A. Tonazzo

Ageing measurements on glass RPCs

Resistive plate chambers (RPC) are widely used as active elements in particle physics detectors. A deterioration of RPC performance with time has been observed in several experiments, after operation at high temperature or with water contamination in the gas mixture, both for detectors with bakelite electrodes and for the ones with float-glass electrodes. We have developed a kind of RPCs suitable for large scale industrial production. Float-glass is employed as electrode material, and the screen-printing technique is used to apply the resistive coating on the electrodes. A dedicated intensive measurement program on these detectors has been carried out, to assess their long-term behavior and aging properties under different operational conditions.

Expectation values of exclusion limits in future experiments

Abstract The methods used so far for quoting the exclusion limit that a future experiment will be able to set involve some degree of arbitrariness. A general validity procedure is proposed, which should settle the controversy.

Performance of glass RPC with industrial silk-screen-printed electrodes

In this paper we describe the performance of several Glass RPCs, where the water-based graphite coating is replaced by a synthetic coating applied using the screen printing technique. As expected, the performance of the detectors is good and reproducible due to the accurate control of the coating resistivity value. The resistance of the coating to the action of mechanical and chemical agents permits an easy electrode cleaning and mounting with respect to the RPC coated with the graphite varnish. This coating, together with the use of float glass as electrode material, allows an industrial production, where the detector characteristics can be tailored as a function of the experiment requirements.

Performance of an artificially aged module of the DELPHI HPC calorimeter

Abstract The readout proportional chambers of the HPC electromagnetic calorimeter in the DELPHI experiment are affected by large ageing. In order to study the calorimeter long-term behaviour, one HPC module was extracted from DELPHI in 1992 and was brought to a test area where it was artificially aged during a period of two years; an ageing level exceeding that expected for the HPC at the end of the LEP era was reached. During this period the performance of the module was periodically tested by means of dedicated beam tests whose results are discussed in this paper. These show that ageing has no significant effects on the response linearity and on the energy resolution for electromagnetic showers, once the analog response loss is compensated for by increasing the chamber gain through the anode voltage.

Baseline concept for a precise measurement of atmospheric neutrino oscillation

A high-density calorimeter, consisting of magnetized planes interleaved by Resistive Plates Chambers (RPCs, Ref. (1)) , as tracking and timing devices, is a good candidate for a new experiment on atmospheric neutrinos. With 34 kt of mass and in four years of data taking, this experiment will be sensitive to νμ→νx oscillation with Δm2>6×10−5 and large mixing, covering the region suggested by the SuperKamiokande results. Moreover, the experimental method will enable to measure the oscillation parameters from the modulation of the L/E spectrum (νμ disappearance). For >m2>3×10−3u200aeV2, this experiment can also establish whether the oscillation occurs into a tau or a sterile neutrino, by looking for an excess of muon-less events at high energies produced by upward-going tau neutrinos(ντ appearence).

A new high-density detector for atmospheric neutrinos. Towards neutrino stoichiometry

Abstract A high-density calorimeter, consisting of magnetised iron planes interleaved by RPCs, as tracking and timing devices, is a good candidate for a next generation experiment on atmospheric neutrinos. With 34 kt of mass and in four years of data taking, this experiment will be sensitive to v μ → v χ oscillation with Δm 2 > 6 × 10 −5 and mixing near to maximal and fuly cover the region of oscillation parameters suggested by Super-Kamiokande results. Moreover, the experimental method will enable to measure the oscillation parameters from the modulation of the L E spectrum ( v μ disappearance). For Δm 2 > 3 × 10 −3 eV 2 , this experiment can also establish whether the oscillation occurs into a tau or a sterile neutrino, by looking for an excess of muon-less events at high energies produced by upward-going tau neutrinos ( v τ appearance).

Calibration of the DELPHI HPC calorimeter during the LEP2 programme

Abstract The readout chambers of the DELPHI HPC calorimeter are affected by large ageing which results in a module-dependent loss of gain. The calorimeter response thus needs to be tuned on a module-by-module basis. During the LEP operation phase at energies close to the Z resonance (LEP1), the tuning was based on the high available statistics of Z→e+e− events. In the high energy operation phase (LEP2), no such clear monochromatic physics channel is available with high statistics. A monitoring of the analog response of the readout chambers of each module is provided by the periodic calibration with radioactive 83mKr; using this information to account for module-dependent effects ensures the stability of the energy resolution throughout the LEP2 programme.

Study of ageing side effects in the Delphi HPC calorimeter

The readout proportional chambers of the HPC electromagnetic calorimeter in the DELPHI experiment are affected by large ageing. In order to study the long-term behaviour fo the calorimeter, one HPC module was extracted from DELPHI in 1992 and was brought to a test area where it was artificially aged during a period of two years; an ageing level exceeding the one expected for the HPC at the end of the LEP era was reached. During this period the performance of the module was periodically tested by means of dedicated beam tests whose results are discussed in this paper. These show that ageing has no significant effects on the response linearity and on the energy resolution for electromagnetic showers, once the analog response loss is compensated for by increasing the chamber gain through the anode voltage.