Search for electric dipole moments at storage rings

Abstract

Permanent electric dipole moments (EDMs) violate parity and timereversal symmetry. Within the Standard Model (SM) they are many orders of magnitude below present experimental sensitivity. Many extensions of the SM predict much larger EDMs, which are therefore an excellent probe for the existence of "new physics". Until recently it was believed that only electrically neutral systems could be used for sensitive searches of EDMs. With the introduction of a novel experimental method, high precision for charged systems will be within reach as well. The features of this method and its possibilities are discussed.Keywords Permanent electric dipole moment · Standard model test · New physics search MotivationThe symmetry properties of fundamental processes and particles are a strong guide to understand the underlying interactions. The QED Lagrangian in the current Standard Model (SM) predicts that all electromagnetic observables are even under the discrete symmetries C (charge conjugation), P (parity) and T (time reversal) individually and thus under each combinations of them. Strong interaction observables, described by QCD, are also predicted to be even under C, P and T , with the exception of those proportional toθ which are P and T -odd [1]. The weak interaction violates both P and C because of the handedness of the coupling of the W and Z-bosons. Many observables are even under their combination CP. Nevertheless, the weak interaction also predicts CP-odd ones. These are all proportional to the Jarlskog invariant, J ∝ sin 2 θ 12 sin θ 23 sin θ 13 sin δ ∼ 3 × 10 −5 [2]. Here θ 12 , θ 23 and θ 13 are the quark flavor mixing angles and δ the CP-violating complex phase associated

Electric dipole moments of nucleons, nuclei, and atoms: The Standard Model and beyond

“…It can be expected that dedicated experiments in rings with optimized parameters will allow sensitive probing of the EDMs of light nuclei. For example, it has been proposed [98,99] that for d p a sensitivity of 10 −16 e fm can be achieved. Similar sensitivity could be attained also for the deuteron ( 2 H nucleus) and helion ( 3 He nucleus) EDMs, d d and d h respectively.…”

“…In addition to the continuous improvement in experiments on neutral systems, a new, exciting prospect is the direct measurement of the EDMs of charged particles in storage rings [98,99]. When a particle moves in an electric and/or magnetic field, its spin will precess at a rate that depends not only on the magnetic dipole moment but also on the EDM.…”

Matter‐antimatter asymmetry ‐ aspects at low energy

“…Another approach towards EDMs are light charged particles or nuclei in magnetic storage rings (see, e.g. [31][32][33]). In such an experiment, an EDM could manifest itself as an out of orbit plane precession of the particle spin.…”

g-2 of the Muon

“…They arise from electromagnetic interactions a would indicate the presence of physics beyond the Standard Model, which is searched for with various approaches in high energy physics, such as, e.g., experiments at LHC or in dedicated precision experiments at lower energies, such as searches for permanent electric dipole moments [8], or violations of fundamental symmetries [9][10][11][12].…”