Light Guides for the High Luminosity Zero Degree Calorimeter

The transition to High Luminosity (HL) operations of the CERN LHC requires the upgrade of several detector systems, including the Zero Degree Calorimeters (ZDCs) in ATLAS and CMS. The joint upgrade of these detector systems is led by the University of Illinois at Urbana-Champaign.

The importance of the ZDC lies in its responsibility for triggering and event geometry characterization in Heavy Ion (HI) collisions. The ZDC is a sampling calorimeter using tungsten absorbers, radiation hard fused-silica Cherenkov radiators, and photomultiplier tubes (PMTs) for light conversion into analog electric signals. The detector uses reflective air Light Guides (LGs) to transport Cherenkov light from the fused silica radiators to the PMT windows. Optimizing the efficiency and acceptance uniformity for the light transport is an important goal for the final HL-ZDC design’s performance.

In this contribution we validate our Monte Carlo simulation and report the performance of different LG geometries (nominally Winston cone and trapezoidal light guides) in the Electromagnetic and Hadronic sections of the HL-ZDC. With these simulation results, alongside data from in-lab experiments and on-site CERN electron beam tests, we determine what the HL-ZDC LG designs will be and develop a full mapping of their characteristics.