122 research outputs found
Pion LINAC as an Energy-Tagged Neutrino Source
The energy spectrum and flux of neutrinos from a linear pion accelerator are
calculated analytically under the assumption of a uniform accelerating
gradient. The energy of a neutrino from this source reacting in a detector can
be determined from timing and event position information.Comment: 16 pages, 4 figures. Replacement of Section II.D and minor
corrections elsewhere. The basic point and conclusions of the paper are
unchanged. Phys. Rev. ST Accel. Beams 11,124701 (2008); Erratum submitte
On the Bragg, Leibfried, and Modified Leibfried Numbers
The Bragg, Leibfried, and modified Leibfried numbers are defined in the
context of a theory of dislocation-mediated melting, and their values are
determined from the properties of the dislocation ensemble at the melting
temperature. The approximate numerical coincidence of the Bragg and modified
Leibfried numbers is explained. The parameter K in the definition of the
modified Leibfried number is shown to be the natural logarithm of the effective
coordination number. Our analysis reveals that the Bragg number can be
considered an elemental constant, in contrast to the Leibfried and modified
Leibfried numbers.Comment: 5 pages, LaTe
Charmed Mesons Have No Discernable Color-Coulomb Attraction
Starting with a confining linear Lorentz scalar potential V_s and a Lorentz
vector potential V_v which is also linear but has in addition a color-Coulomb
attraction piece, -alpha_s/r, we solve the Dirac equation for the ground-state
c- and u-quark wave functions. Then, convolving V_v with the u-quark density,
we find that the Coulomb attraction mostly disappears, making an essentially
linear barV_v for the c-quark. A similar convolution using the c-quark density
also leads to an essentially linear tildeV_v for the u-quark. For bound cbar-c
charmonia, where one must solve using a reduced mass for the c-quarks, we also
find an essentially linear widehatV_v. Thus, the relativistic quark model
describes how the charmed-meson mass spectrum avoids the need for a
color-Coulomb attraction.Comment: 9 pages, 5 PDF figure
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Report on the Los Alamos Kaon Factory seminar: physics
The motivations, discussions, and preliminary conclusions of the LASL Kaon Factory Seminar, which met 15 times in the Spring of 1979, are reported. It is technically feasible, but expensive, to build a kaon factory using LAMPF as an injector. Taking advantage of the increased beam intensity, excellent secondary beam lines could be built. While we continue further study of the physics justification for a kaon factory, we also propose to gradually increase LASL participation in kaon and antiproton physics
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Toward automated beam optics control
We have begun a program aiming toward automatic control of charged-particle beam optics using artificial intelligence programming techniques. In developing our prototype, we are working with LISP machines and the KEE expert system shell. Our first goal was to develop a ''mouseable'' representation of a typical beam line. This responds actively to changes entered from the mouse or keyboard, giving an updated display of the beam line itself, its optical properties, and the instrumentation and control devices as seen by the operater. We have incorporated TRANSPORT, written in Fortran but running as a callable procedure in the LISP environment, for simulation of the beam-line optics. This paper describes the experience gained in meeting our first goal and discusses plans to extend the work so that it is usable, in realtime, on an operating beam line. 11 refs
Solution processed large area field effect transistors from dielectrophoreticly aligned arrays of carbon nanotubes
We demonstrate solution processable large area field effect transistors
(FETs) from aligned arrays of carbon nanotubes (CNTs). Commercially available,
surfactant free CNTs suspended in aqueous solution were aligned between source
and drain electrodes using ac dielectrophoresis technique. After removing the
metallic nanotubes using electrical breakdown, the devices displayed p-type
behavior with on-off ratios up to ~ 2X10^4. The measured field effect
mobilities are as high as 123 cm2/Vs, which is three orders of magnitude higher
than typical solution processed organic FET devices.Comment: 5 pages, 3 figure
Analysis of Dislocation Mechanism for Melting of Elements: Pressure Dependence
In the framework of melting as a dislocation-mediated phase transition we
derive an equation for the pressure dependence of the melting temperatures of
the elements valid up to pressures of order their ambient bulk moduli. Melting
curves are calculated for Al, Mg, Ni, Pb, the iron group (Fe, Ru, Os), the
chromium group (Cr, Mo, W), the copper group (Cu, Ag, Au), noble gases (Ne, Ar,
Kr, Xe, Rn), and six actinides (Am, Cm, Np, Pa, Th, U). These calculated
melting curves are in good agreement with existing data. We also discuss the
apparent equivalence of our melting relation and the Lindemann criterion, and
the lack of the rigorous proof of their equivalence. We show that the would-be
mathematical equivalence of both formulas must manifest itself in a new
relation between the Gr\"{u}neisen constant, bulk and shear moduli, and the
pressure derivative of the shear modulus.Comment: 19 pages, LaTeX, 9 eps figure
Phenomenological study on the significance of the scalar potential and Lamb shift
We indicated in our previous work that for QED the contributions of the
scalar potential which appears at the loop level is much smaller than that of
the vector potential and in fact negligible. But the situation may be different
for QCD, one reason is that the loop effects are more significant because
is much larger than , and secondly the non-perturbative QCD
effects may induce the scalar potential. In this work, we phenomenologically
study the contribution of the scalar potential to the spectra of charmonia.
Taking into account both vector and scalar potentials, by fitting the well
measured charmonia spectra, we re-fix the relevant parameters and test them by
calculating other states of the charmonia family. We also consider the role of
the Lamb shift and present the numerical results with and without involving the
Lamb shift
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