288 research outputs found
The measurement of the anomalous magnetic moment of the muon at fermilab
The anomalous magnetic moment of the muon is one of the most precisely measured quantities in experimental particle physics. Its latest measurement at Brookhaven National Laboratory deviates from the Standard Model expectation by approximately 3.5 standard deviations. The goal of the new experiment, E989, now under construction at Fermilab, is a fourfold improvement in precision. Here, we discuss the details of the future measurement and its current status
Verallgemeinerte filternde IBLU-Zerlegungen der Ordnung l
Die vorliegende Arbeit befasst sich mit der Konstruktion und Analyse einer neuen Klasse frequenzfilternder IBLU-Zerlegungen für schwachbesetzte lineare Gleichungssysteme, die bei Diskretisierungen elliptischer partieller Differentialgleichungen entstehen. Die wichtigste Eigenschaft dieser Zerlegungen ist ihre Anwendbarkeit auf nicht-triviale Gebietsgeometrien. Des Weiteren werden Folgen der eingeführten Zerlegungen als frequenzfilternder Vorkonditionierer des Gradientenverfahrens für Eigenwertprobleme für elliptische Differentialoperatoren zur Beschleunigung des Lösungsprozesses verwendet
Uncertainty quantification in coastal aquifers using the multilevel Monte Carlo method
We consider a class of density-driven flow problems. We are particularly
interested in the problem of the salinization of coastal aquifers. We consider
the Henry saltwater intrusion problem with uncertain porosity, permeability,
and recharge parameters as a test case. The reason for the presence of
uncertainties is the lack of knowledge, inaccurate measurements, and inability
to measure parameters at each spatial or time location. This problem is
nonlinear and time-dependent. The solution is the salt mass fraction, which is
uncertain and changes in time. Uncertainties in porosity, permeability,
recharge, and mass fraction are modeled using random fields. This work
investigates the applicability of the well-known multilevel Monte Carlo (MLMC)
method for such problems. The MLMC method can reduce the total computational
and storage costs. Moreover, the MLMC method runs multiple scenarios on
different spatial and time meshes and then estimates the mean value of the mass
fraction. The parallelization is performed in both the physical space and
stochastic space. To solve every deterministic scenario, we run the parallel
multigrid solver ug4 in a black-box fashion. We use the solution obtained from
the quasi-Monte Carlo method as a reference solution.Comment: 24 pages, 3 tables, 11 figure
Data acquisition system for the MuLan muon lifetime experiment
We describe the data acquisition system for the MuLan muon lifetime
experiment at Paul Scherrer Institute. The system was designed to record muon
decays at rates up to 1 MHz and acquire data at rates up to 60 MB/sec. The
system employed a parallel network of dual-processor machines and repeating
acquisition cycles of deadtime-free time segments in order to reach the design
goals. The system incorporated a versatile scheme for control and diagnostics
and a custom web interface for monitoring experimental conditions.Comment: 19 pages, 8 figures, submitted to Nuclear Instruments and Methods
Cross section of the processes , , , in the energy region 200 MeV 3 GeV
The cross section for different processes induced by annihilation,
in the kinematical limit
, is
calculated taking into account first order corrections to the amplitudes and
the corrections due to soft emitted photons, with energy in the center of mass of the colliding beams. The results
are given separately for charge--odd and charge--even terms in the final
channels and . In case of pions, form
factors are taken into account. The differential cross sections for the
processes: , , have been calculated and the
corresponding formula are given in the ultrarelativistic limit . For a quantitative evaluation of the
contribution of higher order of the perturbation theory, the production of
, including radiative corrections, is calculated in the approach of
the lepton structure functions. This allows to estimate the precision of the
obtained results as better than 0.5% outside the energy region corresponding to
narrow resonances. A method to integrate the cross section, avoiding the
difficulties which arise from singularities is also described.Comment: 25 pages 3 firgur
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Modeling saltwater intrusion scenarios for a coastal aquifer at the German North Sea
A 3d regional density-driven flow model of a heterogeneous aquifer system at the German North Sea Coast is set up within the joint project NAWAK (“Development of sustainable adaption strategies for the water supply and distribution infrastructure on condition of climatic and demographic change”). The development of the freshwater-saltwater interface is simulated for three climate and demographic scenarios.
Groundwater flow simulations are performed with the finite volume code d3f++ (distributed density driven flow) that has been developed with a view to the modelling of large, complex, strongly density-influenced aquifer systems over long time periods
New results on the hadronic vacuum polarization to the muon g-2
Results on the lowest-order hadronic vacuum polarization contribution to the
muon magnetic anomaly are presented. They are based on the latest published
experimental data used as input to the dispersion integral. Thus recent results
on tau to nutau pi pi0 decays from Belle and on e+ e- annihilation to pi+ pi-
from BABAR and KLOE are included. The new data, together with improved
isospin-breaking corrections for tau decays, result into a much better
consistency among the different results. A discrepancy between the Standard
Model prediction and the direct g-2 measurement is found at the level of 3
sigma.Comment: proceedings of the PhiPsi09 conference, Oct. 13-16, 2009, Beijing,
Chin
Measurement of the Positive Muon Lifetime and Determination of the Fermi Constant to Part-per-Million Precision
We report a measurement of the positive muon lifetime to a precision of 1.0
parts per million (ppm); it is the most precise particle lifetime ever
measured. The experiment used a time-structured, low-energy muon beam and a
segmented plastic scintillator array to record more than 2 x 10^{12} decays.
Two different stopping target configurations were employed in independent
data-taking periods. The combined results give tau_{mu^+}(MuLan) =
2196980.3(2.2) ps, more than 15 times as precise as any previous experiment.
The muon lifetime gives the most precise value for the Fermi constant:
G_F(MuLan) = 1.1663788 (7) x 10^-5 GeV^-2 (0.6 ppm). It is also used to extract
the mu^-p singlet capture rate, which determines the proton's weak induced
pseudoscalar coupling g_P.Comment: Accepted for publication in Phys. Rev. Let
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