Magnetic field dependence of muonium-antimuonium conversion
Abstract We study the magnetic field dependence of muonium-antimuonium conversion for all relevent operators, such as ( V − A ) ( V − A ), ( V − A ) ( V + A ), SS and PP . The traditional ( V − A ) ( V − A ) interaction suffers two stage quenching and becomes strongly suppressed by 10 3 Gauss fields or higher. In contrast, all other operator types (except ( S − P ) ( S − P )) have a weaker field dependence and in general are not strongly quenched by strong fields. Since ongoing experiments are done with sizable magnetic fields, our results are useful for the interpretation of experimental results as bounds on different effective interactions.
Flavor unification, tau decay, and b decay within the six-quark--six-lepton Weinberg-Salam model
The leptons ..nu../sub e/, e, ..nu../sub ..mu../, ..mu.., ..nu../sub tau/, tau, and analogously the quarks u, d, c, s, t, b, are unified within the Weinberg-Salam SU/sub 2/ x U/sub 1/ gauge model without enlarging the gauge group. The result is a theory in which the familiar leptons, quarks, and gauge bosons, plus some extra Higgs bosons necessary for unification, all carry a new multiplicatively conserved quantum number ..pi.. = +- 1. The most striking results of this unification are (1) ..pi.. conservation forbids ..mu.. ..-->.. e..gamma.. but allows the Higgs-boson-mediated decays tau ..-->.. l..gamma.. (l = e or ..mu..) and tau ..-->.. ..mu..ee or e..mu mu.., at a calculable rate with a calculable lower limit; (2) for quarks, two of the three Cabibbo angles must be zero, so that the b quark (assumed lighter than t) decays only via Higgs-boson exchange, always semileptonically and always with lepton-number violation, e.g., b ..-->.. de/sup +/..mu../sup -/. This singular prediction will confirm or exclude the model as soon as b-flavored mesons are discovered. These and other phenomenological consequences of this unification are explained, and rates are estimated.
High-frequency hearing thresholds: effects of age, occupational ultrasound and noise exposure
AbstractPurpose
It has been suggested that high-frequency audiometry (HFA) could represent a useful preventive measure in exposed workers. The aim was to investigate the effects of age, ultrasound and noise on high-frequency hearing thresholds.MethodsWe tested 24 industrial ultrasound-exposed subjects, 113 industrial noise-exposed subjects and 148 non-exposed subjects. Each subject was tested with both conventional-frequency (0.125–8 kHz) and high-frequency (9–18 kHz) audiometry.ResultsThe hearing threshold at high frequency deteriorated as a function of age, especially in subjects more than 30 years old. The ultrasound-exposed subjects had significantly higher hearing thresholds than the non-exposed ones at the high frequencies, being greatest from 10 to 14 kHz. This hearing loss was already significantly evident in subjects with exposure <5 years and increased with years of exposure and advancing age. The noise exposure group had significantly higher hearing thresholds than the non-exposed group at the conventional frequencies 4 and 6 kHz and at the high frequency of 14 kHz. After stratification for age, there was a significant difference between the two groups at 9–10 and 14–15 kHz only for those under 30 years of age.ConclusionMultivariate analysis indicated that age was the primary predictor, and noise and ultrasound exposure the secondary predictors of hearing thresholds in the high-frequency range. The results suggest that HFA could be useful in the early diagnosis of noise-induced hearing loss in younger groups of workers (under 30 years of age).
