1,387 research outputs found
Direct Wimp Detection in Directional Experiments
The recent WMAP data have confirmed that exotic dark matter together with the
vacuum energy (cosmological constant) dominate in the flat Universe. Thus the
direct dark matter search, consisting of detecting the recoiling nucleus, is
central to particle physics and cosmology. Modern particle theories naturally
provide viable cold dark matter candidates with masses in the GeV-TeV region.
Supersymmetry provides the lightest supersymmetric particle (LSP), theories in
extra dimensions the lightest Kaluza-Klein particle (LKP) etc. In such theories
the expected rates are much lower than the present experimental goals. So one
should exploit characteristic signatures of the reaction, such as the
modulation effect and, in directional experiments, the correlation of the event
rates with the sun's motion.
In standard non directional experiments the modulation is small, less than
two per cent and the location of the maximum depends on the unknown particle's
mass.
In directional experiments, in addition to the forward-backward asymmetry due
to the sun's motion, one expects a larger modulation, which depends on the
direction of observation. We study such effects both in the case of a light and
a heavy target. Furthermore, since it now appears that the planned experiments
will be partly directional, in the sense that they can only detect the line of
the recoiling nucleus, but not the sense of direction on it, we study which of
the above mentioned interesting features, if any, will persist in these less
ambitious experiments.Comment: 22 LaTex pages, 28 figure
Possible implications of the channeling effect in NaI(Tl) crystals
The channeling effect of low energy ions along the crystallographic axes and
planes of NaI(Tl) crystals is discussed in the framework of corollary
investigations on WIMP Dark Matter candidates. In fact, the modeling of this
existing effect implies a more complex evaluation of the luminosity yield for
low energy recoiling Na and I ions. In the present paper related
phenomenological arguments are developed and possible implications are
discussed at some extent.Comment: 16 pages, 10 figures, preprint ROM2F/2007/15, submitted for
publicatio
Quantitative Perspectives on Fifty Years of the Journal of the History of Biology
Journal of the History of Biology provides a fifty-year long record for
examining the evolution of the history of biology as a scholarly discipline. In
this paper, we present a new dataset and preliminary quantitative analysis of
the thematic content of JHB from the perspectives of geography, organisms, and
thematic fields. The geographic diversity of authors whose work appears in JHB
has increased steadily since 1968, but the geographic coverage of the content
of JHB articles remains strongly lopsided toward the United States, United
Kingdom, and western Europe and has diversified much less dramatically over
time. The taxonomic diversity of organisms discussed in JHB increased steadily
between 1968 and the late 1990s but declined in later years, mirroring broader
patterns of diversification previously reported in the biomedical research
literature. Finally, we used a combination of topic modeling and nonlinear
dimensionality reduction techniques to develop a model of multi-article fields
within JHB. We found evidence for directional changes in the representation of
fields on multiple scales. The diversity of JHB with regard to the
representation of thematic fields has increased overall, with most of that
diversification occurring in recent years. Drawing on the dataset generated in
the course of this analysis, as well as web services in the emerging digital
history and philosophy of science ecosystem, we have developed an interactive
web platform for exploring the content of JHB, and we provide a brief overview
of the platform in this article. As a whole, the data and analyses presented
here provide a starting-place for further critical reflection on the evolution
of the history of biology over the past half-century.Comment: 45 pages, 14 figures, 4 table
Extending the DAMA annual-modulation region by inclusion of the uncertainties in the astrophysical velocities
The original annual-modulation region, singled out by the DAMA/NaI experiment
for direct detection of WIMPs, is extended by taking into account the
uncertainties in the galactic astrophysical velocities. Also the effect due to
a possible bulk rotation for the dark matter halo is considered. We find that
the range for the WIMP mass becomes 30 GeV < m_chi < 130 GeV at 1-sigma C.L.
with a further extension in the upper bound, when a possible bulk rotation of
the dark matter halo is taken into account. We show that the DAMA results, when
interpreted in the framework of the Minimal Supersymmetric extension of the
Standard Model, are consistent with a relic neutralino as a dominant component
of cold dark matter (on the average in our universe and in our galactic halo).
It is also discussed the discovery potential for the relevant supersymmetric
configurations at accelerators of present generation.Comment: ReVTeX, 12 pages, 1 table, 7 figure
Detection Rates for Kaluza-Klein Dark Matter
We consider the lightest Kaluza-Klein particle at N=1 mode (LKP) of universal
extra dimension to be the candidate for Dark Matter and predict the detection
rates for such particles for Germenium and NaI detectors. We have also
calculated the nature of annual modulation for the signals in these two types
of detectors for LKP Dark Matter. The rates with different values of speed of
solar system in the Galactic rest frame are also evaluated.Comment: Submitted to Phys. Rev.
Does Solar Physics Provide Constraints to Weakly Interacting Massive Particles?
