Measurement of Electric Dipole Moments of Charged Particles in Storage Rings

Size: px

Start display at page:

Download "Measurement of Electric Dipole Moments of Charged Particles in Storage Rings"

Milo Foster
5 years ago
Views:

1 1 / 52 Measurement of Electric Dipole Moments of Charged Particles in Storage Rings J. Pretz RWTH Aachen/ FZ Jülich on behalf of the JEDI collaboration NUPECC workshop, Jülich, March 2013

2 2 / 52 Outline Introduction & Motivation Measurement of charged particle EDMs Jülich efforts to measure EDMs ( Jülich Electric Dipole Moment Investigations (JEDI) collaboration) Summary

3 Introduction & Motivation 3 / 52

4 4 / 52 Electric Dipoles Classical definition: r 1 d = q i r i i 0 + r 2

5 5 / 52 Order of magnitude atomic physics: q 1 = q 2 = e, r 1 r 2 = 1Å= m d = 8 e cm Water molecule: d = 2 9 e cm

6 6 / 52 Order of magnitude atomic physics: q 1 = q 2 = e, r 1 r 2 = 1Å= m d = 8 e cm Water molecule: d = 2 9 e cm hadron physics: r 1 r 2 = 1fm = 13 cm d = 13 e cm Limit on neutron EDM < 3 26 e cm

7 7 / 52 Operator d = q r is odd under parity transformation ( r r): P 1 dp = d Consequences: In a state a of given parity the expectation value is 0: a d a = a d a If a = α P = + + β P = in general a d a 0

8 8 / 52 Order of magnitude Molecules can have large EDM because of degenerated ground states with different parity

9 9 / 52 Order of magnitude Molecules can have large EDM because of degenerated ground states with different parity Elementary particles (including hadrons) have a definte parity and cannot posess an EDM P had >= ±1 had >

10 / 52 Order of magnitude Molecules can have large EDM because of degenerated ground states with different parity Elementary particles (including hadrons) have a definte parity and cannot posess an EDM P had >= ±1 had > unless P and time reversal T invariance are violated!

11 11 / 52 T and P violation of EDM d: EDM µ: magnetic moment both to spin s H = µ σ B d σ E d µ P + T : H = µ σ B+d σ E + P : H = µ σ B+d σ E - T + EDM measurement tests violation of fundamental symmetries P and T ( CPT = CP)

12 12 / 52 CP violation We are surounded by matter (and not anti matter) η = n B n B n γ = Starting from equal amount of matter and anti-matter at the Big Bang, from CP-violation in Standard Model we expect only 18 In 1967 Sakharov formulated three prerequisites for baryogenesis. One of these is the combined violation of the charge and parity, CP, symmetry. New CP violating sources outside the realm of the SM are clearly needed to explain this discrepancy of eight orders of magnitude. They could manifest in EDMs of elementary particles

13 Sources of CP violation 13 / 52

14 14 / 52 Sources of CP violation It is mandatory to measure EDM of many different particles to disentangle various sources of CP violation.

15 15 / 52 What do we know about EDMs? edm/e cm SUSY deuteron Λ 199 proton ( Hg) neutron muon tau electron (YbF) Standard Model?

16 16 / 52 What do we know about EDMs? edm/e cm SUSY Λ proton ( neutron muon tau electron (YbF) Standard Model 199 Hg)? deuteron no EDM observed yet, only limits

17 17 / 52 What do we know about EDMs? edm/e cm SUSY Λ proton ( neutron muon tau electron (YbF) Standard Model 199 Hg)? deuteron no EDM observed yet, only limits no measurement for deuteron (or heavier nuclei),

18 18 / 52 What do we know about EDMs? edm/e cm SUSY Λ proton ( neutron muon tau electron (YbF) Standard Model 199 Hg)? deuteron no EDM observed yet, only limits no measurement for deuteron (or heavier nuclei), no direct measurement for proton

19 19 / 52 What do we know about EDMs? edm/e cm SUSY Λ proton ( neutron muon tau electron (YbF) Standard Model 199 Hg)? deuteron no EDM observed yet, only limits no measurement for deuteron (or heavier nuclei), no direct measurement for proton Standard Model value essentially 0

20 What do we know about EDMs? edm/e cm SUSY Λ proton ( neutron muon tau electron (YbF) Standard Model 199 Hg)? deuteron no EDM observed yet, only limits no measurement for deuteron (or heavier nuclei), no direct measurement for proton Standard Model value essentially 0 Beyond SM values accessible by experiments 20 / 52

