Last Update: October 2000

ICARUS

Laboratory: LNGS

Collaboration:

F. Arneodoa, B. Babussinovb, A. Badertscherc, G. Battistonid, P. Benettie, E. Bernardinia, A. Borio di Tigliolef, R. Brunettie, A. Buenoc, E. Calligariche, M. Campanellic, C. Carpanesec, D. Cavallid, F. Cavannag, P. Cenninih, S. Centrob, A. Cesanaf, C. Cheni, Y. Cheni, D. Clinej, R. Dolfnie, A. Ferrarih, A. Gigli Berzolarie, K. Hei, X. Huangi, Z. Lii, F. Lui, J. Mai, C. Mattheyj, F. Maurie, D. Mazzag, G. Mengb, C. Montanarie, G. Nurziag, S. Otwinowskij, O. Palamaraa, D. Pascolib, S. Petrerag, G. Piano Mortarig, A. Piazzolie, P. Picchik, F. Pietropaolob, T. Rancatid, A. Rappoldie, G.L. Rasellie, J. Ricoc, M. Rossellae, C. Rossig, A. Rubbiac, C. Rubbiae, P. Salad, D. Scannicchioe, F. Sergiampietril, N. Sinanisc, M. Terranif, P. Torree, S. Venturab, C. Vignolie, H. Wangj, J. Wooj, Z. Xue, G. Xui, C. Zhangi, Q. Zhangi, S. Zheni,

a) Laboratori Nazionali di Gran Sasso, INFN, Assergi (AQ), Italy

b) Dipartimento di Fisica e INFN, Università di Padova, Italy

c) Institute for Particle Physics, ETH Honggerberg, Zurich, Switzerland

d) Dipartimento di Fisica e INFN, Università di Milano, Italy

e) Dipartimento di Fisica e INFN, Università di Pavia, Italy

f) Politecnico di Milano (CESNEF), Università di Milano, Milano, Italy

g) Dipartimento d Fisica e INFN, Università dell'Aquila, L'Aquila, Italy

h) CERN, CH 1211 Geneva 23, Switzerland

i) IHEP - Academia Sinica, Beijing, People's Republic of China

j) Department of Physics, UCLA, Los Angeles, CA 90024, USA

k) University of Torino, Torino, Italy

l) INFN Pisa, San Piero a Grado (PI), Italy

1. Goal of the experiment

> The experiment aims at the demonstration and a comprehensive study of neutrino oscillations through the detection and detailed analysis of neutrino events coming both from natural (solar and atmospheric neutrinos) and artificial (CNGS Long Baseline Neutrino Beam) sources. According to present expectations, the simultaneous analysis of the different classes of events (classified from neutrinos sources and species) would allow to determine most of the parameters relevant to neutrinos mixing. The other major issue of the ICARUS scientific program is the search for nucleon decay especially in SUSY favoured (N --> n k) or exotic channels.

> Key element of the scientific program is the adopted detection technique. With its superior performance in terms of space and energy resolution together with the other characteristics (homogeneous and isotropic response, high sensitivity both at low and high energy, self triggering capability) the Liquid Argon TPC is the most advanced instrument within its class (large volume underground detectors), especially suited for the search of rare events. Originally conceived by Carlo Rubbia, spokesman of the Collaboration, the Liquid Argon TPC technology has been developed and finally transported to full industrial methods in years of intense R&D.

> First step of the ICARUS scientific program is the construction of a module of about 600 ton sensitive mass (T600). Being assembled in the INFN Pavia Laboratories, the T600 will be there fully tested around the end of year 2000 and then transported to the INFN LNGS Underground Laboratories.

> The T600 has its own scientific program, mainly devoted to solar neutrinos studies, which is somehow limited by the mass but can still be considered as relevant to neutrino physics. However, as clearly stated in the original proposal, the T600 has to be considered as one more step towards larger detector masses and it finds its main justification in solving technical issues associated with the actual operation of a large mass liquid argon device in the LNGS tunnel.

> The program will continue (starting from 2001) with the design and construction of a larger volume unit (according to the preliminary design it will be about 1.4 kton sensitive mass) to be hopefully repeated up to four times in Hall B of the LNGS Laboratories. Coupled with an external muon spectrometer, this detector will allow to reach the anticipated scientific goals.

2. Physics achievements

> The Collaboration has been fully involved in prototyping activities and is now completing the construction of the T600 module. Here follows a list of the recent major achievements status of construction of the T600 module.

> a) A full set of tests has been successfully completed on a 10 m3 prototype installed in the Pavia INFN Laboratories and built using the same, fully industrial, techniques adopted for the T600. The prototype, originally motivated by the necessity to test the solutions for cryogenics and argon purification, was also used as a test ground for most of the internal detector components (wires chambers mechanics, control systems, cryogenic feedthroughs, etc.). Results allowed to fix some basic detector parameters especially for cryogenics and argon purification systems. Detector operation schemes (start-up, run, stop, emergency, etc.) and assembly procedures (for cleanliness) have also been defined.

> b) The 10 m3 prototype has been then re-installed in the LNGS external laboratories for a new set of tests. In this case the prototype was equipped with a fully functional TPC and a set of new instruments (newly designed purity monitors, photonmultipliers working in liquid argon, external triggering system). The prototype was operated continuously for about 4 months recoding cosmic rays events that allowed a detailed analysis about the detector performance in nominal environmental conditions. Operational data on this relatively long duration test confirmed the previously obtained results.

> c) Preparation of the detector assembly hall in Pavia has been completed during 1999.

> d) The two main cryostats (half-modules) have been tested for vacuum tightness and delivered and positioned in the Pavia Laboratory. Assembly of the external thermal insulation layer is proceeding. Installation of cryogenic circuits is also advancing.

> e) Assembly of the internal detector for the first half-module was started in march 2000, after the delivery of the first half-module cryostat, and is now near to completion: mechanical structures are complete and aligned to within 0.2 mm with respect to the design position, wires are positioned and tensioned, auxiliary instrumentation has been tested and installed (level and position meter, temperature probes, purity monitors, PMTs for internal triggering and time zero detection), internal cabling is almost complete.

3. INFN contribution to the experiment in terms of manpower and financial support

> Support to the experiment is largely dominated by the INFN contribution both for funding and for manpower. Contribution of INFN to the T600 corresponds to about 90 % of the total cost. Correspondingly, the INFN groups have the construction responsibility for the most relevant items (cryogenics and purification systems, internal detector mechanics, readout electronics, trigger systems, logistics).

> Contributions from non INFN groups concern the slow control system (ETH group) and the HV supply and control (UCLA group), while the contribution of the IHEP-Beijing group is expressed in terms of manpower for the wiring of the chambers.

4. Number of publications in refereed journals: 2

5. Number of talks to conferences: 5

6. Number of undergraduate and doctoral thesis on the experiment: 0

7. Leadership role in the experiment

> C. Rubbia — Università degli Studi di Pavia ed INFN Sezione di Pavia — Spokesman

> E. Calligarich — INFN Sezione di Pavia — Project leader

8. Innovative instruments

> As a by-product of the activity dedicated to the measurement of the natural radioactivity background in the LNGS Hall C, a portable neutrons detector was developed with sensitivity near to the natural background limit. This detector may find an application in the medical field.

9. Competing experiments

> The project is in competition with the Japanese (K2K) and American (MINOS) programs for the search of neutrino oscillations on long baselines. Points in favour of the experiment are the direct demonstration of the oscillation phenomenon by means of the identification of nt and n e, the combined analysis of beam and atmospheric neutrinos, the possibility to extend the sensitivity by adding more detector units.