Glass resistive plate chambers in the OPERA experiment

Abstract OPERA is an underground neutrino oscillation experiment to search for ν τ appearance from a pure ν μ beam produced at CERN. To flag the events due to the neutrino interactions with the rock surrounding the OPERA detector, a large VETO system, based on the use of Glass Resistive Plate Chambers (GRPC) has been realized. We describe the detectors, the tests performed before the installation in the underground laboratories and the monitor system for the water pollution in the GRPC gas mixture

Muon Energy Estimate Through Multiple Scattering with the Macro Detector

Muon energy measurement represents an important issue for any experiment addressing neutrino induced upgoing muon studies. Since the neutrino oscillation probability depends on the neutrino energy, a measurement of the muon energy adds an important piece of information concerning the neutrino system. We show in this paper how the MACRO limited streamer tube system can be operated in drift mode by using the TDC's included in the QTPs, an electronics designed for magnetic monopole search. An improvement of the space resolution is obtained, through an analysis of the multiple scattering of muon tracks as they pass through our detector. This information can be used further to obtain an estimate of the energy of muons crossing the detector. Here we present the results of two dedicated tests, performed at CERN PS-T9 and SPS-X7 beam lines, to provide a full check of the electronics and to exploit the feasibility of such a multiple scattering analysis. We show that by using a neural network approach, we are able to reconstruct the muon energy for $E_\mu<$40 GeV. The test beam data provide an absolute energy calibration, which allows us to apply this method to MACRO data.Comment: 25 pages, 11 figures, Submitted to Nucl. Instr. & Meth.

performance and aging of opera bakelite rpcs

OPERA is an experiment dedicated to the observation of νμ into ντ oscillations through τ appearance on the CNGS beam. The experiment is composed by two identical super-modules, each with a target section (made of emulsion/lead bricks alternated to a scintillator Target Tracker) and a muon spectromter (instrumented with bakelite electrodes RPCs and drift tubes). The OPERA RPC system is composed of about 1000 RPCs for an instrumented area of 3000 m2. The RPCs are operated in streamer mode and flushed with the gas mixture Ar/C2H2F4/i−C4H10/SF6 = 75.4/20.0/4.0/0.6 at five refills/day in open flow. The present performance of the RPC system after six years of operation are presented. The aging status of the detector is also described

Muon Energy Estimate through Multiple Scattering with the MACRO detector

Abstract Muon energy measurement represents an important issue for any experiment addressing neutrino-induced up-going muon studies. Since the neutrino oscillation probability depends on the neutrino energy, a measurement of the muon energy adds an important piece of information concerning the neutrino system. We show in this paper how the MACRO limited streamer tube system can be operated in drift mode by using the TDCs included in the QTPs, an electronics designed for magnetic monopole search. An improvement of the space resolution is obtained, through an analysis of the multiple scattering of muon tracks as they pass through our detector. This information can be used further to obtain an estimate of the energy of muons crossing the detector. Here we present the results of two dedicated tests, performed at CERN PS-T9 and SPS-X7 beam lines, to provide a full check of the electronics and to exploit the feasibility of such a multiple scattering analysis. We show that by using a neural network approach, we are able to reconstruct the muon energy for E m o40 GeV: The test beam data provide an absolute energy calibration, which allows us to apply this method to MACRO data.

Analysis of the performance of the MONOLITH prototype

In the framework of the study for a large magnetic detector suitable for the physics at a neutrino factory, the data collected with the MONOLITH prototype at the T7-PS facility at CERN has been analyzed. The hadron shower angular resolution for pions followed a 10.4/ root E(GeV) + 10.1/E law for orthogonally incident particles. For a baseline of 732 km, this performance would allow the rejection of wrong sign muon background at the level of 10**-**6, and a capability to measure sintheta//1//3 down to 10**-**3. A preliminary analysis of about 10**6 downward going muons collected at LNGS is also presented. The readout system upgrade allowed the monitoring of each glass RPC with a granularity of 1 cm**2

Underground neutron flux measurement

To be submitted to Nuclear Instr. MethSIGLEITItal

Long-term operation test of RPCs for the OPERA experiment

OPERA is one of the two detectors foreseen in the CERN Neutrino to Gran Sasso project, devoted to the detection of v(mu) into v(tau) oscillations in the parameter region suggested by SuperKamiokande data on atmospheric neutrinos. Bakelite RPCs will be used to instrument the iron yoke of the muon spectrometers. We present the results of long-term (greater than 6 months) streamer operations of real size OPERA RPCs at cosmic rays fluxes. Given the very low rate observed in the underground Gran Sasso Laboratories, under 3 kin w.e., even this short time period is equivalent to more than 10 OPERA years. Results of tests with different gas mixtures are reported, in view of decreasing the streamer charge of operation for the RPCs employed in the experiment

Long-term operation test of RPCs for the OPERA experiment

OPERA is one of the two detectors foreseen in the CERN Neutrino to Gran Sasso project, devoted to the detection of nu//mu into nu //tau oscillations in the parameter region suggested by SuperKamiokande data on atmospheric neutrinos. Bakelite RPCs will be used to instrument the iron yoke of the muon spectrometers. We present the results of long-term (greater than 6 months) streamer operations of real size OPERA RPCs at cosmic rays fluxes. Given the very low rate observed in the underground Gran Sasso Laboratories, under 3 km w.e., even this short time period is equivalent to more than 10 OPERA years. Results of tests with different gas mixtures are reported, in view of decreasing the streamer charge of operation for the RPCs employed in the experiment

Long term performances of OPERA bakelite RPC system

OPERA is an experiment dedicated to the observation of \u3bd \u3bc into \u3bd \u3c4 oscillations through \u3c4 appearance exploiting the CNGS beam. The experiment is composed by two identical super-modules, each with a target section (made of emulsion/lead bricks alternated with a scintillator Target Tracker) and a muon spectrometer (instrumented with bakelite RPCs and drift tubes). The RPCs are operated in streamer mode with the gas mixture Ar/C 2H 2F 4/isoC 4H 10/ SF 6=75.4/20/4/0.6. The present performances of the RPC detectors are presented and the aging status of the system after four years of operation is described. The sample of events induced by the CNGS neutrino beam as well as a large sample of cosmic rays have also been used to study general properties of streamer-operated RPCs