Search

OPERA is a dedicated experiment for the observation of ν μ into ν τ oscillations through τ appearance using a 730 km long baseline ν μ beam from CERN to the Gran Sasso underground laboratory. The detector is equipped with two spectrometers for muon identification and charm background rejection. Bakelite RPCs are used as inner trackers inside the iron magnet of the spectrometers. The experiment has already performed two short runs in 2006 and 2007. Results about the RPC performances are presented.

OPERA is a neutrino oscillation experiment to search the ν τ appearance in the future CNGS beam from CERN to Gran Sasso. A large VETO system, consisting of two 9.6 × 9.2 m2 planes made of glass RPCs, is foreseen to flag the events due to the neutrino interactions with the rock surrounding the OPERA detector. We describe the VETO system, its monitoring system, the glass RPC developed.

The OPERA experiment [M. Guler et al., CERN/SPSC 2000-028, SPSC/P318, LNGS P25/2000, July 10, 2000; M. Guler et al., CERN/SPSC 2001-025, SPSC/M668, LNGS-EXP 30/2001 Add. 1/01, August 21, 2001] will study νμ→ ντoscillations through τ appearance on the 732 Km long CERN to Gran Sasso baseline. The magnet yokes of the two muon spectrometers are instrumented with 44 layers of high resistivity bakelite Resistive Plate Chambers (RPCs) operated in streamer mode. Each layer covers about 70 m2. Four RPC planes were instrumented and the first tests were performed confirming a good behaviour of the installed RPCs in terms of intrinsic noise and operating currents. The measured noise maps agree with those obtained in the extensive quality tests performed at surface. Counting rates are below 20 Hz/m2. Single an multiple cosmic muon tracks were also reconstructed. The estimated efficiency is close to the geometrical limit and the very first measurements of the absolute and differential muon flux are in agreement with expectations. © 2006 Elsevier B.V. All rights reserved.

OPERA is one of the two detectors foreseen in the CERN Neutrino to Gran Sasso project, devoted to the detection of νμinto ντoscillations 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. © 2004 Elsevier B.V. All rights reserved.

The OPERA experiment foresees the use of about 3000m2of RPCs, that will be tested before the installation in a dedicated cosmic ray test facility. The test facility is composed of 2 triggering walls selecting horizontal cosmic rays muons. Each wall houses 64 glass RPCs equipped with 128 horizontal Flat Cable Strips. The z-coordinate is measured with a standard digital chain, while the x-coordinate is obtained by measuring the propagation time of the signals along the strips. In this paper the performance of the trigger walls and the first results of the RFC debug are presented. © 2004 Published by Elsevier B.V.

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.

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/ 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 sin θ 13 down to 10−3. A preliminary analysis of about 106 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 .

MONOLITH (Massive Observatory for Neutrino Oscillation or LImits on THeir existence) is the project of an experiment to study atmospheric neutrino oscillations with a massive magnetized iron detector. The baseline option is a 34 kt iron detector based on the use of about 50 000 m2 of the glass Resistive Plate Chambers (glass RPCs) developed at the Laboratori Nazionali del Gran Sasso (LNGS). An 8 ton prototype equipped with 23 m2 of glass RPC has been realized and tested at the T7-PS beam at CERN. The energy resolution for pions follows a 68%/ E( GeV ) +2% law for orthogonally incident particles, in the energy range between 2 and 10 GeV. The time resolution and the tracking capability of the glass RPC are suitable for the MONOLITH experiment.

Several measurements have been made on different phototubes in order to select the type to be used for the readout system of the NOE magnetized scintillating fiber calorimeter. Characteristics such as gain, linearity, time resolution and cathode uniformity have been examined on several PMT types with standard, fine mesh or channel multiplier structure. The PMT response in the presence of the magnetized calorimeter fringe fields has also been studied. Here we report on the results of these measurements and of the comparisons between the different PMT types.

We present an overview of the data acquisition system (DAQ) and event building of OPERA. OPERA is a long baseline neutrino experiment with a high modularity detector and low event rate. To deal with these features a distributed DAQ system base on Ethernet standards for the data transfer has been chosen. A distributed GPS clock signal is used for synchronizations and time stamp of the data. This architecture allows very modular and flexible event building based on a software trigger strategy. We also present its specific application to the spectrometer sub-detector where RPC trackers are installed. Self-triggerability is a dedicated feature to be also sensitive to out-of-spill events and to possibly allow data taking before the official start of the experiment.

