The Instrumented Flux Return Detector of the SuperB Experiment: R&D Studies and First Results of the Fermilab Beam Test

SuperB is a super-flavor factory that will be built in Tor Vergata (Italy). The project, recently approved by the Italian Government, and classified as the flagship project of the Italian INFN, foresees the construction of a high intensity asymmetric electron-positron collider and of the related detector. The expected luminosity of 2x1036cm−2s−1, a factor 100 higher than the last generation of B-factories, will allow the high statistic study of rare decays and, possibly, will allow a deeper insight in the field of new physics. Part of the SuperB apparatus is the Instrumented Flux Return (IFR). This detector exploits the flux return iron structure of the superconducting solenoid as absorber for the identification of muons and neutral hadrons. In more details, It consists of ≃ 92 cm of iron interleaved by 9 layers of highly segmented scintillators. The detection technique is based on relatively inexpensive extruded plastic scintillator bars produced at the FNAL-NICADD facility. The scintillation light is collected through Wave Length Shifting fibers and guided to recently developed devices called Silicon Photon Multipliers used as photodetectors. The use of plastic scintillator as active material ensures reliability, robustness and long term stability while the high granularity and the fast response guarantee a good space-time resolution, extremely important to cope with the expected high particles flux. The readout scheme under evaluation is this manuscript is the double coordinate readout (”BIRO readout”) where two layers of orthogonal scintillator bars provide both, the polar and azimuthal coordinate. In order to deeply understand the performances and possible drawbacks of the above technique, a full depth prototype has been designed and built in Ferrara and Padova, and tested at the Fermilab Test Beam Facility (FBTF) in December 2010. In this paper a comprehensive description of the IFR related R&D studies will be presented. In particular, we will focus on the results of the Fermilab beam test, issues and future activities will also be outlined.