PERFORMANCE OF AN ENDCAP PROTOTYPE OF THE ATLAS ACCORDION ELECTROMAGNETIC CALORIMETER

The design and construction of a lead-liquid argon endcap calorimeterprototype using an accordiongeometry and conceived as a sector of the inner wheel of the endcap calorimeterof the future ATLAS experimentat the LHC is described. The performance obtained using electron beam data is presented. The main results are an energy resolution with a sampling term below $11\%/\sqrt{E(\rm GeV)}$ and a small local constant term, a good linearity of the response with the incident energy and a global constant termof 0.8\% over an extended area in the rapidity range of $2.2\eta 2.9$. These properties make the design suitable for the ATLAS electromagnetic endcap calorimeter.