OPERA is an experiment dedicated to the observation of into oscillations through 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 to 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/C2H2F4/isoC4H10/SF6=75.4/20/4/0.6. The present performances of the RPC system are presented and the aging status of the detector 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.

An experimental investigation has been carried out on the properties of electromagnetic shower detectors composed of a uniform array of plastic scintil

This article reports on studies aimed to characterise the properties of plastic scintillating fibres to be used in head-on, 1:1 Pb-SCIFI calorimetric modules. The effect of glue on the attenuation of the light transported by cladding close to the photomultiplier tube is studied and found to effectively decrease the contribution of cladding light. Pb-SCIFI modules have been assembled and tested on a 20–80 MeV tagged photon beam. Good linearity and energy resolution better than 6% / √ E [GeV] were achieved, therefore showing that this technique is suitable for experimentation at ⊼-factories.

The OPERA experiment will study ν μ to ν τ oscillations through τ appearance on the 732 km long CERN to Gran Sasso baseline. The magnet yokes of the two muon spectrometers are instrumented with 48 planes of high resistivity bakelite Resistive Plate Chambers (RPC) operated in streamer mode. Each plane covers about 70 m 2 . A general introduction to the system installation and commissioning will be given. Four RPC planes were instrumented and the first tests were performed confirming a good behavior of the installed RPCs in terms of intrinsic noise and operating currents. The measured noise maps agree with those obtained in the extensive quality test performed at surface. Counting rates are below 20 Hz / m 2 . Single and multiple cosmic muon tracks were also reconstructed. The estimated efficiency is close to the geometrical limit and the very first measurements of the absolute and differential muon flux are in agreement with the expectations. Finally, a description of the readout electronics and of the slow control system is given.

OPERA is an experiment for the observation of νμinto ντoscillations through τ appearance using a 730 km baseline νμbeam from CERN to Gran Sasso underground laboratory. The magnet yokes of the two muon spectrometers are instrumented with high resistivity bakelite RPCs operated in streamer mode. The RPC installation ended in March 2005. As the detectors will be inaccessible during the operation, we performed long term operation as well as quality control tests. The results of the long term and of the Quality Control tests are presented. © 2006 Elsevier B.V. All rights reserved.

OPERA is part of the CNGS project and it is an experiment dedicated to the observation of long-baseline νμinto ντoscillations through τ appearance. Resistive Plate Chambers (RPCs) with bakelite electrodes are used to instrument the 2 cm gaps between the magnetized iron slabs of the two spectrometers. The RPC installation ended in may 2004 on the first spectrometer and in march 2005 on the second one. Before the installation, every RPC is subjected to a complete test chain in order to reject the poorer quality detectors. The tests are performed in dedicated facilities to ensure the proper RPC gluing, to measure its electrical properties and to verify the response to cosmic rays and the intrinsic noise levels. We have also tested the long term stability of real size OPERA RPC prototypes operated at cosmic ray fluxes for more than one year. On small size prototypes we are performing studies on the gas mixtures in order to reduce the total charge released in the gas for each detector count. The validation of the installed RPCs has been performed with pure nitrogen. A small part of them has been also tested with the gas mixture Ar/C2H2F4/i - C4H10/SF6= 75.4/20/4/0.6. © 2005 IEEE.

Before the installation in the OPERA experiment, bakelite Resistive Plate Chambers are subjected to a chain of quality tests performed at the Gran Sasso Laboratories. Mechanical properties are first investigated in a fully automatized station, measuring the gas leakage and checking the gluing of the internal spacers. Then electrical properties are tested: current vs. voltage characteristics are measured both with pure argon and with gas mixture filling; moreover the short term behavior of the current is monitored. Finally the response uniformity is tested, measuring the efficiency on the entire detector surface at cosmic rays fluxes. In this paper we present the test chain and the results on a large set of chambers. © 2004 Elsevier B.V. All rights reserved.

In this paper we present a study of the momentum measurement ability of the magnetized calorimeter proposed for the ICANOE experiment. For the calorimeter tracker we have designed a system based on aluminum drift tubes 8.5 m long and with a square inner cross-section of 2.6×2.6 cm 2 , fed by an Ar–CO2 gas mixture. Magnetic field measurements performed on reduced scale prototypes show that an average magnetic flux density of ∼1.3 T can be achieved. From tests with cosmic rays and beam particles, we also show that the drift tubes used for the tracker allow to obtain spatial resolutions better than 400 μm . The muon momentum resolution achievable with the proposed layout is ∼30%.

