L3 Data Research Articles

The L3 vertex detector: design and performance

The L3 vertex detector is comprised of the time expansion chamber (TEC), the Z-chamber and a layer of plastic scintillating fibers. The TEC has shown a high spatial resolution and an excellent multi-track reconstruction capability at LEP luminosity. The Z-chamber provides information about the z-coordinates of the tracks and the fibers are used for calibrating the drift velocity with a high precision. A description of the L3 vertex detector, its readout and data acquisition and its performance during the 1990 LEP running period is presented in this paper.

Performances of the central L3 Data Acquisition system

In this article we present the central L3 Data Acquisition system which is entirely built in FASTBUS. Performance and reliability during the first year of data taking at LEP is reported. Special emphasis is placed on the system functionality and the chosen data structure.

A dual-port FASTBUS memory to test the L3 data acquisition system

A dual-port 0.25-Mbytes (64 K*32 bits) FASTBUS memory module is described which implements a large set of functions on the Crate Port, while the Cable Port is mainly used for data transfers. Both linear and circular FIFO-like modes are software-selectable. Two pointers are available for write and read operations, respectively. The memory, successfully used to test the L3 event builders, exhibits features of an interesting, general purpose, FASTBUS module for event buffering in large data acquisition systems. >

L-shell ionisation of medium and heavy elements by 1.2-3.0 MeV incident alpha particles

Thin targets of Yb, W, Au, Pb and Bi were bombarded by 1.2-3.0 MeV alpha particles. From the resulting L X-rays experimental Li-subshell ionisation cross section were deduced. The measured cross sections are compared with the predictions of the ECPSSR theory by expressing the data in terms of ratios of experimental to theoretical values as a function of the corrected reduced velocity xi (Li)R. Disagreements of up to 50% were revealed for the L1 subshell at xi (L1)R<or=0.3. The ECPSSR theory underestimate the L2 ionisation cross sections for all elements studied by as much as a factor of 3.3 but explains the L3 data to within 30%. In general, for heavy elements, the ECPSSR is unsuccessful in explaining the velocity dependence of the cross sections. Several factors were highlighted which may explain some of the observed disagreements. The target atomic number dependence of the experimental Li subshell and total ionisation cross sections were also investigated and the results are presented.

L shell ionisation of medium and heavy elements by 1.2–3.0 Mev incident deuterons

L subshell ionisation cross sections, σ exp L i have been measured for a number of selected elements with atomic number 66 ⩽ Z ⩽ 83. The L shell X-rays, produced by bombarding carbon backed thin targets ∼ 50 μg/cm 2 thick with deuterons in the energy range 1.2–3 MeV, were detected using a Si(Li) detector. The cross sections were obtained from the measured X-ray yields, the experimentally determined target thicknesses and detector efficiency. The cross sections have been compared with the ECPSSR theory by expressing graphically the ratio σ exp Li σ ECPSSR Li as a function of the corrected reduced velocity parameter ξ R L i Discrepancies of up to 50% were observed for σ exp L i which appear to be Z dependent. In all cases the theory underpredicts σ exp L2 by 10–60%, with the larger deviations occurring at lower reduced velocity parameters. The σ exp L3 data are in reasonable agreement with the ECPSSR predictions. Possible reasons for these discrepancies are discussed.