Study of timing properties of single gap high-resistive bakelite RPC

The time resolution for several single gap (2 mm) prototype Resistive Plate Chambers (RPC) made of high resistive (bulk resistivity ~ 10^10 - 10^12 ohm cm), 2 mm thick matt finished bakelite paper laminates with silicone coating on the inner surfaces, has been measured. The time resolution for all the modules has been found to be ~ 2 ns at the plateau region.Comment: 5 figures, Presented in Frontier Detectors for Frontier Physics (11th Pisa meeting on advanced detectors), La Biodala, Isola d'Elba, Italy, May 24-30, 200

Performances of linseed oil-free bakelite RPC prototypes with cosmic ray muons

A comparative study has been performed on Resistive Plate Chambers (RPC) made of two different grades of bakelite paper laminates, produced and commercially available in India. The chambers, operated in the streamer mode using argon, tetrafluroethane and isobutane in 34:59:7 mixing ratio, are tested for the efficiency and the stability with cosmic rays. A particular grade of bakelite (P-120, NEMA LI-1989 Grade XXX), used for high voltage insulation in humid conditions, was found to give satisfactory performance with stable efficiency of > 96% continuously for more than 130 days. A thin coating of silicone fluid on the inner surfaces of the bakelite RPC is found to be necessary for operation of the detector.Comment: 6 figures, Presented in IX International Workshop on Resistive Plate Chamber and related Detectors-2007, TIFR, Mumbai, India, February 13-16, 200

Performances of silicone coated high resistive bakelite RPC

Performances of several single gap (gas gap 2 mm) prototype Resistive Plate Chambers (RPC) made of high resistive ({\rho} \sim 1010 - 1012 {\Omega} cm) bakelite, commercially available in India have been studied in recent times. To make the inner electrode surfaces smooth, a thin coating of silicone has been applied. An efficiency > 90% and time resolution \sim 2 ns (FWHM) have been obtained for both the streamer and the avalanche mode. The induced charge distributions of those silicone coated RPC are studied and the results are presented. A numerical study on the effect of surface roughness of the resistive electrodes on the electric field of the device has been carried out using Garfield-neBEM code. A few results for a simplified model representing surface roughness, measured using a surface profilometer for the bakelite surfaces, have also been presented

Effect of Finite Granularity of Detectors on Anisotropy Coefficients

The coefficients that describe the anisotropy in the azimuthal distribution of particles are lower when the particles are recorded in a detector with finite granularity and measures only hits. This arises due to loss of information because of multiple hits in any channel. The magnitude of this loss of signal depends both on the occupancy and on the value of the coefficient. These correction factors are obtained for analysis methods differing in detail, and are found to be different.Comment: 11 pages including 2 figure

A Honeycomb Proportional Counter for Photon Multiplicity Measurement in the ALICE Experiment

A honeycomb detector consisting of a matrix of 96 closely packed hexagonal cells, each working as a proportional counter with a wire readout, was fabricated and tested at the CERN PS. The cell depth and the radial dimensions of the cell were small, in the range of 5-10 mm. The appropriate cell design was arrived at using GARFIELD simulations. Two geometries are described illustrating the effect of field shaping. The charged particle detection efficiency and the preshower characteristics have been studied using pion and electron beams. Average charged particle detection efficiency was found to be 98%, which is almost uniform within the cell volume and also within the array. The preshower data show that the transverse size of the shower is in close agreement with the results of simulations for a range of energies and converter thicknesses.Comment: To be published in NIM

Sequential Decay Distortion of Goldhaber Model Widths for Spectator Fragments

Momentum widths of the primary fragments and observed final fragments have been investigated within the framework of an Antisymmetrized Molecular Dynamics transport model code (AMD-V) with a sequential decay afterburner (GEMINI). It is found that the secondary evaporation effects cause the values of a reduced momentum width, $\sigma_0$, derived from momentum widths of the final fragments to be significantly less than those appropriate to the primary fragment but close to those observed in many experiments. Therefore, a new interpretation for experiemental momentum widths of projectile-like fragments is presented.Comment: 4 pages, 3 figs. Accepted for publication in Phys. Rev. C as a Rapid Communicatio

Sequential Decay Distortion of Goldhaber Model Widths for Spectator Fragments

Momentum widths of the primary fragments and observed final fragments have been investigated within the framework of an Antisymmetrized Molecular Dynamics transport model code (AMD-V) with a sequential decay afterburner (GEMINI). It is found that the secondary evaporation effects cause the values of a reduced momentum width, $\sigma_0$, derived from momentum widths of the final fragments to be significantly less than those appropriate to the primary fragment but close to those observed in many experiments. Therefore, a new interpretation for experiemental momentum widths of projectile-like fragments is presented.Comment: 4 pages, 3 figs. Accepted for publication in Phys. Rev. C as a Rapid Communicatio

The STAR Photon Multiplicity Detector

Details concerning the design, fabrication and performance of STAR Photon Multiplicity Detector (PMD) are presented. The PMD will cover the forward region, within the pseudorapidity range 2.3--3.5, behind the forward time projection chamber. It will measure the spatial distribution of photons in order to study collective flow, fluctuation and chiral symmetry restoration.Comment: 15 pages, including 11 figures; to appear in a special NIM volume dedicated to the accelerator and detectors at RHI

Central Pb+Pb Collisions at 158 A GeV/c Studied by Pion-Pion Interferometry

Two-particle correlations have been measured for identified negative pions from central 158 AGeV Pb+Pb collisions and fitted radii of about 7 fm in all dimensions have been obtained. A multi-dimensional study of the radii as a function of kT is presented, including a full correction for the resolution effects of the apparatus. The cross term Rout-long of the standard fit in the Longitudinally CoMoving System (LCMS) and the vl parameter of the generalised Yano-Koonin fit are compatible with 0, suggesting that the source undergoes a boost invariant expansion. The shapes of the correlation functions in Qinv and Qspace have been analyzed in detail. They are not Gaussian but better represented by exponentials. As a consequence, fitting Gaussians to these correlation functions may produce different radii depending on the acceptance of the experimental setup used for the measurement.Comment: 13 pages including 10 figure