The construction technique of the new MEG II tracker

Abstract The MEG experiment, at the PSI, aims to search for the charged lepton flavor violating decay μ + → e + γ . MEG has established the world best upper limit for the branching ratio: BR ( μ + → e + γ ) 4 . 2 × 1 0 − 13 at 90% CL. An upgrade (MEG II) of the whole detector has been approved to obtain a substantial increase in sensitivity. The new positron tracker is a single volume, full stereo cylindrical Drift Chamber (CDCH), filled with a gas mixture of 85: 15 H e ∕ i − C 4 H 10 . Due to their high wires density (12 wires/cm 2 ) and the stringent requirements on spatial resolution, the use of the classical feed-through technique as wire anchoring system can hardly be implemented and therefore it is necessary to develop an automatic system (wiring robot) with a high-performing control. A wiring robot, designed and built at the INFN Lecce and University of Salento laboratories was used for the wiring phase of the MEG CDCH. The new CDCH is currently in the test phase at INFN Lecce and Pisa, and later it will be delivered to PSI for commissioning.