629 research outputs found
Response of Mica to Weakly Interacting Massive Particles
We calculate spin-dependent cross sections for the scattering from mica of
hypothetical weakly interacting dark-matter particles such as neutralinos. The
most abundant odd-A isotopes in mica, Al27 and K39, require different
shell-model treatments. The calculated cross sections will allow the
interpretation of ongoing experiments that look for tracks due to the
interaction of dark-matter particles with nuclei in ancient mica.Comment: 11 pages, RevTex, 2 uuencoded figures, submittted to Phys. Rev.
Minimal Composite Higgs Model with Light Bosons
We analyze a composite Higgs model with the minimal content that allows a
light Standard-Model-like Higgs boson, potentially just above the current LEP
limit. The Higgs boson is a bound state made up of the top quark and a heavy
vector-like quark. The model predicts that only one other bound state may be
lighter than the electroweak scale, namely a CP-odd neutral scalar. Several
other composite scalars are expected to have masses in the TeV range. If the
Higgs decay into a pair of CP-odd scalars is kinematically open, then this
decay mode is dominant, with important implications for Higgs searches. The
lower bound on the CP-odd scalar mass is loose, in some cases as low as
100 MeV, being set only by astrophysical constraints.Comment: 33 pages, latex. Corrections in eqs. 3.21, 3.23, 4.1, 4.5-10. One
figure adde
A Full Shell Model Study of a~=~48 Nuclei
Exact diagonalizations with a minimally modified realistic force lead to
detailed agreement with measured level schemes and electromagnetic transitions
in Ca, Sc, Ti, V, Cr and Mn.
Gamow-Teller strength functions are systematically calculated and reproduce the
data to within the standard quenching factor. Their fine structure indicates
that fragmentation makes much strength unobservable. As a by-product, the
calculations suggest a microscopic description of the onset of rotational
motion. The spectroscopic quality of the results provides strong arguments in
favour of the general validity of monopole corrected realistic forces, which is
discussed.Comment: 30 pages, LaTeX with epsf.sty, 14 Postscript figures included and
compressed using uufiles. Completely new version of previous preprint
nucl-th/9307001. FTUAM-93/01, CRN/PT 93-3
Simian Foamy Virus Transmission from Apes to Humans, Rural Cameroon
Bites from apes efficiently transmit the foamy virus to humans in natural settings in central Africa
Properties of odd nuclei and the impact of time-odd mean fields: A systematic Skyrme-Hartree-Fock analysis
We present a systematic analysis of the description of odd nuclei by the
Skyrme-Hartree-Fock approach augmented with pairing in BCS approximation and
blocking of the odd nucleon. Current and spin densities in the Skyrme
functional produce time-odd mean fields (TOMF) for odd nuclei. Their effect on
basic properties (binding energies, odd-even staggering, separation energies
and spectra) is investigated for the three Skyrme parameterizations SkI3, SLy6,
and SV-bas. About 1300 spherical and axially-deformed odd nuclei with 16 < Z <
92 are considered. The calculations demonstrate that the TOMF effect is
generally small, although not fully negligible. The influence of the Skyrme
parameterization and the consistency of the calculations are much more
important. With a proper choice of the parameterization, a good description of
binding energies and their differences is obtained, comparable to that for even
nuclei. The description of low-energy excitation spectra of odd nuclei is of
varying quality depending on the nucleus
Pre-diagnostic serum concentrations of organochlorines and risk of acute myeloid leukemia: A nested case-control study in the Norwegian Janus Serum Bank Cohort
Background: Epidemiologic studies suggest an increased risk of leukemia among individuals occupationally exposed to some organochlorine (OC) compounds. Associations between serum OC pesticide and polychlorinated biphenyl (PCB) levels and risk of acute myeloid leukemia (AML), the most common subtype of acute leukemia in adult populations, have not been evaluated prospectively in the general population. Objective: We evaluated the risk of AML in relation to pre-diagnostic serum levels of OC pesticides and PCBs in a case-control study nested within the Janus Serum Bank Cohort. Methods: Janus is a large population-based cohort containing biologic samples collected beginning in the early 1970s from ~318,000 individuals in Norway. Serum levels of 11 OC pesticides or their metabolites and 34 PCB congeners were measured in 56 AML cases and 288 controls. Conditional logistic regression was conducted to evaluate associations between lipid-adjusted serum OC levels and risk of AML. Results: Higher serum levels of total chlordane/heptachlor metabolites were associated with AML risk (3rd vs. 1st tertile odds ratio (OR) = 2.26, 95% confidence interval (CI) = 0.91–5.63; ptrend = 0.11). Significant exposure-response associations were observed for levels of heptachlor epoxide (3rd vs. 1st tertile OR = 2.85, 95% CI = 1.05–7.73; ptrend = 0.02) and dieldrin (3rd vs. 1st tertile OR = 2.71, 95% CI = 