Executive Summary:
In this Letter of Intent, we propose a broad experimental programme for the “New QCD facility at the M2 beam line of the CERN SPS”. This unrivalled installation will provide the site for a great variety of measurements to address fundamental issues of Quantum Chromodynamics, which are expected to lead to significant improvements in the understanding of QCD as our present theory of strong interactions. The proposed measurements cover the range from lowest-Q² physics as the determination of the proton radius by elastic muon-proton scattering, over average-Q²-reactions to study hadron spectroscopy, to high-Q² hadron-structure investigations using the Drell-Yan process and Deeply Virtual Compton Scattering.
In this Executive Summary, we briefly describe a number of unique first-generation experiments that are already possible using the existing M2 beam line with muons or unseparated hadrons. We also describe a number of unique second-generation experiments that rely on high-energy high-intensity radio-frequency (RF) separated hadron beams, which could be made possible by a major upgrade of the M2 beam line. Such an upgrade, which is presently under study by CERN EN-EA in the context of the Physics beyond Colliders Initiative, would make the CERN SPS M2 beam line absolutely unique in the world for many years to come. For every proposed experiment, individual instrumentation using modern detector architecture will be constructed and installed in the experimental hall EHN2, where the upgraded multi-purpose two-stage magnetic spectrometer will serve as experimental backbone of the new facility.
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