 pages, 6 figure
B's with Direct Decays: Tevatron and LHC Discovery Prospects in the b\bar{b}+MET Channel
We explore the discovery prospects for B'\bar{B}' pair production followed by
direct decays B'->bX, where B' is a new quark and X is a long-lived neutral
particle. We develop optimized cuts in the (m_B', m_X) plane and show that the
7 TeV LHC with an integrated luminosity of 1 (10) fb^-1 may exclude masses up
to m_B' ~ 620 (800) GeV, completely covering the mass range allowed for new
quarks that get mass from electroweak symmetry breaking. This analysis is
applicable to other models with b\bar{b}+MET signals, including supersymmetric
models with bottom squarks decaying directly to neutralinos, and models with
exotic quarks decaying directly to GeV-scale dark matter. To accommodate these
and other interpretations, we also present model-independent results for the
b\bar{b}+MET cross section required for exclusion and discovery.Comment: 18 pages; v2: published versio
The Enigma of the Dark Matter
One of the great scientific enigmas still unsolved, the existence of dark
matter, is reviewed. Simple gravitational arguments imply that most of the mass
in the Universe, at least 90%, is some (unknown) non-luminous matter. Some
particle candidates for dark matter are discussed with particular emphasis on
the neutralino, a particle predicted by the supersymmetric extension of the
Standard Model of particle physics. Experiments searching for these relic
particles, carried out by many groups around the world, are also discussed.
These experiments are becoming more sensitive every year and in fact one of the
collaborations claims that the first direct evidence for dark matter has
already been observed.Comment: Invited review article for the journal Contemporary Physics. The
level is suitable for researchers which are non-specialists in the subject,
and also for students. Latex, 20 pages, 5 figure
Inelastic Dark Matter
Many observations suggest that much of the matter of the universe is
non-baryonic. Recently, the DAMA NaI dark matter direct detection experiment
reported an annual modulation in their event rate consistent with a WIMP relic.
However, the Cryogenic Dark Matter Search (CDMS) Ge experiment excludes most of
the region preferred by DAMA. We demonstrate that if the dark matter can only
scatter by making a transition to a slightly heavier state (Delta m ~ 100kev),
the experiments are no longer in conflict. Moreover, differences in the energy
spectrum of nuclear recoil events could distinguish such a scenario from the
standard WIMP scenario. Finally, we discuss the sneutrino as a candidate for
inelastic dark matter in supersymmetric theories.Comment: 20 pages, 6 figure
Dark Matter-Motivated Searches for Exotic 4th Generation Quarks in Tevatron and Early LHC Data
We determine the prospects for finding dark matter at the Tevatron and LHC
through the production of exotic 4th generation quarks T' that decay through T'
\to t X, where X is dark matter. The resulting signal of t \bar{t} + \met has
not previously been considered in searches for 4th generation quarks, but there
are both general and specific dark matter motivations for this signal, and with
slight modifications, this analysis applies to any scenario where invisible
particles are produced in association with top quarks. Current direct and
indirect bounds on such exotic quarks restrict their masses to be between 300
and 600 GeV, and the dark matter's mass may be anywhere below m_T'. We simulate
the signal and main backgrounds with MadGraph/MadEvent-Pythia-PGS4. For the
Tevatron, we find that an integrated luminosity of 20 fb^-1 will allow 3\sigma
discovery up to m_T' = 400 GeV and 95% exclusion up to m_T' = 455 GeV. For the
10 TeV LHC with 300 pb^-1, the discovery and exclusion sensitivities rise to
490 GeV and 600 GeV. These scenarios are therefore among the most promising for
dark matter at colliders. Perhaps most interestingly, we find that dark matter
models that can explain results from the DAMA, CDMS and CoGeNT Collaborations
can be tested with high statistical significance using data already collected
at the Tevatron and have extraordinarily promising implications for early runs
of the LHC.Comment: 22 pages; v2: additional discussion of relation to DAMA, CDMS, and
CoGeNT results, references adde
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