Search

D-meson lifetimes have been determined from decays observed in an exposure of the high resolution hydrogen bubble chamber LEBC in association with the European Hybrid Spectrometer (EHS) to an incident 360 GeV π− beam. Various techniques for lifetime determination are presented and the results compared. A new model-independent analysis based on the distribution in transverse decay length is introduced and preferred over other techniques. Best values are found to be: $$\begin{gathered} \tau (D^0 ) = \left( {4.1_{ - 0.3}^{ + 0.7} } \right) \times 10^{ - 13} s (60 decays) \hfill \\ \tau (D^ \pm ) = \left( {10.7_{ - 1.8}^{ + 2.8} } \right) \times 10^{ - 13} s (40 decays) \hfill \\ \end{gathered} $$ . The lifetime ratio is: $$T = \frac{{\tau (D^ \pm )}}{{\tau (D^0 )}} = 2.6_{ - 0.6}^{ + 0.8} $$ .

Real interfaces are complicated. Even for a surface resulting from a crystal cleaved in vacuum, it is difficult to eliminate steps, vacancies, and dislocations. If an ideal surface is obtained, reconstruction and charge redistribution are common properties. For solid-solid interfaces, diffusion, misfit dislocations, and other “nonideal” phenomena are common. However, it is still important to understand the ideal cases. A good description of an ideal interface provides a basis for comparison with real systems and allows an identification of observed properties in terms of deviations from ideal behavior.

The phenomenology of CPT violation in the neutral kaon system is presented and the relevance of the measurement of the phase difference (Φ+- – Φ00) briefly discussed. The method, its advantages, and the limits expected of the measurements of the CPLEAR experiment are presented.

We show for the first time that the reoxidation step after the gate patterning strongly affects the transistor short channel behavior. This particular oxidation induces a laterally non-uniform channel profile. From the comparison of simulation and experimental transistor data an effective interstitial decay length L i is extracted, determining the extent of local OED effects. We find L i =1.4µm for dry oxidation at 900°C.

The measurements of charmed particle lifetimes are based on experimental apparatus which combine a forward multiparticle spectrometer with a high resolution vertex detector.

The subject of this talk is the possibility of using for the trigger the change in secondary track multiplicity which is due to a multi-charged decay of one of the particles produced in the interaction. The process under study is the associated production of two charmed states one of which has a decay length of the order of 1 cm, the other decay length being shorter. The target used is a silicon detector telescope, made of 10 layers 300 μ thick put at a distance of 100 μ.

In the next two chapters we are going to apply the general formalism to two very simple examples. The aim is twofold: first of all, pedagogical. We want to demonstrate how some well-known results manifest themselves in the framework of the formalism of the foregoing sections. Secondly, we want to use the equations of Brownian motion as a heuristic starting point for more general kinetic equations.

The segregation of Si to the surface of Cu as inferred by secondary ion mass spectrometry, SIMS, is shown to set in dramatically when O is present at the sputtered surface. Copper depth profiles obtained from Cu implanted silicon wafers or Cu-Si sandwiches using O 2 + or Ar+ bombardment at angles of incidence > 30° show no unusual perturbation. However, with O bombardment at ≤15° or with O incorporation from the ambient with either O 2 + or Ar+; bombardment, the measured Cu profiles become deeply penetrating. The results can be understood in terms of an interplay between bombardment-induced Gibbsian segregation (Cu is excluded fron the surface of Si in the presence of O) and room-temperature diffusional mobility (Cu is highly mobile in amorphous SiO2).

A simple physical explanation for the observed exponential behavior of the density of states based on short range Gaussian fluctuations is presented. Several techniques for obtaining the density of states and other quantities of physical interest are briefly reviewed. The universal and quasi-universal features of the electronic behavior near a band edge in a disordered material are also presented.

Prompt neutrinos are those originating from the (semi)leptonic decays of particles whose decay length is much shorter than their interaction length in matter.

