167 research outputs found
Weak capture of protons by protons
The cross section for the proton weak capture reaction
is calculated with wave functions obtained from a number of modern, realistic
high-precision interactions. To minimize the uncertainty in the axial two-body
current operator, its matrix element has been adjusted to reproduce the
measured Gamow-Teller matrix element of tritium decay in model
calculations using trinucleon wave functions from these interactions. A
thorough analysis of the ambiguities that this procedure introduces in
evaluating the two-body current contribution to the pp capture is given. Its
inherent model dependence is in fact found to be very weak. The overlap
integral for the pp capture is predicted to be in the range
7.05--7.06, including the axial two-body current contribution, for all
interactions considered.Comment: 17 pages RevTeX (twocolumn), 5 postscript figure
Accurate fundamental parameters and detailed abundance patterns from spectroscopy of 93 solar-type Kepler targets
We present a detailed spectroscopic study of 93 solar-type stars that are
targets of the NASA/Kepler mission and provide detailed chemical composition of
each target. We find that the overall metallicity is well-represented by Fe
lines. Relative abundances of light elements (CNO) and alpha-elements are
generally higher for low-metallicity stars. Our spectroscopic analysis benefits
from the accurately measured surface gravity from the asteroseismic analysis of
the Kepler light curves. The log g parameter is known to better than 0.03 dex
and is held fixed in the analysis. We compare our Teff determination with a
recent colour calibration of V-K (TYCHO V magnitude minus 2MASS Ks magnitude)
and find very good agreement and a scatter of only 80 K, showing that for other
nearby Kepler targets this index can be used. The asteroseismic log g values
agree very well with the classical determination using Fe1-Fe2 balance,
although we find a small systematic offset of 0.08 dex (asteroseismic log g
values are lower). The abundance patterns of metals, alpha elements, and the
light elements (CNO) show that a simple scaling by [Fe/H] is adequate to
represent the metallicity of the stars, except for the stars with metallicity
below -0.3, where alpha-enhancement becomes important. However, this is only
important for a very small fraction of the Kepler sample. We therefore
recommend that a simple scaling with [Fe/H] be employed in the asteroseismic
analyses of large ensembles of solar-type stars.Comment: MNRAS, in press, 12 page
Democracy and governance networks: compatible or not?
The relationship between representative democracy and governance networks is investigated
at a theoretical level. Four conjectures about the relationship are defined. The
incompatibility conjectures rests on the primacy of politics and sees governance networks as a
threat. The complementarity conjecture presents governance networks as a means of enabling
greater participation in the policy process and sensitivity in programme implementation. The
transitional conjecture posits a wider evolution of governance forms towards network
relationships. The instrumental conjecture views governance networks as a powerful means
through which dominant interests can achieve their goals. Illustrative implications for theory
and practice are identified, in relation to power in the policy process, the public interest, and
the role of public managers. The heuristic potential of the conjectures is demonstrated
through the identification of an outline research agenda
Hadronization properties of b quarks compared to light quarks in e+e- -> q qbar from 183 to 200 GeV
The DELPHI detector at LEP has collected 54 pb^{-1} of data at a
centre-of-mass energy around 183 GeV during 1997, 158 pb^{-1} around 189 GeV
during 1998, and 187 pb^{-1} between 192 and 200 GeV during 1999. These data
were used to measure the average charged particle multiplicity in e+e- -> b
bbar events, _{bb}, and the difference delta_{bl} between _{bb} and the
multiplicity, _{ll}, in generic light quark (u,d,s) events: delta_{bl}(183
GeV) = 4.55 +/- 1.31 (stat) +/- 0.73 (syst) delta_{bl}(189 GeV) = 4.43 +/- 0.85
(stat) +/- 0.61 (syst) delta_{bl}(200 GeV) = 3.39 +/- 0.89 (stat) +/- 1.01
(syst). This result is consistent with QCD predictions, while it is
inconsistent with calculations assuming that the multiplicity accompanying the
decay of a heavy quark is independent of the mass of the quark itself.Comment: 13 pages, 2 figure
Speeding up the spatial adiabatic passage of matter waves in optical microtraps by optimal control
We numerically investigate the performance of atomic transport in optical
microtraps via the so called spatial adiabatic passage technique. Our analysis
is carried out by means of optimal control methods, which enable us to
determine suitable transport control pulses. We investigate the ultimate limits
of the optimal control in speeding up the transport process in a triple well
configuration for both a single atomic wave packet and a Bose-Einstein
condensate within a regime of experimental parameters achievable with current
optical technology.Comment: 17 pages, 14 figure
TESS Reveals HD 118203 b to be a Transiting Planet
The exoplanet HD 118203 b, orbiting a bright (V = 8.05) host star, was discovered using the radial velocity method by da Silva et al., but was not previously known to transit. Transiting Exoplanet Survey Satellite (TESS) photometry has revealed that this planet transits its host star. Nine planetary transits were observed by TESS, allowing us to measure the radius of the planet to be 1.136-0.028 +0.029 R J, and to calculate the planet mass to be 2.166-0.079 +0.074 M J. The host star is slightly evolved with an effective temperature of T eff=5683-85 +84 K and a surface gravity of log\,g=3.889 0.018-0.017. With an orbital period of 6.134985-0.000030 +0.000029 days and an eccentricity of 0.314 ± 0.017, the planet occupies a transitional regime between circularized hot Jupiters and more dynamically active planets at longer orbital periods. The host star is among the 10 brightest known to have transiting giant planets, providing opportunities for both planetary atmospheric and asteroseismic studies
The design, construction, and commissioning of the KATRIN experiment
The KArlsruhe TRItium Neutrino (KATRIN) experiment, which aims to make a direct and model-independent determination of the absolute neutrino mass scale, is a complex experiment with many components. More than 15 years ago, we published a technical design report (TDR) [1] to describe the hardware design and requirements to achieve our sensitivity goal of 0.2 eV at 90% C.L. on the neutrino mass. Since then there has been considerable progress, culminating in the publication of first neutrino mass results with the entire beamline operating [2]. In this paper, we document the current state of all completed beamline components (as of the first neutrino mass measurement campaign), demonstrate our ability to reliably and stably control them over long times, and present details on their respective commissioning campaigns
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