H. Fessler

Multiplicity and transverse energy flux in 16O+Pb at 200 GeV per nucleon

Abstract First results from ultrarelativistic 16 O+Pb collisions at 200 GeV/nucleon are presented. The transverse energy E T in average central collisions is ≈ 75 GeV for the interval 2.2⩽ y ⩽3.8. A 16-fold convolution of the inelastic p+Au transverse energy spectrum, also measured at 200 GeV, reproduces the mean E T of 16 O+Pb. The amount of nuclear stopping power appears to be high.

Probing the space-time geometry of ultra-relativistic heavy-ion collisions

Abstract We report results from a pion interferometry analysis of 200 GeV/nucleon 16 O+Au collisions. Both a gaussian source model and a model based on the inside-outside cascade are used to fit the experimental correlation function, giving transverse and longitudinal shape parameters, a freeze-out time parameter, and a chaoticity parameter for the pion emitting source. We find a transverse source size consistent with the projectile radius except at the CM rapidity, where significantly larger transverse and longitudinal sizes and a longer freeze-out time are measured suggesting a thermalized source. Calculation of correlation lengths, and comparisons with a simple freeze-out model and other pion interferometry experiments are presented.

The forward time projection chamber in STAR

Two cylindrical forward TPC detectors are described which were constructed to extend the phase space coverage of the STAR experiment to the region 2.5 < |�| < 4.0. For optimal use of the available space and in order to cope with the high track density of central Au+Au collisions at RHIC, a novel design was developed using radial drift in a low diffusion gas. From prototype measurements a 2-track resolution of 1 - 2 mm is expected.

A scintillator-lead photon calorimeter using optical fiber readout systems

The construction and performance of a tower structured scintillator-lead photon calorimeter using a novel fiber optics readout system is described. An energy resolution of σE = 0.10√E was obtained with incident electrons in the range of 0.5–5.0 GeV/c. The uniformity of response across the front face of the tower was measured. Results obtained with a silicon photodiode are compared to those obtained with a photomultiplier.

Charged particle multiplicities and inelastic cross sections in high energy nuclear collisions

Abstract Inelastic cross sections at 60 and 200 GeV/nucleon are determined in a streamer chamber for 16 O on several nuclear targets. Charged particle multiplicity distributions for inelastic and central collisions are studied and compared with theoretical predictions. The inelastic cross section exhibit a geometrical dependence on nuclear radii. The multiplicity data are governed by the collision geometry. They are consistent with a picture of superposition of independent nucleon-nucleus interactions.

Pion Interferometry With Ultrarelativistic Heavy Ion Collisions From the Na35 Experiment

Results from a pion interferometric analysis of the system 200 GeV/nucleon16O+Au, central collisions, are reported. Both a Gaussian source model and a model based on the inside-outside cascade are used to fit to the experimental correlation function, giving transverse and longitudinal shape parameters, a freezeout time parameter, and a chaoticity parameter for the pion emitting source. We find a transverse

A tower structured scintillator-lead photon calorimeter using a novel fiber optics readout system

Described is the construction and the performance of a tower-structured scintillator-lead photon calorimeter using a novel fiber optics readout system. The calorimeter is divided into 9 individual towers. Each tower has a cross section of 5 × 5 cm2 and consists of 60 layers of 2 mm lead plus 5 mm thick scintillator. The four sides of each tower are covered by thin acrylic sheets (1.5 mm thick) doped with a wavelength shifting material. The light produced in each scintillator plate is first converted in these sheets, then converted a second time in a set of polystyrene optical fibers (diameter 2 mm) which run longitudinally through the calorimeter along the corners of each tower. A small diameter photomultiplier was attached to the fibers at the back end of the calorimeter. The obtained energy resolution with incident electrons in the range of 0.25−5.0 GeVc is σE = 0.10√E. The uniformity of response across the front face of each tower was measured.

A study of argon, neon and helium based gas mixtures for improving the spatial resolution in time projection chambers

Abstract For large TPCs in future experiments at the Large Hadron Collider (LHC, CERN) and at the Relativistic Heavy Ion Collider (RHIC, Brookhaven) it is of great interest to optimize the gas characteristics and the readout geometry for the planned application. For this a large number of argon, neon and helium based gases with CH4, C2H6 and CO2 admixtures as quenchers were studied. The drift velocity and the transverse and longitudinal electron diffusion were measured for drift field strengths between 70 and 200 V/cm. Improvements of the readout chambers were tested. Effects on the spatial and the two-track resolution are discussed.

Study of the energy flow in16O-nucleus collisions at 60 and 200 GeV/nucleon

We report a systematic study of mid-rapidityET production and forward energy flow in the interaction of16O projectiles on Al, Cu, Ag and Au at 60 and 200 GeV/nucleon. First results onET production with32S projectiles are presented.

Design and performance of TPC readout electronics for the NA49 experiment

Abstract Highly integrated readout electronics were developed and produced for the 182000 channels of the four TPCs of the NA49 heavy-ion fixed target experiment at the CERN SPS. The large number of channels, the high packing density and required cost minimization led to the choice of a custom electronics system. The requirements, the design and the performance of the electronics components are described.