1,541 research outputs found
The Fluorescence Detector of the Pierre Auger Observatory - A Calorimeter for UHECR
The Pierre Auger Observatory is a hybrid detector for ultrahigh energy cosmic
rays (UHECR) with energies above 10 eV. Currently the first part of
the Observatory nears completion in the southern hemisphere in Argentina. One
detection technique uses over 1600 water Cherenkov tanks at ground where
samples of secondary particles of extensive air showers (EAS) are detected. The
second technique is a calorimetric measurement of the energy deposited by EAS
in the atmosphere. Charged secondary particles of EAS lose part of their energy
in the atmosphere via ionization. The deposited energy is converted into
excitation of molecules of the air and afterwards partly emitted as
fluorescence light mainly from nitrogen in the wavelength region between 300
and 400 nm. This light is observed with 24 fluorescence telescopes in 4
stations placed at the boundary of the surface array. This setup provides a
combined measurement of the longitudinal shower development and the lateral
particle distribution at ground of the same event. Details on the fluorescence
technique and the necessary atmospheric monitoring will be presented, as well
as first physics results on UHECR.Comment: Proceedings of XII International Conference on Calorimetry in High
Energy Physics (CALOR06), Chicago, USA, 2006 submitted to AIP proceeding
Four-Flavour Leading-Order Hadronic Contribution To The Muon Anomalous Magnetic Moment
We present a four-flavour lattice calculation of the leading-order hadronic
vacuum polarisation contribution to the anomalous magnetic moment of the muon,
, arising from quark-connected Feynman graphs. It is
based on ensembles featuring dynamical twisted mass fermions
generated by the European Twisted Mass Collaboration (ETMC). Several light
quark masses are used in order to yield a controlled extrapolation to the
physical pion mass. We employ three lattice spacings to examine lattice
artefacts and several different volumes to check for finite-size effects.
Incorporating the complete first two generations of quarks allows for a direct
comparison with phenomenological determinations of .
Our final result including an estimate of the systematic uncertainty
shows a good
overall agreement with these computations.Comment: 24 pages, 11 figures, accepted for publication in JHE
Υ and Υ′ leptonic widths, abμ, and mb from full lattice QCD
We determine the decay rate to leptons of the ground-state ϒ meson and its first radial excitation in lattice
QCD for the first time. We use radiatively improved nonrelativistic QCD for the b quarks and include u, d,
s and c quarks in the sea with u=d masses down to their physical values. We find Γðϒ → eþe−Þ ¼
1.19ð11Þ keV and Γðϒ0 → eþe−Þ ¼ 0.69ð9Þ keV, both in good agreement with experimental results. The
decay constants we obtain are included in a summary plot of meson decay constants from lattice QCD
given in the Conclusions. We also test time moments of the vector current-current correlator against values
determined from the b-quark contribution to σðeþe− → hadronsÞ and calculate the b-quark piece of the
hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon,
ab
μ ¼ 0.271ð37Þ × 10−10. Finally we determine the b-quark mass, obtaining in the MS scheme, ¯
m¯ bðm¯ b; nf ¼ 5Þ ¼ 4.196ð23Þ GeV, the most accurate result from lattice QCD to date
Are we overusing IVF?
Peer reviewedPublisher PD
Future Investigations of the Flavor Dependence of Sea Quark Helicities at STAR
The flavor dependence of polarized and unpolarized quark distributions in the
nucleon can lead to insights into the formation of the sea. Drell-Yan
measurements have pointed to flavor asymmetries in the unpolarized
distributions. Collisions at sqrt{s}=500 GeV with polarized protons at RHIC
will soon allow investigations of the flavor separated polarized quark
distributions via W production to complement measurements from semi-inclusive
DIS. We report on STAR's current plans, tracking upgrade, and expected
sensitivities.Comment: 4 pages, to appear in the proceedings of the 18th International Spin
Physics Symposium (Spin08), Charlottesville, Virginia, USA, October 6 - 11,
200
Effect of ferromagnetic contacts on spin accumulation in an all-metallic lateral spin-valve system: Semiclassical spin drift-diffusion equations
We study the effect of the ferromagnetic (FM) contacts on the spin
accumulation in the lateral spin valve system for the collinear magnetization
configurations. When an additional FM electrode is introduced in the
all-metallic lateral spin-valve system, we find that the transresistance can be
fractionally suppressed or very weakly influenced depending on the position of
the additional FM electrode, and relative magnitudes of contact resistance and
the bulk resistance defined over the spin diffusion length. Nonlocal spin
signals such as nonlocal voltage drop and leakage spin currents are independent
of the magnetization orientation of the additional FM electrode. Even when the
additional contact is nonmagnetic, nonlocal spin signals can be changed by the
spin current leaking into the nonmagnetic electrode.Comment: 13 pages, 1 figure, revised versio
The Transformation of Sediment Into Rock : Insights From IODP Site U1352, Canterbury Basin, New Zealand
ACKNOWLEDGMENTS We thank the crew of the RV JOIDES Resolution for professional seamanship, excellent drilling, and the scientific support on board. GHB and SCG thank the Australia–New Zealand IODP Consortium (ANZIC), and KMM thanks the Consortium for Ocean Leadership U.S. Science Support Program for partly funding this work. Thanks also to funding agencies of the respective authors, and Mark Lawrence (GNS Science) and Cam Nelson (University of Waikato) for their thoughtful comments on an earlier draft. Karsten Kroeger (GNS Science) helped by providing compaction data for New Zealand basins, and Michelle Kominz (Western Michigan University) provided data on which Figure 8 was developed. Further improvements were the result of thoughtful detailed reviews by Gemma Barrie, Bill Heins, Stan Paxton, Associate Editor Joe Macquaker, and Editor Leslie Melim.Peer reviewedPostprin
Hadron-Hadron Interactions from Lattice QCD: isospin-2 scattering length
We present results for the scattering length using
twisted mass lattice QCD for three values of the lattice spacing and a range of
pion mass values. Due to the use of Laplacian Heaviside smearing our
statistical errors are reduced compared to previous lattice studies. A detailed
investigation of systematic effects such as discretisation effects, volume
effects, and pollution of excited and thermal states is performed. After
extrapolation to the physical point using chiral perturbation theory at NLO we
obtain .Comment: Edited for typos, overhauled figures, more detailed comparison to
existing lattice result
OGLE-2016-BLG-0613LABb: A Microlensing Planet in a Binary System
We present the analysis of OGLE-2016-BLG-0613, for which the lensing light
curve appears to be that of a typical binary-lens event with two caustic spikes
but with a discontinuous feature on the trough between the spikes. We find that
the discontinuous feature was produced by a planetary companion to the binary
lens. We find 4 degenerate triple-lens solution classes, each composed of a
pair of solutions according to the well-known wide/close planetary degeneracy.
One of these solution classes is excluded due to its relatively poor fit. For
the remaining three pairs of solutions, the most-likely primary mass is about
while the planet is a super-Jupiter. In all cases the
system lies in the Galactic disk, about half-way toward the Galactic bulge.
However, in one of these three solution classes, the secondary of the binary
system is a low-mass brown dwarf, with relative mass ratios (1 : 0.03 : 0.003),
while in the two others the masses of the binary components are comparable.
These two possibilities can be distinguished in about 2024 when the measured
lens-source relative proper motion will permit separate resolution of the lens
and source.Comment: 14 pages, 9 figure
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