81,348 research outputs found
Fitting Precision Electroweak Data with Exotic Heavy Quarks
The 1999 precision electroweak data from LEP and SLC persist in showing some
slight discrepancies from the assumed standard model, mostly regarding and
quarks. We show how their mixing with exotic heavy quarks could result in a
more consistent fit of all the data, including two unconventional
interpretations of the top quark.Comment: 7 pages, no figure, 2 typos corrected, 1 reference update
Theoretical study of space plasmas Final report, 16 Feb. 1964 - 15 Mar. 1965
Interchange stability of Van Allen belt - Effect of resonant magnetic moment violation on trapped particles - Exact solution of universal instabilit
Effective-Field-Theory Approach to Top-Quark Production and Decay
We discuss new physics in top-quark interactions, using an effective field
theory approach. We consider top-quark decay, single top production, and
top-quark pair production. We identify 15 dimension-six operators that
contribute to these processes, and we compute the deviation from the Standard
Model induced by these operators. The results provide a systematic way of
searching for (or obtaining bounds on) physics beyond the Standard Model.Comment: 24 pages, 12 figures; references added, typos correcte
A secondary ejecta explanation of a lunar seismogram
Secondary ejecta explanation to seismograph of Apollo 12 LM impac
Rotational CARS application to simultaneous and multiple-point temperature and concentration determination in a turbulent flow
Coherent anti-Stokes Raman scattering (CARS) from the pure rotational Raman lines of N2 is employed to measure the instantaneous (approximately 10 ns) rotational temperature of N2 gas at room temperature and below with good spatial resolution (0.2 x 0.2 x 3.0 cu mm). A broad bandwidth dye laser is used to obtain the entire rotational spectrum from a single laser pulse; the CARS signal is then dispersed by a spectrograph and recorded on an optical multichannel analyzer. A best fit temperature is found in several seconds with the aid of a computer for each experimental spectrum by a least squares comparison with calculated spectra. The model used to calculate the theoretical spectra incorporates the temperature and pressure dependence of the pressure-broadened rotational Raman lines, includes the nonresonant background susceptibility, and assumes that the pump laser has a finite linewidth. Temperatures are fit to experimental spectra recorded over the temperature range of 135 to 296 K, and over the pressure range of .13 to 15.3 atm
Electrodynamics of Magnetars III: Pair Creation Processes in an Ultrastrong Magnetic Field and Particle Heating in a Dynamic Magnetosphere
We consider the details of the QED processes that create electron-positron
pairs in magnetic fields approaching and exceeding 10^{14} G. The formation of
free and bound pairs is addressed, and the importance of positronium
dissociation by thermal X-rays is noted. We calculate the collision cross
section between an X-ray and a gamma ray, and point out a resonance in the
cross section when the gamma ray is close to the threshold for pair conversion.
We also discuss how the pair creation rate in the open-field circuit and the
outer magnetosphere can be strongly enhanced by instabilities near the light
cylinder. When the current has a strong fluctuating component, a cascade
develops. We examine the details of particle heating, and show that a high rate
of pair creation can be sustained close to the star, but only if the spin
period is shorter than several seconds. The dissipation rate in this turbulent
state can easily accommodate the observed radio output of the transient
radio-emitting magnetars, and even their infrared emission. Finally, we outline
how a very high rate of pair creation on the open magnetic field lines can help
to stabilize a static twist in the closed magnetosphere and to regulate the
loss of magnetic helicity by reconnection at the light cylinder.Comment: 25 pages, submitted to the Astrophysical Journa
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