Feb 15 – 19, 2016
Vienna University of Technology
Europe/Vienna timezone

FoCal - a high-granularity electromagnetic calorimeter for forward direct photon measurements at LHC

Feb 17, 2016, 9:00 AM
EI8 (Vienna University of Technology)


Vienna University of Technology

Gusshausstraße 27-29, 1040 Wien
Talk Calorimeters Calorimeter


Chunhui Zhang (Nikhef National institute for subatomic physics (NL))


The measurement of direct photon production at forward rapidity (y~3-5) at the LHC provides access to the structure of protons and nuclei at very small values of fraction momentum (x~10^-5). FoCal, an extremely-high-granularity Forward Calorimeter covering 3.5 < η < 5.3 is proposed as a detector upgrade to the ALICE experiment. To facilitate the design of the upgrade and to perform generic R&D necessary for such a novel calorimeter, a compact high-granularity electromagnetic calorimeter prototype has been built. The corresponding R&D studies will be the focus of this presentation. The prototype is a Si/W sampling calorimeter. It was instrumented with 24 layers of Monolithic Active Pixel Sensors, a total of 39M pixels. We will report on performance studies of the prototype with test beams at DESY and CERN in a broad energy range. The results of the measurements demonstrate a very small Molière radius (~11 mm) and good linearity of the response. Unique results on the detailed lateral shower shape, which are crucial for the two-shower separation capabilities, will be presented. We will compare the measurements to GEANT-based MC simulations, which additionally include a modeling of charge diffusion. The studies demonstrate the feasibility of this high-granularity technology for use in the proposed detector upgrade. They also show the extremely high potential of this technology for future calorimeter development.

Primary authors

Chunhui Zhang (Nikhef National institute for subatomic physics (NL)) Thomas Peitzmann (Nikhef National institute for subatomic physics (NL))


Gerardus Nooren (Nikhef National institute for subatomic physics (NL)) Hongkai Wang (Nikhef National institute for subatomic physics (NL)) Marco Van Leeuwen (Nikhef National institute for subatomic physics (NL)) Ton Van Den Brink (Nikhef National institute for subatomic physics (NL))

Presentation materials