electric dipole moments (EDM) Static and oscillating Hans ströher I Matter and the universe days 2019 (desy)

Electric dipole moments Introduction EDM: a permanent separation of positive and negative charge (vector along spin direction) Fundamental property of particles (like mass, charge, magnetic moment) Existence of EDM only possible if violation of time reversal and parity symmetry; note: Close connection to matter-antimatter asymmetry of Universe Sensitive to new physics beyond the Standard Model Axion field (coupling to gluons) leads to oscillating EDM

Electric dipole moments Experimental effort Original by Klaus Jungman

Electric dipole moments Measurements – status and prospects New: charged particles (proton, deuteron …) Potentially highest sensitivity Identification of source requires neutron and proton (maybe even deuteron …) p Current proton limit > neutron; only indirect measurement (199Hg)

Electric dipole moments Measurement principle (charged particles) Longitudinally polarized beam in storage ring Radial electric field interacting with EDM (torque) Observable: slow rotation of spin direction ( polarimetry) Thomas-BMT eq.: Ideal situation: B = 0, magic momentum  WMDM = 0 („frozen spin“)

Electric dipole moments Sensitivities Statistical sensitivity (one cycle): 10.000 cycles (w/ parameters of table): Challenge: Identify and suppress all systematic errors to the same level!

Electric dipole moments Systematic errors – one example Major source: radial magnetic field Br  mimics EDM, if m Br ~ d Er Order of magnitude estimate: assume d = 10-29 e cm, Er = 10 MV/m Corresponding magnetic field Br: ! Potential solution: Use two beams running clockwise and counter-clockwise  Separation of the two beams is sensitive to Br

Electric dipole moments Vision – a dedicated precision pEDM storage ring Electrostatic ring (at least 4 beam bunches) Running at magic momentum (p = 0.7 GeV/c) Counter-rotating beams (simultaneously, same orbit)  many systematic effects cancel  Many open questions, e.g.: Intensity and spin coherence time Injection, phase space cooling of the beams Polarimetry, orbit control, shielding, … General: ideal  realistic machine (tolerances) Staged approach

Electric dipole moments Staged approach COSY

Electric dipole moments Stage-0: recent achievements at COSY (JEDI collaboration) Precise determination of spin tune PR ST-AB (2014), PRL (2015) Long spin coherence time PRL (2016) Phase-lock of spin precession PRL (2017) Polarimeter development Beam instrumentation RF-Wien filter development COSY is world-wide unique to perform these measurements

Electric dipole moments Stage-0: recent achievements at COSY (JEDI collaboration) Precise determination of spin tune PR ST-AB (2014), PRL (2015) Long spin coherence time PRL (2016) Phase-lock of spin precession PRL (2017) Polarimeter development Beam instrumentation RF-Wien filter development COSY is world-wide unique to perform these measurements

Electric dipole moments Stage-1: precursor experiment at COSY COSY (magnetic storage ring)  spin precession; use of deuteron beams Problem: no EDM effect RF Wien Filter: RF-fields such that forward-backward effect does not cancel Sensitivity to EDM Wien Filter EDM (or a field in x): rotates in x-direction (...) 2D map … should have minimum at (0,0) d = 0 or away from (0,0) d > 0 RF Wien Filter invariant spin axis: d = 0 d > 0 Exptl. data (Dec.2018) COSY ? First-ever deuteron EDM measurement Statistical sensitivity 10-(23-24) e cm; systematics: imperfections, alignment, …  limit: ~ 10-19 e cm systematics: imperfections, alignment, …  limit: ~ 10-19 e cm

Electric dipole moments Stage-2: prototype ring 30 MeV all-electric p ring Storage time CW/CCW operation Spin coherence time Polarimetry Phase space cooling mp effects Option: add B-field, 45 MeV pEDM measurement  Possible host: COSY Inevitable next step

Electric dipole moments Stage-3: precision EDM ring All-electric deflection Magic momentum (p = 701 MeV/c) Simultaneous CW/CCW beams Phase-space cooled beams Long spin coherence time (> 1000 s) Non-destructive precision polarimetry Optimum orbit control Optimum shielding of external fields Control of residual (intentional) Br field „Holy Grail“ of storage rings (largest ever conceived)

Electric dipole moments Staged approach Step 1: Precursor Now 5 yrs 10 yrs Step 2: Prototype Step 3: Final ring p Submission to ESPP Update

Electric dipole moments - oscillating Interaction of coherently oscillating axion DM field with gluons … oEDM Static EDM: accumulation in „frozen spin“ condition Oscillating EDM: spin precesses, but oEDM flip  right frequency: accumulation frequency (axion mass) not known  resonance scan Phase unknown static EDM (see above) now: oscillating EDM Oscillating EDM easier to detect (resonance) Proof-of-principle possible at COSY Axion (DM) / oEDM: additional science case for CPEDM

Electric dipole moments Summary Electrostatic storage rings offer a unique possibility to search for important new physics (EDM, DM) Ongoing: precursor experiment at COSY (RF Wien filter) Next step: prototype ring (design study under preparation) Long-term vision: precision storage ring (CW/CCW, magic momentum) Projects discussed in the framework of Physics Beyond Colliders (PBC) at CERN Input for update of European Strategy for Particle Physics (ESPP) 00 Month 2018

Electric dipole moments Experimental EDM limits

Electric dipole moments Experimental EDM limits

Electric dipole moments Why so many (different) experiments? Experiments Theoretical analysis Sources Ultimate goal

Electric dipole moments Dark Matter – accessible frequency/mass range