Initiated by the demand for improved depth resolution, we have carried out a series of depth profiling experiments at various angles of incidence between s = 0° and s = 85°, while maintaining a high primary beam energy, namely 12 keV. In order to reduce the experimental difficulties involved with high angles of incidence, we took advantage of our “mini-chip” sample preparation technique and our “checkerboard” data evaluation technique [1].

Beam-induced broadening effects in SIMS depth profiling have been studied for eight impurities (Li through Al) implanted in amorphized silicon at energies between 1 and 15 keV. Depth profiling was performed under Ar+ (⩽2.5 keV) or O (⩽3 keV) impact. In selected cases (Li, N) the effect of the probe energy has also been investigated. The measured profiles show exponential tails. The decay length γ characterizing these tails exhibits strong oscillations when plotted as a function of the atomic number of the dopant. Maxima are seen for N and O (γ ≃ 7 nm) as well as for Mg (γ ≃ 13 nm), minima for B and Na (γ ≃ 2 nm). The results suggest that the observed effects are due to a yet unpredictable combination of collisional mixing, defect-assisted diffusion and selective sputtering.

A new measurement of the τ lifetime is presented. It uses data collected with the Opal detector during 1994, which almost doubles the size of the Opal τ sample. Two statistically independent techniques are used: an impact parameter analysis of one-prong decay tracks and a fit to the decay length distribution of three-prong decays. The lifetime obtained from the 1994 data by combining the results of these methods is τ τ = 289.7 ± 2.5 (stat)± 1.5 (sys) fs. When combined with the previous Opal τ lifetime measurement the improved τ lifetime is τ τ = 289.2 ± 1.7 (stat.) ± 1.2 (sys.) fs.

Numerical simulations of L-mode turbulence in the scrape-off layer (SOL) are used to construct power scaling laws for the characteristic decay lengths of the temperature, density and heat flux at the outer mid-plane. Most of the results obtained are in qualitative agreement with the experimental observations despite the known limitation of the model. Quantitative agreement is also obtained for some exponents. In particular, an almost linear inverse dependence of the heat flux decay length with the plasma current is recovered. The relative simplicity of the theoretical model used allows one to gain insight into the mechanisms determining the width of the SOL.

We have measured the charged kaon lifetime using a sample of 15 \times 10^6 tagged kaon decays. Charged kaons were produced in pairs at the DA\PhiNE \phi-factory, e^+e^- \to \phi \to K^+ K^-. The decay of a K^+ was tagged by the production of a K^- and viceversa. The lifetime was obtained, for both charges, from independent measurements of the decay time and decay lenght distributions. From fits to the four distributions we find \tau = (12.347\pm0.030) ns., Comment: 13 pages, 14 figures

The nonlocal electrostatic contribution to the hydration (structural) repulsion of neutral hydrophilicsurfaces separated by thin water layer is considered. This contribution arises from the form of the image–charge interaction of alternating positively and negatively charged polar groups attached to one of the surfaces with nonpolar background of another surface. Characteristic features of this interaction are shown to be determined by the lateral ordering of the polar groups. Similar features were found previously in generalized free‐field model of the interaction. Both models are in a good quantitative agreement with the experimental data on lipid membranes, and give consistent physical explanation to observable dependences of amplitude and decay length of the hydration force on the nature and structure of the surfaces. This similarity makes it impossible to distinguish any particular mediator of the hydration force at the present state of the knowledge. At the same time it provides a quite general picture of the role of lateral structure of the surfaces in the hydration force.

