Desktop Experiment with a Cloud Chamber for Deep-Inelastic Scattering of Cosmic Muons off Nuclei

DIS (deep-inelastic scattering) is observed normally using a huge accelerator and a large detector such as EMC at CERN (European Muon Colllaboration, NA2, NA9, NA28, or NMC as NA37 etc.). Here DIS is a deeply inelastic scattering of incoming leptons (usually electrons or muons) off nuclei observed typically at high energies. The DIS is a textbook experiment, which is well known and pedagogical but actually hard to witness without using a big facility. Here we have tried to compose a possibly simplest setup for the detector to observe DIS events as a kind of pedagogical material. We got succeeded with a cloud chamber employed herewith in order to observe easily the events including the zero-degree scattering. This novel method dramatically increased the event rate of DIS at forward angles with low Q 2 . Here Q 2 is the four-momentum transfer squared in the scattering process. It is well known that the scattering cross section of electromagnetic process, like Rutherford scattering, is proportional to 1/Q 4 , which enhances the cross section at forward angles dramatically. In this paper we describe the experimental setup, the measurement procedure, the event rate estimate, the experimental result, and some educational consequences.