An ultra-light cylindrical GEM detector as inner tracker at KLOE-2

Abstract We are developing a low-mass, fully cylindrical and dead-zone-free GEM detector as inner tracker for the KLOE experiment upgrade at the DA Φ NE Φ factory. The inner tracker will be composed of five concentric layers of cylindrical triple-GEM detectors (C-GEM), completely realized with very thin polyimide foils. The final result is a very light detector: only 0.2% of X 0 per layer inside the active area. We successfully built and tested with an X-ray gun a small-size prototype operated in current mode with an Ar/CO 2 = 70 / 30 gas mixture. The very positive results obtained with the prototype open the way for a completely new and competitive category of ultra-light fully sensitive vertex detectors for high-energy physics experiments