The first angular distribution data from 5547 hours of operation of the LVD detector are presented. The technique of track reconstruction is described. A total of 452 657 single muons were reconstructed for this period. The data are acceptance corrected in our final plots. The total single muon flux (the total flux from above impinging on a sphere of unit cross sectional area) in the Gran Sasso Laboratory is 1.03 muons per hour per square meter. The total flux crossing a unit horizontal area from above is 0.79 muons per hour per square meter. The acceptance-corrected intensity at cos θ = 1 is 0.349 muons per hour per square meter per steradian (9.7× l0 − 9 muons per second per square centimeter per steradian). We present, for the first time from Gran Sasso Laboratory, data at near-horizontal zenith angles.

In this work we report the complete set of measurements carried out at LADON on small size calorimeter modules composed of a uniform array of plastic scintillating fibers and lead (50:35 by volume ratio) for photons in the energy range 20-80 MeV. Calorimeter properties for both head-on and side-on incidence conditions have been investigated. With photons hitting the fibers laterally, an energy resolution of 4.8%/\\sqrt{E[GeV]} is obtained. This figure includes a 2%/\\sqrt{E[GeV]} term added in quadrature due to the photoelectron statistics.

ICSCWorldLaboratory, Lausanne, SwitzerlandReceived5 November 19921. IntroductionThe LVDdetector[11 can be defined as an under-groundobservatory with the main objectives of study-ing neutrinos from stellar collapse and searching forpoint-like sources of gammas and neutrinos of veryhigh energy. This multipurpose apparatus is being in-stalled in hall Aofthe Gran Sasso Laboratory [21 at avertical depth of 3600 m.w.e. It consists of a largevolume of liquid scintillator divided into modules andofa tracking system madeof layers ofstreamertubes.The detectordesignfulfils the following aims:- the study ofthe neutrino interactions inside thedetectorwithenergymeasurementfor low-energyneu-trino interactions, and patternidentification for higherenergyevents;- the detectionofpassing muonswith track recon-struction, up-down discrimination and time of flightmeasurement.The apparatus consists of 190 basically identicalmodules. Each module comprises 9.6 t ofliquid scintil-lator divided into eight modular counters and an L-shaped tracking chamber, containing adouble layer ofstreamer tubes andfacingthe bottom andone verticalside ofthemodule. Thesemodules areinserted into an0168-9002/93/$06.00 0 1993 -Elsevier Science Publishers B.V. All rights reservediron support structure. The whole array, which mea-sures 40X 12

This article reports on studies aimed to characterise the properties of plastic scintillating fibres to be used in head-on, 1:1 Pb-SCIFI calorimetric modules. The effect of glue on the attenuation of the light transported by cladding close to the photomultiplier tube is studied and found to effectively decrease the contribution of cladding light. Pb-SCIFI modules have been assembled and tested on a 20-80 MeV tagged photon beam. Good linearity and energy resolution better than 6%/ \\sqrt{E[GeV]} were achieved, therefore showing that this technique is suitable for experimentation at \ϕ-factories.

In this paper the physical performances of a calorimeter composed of a highly segmented tracking section (5X_0) that uses CsI(TI) elements, followed by a total absorption 10X_0 Pb-scintillating fiber segment, are compaired with those of a more conventional Pb-scintillating fiber detector. The γ energy range covered by these detectors is (20 - 300)MeV, as requested by the experimentation at e^+e^- ϕ factory machines.

The article reports on performances of head-on Pb-scintillating fibres e.m. calorimetric modules ('H.O.P.S. ') exposed to a 20-80 MeV tagged photon beam. Good linearity and energy resolution better than 6%/ \\sqrt{E} were achieved therefore showing that this technique is suitable for experimentation at ϕ-factories, even at the lowest end of the photon energy range.

The tracking system of the Large Volume Detector, an underground experiment to study muons and nutrino astronomy, will use −15000 limited streamer chambers. We describe a comparison between the standard binary mixture (30% argon + 70% isobutane) and a low-hydrocarbon ternary mixture (2% argon + 10% isobutane + 88% carbon dioxide). The ternary composition results in a 400-volt-shorter single count-rate plateau, a 20% smaller primary streamer pulse-height, and a much higher streamer multiplicity. The count-rate plateaux have also been studied over a wide composition range of isobutane, argon, and carbon dioxide mixtures. We also discuss the streamer chamber quality control procedures and the results obtained from a simple of 2900 devices operated with the binary mixture.