Measurement of the branching fraction for Υ(1S)→τ+τ−\Upsilon (1S) \to \tau^+ \tau^-

We have studied the leptonic decay of the $\Upsilon (1S)$ resonance into tau pairs using the CLEO II detector. A clean sample of tau pair events is identified via events containing two charged particles where exactly one of the particles is an identified electron. We find $B(\Upsilon(1S) \to \tau^+ \tau^-) = (2.61~\pm~0.12~{+0.09\atop{-0.13}})$. The result is consistent with expectations from lepton universality.Comment: 9 pages, RevTeX, two Postscript figures available upon request, CLNS 94/1297, CLEO 94-20 (submitted to Physics Letters B

Production and Decay of D_1(2420)^0 and D_2^*(2460)^0

We have investigated $D^{+}\pi^{-}$ and $D^{*+}\pi^{-}$ final states and observed the two established $L=1$ charmed mesons, the $D_1(2420)^0$ with mass $2421^{+1+2}_{-2-2}$ MeV/c$^{2}$ and width $20^{+6+3}_{-5-3}$ MeV/c$^{2}$ and the $D_2^*(2460)^0$ with mass $2465 \pm 3 \pm 3$ MeV/c$^{2}$ and width $28^{+8+6}_{-7-6}$ MeV/c$^{2}$. Properties of these final states, including their decay angular distributions and spin-parity assignments, have been studied. We identify these two mesons as the $j_{light}=3/2$ doublet predicted by HQET. We also obtain constraints on {\footnotesize $\Gamma_S/(\Gamma_S + \Gamma_D)$} as a function of the cosine of the relative phase of the two amplitudes in the $D_1(2420)^0$ decay.Comment: 15 pages in REVTEX format. hardcopies with figures can be obtained by sending mail to: [email protected]

Measurement of the Decay Asymmetry Parameters in Λc+→Λπ+\Lambda_c^+ \to \Lambda\pi^+ and Λc+→Σ+π0\Lambda_c^+ \to \Sigma^+\pi^0

We have measured the weak decay asymmetry parameters (\aLC ) for two \LC\ decay modes. Our measurements are \aLC = -0.94^{+0.21+0.12}_{-0.06-0.06} for the decay mode $\Lambda_c^+ \to \Lambda\pi^+$ and \aLC = -0.45\pm 0.31 \pm 0.06 for the decay mode $\Lambda_c \to \Sigma^+\pi^0$. By combining these measurements with the previously measured decay rates, we have extracted the parity-violating and parity-conserving amplitudes. These amplitudes are used to test models of nonleptonic charmed baryon decay.Comment: 11 pages including the figures. Uses REVTEX and psfig macros. Figures as uuencoded postscript. Also available as http://w4.lns.cornell.edu/public/CLNS/1995/CLNS95-1319.p

A measurement of B(D+S → φl+ν) B(D+S → φπ+)

Using the CLEO II detector at CESR, we have measured the ratio of branching fractions B (D + S → φl + ν) B (D + S → φπ + ) = 0.54 ± 0.05 ± 0.04 . We use this measurement to obtain a model dependent estimate of B (D + S → φπ + )

Dermatologie in Beruf und Umwelt : Organ der Arbeitsgemeinschaft für Berufs- und Umweltdermatologie in der Deutschen Dermatologischen Gesellschaft = Occupational and environmental dermatology

Site effects characterize the filtering mechanisms within the soil sedimentary layers overlying bedrock. In regions of high seismicity such as California where strong motion records are relatively abundant, site coefficients can be developed by regression of recorded ground shaking parameters. In regions of low-to-moderate seismicity or of high seismicity but with a paucity of recorded strong motion data, such empirical models cannot be obtained in the same way. This study describes the theoretical development of a simple, rational manual procedure to calculate site coefficients, based on a single period approximation (SPA), and to construct displacement response spectra (RSD) for soil sites. The proposed simplified model, which takes into account the non-linear behaviour of soil that is dependent on the level of shaking, impedance contrast at the soil-bedrock interface and the plasticity of soil material, has been verified by comparison with results obtained from non-linear shear wave analyses and data recorded during the 1994 Northridge earthquake. The proposed model is believed to be a convenient tool for calculating non-linear site responses and constructing site-specific response spectra, which has the potential of being incorporated into code provisions

Simple models for estimating period-shift and damping in soil

This study describes the development of a simple, heuristic manual calculation procedure for estimating the site period-shift factor and soil damping ratio, with appropriate considerations for the level of shaking, impedance contrast between soil and bedrock interface and the plasticity of the soil layers. Essentially, the analogy of a building shear-frame has been used to represent the seismic response behaviour of a soil column. The proposed procedure has been verified by comparing the predictions with results obtained directly from non-linear shear wave analyses of soil column models

Shaking table tests on strength degradation behaviour

Structures such as unreinforced masonry walls, soft-storey buildings, gravity structures and components which include free-standing objects are well known to be non-ductile and yet they are commonly found in regions of low-moderate seismicity. Potential significant degradation in strength in these structural systems in projected earthquake scenarios has been a cause for concern. Shaking table experiments undertaken recently by the authors revealed very interesting phenomena with the behaviour of the (“non-ductile”) free-standing objects in an earthquake. Vulnerability to overturning is shown not to be sensitive to the height of the object nor its aspect ratio. The trends revealed earlier by the authors based on analytical modeling have been confirmed experimentally. Importantly, the displacement time histories predicted by program Rowmanry and Romain are shown to be very consistent with recordings from the shaking table experiments

Choice of intensity measure in incremental dynamic analysis

Incremental Dynamic Analysis (IDA) is a powerful method for evaluating the seismic performance of structural systems. When undertaking IDA, ground motion records are scaled in accordance with a certain seismic intensity level up until the limit of collapse of the structure is reached. Peak ground acceleration (PGA) is often used as intensity measure (IM) for scaling purposes whilst peak ground velocity and response spectral accelerations can also be used as IM parameters. One of the challenges with the IDA methodology is that the performance (IDA) curve obtained for a structural system is non-unique meaning that it can be sensitive to changes in the frequency properties of the input excitations. Thus, there is a practice of holding the frequency content of the excitation unchanged (or constrained to a model design spectrum) when applying the scaling. The shortcomings with this modelling approach is that real conditions can be misrepresented given that frequency contents of the earthquake changes with magnitude and distance. This paper presents findings from an investigation which was aimed at determining what ground motion parameters are most suitable for use as IM whilst allowing the frequency content of the earthquake to vary in an IDA. This paper presents findings of an investigation wherein nonlinear dynamic time-history analyses involving the use of both recorded and mtificial accelerograms were undertaken on models representing buildings constructed of cold-formed steel. For systems with natural pedod of less than 0.4s; PGA and the peak acceleration demand (PAD) have been found to be desirable choices of IM parameters given that the associated IDA curves are generally insensitive to the choice of the accelerogram ensemble used. For systems possessing longer natural pedods of vibration, other ground motion parameters have been found to be more desirable choices