Speaker
Description
A reliable description of material in particle detectors is a key ingredient for precision measurements, particularly in tracking systems where both momentum determination and hit resolution depend crucially on the material content. In many experiments, this information is derived from simplified detector models estimated from design specifications. In practice, such models can deviate significantly from reality due to incomplete knowledge of components or construction effects, leading to material uncertainties that can exceed O(10%). Incorporating direct measurements of radiation length during the development stage of new detectors enables better-informed design decisions and improved detector modelling.
In this talk, a measurement approach based on the multiple scattering of electrons in test beams is presented. Central to this method is the lightweight MONSTAR tracking telescope, developed specifically to minimise its own material impact whilst maintaining high angular resolution. The interplay between telescope performance, beam energy, and the range of measurable material thicknesses is examined using simulation studies.
The methodology is illustrated using data from an experimental campaign at the PSI PiM1 beamline, where the material content of a wide variety of samples—including detector modules, support elements, and services from ATLAS, CMS and Mu3e—was measured, along with dedicated calibration targets, amounting to more than 500 cm$^2$ of scanned material. The talk will outline the analysis strategy, discuss different modelling approaches to multiple scattering (theoretical and data-driven), and highlight the potential of this technique for broader use in future detector R&D and validation.