P. Rehak

SEMICONDUCTOR DRIFT CHAMBER - AN APPLICATION OF A NOVEL CHARGE TRANSPORT SCHEME

The purpose of this paper is to describe a novel charge tranport scheme in semiconductors in which the field responsible for the charge transport is independent of the depletion field. The application of the novel charge transport scheme leads to the following new semiconductor detectors: (1) Semiconductor Draft Chamber; (2) Ultra low capacitance - large semiconductor x-ray spectrometers and photodiodes; and (3) Fully depleted thick CCD. Special attention is paid to the concept of the Semiconductor Draft Chamber as a position sensing detector for high energy charged particles. Position resolution limiting factors are considered, and the values of the resolutions are given.

Low-mass e+e− pair production in 158 A GeV Pb-Au collisions at the CERN SPS, its dependence on multiplicity and transverse momentum

We report a measurement of low-mass electron pairs observed in 158 GeV/nucleon Pb-Au collisions. The pair yield integrated over the range of invariant masses 0.2<m<2.0 GeV is enhanced by a factor of 3.5 +/- 0.4 (stat) +/- 0.9 (syst) over the expectation from neutral meson decays. As observed previously in S-Au collisions, the enhancement is most pronounced in the invariant-mass region 300-700 MeV. For Pb-Au we find evidence for a strong increase of the enhancement with centrality. In addition, we show that the enhancement covers a wide range in transverse momentum, but is largest at the lowest observed pt.We report a measurement of low-mass electron pairs observed in 158 GeV/nucleon Pb-Au collisions. The pair yield integrated over the range of invariant masses 0.2 < m < 2.0 GeV is enhanced by a factor of 3.5 +/- 0.4 (stat) +/- 0.9 (syst) over the expectation from neutral meson decays. As observed previously in S-Au collisions, the enhancement is most pronounced in the invariant-mass region 300-700 MeV. For Pb-Au we find evidence for a strong increase of the enhancement with centrality. In addition, we show that the enhancement covers a wide range in transverse momentum, but is largest at the lowest observed pt.Abstract We report a measurement of low-mass electron pairs observed in 158 GeV/nucleon Pb-Au collisions. The pair yield integrated over the range of invariant masses 0.2 ≤ m ≤ 2.0 GeV/c 2 is enhanced by a factor of 3.5 ± 0.4 (stat) ± 0.9 (syst) over the expectation from neutral meson decays. As observed previously in S-Au collisions, the enhancement is most pronounced in the invariant-mass region 300-700 MeV/c 2 . For Pb-Au we find evidence for a strong increase of the enhancement with centrality. In addition, we show that the enhancement covers a wide range in transverse momentum, but is largest at the lowest observed p ⊥ .

Semiconductor drift chambers for position and energy measurements

Abstract Semiconductor drift chambers have been recently suggested and feasibility tests performed. This paper presents the first operative silicon drift detectors for position and energy measurements. Design criteria and experimental results in the laboratory and on an accelerator beam are reported.

A novel charge sensitive preamplifier without the feedback resistor

A novel charge sensitive preamplifier which has no resistor in parallel with the feedback capacitor is presented. No external device or circuit is required to discharge the feedback capacitor. The detector leakage and signal current flows away through the gate of the first JFET which works with its gate to source junction slightly forward biased. The DC stabilization of the preamplifier is accomplished by an additional feedback loop, which permits to equalize the current flowing through the forward baised gate to source junction and the current coming from the detector. An equivalent noise charge of less than 20 electrons r.m.s. has been measured at room temperature by using an input JFET with a transconductance to gate capacitance ratio of 4 mS/5.4 pF.

High statistics measurement of K(e4) decay properties

We report experimental details and results of a new measurement of the decay K+ -> pi+pi-e+nue (Ke4}. A sample of more than 400,000 Ke4 events with low background has been collected by Experiment 865 at the Brookhaven Alternate Gradient Synchrotron. From these data, the branching ratio (4.11+-0.01+-0.11)*10**(-5) and the pi-pi invariant mass dependence of the form factors F, G, and H of the weak hadronic current as well as the phase shift difference delta00-delta11 for pi-pi-scattering were extracted. Using constraints based on analyticity and chiral symmetry, a new value with considerably improved accuracy for the s-wave pi-pi-scattering length a00 has been obtained also: a00=0.216+-0.013 (stat.)+-0.002(syst.)+-0.002(theor.).

SILICON DRIFT CHAMBERS - FIRST RESULTS AND OPTIMUM PROCESSING OF SIGNALS

Abstract A Semiconductor Drift Chamber was produced and tested. The paper describes: 1. 1)|principle of the chamber operation; 2. 2)|the performance of the test chamber; 3. 3)|the signal processing to obtain the best position resolution.

Dynamics of electrons in drift detectors

Abstract The dynamics of electrons generated in silicon drift chambers by ionizing events is studied. Diffusion effects, mutual electrostatic repulsion between the electrons as well as the focusing properties of the depletion field during the electron transport to the anode are considered. The theoretical computations show that the effect of the mutual electrostatic repulsion in the spreading of the charge packet are not negligible even at charge densities produced by a minimum ionizing particle traversing 300 μm of the detector. Experimental results support theoretical expectations.

Progress in semiconductor drift detectors

Progress in testing semiconductor drift detectors is reported. Generally better position and energy resolutions were obtained than resolutions published previously. The improvement is mostly due to new electronics better matched to different detectors. It is shown that semiconductor drift detectors are becoming versatile and reliable detectors for position and energy measurements.

e + e − -pair production in Pb-Au collisions at 158 GeV per nucleon

Abstract.We present the combined results on electron-pair production in 158 GeV/n Pb-Au (

The pn-CCD on-chip electronics.

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