This proposal will fund the R&D needed for future lepton collider detector and in particular the International Large Detector (ILD) detector concept. The R&D projects will address critical issues related to the design of the ILD concept and associated beam instrumentation. The future lepton collider is expected to be a frontier scientific facility, exploring the interactions of electrons and positrons at energy scales of up to about 1 TeV. To fully exploit the physics opportunities of such an accelerator, it is essential to design a particle physics detector of unprecedented granularity, robustness and precision, and demonstrate that its feasibility. ILD is based around particle flow, a paradigm which aims for reconstruction of individual particles, using a highly robust tracking system centered on a time projection chamber supplemented with silicon tracking, and high granularity "camera-like" electro-magnetic and hadronic calorimetry suited to separation of individual energy deposits. Particle Flow calorimeters offer an exciting new approach to achieve significant better energy resolution needed by the new physics. If proven to work they could be useful for many future applications in High energy and Nuclear Physics experiments. This proposal will support the development and validation of Particle Flow Algorithms using test beam data. The detector projects address complementary aspects associated with advancing the design of the ILD detector with projects focused on tracking, calorimetry as well as beam instrumentation. This proposal will support the development of Low mass TPC endplates and luminosity monitoring system.
The proposal will have broader impact in that a number of the R&D projects utilize a significant numbers of undergraduate students who are highly integrated into the planned research. The university groups have a strong track record of encouraging the participation of under-represented groups in their research and this will continue to be emphasized. Many of the detector R&D projects have potential to lead to applications in areas such as medical imaging, and will lead to a cadre of scientists well trained in the art of experimentation and detector technologies.
Particle Flow Algorithms (PFAs) are a promising avenue for obtaining superior hadronic energy resolution which is essential for realizing the full promise of future electron-positron colliders. PFAs try to reach this goal by using the best information in the event; calorimeter information for neutral electromagnetic and hadronic particles and tracker momenta for the charged constituents. This approach requires fine lateral and longitudinal segmentation of the calorimeter to individually reconstruct the showers constituting a jet. This project contributed to the design and protoyping of a detector optimized for PFAs in the context of the International Large Detector concept. Specifically research was carried out on fine-granularity scintillator-Silicon Photomultiplier hadron calorimetry. The main challenge for a scintillator-based hadron calorimeter is the architecture and cost of converting light, from a large number of channels to electrical signal. The complexity and cost of signal transport, processing and acqusition require novel solutions. The main outcome of the R&D partially supported by this project is the prototyping of an Integrated Readout Layer which addresses these issues using innovative techniques which makes the design nd construction of such a calorimeter feasible. In general, for the integrated readout layer, we propose and provide a proof-of-principle for a printed circuit board sitting inside the detector which will support the directly-coupled scintillator tiles, connect to the surface-mount photodetectors and carry the necessary front-end electronics and signal/bias traces. The design is based on the introdction of a number of innovative design concepts like the in situ use of silicon photomultipliers and their direct or fiberless coupling to rigid and optically isolated tile arrays mounted on the electronics board to which the sensors have been surface-mounted. Another outcome of the research partially supported by this project was addressing design questions on the depth of the hadron calorimeter for the ILD concept in particular. Since momentum measurement is key to the kinematical measurements in a PFA-based detector a strong magnetic field is needed. However, the coil contains substantial material which can smear the showers to the point that individual particle reconstruction in the calorimeter becomes impossible. This implies that both the tracking and calorimeter systems need to be contained within the solenoid which imposes restrictions on the depth of the calorimeter as the cost of the magnet increases with the radius. NIU was the lead on the design, construction, commissioning and analysis of a Tail-catcher/muon tracker scintillator-strip/Silicon Photomultiplier device that allowed detailed studies of the tail end of hadronic showers (crucial for faith in PFAs as the biggest differences in hadronic shower Monte Carlo's occur in the tail) , hadronic leakage, punch-through from thin calorimeters and the impact of the coil in correcting for this leakage. These studies have informed the design of the ILD concept hadron calorimeter. The project has provided ample opportunities for training of students and post-docs in software and hardware. As part of the continuum of detector R&D activities carried out by the NIU HEP group it has provided in-depth familiarity with instrumentation and algorithms which has been useful to students and post-docs both inside and outside the field.
