We carried out a careful evaluation of the performance of the large cathode area ETL 9357FLA photomultiplier tube operating at cryogenic temperature. The measurements were focused on evaluating the parameters which mainly characterize the operating performances of the device down to 77 K and the spread of the distinctive features over 54 samples assembled in the ICARUS apparatus. The results that we obtained demonstrate that the photomultiplier is suited for light detection in such unconventional operating conditions, certifying this device for the direct measurement of scintillation light coming from noble-gas liquids in detectors dedicated to neutrino physics and dark matter research.

The ICARUS collaboration has demonstrated, following the operation of a 600 ton (T600) detector at shallow depth, that the technique based on liquid argon time projection chambers is now mature. The study of rare events, not contemplated in the standard model, can greatly benefit from the use of this kind of detectors. In particular, a deeper understanding of atmospheric neutrino properties will be obtained thanks to the unprecedented quality of the data ICARUS provides. However if we concentrate on the T600 performance, most of the νμ charged current sample will be partially contained, due to the reduced dimensions of the detector. In this article, we address the problem of how well we can determine the kinematics of events having partially contained tracks. The analysis of a large sample of atmospheric muons collected during the T600 test run demonstrates that, in case the recorded track is at least one meter long, the muon momentum can be reconstructed by an algorithm that measures the multiple Coulomb scattering along the particle’s path. Moreover, we show that momentum resolution can be improved by almost a factor two using an algorithm based on the Kalman filtering technique.

The ICARUS collaboration has demonstrated, following the operation of a 600 ton (T600) detector at shallow depth, that the technique based on liquid Argon TPCs is now mature. The study of rare events, not contemplated in the Standard Model, can greatly benefit from the use of this kind of detectors. In particular, a deeper understanding of atmospheric neutrino properties will be obtained thanks to the unprecedented quality of the data ICARUS provides. However if we concentrate on the T600 performance, most of the νμ charged current sample will be partially contained, due to the reduced dimensions of the detector. In this article, we address the problem of how well we can determine the kinematics of events having partially contained tracks. The analysis of a large sample of atmospheric muons collected during the T600 test run demonstrate that, in case the recorded track is at least one meter long, the muon momentum can be reconstructed by an algorithm that measures the Multiple Coulomb Scattering along the particle’s path. Moreover, we show that momentum resolution can be improved by a factor two using an algorithm based on the Kalman Filtering technique.

We have constructed and operated the ICARUS T600 liquid argon (LAr) time projection chamber (TPC). The ICARUS T600 detector is the largest LAr TPC ever built, with a size of about 500 tons of fully imaging mass. The design and assembly of the detector relied on industrial support and represents the applications of concepts matured in laboratory tests to the kton scale.The ICARUS T600 was commissioned for a technical run that lasted about 3 months. During this period all the detector features were extensively tested with an exposure to cosmic-rays at surface with a resulting data collection of about 30000 events.The detector was developed as the first element of a modular design. Thanks to the concept of modularity, it will be possible to realize a detector with several ktons active mass, to act as an observatory for astroparticle and neutrino physics at the Gran Sasso Underground Laboratory and a second-generation nucleon decay experiment.In this paper a description of the ICARUS T600 is given, detailing its design specifications, assembly procedures and acceptance tests. Commissioning procedures and results of the technical run are also reported, as well as results from the off-line event reconstruction. (C) 2004 Elsevier B.V. All rights reserved.

Detection of Cherenkov light emission in liquid argon has been obtained with an ICARUS prototype, during a dedicated test run at the Gran Sasso Laboratory external facility. Ionizing tracks from cosmic ray muons crossing the detector active volume have been collected in coincidence with visible light signals from a photo-multiplier (PMT) immersed in liquid argon. A 3D reconstruction of the tracks has been performed exploiting the ICARUS imaging capability. The angular distributions of the tracks triggered by the PMT signals show an evident directionality. By means of a detailed Monte Carlo simulation we show that the geometrical characteristics of the events are compatible with the hypothesis of Cherenkov light emission as the main source of the PMT signals.

The results reported in this paper are based on the analysis of the data recorded with the first half-module of the ICARUS T600 liquid argon Time Projection Chamber (LAr TPC), during a technical run that took place on surface in Pavia (Italy). We include results from the linearity, uniformity and calibration of the electronics, measurements on the electron drift velocity in LAr at different electric fields, as well as the LAr purity achievement of the detector. Two complementary techniques were used to measure the drift electron lifetime inside the active volume: the first, from the data of a purity monitor, gives a measurement localized in space; the second, based on the study of the signals produced by long minimum ionizing tracks crossing the detector, provides a LAr volume averaged value. Both methods yield consistent results over the whole data taking period and are compatible with an uniform LAr purity over the whole volume. The maximal drift electron lifetime value was recorded before the run stop and was about 1.8ms. From an interpretation of the observed drift electron lifetime as a function of time, we conclude that the adopted technology would allow for drift distances exceeding 3m.

Examples are given which prove the ICARUS detector quality through relevant physics measurements. We study the μ decay energy spectrum from a sample of stopping μ events acquired during a also at IFSI del CNR, sezione presso LNF. 234 The ICARUS Collaboration: Measurement of the μ decay spectrum with the ICARUS liquid Argon TPC the test run of the ICARUS T600 detector. This detector allows the spatial reconstruction of the events with fine granularity, hence, the precise measurement of the range and dE/dx of the μ with high sampling rate. This information is used to compute the calibration factors needed for the full calorimetric reconstruction of the events. The Michel ρ parameter is then measured by comparison of the experimental and Monte Carlo simulated μ decay spectra, obtaining ρ = 0.72 ± 0.06 (stat.) ± 0.08 (syst.). The energy resolution for electrons below ∼ 50 MeV is finally extracted from the simulated sample, obtaining (E meas − E MC)/E MC = 11%/ √ E[MeV] ⊕ 2%.