1.07–6.83; ptrend = 0.03). No significant exposure-response associations with AML risk were observed for total DDT or individual isomers and derivatives. Higher serum levels of p,p′-DDT showed a non-significant increase in risk, but the exposure-response became attenuated when co-adjusting for heptachlor epoxide or dieldrin levels. Serum PCB levels were not significantly associated with AML risk. Conclusions: Our data suggest that higher serum levels of dieldrin and metabolites derived from chlordane/heptachlor are associated with risk of AML in the general Norwegian population, based on samples collected on average ~17 years before diagnosis. Further research in populations with historically high or recent exposure to DDT is warranted to assess the association with AML risk with body burden of specific DDT isomers and derivatives
Pion emission from the T2K replica target: method, results and application
The T2K long-baseline neutrino oscillation experiment in Japan needs precise
predictions of the initial neutrino flux. The highest precision can be reached
based on detailed measurements of hadron emission from the same target as used
by T2K exposed to a proton beam of the same kinetic energy of 30 GeV. The
corresponding data were recorded in 2007-2010 by the NA61/SHINE experiment at
the CERN SPS using a replica of the T2K graphite target. In this paper details
of the experiment, data taking, data analysis method and results from the 2007
pilot run are presented. Furthermore, the application of the NA61/SHINE
measurements to the predictions of the T2K initial neutrino flux is described
and discussed.Comment: updated version as published by NIM
The nuclear energy density functional formalism
The present document focuses on the theoretical foundations of the nuclear
energy density functional (EDF) method. As such, it does not aim at reviewing
the status of the field, at covering all possible ramifications of the approach
or at presenting recent achievements and applications. The objective is to
provide a modern account of the nuclear EDF formalism that is at variance with
traditional presentations that rely, at one point or another, on a {\it
Hamiltonian-based} picture. The latter is not general enough to encompass what
the nuclear EDF method represents as of today. Specifically, the traditional
Hamiltonian-based picture does not allow one to grasp the difficulties
associated with the fact that currently available parametrizations of the
energy kernel at play in the method do not derive from a genuine
Hamilton operator, would the latter be effective. The method is formulated from
the outset through the most general multi-reference, i.e. beyond mean-field,
implementation such that the single-reference, i.e. "mean-field", derives as a
particular case. As such, a key point of the presentation provided here is to
demonstrate that the multi-reference EDF method can indeed be formulated in a
{\it mathematically} meaningful fashion even if does {\it not} derive
from a genuine Hamilton operator. In particular, the restoration of symmetries
can be entirely formulated without making {\it any} reference to a projected
state, i.e. within a genuine EDF framework. However, and as is illustrated in
the present document, a mathematically meaningful formulation does not
guarantee that the formalism is sound from a {\it physical} standpoint. The
price at which the latter can be enforced as well in the future is eventually
alluded to.Comment: 64 pages, 8 figures, submitted to Euroschool Lecture Notes in Physics
Vol.IV, Christoph Scheidenberger and Marek Pfutzner editor
Measurement of the open-charm contribution to the diffractive proton structure function
Production of D*+/-(2010) mesons in diffractive deep inelastic scattering has
been measured with the ZEUS detector at HERA using an integrated luminosity of
82 pb^{-1}. Diffractive events were identified by the presence of a large
rapidity gap in the final state. Differential cross sections have been measured
in the kinematic region 1.5 < Q^2 < 200 GeV^2, 0.02 < y < 0.7, x_{IP} < 0.035,
beta 1.5 GeV and |\eta(D*+/-)| < 1.5. The measured cross
sections are compared to theoretical predictions. The results are presented in
terms of the open-charm contribution to the diffractive proton structure
function. The data demonstrate a strong sensitivity to the diffractive parton
densities.Comment: 35 pages, 11 figures, 6 table
Search for composite and exotic fermions at LEP 2
A search for unstable heavy fermions with the DELPHI detector at LEP is
reported. Sequential and non-canonical leptons, as well as excited leptons and
quarks, are considered. The data analysed correspond to an integrated
luminosity of about 48 pb^{-1} at an e^+e^- centre-of-mass energy of 183 GeV
and about 20 pb^{-1} equally shared between the centre-of-mass energies of 172
GeV and 161 GeV. The search for pair-produced new leptons establishes 95%
confidence level mass limits in the region between 70 GeV/c^2 and 90 GeV/c^2,
depending on the channel. The search for singly produced excited leptons and
quarks establishes upper limits on the ratio of the coupling of the excited
fermio
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