A cylindrical GEM Inner Tracker for the BESIII experiment

We are developing a cylindrical GEM detector with analog readout to upgrade the Inner Tracker of the BESIII experiment at IHEP (Beijing). The new detector will match the requirements for momentum resolution (sigma(pt)/pt similar to 0.5% at 1GeV) and radial resolution (sigma(xy) similar to 100 mu m) of the existing drift chamber and will improve significantly the spatial resolution along the beam direction (sigma(z) similar to 150 mu m) with very small material budget (about 1% of X-0). A beam test has been performed at CERN in order to measure the performance of a BESIII GEM prototype in a magnetic field up to 1 tesla. An overview of the project and the preliminary results of the test will be presented in the talk. The project has been recognised as a Significant Research Project within the Executive Programme for Scientific and Technological Cooperation between Italy and PRC for the years 2013-2015, and more recently has been selected as one of the project funded by the European Commission within the call H2020-MSCA-RISE-2014.