Line 5. Symmetries and Fundamental Interactions

Coordinators: G. Bisogni, M. La Cognata

The experiments of this line study fundamental properties of matter and antimatter allowing precision tests of the Standard Model. Here are grouped the experiments for the measurement of the proton radius (FAMU), for the search of the Electric Dipole Moment of light nuclei (JEDI), for the measurements on the antimatter at low energy (LEA) and for the study of possible Pauli principle violation (VIP).

The goal of the FAMU experiment is the study of the proton electromagnetic structure. The measurement of the muonic hydrogen ground state hyperfine splitting will allow to determine the proton Zemach radius. This high precision study will permit to test QED calculations and it will help in understanding better the anomalies observed by using electrons and muons in recent spectroscopic measurements. The experimental apparatus consists in a gaseous target, placed into a cryogenic and pressurized container, placed on a muon beam line at the Rutherford Appleton Laboratory in UK. A powerful mid-infrared laser coupled with an optical cavity is able to excite the hyperfine transition whenever its frequency is resonant with the proton-muon system one. An X-rays detection system is used to determine when the transition occurs.

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Picture of the experimental setup of the FAMU collaboration

 

The JEDI experiment is dedicated to the search for the Electric Dipole Moment (EDM) of light nuclei such as deuton, proton and 3He. The existence of this property in particles violates the symmetries P and T and, consequently, the combined symmetries of CP, which, according to very general criteria, is necessary to explain the dominance of matter over antimatter in the Universe. While the research on the neutron EDM is advanced, for the charged baryons there are no direct measurements. JEDI measures the EDM of the deuton as an accumulation of the vertical component of the beam polarization in the COSY ring. In addition, the collaboration is designing an electrostatic storage ring, which will allow EDM measurement of light nuclei with very high precision.

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JEDI detection principle

 

The LEA (Low Energy Antimatter) collaboration includes several research activities in the field of low energy antimatter. The goal is to probe the fundamental principles and laws of Nature through the study of antimatter and in particular through the comparison between the characteristics of matter and those of antimatter. Experiments at the CERN Antiproton Decelerator allows to test the CPT symmetry with high precision by comparing the spectra of the hydrogen atom with those of the anti-hydrogen and to verify the Weak Equivalence Principle in the gravitational interaction between the Earth and the anti-hydrogen. These activities in LEA are carried out by the AEgIS, ALPHA and ASACUSA experiments. The other experiments of LEA, PsICO and QUPLAS, instead use positrons and positronium atoms to test the fundamental physical laws.

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LEA: Annihilation of an antiproton with a neon nucleus detected with a streamer chamber at LEAR (CERN) 

 

The VIP experiment (VIolation of the Pauli exclusion principle) is aimed at testing the Pauli Exclusion Principle (PEP) and investigating its possible implications for physics, due to a small violation of it. The PEP represents one of the main cornerstones of modern physics. Recently, the experiment has turned its attention to the study of the measurement problem in quantum mechanics, setting new records in the study of the gravity-induced collapse of the wave function model, proposed by Lajos Diósi and Roger Penrose (link).

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Picture of the detection setup of the VIP experiment

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