P. Weilhammer

ππ Phase‐Shift Analysis from 600 to 1900 MeV

Wa have performed an energy‐dependent and an energy‐independent analysis of elastic ππ scattering, using data for the reaction π−p ⇒ π−π+n at 17.2 GeV/c. The ππ energy covers the range from 600 MeV to 1900 MeV. Apart from the well‐known resonances ρ, f and g, we find a strong S‐wave in the ρ and also in the f‐meson region. A P‐wave resonance occurs in both analyses at ∼ 1600 MeV with a total width of 180 MeV and an elasticity of 0.25, which can be identified with the ρ′ meson in its ππ decay mode. The zeros in the complex cos Θ plane of the scattering amplitude are studied as a function of the energy. The position of the real parts of the zeros are in qualitative agreement with the prediction of the Veneziano model. Furthermore, we show that an analogous relation holds also for the imaginary parts of the zero trajectories.

High statistics study of the reaction π−p→π−π+n: Apparatus, method of analysis, and general features of results at 17 GeV/c

Abstract A detailed account is given of a high statistics experiment measuring the reaction π−p→π−π+n at 17.2 GeV/c. The spark chamber and counter triggering system are desribed. The methods of data analysis are described, in particular the determination of angular distributions from apparatus with limited acceptance. Experimental data and their interpretation are presented.

VIKING, a CMOS low noise monolithic 128 channel frontend for Si-strip detector readout

A low noise Si-strip detector readout chip has been designed and built in 1.5 μm CMOS technology. The chip is optimized w.r.t. noise. Measurements with this chip connected to several silicon strip detectors are presented. A noise performance of ENC = 135 e− + 12 e−/pF and signal to noise ratios between 40–80, depending on the detector, for minimum ionizing particles traversing 280300 μm silicon has been achieved.

CMOS low noise amplifier for microstrip readout Design and results

Abstract A low noise preamplifier and shaper chip has been designed and built in 1.5 μm CMOS technology to be used for readout of Si microstrip detectors. The chip is optimized with respect to noise. Measurements on the performance of the prototype chip are presented. A noise performance of ENC = 160 e − + 12 e − /pF has been achieved.

Charge-carrier properties in synthetic single-crystal diamond measured with the transient-current technique

For optimal operation of chemical-vapor deposition (CVD) diamonds as charged particle detectors it is important to have a detailed understanding of the charge-carrier transport mechanism. This includes the determination of electron and hole drift velocities as a function of electric field, charge carrier lifetimes, as well as effective concentration of space charge in the detector bulk. We use the transient-current technique, which allows a direct determination of these parameters in a single measurement, to investigate the charge-carrier properties in a sample of single-crystal CVD diamond. The method is based on the injection of charge using an α source close to the surface and measuring the induced current in the detector electrodes as a function of time.For optimal operation of chemical-vapor deposition (CVD) diamonds as charged particle detectors it is important to have a detailed understanding of the charge-carrier transport mechanism. This includes the determination of electron and hole drift velocities as a function of electric field, charge carrier lifetimes, as well as effective concentration of space charge in the detector bulk. We use the transient-current technique, which allows a direct determination of these parameters in a single measurement, to investigate the charge-carrier properties in a sample of single-crystal CVD diamond. The method is based on the injection of charge using an α source close to the surface and measuring the induced current in the detector electrodes as a function of time.

The Deconvolution method of fast pulse shaping at hadron colliders

Abstract We describe a new technique for front-end signal processing of signals from LHC or SSC detectors which precisely defines the origin of an event in time while maintaining amplitude measurement with an excellent signal to noise ratio. The method is designed for use with silicon detectors whose leakage currents may be substantially increased during the lifetime of an experiment by radiation damage, although it is likely to be applicable to other types of detector. It makes use of a shaping amplifier with a time constant of several beam crossing intervals and is particularlt well matched to CMOS front ends where low power consumption and low noise is best achieved by utilising pulse shapes with time constants ∼50 ns. It is based on discrete time filtering of data extracted from an analogue pipeline after a first level trigger. A finite impulse response type filter deconvolutes the sampled voltages of a shaped pulse to retrieve the original impulse signal with high precision. We describe the mathematical basis of the technique and its implications for timing and signal to noise. Measurements have been made on a CMOS amplifier intended as a prototype for readout of silicon microstrip detectors at LHC which demonstrates the power of this approach. A CMOS circuit emulating the filter is being built. It has been implemented with extremely low power consumption (

Measurement and analysis of the π+π+ system produced at small momentum transfer in the reaction π+p→π+π+n at 12.5 GeV

Abstract From a wire chamber experiment 45 452 events were obtained from the reaction π + p→ π + π + n. The I =2 phase shifts were determined in the π + π + mass region 0.3–1.5 GeV. An amplitude analysis was performed. The results are compared with some theoretical predictions.

SCTA-a rad-hard BiCMOS analogue readout ASIC for the ATLAS semiconductor tracker

Two prototype chips for the analogue readout of silicon strip detectors in the ATLAS Semiconductor Tracker (SCT) have been designed and manufactured, in 32 channels and 128 channel versions, using the radiation hard BiCMOS DMILL process. The SCTA chip comprises three basic blocks: front-end amplifier, analogue pipeline and output multiplexer. The front-end circuit is a fast transresistance amplifier followed by an integrator, providing fast shaping with a peaking time of 25 ns, and an output buffer. The front end output values are sampled at 40 MHz rate and stored in a 112-cell deep analogue pipeline. The delay between the write pointer and trigger pointer is tunable between 2 /spl mu/S and 2.5 /spl mu/s. The chip has been tested successfully and subsequently irradiated up to 10 MraB. Full functionality of all blocks of the chip has been achieved at a clock frequency of 40 MHz both before and after irradiation. Noise figures of ENC=720 e/sup ./+33 e/sup .//pF before irradiation and 840 e/sup ./+33 e/sup .//pF after irradiation have been obtained.

A study of the ππ phase-shift solutions in the mass region 1.0 to 1.8 GeV from π−p → π−π+n at 17.2 GeV

Abstract The ππ phase shifts from 1 to 1.8 GeV are presented. The method used was an essentially energy-independent parametrization of the amplitudes fitted simultaneously to the M ππ and t -dependence of the moments of the dipion angular distribution from the reaction π − p → π − π + n at 17.2 GeV. The various ambiguous solutions are discussed.

The DELPHI Microvertex detector

The DELPHI Microvertex detector, which has been in operation since the start of the 1990 LEP run, consists of three layers of silicon microstrip detectors at average radii of 6.3, 9.0 and 11.0 cm. The 73728 readout strips, oriented along the beam, have a total active area of 0.42 m2. The strip pitch is 25 μm and every other strip is read out by low power charge amplifiers, giving a signal to noise ratio of 15:1 for minimum ionizing particles. On-line zero suppression results in an average data size of 4 kbyte for Z0 events. After a mechanical survey and an alignment with tracks, the impact parameter uncertainty as determined from hadronic Z0 decays is well described by (69pt)2 + 242 μm, with pt in GeV/c. For the 45 GeV/c tracks from Z0 → μ− decays we find an uncertainty of 21 μm for the impact parameter, which corresponds to a precision of 8 μm per point. The stability during the run is monitored using light spots and capacitive probes. An analysis of tracks through sector overlaps provides an additional check of the stability. The same analysis also results in a value of 6 μm for the intrinsic precision of the detector.