21 What do we know about EDMs? edm/e cm SUSY Λ proton ( neutron muon tau electron (YbF) Standard Model 199 Hg)? deuteron GOAL of JEDI collaboration: First measurement of deuteron, 3 He EDM, first direct measurement of proton EDM ultimately with a precision of 29 e cm 21 / 52

22 22 / 52 History of Neutron EDM 50 years of effort Extensions of SM allow for large EDMs from K. Kirch

23 Measurement of charged particle EDMs 23 / 52

24 Measurement of charged particle EDMs General Idea: For all edm experiments (neutron, proton, atom,... ): Interaction of d with electric field E For charged particles: apply electric field in a storage ring: d s dt = E d φ s E Wait for build-up of vertical polarization s d, then determine s using polarimeter In general: d s = Ω dt s 24 / 52

25 25 / 52 Thomas-BMT formula ( ) Ω = e mc [G B+ G 1 v E+ 1 γ η( E+ v B)] e d = η S, 2mc µ = 2(G + 1) e S, 2m G = g 2 2, g:g factor Several Options (try to get rid terms G):

26 26 / 52 Thomas-BMT formula ( ) Ω = e mc [G B+ G 1 v E+ 1 γ η( E+ v B)] e d = η S, 2mc µ = 2(G + 1) e S, 2m G = g 2 2, g:g factor Several Options (try to get rid terms G): 1 Pure( electric ring with G 1 ) γ 2 = 0, works only for G > 0 1

27 27 / 52 Thomas-BMT formula ( ) Ω = e mc [G B+ G 1 v E+ 1 γ η( E+ v B)] e d = η S, 2mc µ = 2(G + 1) e S, 2m G = g 2 2, g:g factor Several Options (try to get rid terms G): 1 Pure( electric ring with G 1 ) γ 2 = 0, works only for G > Combined ( E/ B ring GB + G 1 ) v γ 2 E 1 = 0

28 28 / 52 Thomas-BMT formula ( ) Ω = e mc [G B+ G 1 v E+ 1 γ η( E+ v B)] e d = η S, 2mc µ = 2(G + 1) e S, 2m G = g 2 2, g:g factor Several Options (try to get rid terms G): 1 Pure( electric ring with G 1 ) γ 2 = 0, works only for G > Combined ( E/ B ring GB + G 1 ) v γ 2 E 1 = 0 3 Pure magnetic ring

29 Required field strength G = g 2 2 p/gev/c E R /MV/m B V /T proton deuteron He Ring radius 40m Smaller ring size possible if B V 0 for proton E = GBcβγ2 1 + Gβ 2 γ 2 29 / 52

30 1. Pure Electric Ring Brookhaven National Laboratory (BNL) Proposal 30 / 52

31 2. Combined E/ B ring Under discussion in Jülich (design: R. Talman) 31 / 52

32 3. Pure Magnetic Ring Main advantage: Experiment can be performed at the existing (upgraded) COSY (COoler SYnchrotron) in Jülich on a shorter time scale! COSY provides (polarized ) protons and deuterons with p = GeV/c Ideal starting point 32 / 52

33 Ω = e ( GB mc + 1 ) 2 η v B 3. Pure Magnetic Ring Problem: Due to precession caused by magnetic moment, 50% of time longitudinal polarization component is to momentum, 50% of the time it is anti-. E = v B s p 50% s d = B 50% s d = E 33 / 52

34 Ω = e ( GB mc + 1 ) 2 η v B 3. Pure Magnetic Ring Problem: Due to precession caused by magnetic moment, 50% of time longitudinal polarization component is to momentum, 50% of the time it is anti-. s p E = v B 50% s d = E field in the particle rest frame tilts spin due to EDM up and down no net EDM effect B 50% s d = E 34 / 52

35 Ω = e ( GB mc + 1 ) 2 η v B 3. Pure Magnetic Ring Problem: Due to precession caused by magnetic moment, 50% of time longitudinal polarization component is to momentum, 50% of the time it is anti-. s p E = v B > 50% s d = <50% s d = E E field in the particle rest frame tilts spin due to EDM up and down no net EDM effect Use resonant magic Wien-Filter B in ring ( E + v B = 0): E = 0 part. trajectory is not affected but B 0 mag. mom. is influenced net EDM effect can be observed! 35 / 52

