Introduction

Evidence for neutrino oscillation has been reported both by atmospheric and solar neutrino experiments. In particular the atmospheric neutrino anomaly observed by Superkamiokande, MACRO and Soudan 2 suggests $\nu_\mu$$\rightarrow$$\nu_{\tau}$ oscillation with $\sin^{2}\theta$$\simeq$1 and $\Delta m^{2}$$\simeq$0.0035 e$V^{2}$. In this scenario, an appealing facility is given by long base line neutrino beams, which allow for a direct search of $\nu_{\tau}$ appearance, like the Cern to Gran Sasso project (CNGS).

The NOE Collaboration proposed an electronic experiment composed by alternated modules of TRD, acting as neutrino target, and scintillating fiber calorimeters. Kinematical tagging of $\nu_{\tau}$ requires a detector with high performance, while the low neutrino flux at long distance reflects in the need of large mass detectors. On the other hand the detector granularity has to match with the cost and the number of read-out channels.

The search for $\nu_{\tau}$ appearance in the $\tau$ $\rightarrow$ e $\nu$ $\bar{\nu}$ channel using kinematical criteria, requires a good e/$\pi^{o}$ separation to reject the neutral current with $\pi^{o}$ and a good energy and $E_{t}$ resolution ($\sigma_{E}$, $\sigma_{E_t}$) both for electrons and pions, to reject the residual $\nu_{e}$ in the beam. Therefore good calorimetric features are mandatory to obtain small $\sigma_{E}$ and $\sigma_{E_t}$, the latter requiring also a fine segmentation.

A general purpose electronic detector running deep underground, can also address atmospheric neutrino physics. For this purpose a good timing resolution is highly advisable, in order to distinguish neutrino induced upgoing muons from downgoing ones. Such study would benefit from isotropic detector, running for long periods, due to the low atmospheric neutrino flux.

Taking advantage of the SPACAL R&D, many scintillating fiber (SCIFI) calorimeters were developed in the last ten years, namely SCIFI/Pb calorimeters have been build by the CHORUS, E864 and H1 Collaborations. With respect to these experiments, the main challenge in our case is to increase the calorimeter mass while keeping a good energy resolution at an acceptable cost.

We report in this paper the design consideration, the description and the performance of the scintillating fiber calorimeter prototype, performed by the NOE Collaboration at CERN PS-T7 beam.

Recently the ICARUS and the NOE Collaborations joined the ICANOE proposal, merging the liquid argon imaging capability with the scintillating fiber calorimeter energy resolution.

The R&D carried out by the NOE Collaboration over more than five years, leading to the test beam results described in the present paper, establish the basis for the design, the optimization and the forthcoming test of the ICANOE calorimeter.