We theoretically study the local density of states in superconducting proximity structure where two superconducting terminals are attached to a side surface of a normal-metal wire. Using the quasiclassical Green's function method, the energy spectrum is obtained for both of spin-singlet $s$-wave and spin-triplet $p$-wave junctions. In both of the cases, the decay length of the proximity effect at the zero temperature is limited by a depairing effect due to inelastic scatterings. In addition to the depairing effect, in $p$-wave junctions, the decay length depends sensitively on the transparency at the junction interfaces, which is a unique property to odd-parity superconductors where the anomalous proximity effect occurs., 11 pages, 9 figures

Many proposed and upcoming experiments seek to observe signals from upward going air showers initiated by tau leptons resulting from neutrino interactions inside the Earth. To save calculation time, event estimations for these observation methods are usually performed while making several assumptions about the showers themselves, which simplifies their rich phenomenology and may or may not lead to inaccuracies in results. Here, we present results of extensive CORSIKA simulations of upward going tau initiated showers in the energy range 1 PeV to 10 EeV. Specifically, we monitor the Cherenkov emission, the charged particle distributions, and the timing of the showers for different geometric configurations. We analyze the impact of the decay length and different decay modes of the tau on particle distributions and compare to primaries usually utilized to simulate a tau shower, such as gammas, electrons, and protons. We also check the accuracy of many of the usual assumptions of these showers and analyze the often ignored muon channel of the tau decay., ICRC 2019 Proceedings Paper

Mechanisms setting the density decay in the scrape-off layer (SOL) at the outer midplane of a tokamak plasma are disentangled using two-fluid numerical simulations in a double-null magnetic configuration and analytical estimates. Typical experimental observations are retrieved, in particular increasing intermittency of the turbulence going from the near to the far SOL, which is reflected in two different density decay lengths. The decay length of the near SOL is well described as the result of transport driven by a nonlinearly saturated ballooning instability, while in the far SOL, the density decay length is described using a model of intermittent transport mediated by blobs. The analytical estimates of the decay lengths agree well with the simulation results and typical experimental values and can therefore be used to guide tokamak design and operation.

Limits of g ${10}^{5}$ astronomical units are set on the decay length of an electron antineutrino ${\overline{\ensuremath{\nu}}}_{e}$ via the process ${\overline{\ensuremath{\nu}}}_{e}\ensuremath{\rightarrow}{\ensuremath{\nu}}^{\ensuremath{'}}+\ensuremath{\gamma}$ for ${E}_{\ensuremath{\gamma}}$ in the range 0.1-0.5 MeV using the results from a well-shielded detector in the vicinity of a fission reactor. This mode of decay is therefore ruled out as a possible explanation for the paucity of solar neutrinos revealed by the experiment of Davis.

Critical currents for triple layer superconducting-normal metal-superconducting (SNS) junctions have been measured with the normal metal in the thick-clean limit in order to determine the spatial variation of the order paremeter as a function of magnetic field (H). Critical currents fall exponentially with H as might be expected if the decay length, K -1 N , varies linearly with H. The diffusivity, D N , derived from the measured depairing parameter, α =D N eH/c, agrees with the diffusivity determined from resistivity measurements.

The forces between two mica surfaces immersed in various aqueous electrolyte solutions have been measured. From 200 nm down to contact separations four different types of force are operating. First, there are attractive van der Waals forces; these are non-retarded up to about 6.5 nm with a Hamaker constant of (2.2 ± 0.3)× 10–20 J. The van der Waals forces appear to be slightly stronger than expected from the Lifshitz theory. Second, there are repulsive double-layer forces. In 10–4 mol dm–3 1 : 1, 2 : 1 and 2 : 2 electrolytes these are well accounted for by theory but at concentrations above 10–3 mol dm–3 there are discrepancies with theory, especially for 2 : 1 electrolytes. Third, there are repulsive “hydration” forces; these decay exponentially with distance with the characteristic decay length of about 1.0 nm. Their magnitude varies from mica to mica and is largely independent of ionic strength. They are negligible at separations above 7.5 nm. Fourth, there are adhesion forces; these are complex and depend on a host of factors such as pH, type of electrolyte cations, mica orientation, etc., and are not simply given by extrapolating the long-range forces down to separations of the order of interatomic spacings.