Search for electric dipole moments in storage rings

Paolo Lenisa

doi:10.1051/epjconf/201613001010

Abstract

The JEDI collaboration aims at making use of storage ring to provide the most precise measurement of the electric dipole moments of hadrons. The method makes exploits a longitudinal polarized beam. The existence an electric dipole moment would generate a torque slowly twisting the particle spin out of plan of the storage ring into the vertical direction. The observation of non zero electric dipole moment would represent a clear sign of new physics beyond the Standard Model. Feasiblity tests are presently undergoing at the COSY storage ring Forschungszentrum Julich (Germany), to develop the novel techniques to be implemented in a future dedicated storage ring.

Highlights

The fact that we and the world around us are made of matter and only a minimal amount of antimatter is observed, constitutes one of the fundamental puzzles in modern physics, motivating a variety of theoretical speculations and experimental investigations
One of the necessary mechanisms required for this to happen – namely CP violation – is very small in the Standard Model of particle physics and only able to account for a tiny fraction of the actual imbalance
New sources of CP violation are needed, and one such potential signature would be the appearance of electric dipole moments (EDMs) in fundamental particles

Summary

Introduction

The fact that we and the world around us are made of matter and only a minimal amount of antimatter is observed, constitutes one of the fundamental puzzles in modern physics, motivating a variety of theoretical speculations and experimental investigations. In its centre-of-mass frame, the ground state of a subatomic particle has no direction at its disposal except its spin, which is an axial vector, while the charge separation (EDM) corresponds to a polar vector (see Fig. 1) If such a particle with nonzero mass and spin possesses an EDM, it must violate both parity (P) and time-reversal (T) invariance. EDMs of this size would be large enough to be observed by a new generation of highly sensitive accelerator based experiments with charged particles such as the proton and deuteron. In this respect, EDMs offer a complementary approach to searches for BSM physics at collider experiments, probing scales far beyond the reach of present high-energy machines such as the LHC. The reported EDM limits on more complicated polar molecules can be used to deduce a bound of about 10−28 e·cm – which is even further away from the Standard Model prediction (10−38 e·cm) than is the case for the neutron

Perspectives for storage rings

Achievements at COSY

ERC-Advanced grant