36 36 / 52 Summary of different options 1.) pure electric ring no B field needed works only for p (BNL) 2.) combined ring works for p, d, 3 He,... both E and B (Jülich) required 3.) pure magnetic ring existing (upgraded) COSY lower sensitivity (Jülich) ring can be used, shorter time scale

37 37 / 52 σ NfT τp PEA Statistical Sensitivity P beam polarization 0.8 τ p Spin coherence time/s 00 E Electric field/mv/m A Analyzing Power 0.6 N nb. of stored particles/cycle 4 7 f detection efficiency T running time per year/s 7 σ 29 e cm/year (for magnetic ring 24 e cm/year) Expected signal 3nrad/s (for d = 29 e cm) (BNL proposal)

38 38 / 52 Results on Spin Coherence Time (SCT) Spins decohere during storage time results form Cosy run May 2012 using correction sextupole SCT increase from a few s to 200s already reached (Ed. Stephenson)

39 39 / 52 Systematics One major source: Radial B field mimics an EDM effect: Difficulty: even small radial magnetic field, B r can mimic EDM effect if :µb r de r Suppose d = 29 e cm in a field of E = MV/m This corresponds to a magnetic field: B r = de r 22 ev = µ N ev/t 3 17 T (Earth Magnetic field 5 5 T) Solution: Use two beams running clockwise and counter clockwise, separation of the two beams is sensitive to B r

40 Jülich efforts to measure EDMs 40 / 52

41 41 / 52 JEDI Collaboration JEDI = Jülich Electric Dipole Moment Investigations 80 members (Aachen, Dubna Ferrara, Ithaca, Jülich, Krakow, Michigan, St. Petersburg, Minsk, Novosibirsk, Stockholm, Tbilisi,... ) PhD students

42 42 / 52 Stepwise approach of JEDI project in Jülich JEDI = Jülich Electric Dipole Moment Investigations 1 Spin coherence time studies Systematic Error studies 2 COSY upgrade first (direct) measurement of p and d at 24 e cm 3 Build dedicated ring for p,d and 3 He 4 EDM measurement at 29 e cm

43 43 / 52 Storage Ring EDM Efforts BNL Common R&D work Spin Coherence Time BPMs Spin Tracking Polarimetry... all electric ring (p) Jülich first direct measuremet with upgraded COSY all-in-one ring (p,d, 3 He)

44 JARA FAME JARA=Jülich Aachen Research Alliance New section founded: FAME (=Forces and Matter Experiments) Is there anti-matter in the Universe? yes no AMS will discover it! JEDI will discover it! 44 / 52

45 45 / 52 Summary EDM of charged particles can be measured in storage rings EDM of various hadrons species are of high interest to disentangle various sources of CP violation searched for to explain matter - antimatter asymmetry in the Universe Experimentally very challenging because effect is tiny Efforts at Brookhaven and Jülich to perform such measurements

46 Spare 46 / 52

47 EDM of molecules z z H H N H x H y H x H N y Ψ 1 Ψ 2 z z ground state: mixture of Ψ s = 1 2 (Ψ 1 + Ψ 2 ) P = + Ψ a = 1 (Ψ 2 1 Ψ 2 ) P = (allmost) degenerated states with different parity: a >= α Ψ s > +β Ψ a > (Cohen-Tannoudji, B. Diu, F. Laloë, Mécanique quantique) 47 / 52

48 48 / 52 Main Challenges Spin Coherence Time (SCT) 00s Polarimetry on 1 ppm level (ppm = part per million) Beam positioning nm (relative between CW-CCW) Field Gradients MV/m

49 49 / 52 Spin Coherence Time (SCT) Usally we dont care about decoherence of spins because polarisation with respect to invariant spin axis n is the same. Situation is different if S n Longitudinal Polarization is lost.

50 50 / 52 Polarimeter Principle: Particles hit a target: Left/Right asymmetry gives information on EDM Up/Down asymmetry gives information on g-2

51 51 / 52 Polarimeter Cross Section & Analyzing Power for deuterons

52 52 / 52 Available at COSY for tests: EDDA polarimeter Polarimeter

Storage Ring Based EDM Search Achievements and Goals

Mitglied der Helmholtz-Gemeinschaft Storage Ring Based EDM Search Achievements and Goals October 20, 2014 Andreas Lehrach RWTH Aachen University & Forschungszentrum Jülich on behalf of the JEDI collaboration