Y. Miyamoto

PHENIX central arm particle ID detectors

Abstract The Ring-Imaging Cherenkov (RICH) and the Time-of-Flight (ToF) systems provide identification of charged particles for the PHENIX central arm. The RICH is located between the inner and outer tracking units and is one of the primary devices for identifying electrons among the very large number of charged pions. The ToF is used to identify hadrons and is located between the most outer pad chamber (PC3) and the electromagnetic calorimeter. A Time Zero (T0) counter that enhances charged particle measurements in p–p collisions is described. Details of the construction and performance of both the RICH, ToF and T0 are given along with typical results from the first PHENIX data taking run.

Systematics of inclusive photon production in 158-A-GeV Pb induced reactions on Ni, Nb, and Pb targets

Abstract The multiplicity of inclusive photons has been measured on an event-by-event basis for 158· A GeV Pb induced reactions on Ni, Nb, and Pb targets. The systematics of the pseudorapidity densities at midrapidity ( ρ max ) and the width of the pseudorapidity distributions have been studied for varying centralities for these collisions. A power law fit to the photon yield as a function of the number of participating nucleons gives a value of 1.12±0.03 for the exponent. The mean transverse momentum, 〈 p T 〉, of photons determined from the ratio of the measured electromagnetic transverse energy and photon multiplicity, remains almost constant with increasing ρ max . Results are compared with model predictions.

Elliptic emission of K+ and π+ in 158 A·GeV Pb + Pb collisions

An event-by-event analysis of the azimuthal angular correlation with respect to the reaction plane has been carried out for K+ and pi(+) emission near mid-rapidity in 158 A . GeV Pb + Pb collisions. In semi-central collisions, K+ mesons are found to be preferentially emitted out of the reaction plane, while pi(+) mesons are emitted in the reaction plane. The results suggest that the kaon emission is influenced by in-medium potential effects in addition to collective flow effects

A large-acceptance spectrometer for tracking in a high-multiplicity environment, based on space point measurements and high-resolution time-of-flight

A large acceptance tracking system, specially developed for tracking at very high particle densities encountered in ultra-relativistic heavy-ion collisions is described. The system is a combination of multi-step avalanche chambers equipped with electronic pad readout with high position resolution in two dimensions and streamer-tube detectors with pad readout, with coarser position resolution, that is sufficient for safe pattern recognition. A high-resolution time-of-flight system (time resolution better than 90 ps) provides particle identification up to 8 GeV/c for pions and protons and pion/kaon separation up to 4 GeV/c. All detectors in the tracking system are read out with new, high-performance integrated circuits. The system can operate at high event rates due to efficient zero suppression. The performance of the system for tracking under real running conditions with Pb-beam at 158 A GeV in the WA98 experiment at CERN is presented

Design of a 2 × 2 scintillating tile package for the SDC barrel electromagnetic tile/fiber calorimeter

Abstract We describe R&D results on optical properties of a scintillating tile/fiber system for the SDC barrel electromagnetic calorimeter. The tile/fiber system uses a wavelength shifting fiber to read out the signal of a scintillating plate (tile) and a clear fiber to transmit the signal to a phototube. In the SDC calorimeter design, four of tile/fiber systems are grouped as a 2 × 2 tile package so that the gap width between and the location of the tiles in the absorber slot can be controlled. Optical properties of the tile package such as the light yield, its uniformity, and cross talk were measured in a test bench with a β-ray source and in a 2−GeV c π + test beam. The performance as an electromagnetic calorimeter was evaluated by a GEANT simulation using the measured response map. We discuss a method of correction for the calorimeter non-uniformity.

A gas Cherenkov beam counter with a timing resolution of 30 ps for relativistic heavy ion experiments

Abstract We constructed gas a Cherenkov beam counter for a lead beam to obtain start signals of time of fight measurements for relativistic heavy ion experiments in WA98 at CERN-SPS. The intrinsic timing resolution of the gas Cherenkov counter was found to be ≤ 30 ps at a beam intensity up to 3 × 10 5 ions/s and the charge resolution ( ΔZ Z ) was 2.0% for lead ions of 160 GeV/ c per nucleon. This counter has been successfully operated for more than 1 1 2 month of heavy ion run in 1995.

Beam test of radiation hardness of a scintillating tile/fiber calorimeter

Abstract Radiation hardness of a scintillating tile/fiber calorimeter is studied by irradiating electromagnetic test modules with 2.5 GeV electrons at the KEK linac. The induced damage is evaluated in a 2 GeV electron test beam by measuring the reduction in pulse height after irradiation. The pulse height peak for 2 GeV electrons is found to decrease by 19.3 ± 1.3% for a dose of 0.61 Mrad and 14.9 ± 2.7% for 0.33 Mrad. In addition to these modules, several tile/fiber assemblies were irradiated up to 4.8 Mrad and the damage as a function of dose was measured with a radioactive source. Effects of radiation damage on the linearity and energy resolution at higher energies are evaluated using a GEANT simulation and the measured damage.

Optics of large scintillating tiles with wavelength shifting fiber readout — application to a hadron calorimeter

Abstract Light yield and response uniformity of a scintillating tile/fiber system were measured for tiles with a side length up to ∼50 cm. With increasing the tile size, the light yield at the tile center decreases and the nonuniformity measured near the tile edges increases gradually. These tile size dependences originate in the light attenuation in the scintillator, and hence are specific to the scintillator type. Radiation hardness of large tile/fiber systems was compared with that of small tile/fiber systems. The SDC barrel hadron calorimeter was used as a model to evaluate the performance of a calorimeter composed of tile/fiber systems with such a lateral nonuniformity and with light yield variation in depth. In the evaluation the hadronic shower profile was given by a GEANT simulation and the Hanging File testbeam data.

\Delta ++ abundance in 158 A GeV ^{208} + ^{208} Pb interactions at the CERN SPS

The Delta(++)-resonance production in central 158 A GeV Pb-208 + Pb-208 collisions at the CERN SPS has been studied. The Delta(++) production was estimated from the invariant mass spectrum of p pi(+)-pairs by subtracting a mixed event background. The measured Delta(++) abundance is compared with the results from other experiments at lower energies, and with a model calculation assuming thermal and chemical equilibrium