1,517 research outputs found
Beyond Standard Model Physics
There are many recent results from searches for fundamental new physics using
the TeVatron, the SLAC b-factory and HERA. This talk quickly reviewed searches
for pair-produced stop, for gauge-mediated SUSY breaking, for Higgs bosons in
the MSSM and NMSSM models, for leptoquarks, and v-hadrons. There is a SUSY
model which accommodates the recent astrophysical experimental results that
suggest that dark matter annihilation is occurring in the center of our galaxy,
and a relevant experimental result. Finally, model-independent searches at D0,
CDF, and H1 are discussed
Validation of frequency and mode extraction calculations from time-domain simulations of accelerator cavities
The recently developed frequency extraction algorithm [G.R. Werner and J.R.
Cary, J. Comp. Phys. 227, 5200 (2008)] that enables a simple FDTD algorithm to
be transformed into an efficient eigenmode solver is applied to a realistic
accelerator cavity modeled with embedded boundaries and Richardson
extrapolation. Previously, the frequency extraction method was shown to be
capable of distinguishing M degenerate modes by running M different simulations
and to permit mode extraction with minimal post-processing effort that only
requires solving a small eigenvalue problem. Realistic calculations for an
accelerator cavity are presented in this work to establish the validity of the
method for realistic modeling scenarios and to illustrate the complexities of
the computational validation process. The method is found to be able to extract
the frequencies with error that is less than a part in 10^5. The corrected
experimental and computed values differ by about one parts in 10^$, which is
accounted for (in largest part) by machining errors. The extraction of
frequencies and modes from accelerator cavities provides engineers and
physicists an understanding of potential cavity performance as it depends on
shape without incurring manufacture and measurement costs
The Power of Non-Determinism in Higher-Order Implicit Complexity
We investigate the power of non-determinism in purely functional programming
languages with higher-order types. Specifically, we consider cons-free programs
of varying data orders, equipped with explicit non-deterministic choice.
Cons-freeness roughly means that data constructors cannot occur in function
bodies and all manipulation of storage space thus has to happen indirectly
using the call stack.
While cons-free programs have previously been used by several authors to
characterise complexity classes, the work on non-deterministic programs has
almost exclusively considered programs of data order 0. Previous work has shown
that adding explicit non-determinism to cons-free programs taking data of order
0 does not increase expressivity; we prove that this - dramatically - is not
the case for higher data orders: adding non-determinism to programs with data
order at least 1 allows for a characterisation of the entire class of
elementary-time decidable sets.
Finally we show how, even with non-deterministic choice, the original
hierarchy of characterisations is restored by imposing different restrictions.Comment: pre-edition version of a paper accepted for publication at ESOP'1
Crab cavities for linear colliders
Crab cavities have been proposed for a wide number of accelerators and
interest in crab cavities has recently increased after the successful operation
of a pair of crab cavities in KEK-B. In particular crab cavities are required
for both the ILC and CLIC linear colliders for bunch alignment. Consideration
of bunch structure and size constraints favour a 3.9 GHz superconducting,
multi-cell cavity as the solution for ILC, whilst bunch structure and
beam-loading considerations suggest an X-band copper travelling wave structure
for CLIC. These two cavity solutions are very different in design but share
complex design issues. Phase stabilisation, beam loading, wakefields and mode
damping are fundamental issues for these crab cavities. Requirements and
potential design solutions will be discussed for both colliders.Comment: 3 pages. To be published in proceedings of LINAC 2008, Victoria,
Canad
Measurement of the antineutrino to neutrino charged-current interaction cross section ratio in MINERvA
We present measurements of the neutrino and antineutrino total charged-current cross sections on carbon and their ratio using the MINERvA scintillator-tracker. The measurements span the energy range 2-22 GeV and were performed using forward and reversed horn focusing modes of the Fermilab low-energy NuMI beam to obtain large neutrino and antineutrino samples. The flux is obtained using a subsample of charged-current events at low hadronic energy transfer along with precise higher energy external neutrino cross section data overlapping with our energy range between 12-22 GeV. We also report on the antineutrino-neutrino cross section ratio, R-CC, which does not rely on external normalization information. Our ratio measurement, obtained within the same experiment using the same technique, benefits from the cancellation of common sample systematic uncertainties and reaches a precision of similar to 5% at low energy. Our results for the antineutrino-nucleus scattering cross section and for RCC are the most precise to date in the energy range E-v \u3c 6 GeV
Dynamic critical behavior of the worm algorithm for the Ising model
We study the dynamic critical behavior of the worm algorithm for the two- and three-dimensional Ising models, by Monte Carlo simulation. The autocorrelation functions exhibit an unusual three-time-scale behavior. As a practical matter, the worm algorithm is slightly more efficient than Swendsen-Wang for simulating the two-point function of the three-dimensional Ising model
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Highly Accurate Frequency Calculations of Crab Cavities Using the VORPAL Computational Framework
We have applied the Werner-Cary method [J. Comp. Phys. 227, 5200-5214 (2008)] for extracting modes and mode frequencies from time-domain simulations of crab cavities, as are needed for the ILC and the beam delivery system of the LHC. This method for frequency extraction relies on a small number of simulations, and post-processing using the SVD algorithm with Tikhonov regularization. The time-domain simulations were carried out using the VORPAL computational framework, which is based on the eminently scalable finite-difference time-domain algorithm. A validation study was performed on an aluminum model of the 3.9 GHz RF separators built originally at Fermi National Accelerator Laboratory in the US. Comparisons with measurements of the A15 cavity show that this method can provide accuracy to within 0.01% of experimental results after accounting for manufacturing imperfections. To capture the near degeneracies two simulations, requiring in total a few hours on 600 processors were employed. This method has applications across many areas including obtaining MHD spectra from time-domain simulations
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