565 research outputs found
Isospin Breaking in Low-Energy Charged Pion and Kaon Elastic Scattering
We use chiral perturbation theory to evaluate the scattering amplitude for
the process Pi^+ K^- to Pi^+ K^- at leading and next-to-leading orders in the
chiral counting and in the presence of isospin breaking effects. We also
discuss the influence of the latter on the combination of the S-wave Pi K
scattering lengths which is relevant for the 2S - 2P energy levels shift of K
Pi atoms.Comment: 23 pages, LATEX2e, 2 figures, 2 table
Virtual Photon Correction to the Decay
We consider electromagnetic corrections to the non-leptonic kaon decay,
, due to explicit virtual photons only. The decay
amplitude is calculated at one-loop level in the framework of Chiral
Perturbation Theory. The interest in this process is twofold: It is actually
measured by the NA48 collaboration from one side, and, the value of the
amplitude at the threshold gives access to scattering lengths
from the other side. We found that the present correction is about 5 to 6% the
value of the Born amplitude squared. Combined with another piece published
recently, this fixes the size of isospin breaking correction to the amplitude
squared to 7% its one-loop level value in the absence of isospin breaking and
at the center of Dalitz plot.Comment: 29 pages, 1 LaTeX file, 1 pdf file including all figure
Electromagnetic Corrections to Charged Pion Scattering at Low Energies
The electromagnetic corrections to the low energy scattering amplitude
involving charged pions only are investigated at leading and next-to-leading
orders in the two-flavour chiral expansion. As an application, the
corresponding variation in the strong level shift is evaluated. The
relative variation is of the order of 5%.Comment: LateX2e, 10 pages, 2 figure
Size of Isospin Breaking in Charged K(L4) Decay
We evaluate the size of isospin breaking corrections to form factors and
of the decay process which
is actually measured by the extended NA48 setup at CERN. We found that, keeping
apart the effect of Coulomb interaction, isospin breaking does not affect
modules. This is due to the cancelation between corrections of electromagnetic
origin and those generated by the difference between up and down quark masses.
On the other hand, electromagnetism affects considerably phases if the infrared
divergence is dropped out using a minimal subtraction scheme. Consequently, the
greatest care must be taken in the extraction of phase shifts from
experiment.Comment: 29 pages, LaTeX, 7 postscript figure
Information Requirements for MCM and ISR Missions : PUMA Phase II
This document contains display requirements for Littoral Combat Ship (LCS) control
station displays to be used by unmanned vehicle units in support of heterogeneous
unmanned vehicle missions (such as Special Operations Force (SOF) insertion). The
method used for generating the requirements was that of a Hybrid Cognitive Task
Analysis (CTA)1 which entails describing a scenario overview of a representative
mission, generating event flow diagrams, and depicting decision ladders for the key
decisions identified in the event flow diagrams. These steps are then used together to
generate an informational requirements summary which includes the situational
awareness requirements that are derived from the event flow and display requirements of
the decision ladders. This method was developed in Phase I of the PUMA (Plan
Understanding for Mixed-initiative control of Autonomous systems) project2. In PUMA
I, the mission scenario primarily consisted of Intelligence, Surveillance and
Reconnaissance (ISR) tasks. For PUMA II, the scenario has been expanded to include
Mine Counter Measures (MCM), Harbor Bottom Image-Mapping (HBI), and Anti-
Terrorism / Force Protection (AT/FP) mission types. There is a specific emphasis on the
MCM and ISR missions to highlight the informational requirement differences between
the two task types. This document incorporates the expanded vehicle and mission type
heterogeneities that are present in PUMA II in order to develop a cohesive set of
informational requirements necessary for such a complex mission.Prepared for Charles River Analytic
The Effects of Magnetic Flux on Suspended Particles in Seawater
A study was conducted to investigate the effect of magnetic devices on the precipitates in a condenser’s tubes when seawater is used as cooling water. This test was necessary to evaluate these devices as possible replacements for conventional methods of water treatment. In the test program, a small condenser was operated with conditions similar to utility condensers. This condenser was modified to include twelve tubes. The inlet water box was divided to provide for two parallel magnetic water treatment streams, and one control untreated water stream for comparison purposes. With and without the use of a magnetic device, the chemical analysis and the thickness of the deposits showed no significant difference. The only difference that was observed in these deposits was their crystallogical structure. When the magnetic device was in place, deposits were flaky (powder-like), chipped, and showed no strong adhesion to the inner surface of the condenser’s tubes. Without the use of a magnetic device, deposits were flocculated, hard, and crusty. This thesis proposes a theory which may help explain the differences in the deposits. The theory will include homogenous nucleation to explain the physical changes of the deposits. The discussion will also postulate how well the magnetic energy improved the homogenous nucleation process. A method of analysis is proposed which demonstrates how the critical radius of a nucleus is affected by a magnetic field
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