51,657 research outputs found
Using MiniBooNE neutral current elastic cross section results to constrain 3+1 sterile neutrino models
The MiniBooNE Neutral Current Elastic (NCEL) cross section results are used
to extract limits in the plane for a
3+1 sterile neutrino model with a mass splitting eV. GENIE is used with a cross section model close to the one
employed by MiniBooNE to make event rate predictions using simulations on the
MiniBooNE target material CH. The axial mass is a free parameter in all
fits. Sterile modifications to the flux and changes to the cross section in the
simulation relate the two and allow limits to be set on sterile neutrino mixing
using cross section results. The large axial mass problem makes it necessary
for experiments to perform their own axial mass fits, but a prior fit to the
same dataset could mask a sterile oscillation signal if the sterile and cross
section model parameters are not independent. We find that for the NCEL dataset
there are significant correlations between the sterile and cross section model
parameters, making a fit to both models simultaneously necessary to get robust
results. Failure to do this results in stronger than warranted limits on the
sterile parameters. The general problems that the current uncertainty on
charged-current quasi-elastic (CCQE) and NCEL cross sections at MiniBooNE
energies pose for sterile neutrino measurements are discussed.Comment: Final version accepted for publication in JHE
Techniques for railway restructuring
This report was sponsored by the Union of African Railways, as part of a Sub-Saharan Africa Transport Project task aimed at defining what is involved in restructuring railways so that they behave more like market driven enterprises. The question addressed in this document is not whether the railway should be restructured, but how. The report recommends four types of action to be employed in the process of institutional reform : 1) a strategic plan which defines the environment in which the railway will function and focuses on the crucial policy issues that will guide or influence the railway's planning and actions, 2) a contract plan which defines the roles and responsibilities of the railway and its owner. This plan flows from the strategic plan and should not be developed in isolation from related policy and funding objectives of the government and railway. 3) A management plan that clarifies the objectives of the senior railway executives and their roles and responsibilities in relation to the executive director, and 4) an enabling actions plan, which lists most of the initiatives that must be taken in conjunction with implementation of the first three plans. The focus should be to ensure that the roles and responsibilities defined will actually be realized in law or enforceable agreement.Railways Transport,Banks&Banking Reform,Public Sector Economics&Finance,Environmental Economics&Policies,Roads&Highways
Droplet migration: quantitative comparisons with experiment
An important practical feature of simulating droplet migration computationally,
using the lubrication approach coupled to a disjoining pressure term, is
the need to specify the thickness, H, of a thin energetically stable wetting layer,
or precursor lm, over the entire substrate. The necessity that H be small in
order to improve the accuracy of predicted droplet migration speeds, allied to the
need for mesh resolution of the same order as H near wetting lines, increases the
computational demands signicantly. To date no systematic investigation of these
requirements on the quantitative agreement between prediction and experimental
observation has been reported. Accordingly, this paper combines highly ecient
Multigrid methods for solving the associated lubrication equations with a parallel
computing framework, to explore the eect of H and mesh resolution. The solutions
generated are compared with recent experimentally determined migration
speeds for droplet
ows down an inclined plane
Quantum information approach to Bose-Einstein condensation of composite bosons
We consider composite bosons (cobosons) comprised of two elementary
particles, fermions or bosons, in an entangled state. First, we show that the
effective number of cobosons implies the level of correlation between the two
constituent particles. For the maximum level of correlation, the effective
number of cobosons is the same as the total number of cobosons, which can
exhibit the original Bose-Einstein condensation (BEC). In this context, we
study a model of BEC for indistinguishable cobosons with a controllable
parameter, i.e., entanglement between the two constituent particles. We find
that bi-fermions behave in a predictable way, i.e., the effective number of the
ground state coboson is an increasing function of entanglement between a pair
of constituent fermions. Interestingly, bi-bosons exhibit the opposite
behaviour - the effective number of the ground state coboson is a decreasing
function of entanglement between a pair of constituent bosons.Comment: 10 pages, 5 figures, accepted for publication in New J. Phy
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