We investigate whether present data on helioseismology and solar neutrino
fluxes may constrain WIMP--matter interactions in the range of WIMP parameters
under current exploration in WIMP searches. We find that, for a WIMP mass of 30
GeV, once the effect of the presence of WIMPs in the Sun's interior is
maximized, the squared isothermal sound speed is modified, with respect to the
standard solar model, by at most 0.4% at the Sun's center. The maximal effect
on the Boron-8 solar neutrino flux is a reduction of 4.5%. Larger masses lead
to smaller effects. These results imply that present sensitivities in the
measurements of solar properties, though greatly improved in recent years, do
not provide information or constraints on WIMP properties of relevance for dark
matter. Furthermore, we show that, when current bounds from direct WIMP
searches are taken into account, the effect induced by WIMPs with dominant
coherent interactions are drastically reduced as compared to the values quoted
above. The case of neutralinos in the minimal supersymmetric standard model is
also discussed.Comment: 31 pages, 2 tables and 9 figures, typeset with ReVTeX4. The paper may
also be found at http://www.to.infn.it/~fornengo/papers/helio.ps.gz or
through http://www.to.infn.it/astropart/index.htm
Mass and Scalar Cross-sections for Neutralino Dark Matter in Anomaly Mediated Supersymmetry Breaking Model
We have considered neutralino to be the lightest supersymmetric particle
(LSP) in the framework of minimal Anomaly Mediated Supersymmetric (mAMSB)
model. We have studied variation of neutralino mass with the supersymmetric
parameters. Considering these neutralinos to be the candidates for weakly
interacting massive particle (WIMP) or cold dark matter (CDM), we have
calculated the neutralino nucleon scalar cross-sections and compared them with
DAMA-NaI neutralino direct detection search results. From this study we observe
that the mAMSB model results cannot explain the allowed region in WIMP mass and
WIMP-nucleon scalar cross-section space obtained from annual modulation
signature in DAMA-NaI experiment.Comment: 7 Pages LaTeX, 4 figures, J. Phys. G., to appea
Indirect signals from light neutralinos in supersymmetric models without gaugino mass unification
We examine indirect signals produced by neutralino self-annihilations, in the
galactic halo or inside celestial bodies, in the frame of an effective MSSM
model without gaugino-mass unification at a grand unification scale. We compare
our theoretical predictions with current experimental data of gamma-rays and
antiprotons in space and of upgoing muons at neutrino telescopes. Results are
presented for a wide range of the neutralino mass, though our discussions are
focused on light neutralinos. We find that only the antiproton signal is
potentially able to set constraints on very low-mass neutralinos, below 20 GeV.
The gamma-ray signal, both from the galactic center and from high galactic
latitudes, requires significantly steep profiles or substantial clumpiness in
order to reach detectable levels. The up-going muon signal is largely below
experimental sensitivities for the neutrino flux coming from the Sun; for the
flux from the Earth an improvement of about one order of magnitude in
experimental sensitivities (with a low energy threshold) can make accessible
neutralino masses close to O, Si and Mg nuclei masses, for which resonant
capture is operative.Comment: 17 pages, 1 tables and 5 figures, typeset with ReVTeX4. The paper may
also be found at http://www.to.infn.it/~fornengo/papers/indirect04.ps.gz or
through http://www.astroparticle.to.infn.it/. Limit from BR(Bs--> mu+ mu-)
adde
The Intrinsic Dimensionality of Attractiveness: A Study in Face Profiles
The study of human attractiveness with pattern analysis techniques is an emerging research field. One still largely unresolved problem is which are the facial features relevant to attractiveness, how they combine together, and the number of independent parameters required for describing and identifying harmonious faces. In this paper, we present a first study about this problem, applied to face profiles. First, according to several empirical results, we hypothesize the existence of two well separated manifolds of attractive and unattractive face profiles. Then, we analyze with manifold learning techniques their intrinsic dimensionality. Finally, we show that the profile data can be reduced, with various techniques, to the intrinsic dimensions, largely without loosing their ability to discriminate between attractive and unattractive face
Light Relic Neutralinos
The relic abundance and the scalar cross{section o nucleon for light neutralinos (of mass m below about 45 GeV) are evaluated in an e ective MSSM model with R-parity conservation and without GUT{inspired relations among gaugino masses. It is shown that these neutralinos may provide a sizeable contribution to the matter density in the Universe CDM. By requiring that its relic abundance does not exceed the upper bound on CDM based on the new WMAP data, a lower bound on the neutralino mass m > 6 GeV is derived. These light neutralinos can also produce measurable e ects in WIMP direct detection experiments, and in particular could explain the modulation result recently con rmed by DAMA. Uncertainties in direct detection calculations due to the modeling of the WIMP velocity distribution function are also discussed
- …