Electron recombination in liquid argon (LAr) is studied by means of charged particle tracks collected in various ICARUS liquid argon TPC prototypes. The dependence of the recombination on the particle stopping power has been fitted with a Birks functional dependence. The simulation of the process of electron recombination in Monte Carlo calculations is discussed. A quantitative comparison with previously published data is carried out.

Liquid noble gas detectors have driven particle physics research and technology in many sub-fields for many years. Recently their impact as a target and detector medium has been applied to neutrino physics research. As new results and new questions appear in neutrino physics, new detector technologies in general have been explored to keep pace with the requirement of higher statistics, higher precision experiments. Liquid argon time projection chamber devices have emerged as the detector of choice for accelerator based, massive, precision, neutrino detection. In particular, in the last decade, results from test stands and experiments have driven the development of this technology towards large scales. From the MicroBooNE experiment, SBND, and ICARUS on the Short Baseline program at Fermilab to the scale required for the huge DUNE experiment, these detectors are enabling precision neutrino physics for neutrino oscillations. And if history is our guide, as a new detection technology, liquid argon time projection chambers will likely teach us unexpected things.In this paper we present the general features of liquid argon time projection chambers for neutrino physics, a brief history of the technology and details of recent research and development that is driving the design of the detectors under construction. Finally, some comments on future R&D envisioned and the impact of this work on other fields is described.

Examples are given which prove the ICARUS detector quality through relevant physics measurements. We study the μ decay energy spectrum from a sample of stopping μ events acquired during the test run of the ICARUS T600 detector. This detector allows the spatial reconstruction of the events with fine granularity, hence, the precise measurement of the range and dE/dx of the μ with high sampling rate. This information is used to compute the calibration factors needed for the full calorimetric reconstruction of the events. The Michel ρ parameter is then measured by comparison of the experimental and Monte Carlo simulated μ decay spectra, obtaining ρ = 0.72 ± 0.06 (stat.) ± 0.08 (syst.). The energy resolution for electrons below ∼ 50 MeV is finally extracted from the simulated sample, obtaining (Ee meas − Ee MC)/E e MC = 11%/ √

In the standard model (SM) Of electroweak interactions the positron from the decay of polarized positive muons is mainly longitudinally polarized. The measurement of the two transverse polarization components, therefore, is a sensitive tool for contributions from additional, exotic, interactions.The energy dependence of the transverse polarization component P-T1, which lies in the plane spanned by muon-spin and positron momentum, yields the low energy parameter eta and thus an improved model-independent value of the Fermi coupling constant. A non-zero value of the transverse component PT2, which is perpendicular to the above mentioned plane, would be the first observation of time reversal violation in a purely leptonic decay.The mu (PT) experiment at the Paul Scherrer Institute determines the three polarization components simultaneously with the same apparatus by making use of three different reactions (spatial and temporal dependence of annihilation-in-flight with polarized electrons as well as muon decay asymmetry). The use of a stroboscopic method greatly reduces systematic errors. The measurement of the longitudinal polarization serves mainly as a test of the sensitivity of the apparatus, while the measurement of the two transverse components will improve the current experimental limits. The preliminary results are P-T1 = (7 +/- 13) x 10(-3), P-T2 = (19 +/- 13) x 10(-3).

A multiwire proportional chamber has been developed to study the properties of a detector for tracking of low energy electrons (0.2–1MeV). The geometry and the materials used have been optimized to minimize energy losses and multiple Coulomb scattering. The detector is equipped with a special electronic readout and event selection system, consisting of an amplifier/comparator stage, a fast trigger unit and a data multiplexer. The fast trigger system identifies the desired events within 30ns. Based on this prototype, the full scale detectors (50×100cm2) will be constructed to determine the electron tracks in neutron decay experiments.

Muon decay allows for the most precise experiments in testing the Standard Model of electroweak interactions. An experiment aimed to measure one of the Michel parameters with an improvement of 70 is described. A production run is foreseen for summer 2000.

Over the half century since the first observation that the free neutron is an unstable particle, the neutron decay process has always posed questions at the forefront of particle physics. Nowadays the neutron attracts great attention as a tool for investigating subtle effects in the interaction between quarks and leptons [l]. This concerns hadronic corrections to the dominating “vector—axial vector” (V–A) component, as well as searches for the other weak interaction terms, “vector + axial vector,” scalar, tensor and pseudoscalar (V+A, S, T and P), which conform to relativistic quantum field theory. The main questions considered at present are: why does nature not make use of all interaction terms which are allowed by the Lorentz invariance? what is the role of parity and time reversal symmetries and/or their violation? and what are the characteristics (masses and coupling constants) of the subnuclear or subquarkllepton virtual particles responsible for a hypothetical, very weak and short range new interaction?

A new facility for particle physics has been installed at the spallation source SINQ. An experimental area has been constructed for a series of experiments fed by a high intensity, polarized cold neutron beam. The physics program for this new facility will focus on free neutron decay studies addressing mainly the questions of fundamental symmetries (time reversal and parity) in the weak interactions.

A new facility for particle physics with polarized cold neutrons has been taken into operation at the spallation source SINQ at PSI. After extraction of the first beam, its intensity and polarization have been measured as a function of the neutron wavelength. The beam characteristics are among the best in the world for studies of neutron decay. An experimental area was constructed with infrastructure support for convenient experimentation. The physics program will focus on detailed investigations of the free neutron decay process, in particular fundamental symmetries of the weak interaction. The first approved experiment is a novel search for time reversal violation.