The CGEM detector.

Morello G., per la Collaborazione BESIII
  Venerdì 30/09   09:00 - 12:00   Edificio CLA - Aula T3   I - Fisica nucleare e subnucleare
The BESIII experiment, installed at the BEPCII $e^{+}e^{-}$ collider at IHEP Beijing, will replace the inner part of the Drift Chamber, due to detecting performance degradation. Composed of three coaxial cylindrical triple-GEM, the detector will work in a $1 T$ axial magnetic field. To reach the required spatial resolution, two readout methods have been developed: charge centroid and micro-TPC mode (first time ever for GEM). During tests the two methods provided, respectively, $\sigma_{r}\varphi$ below 100 microns at 0 T and below 150 microns for tracks incident angle ranging between $10^{\circ}$ to $45^{\circ}$. These results, together with the cylindrical prototype construction steps, will be shown.