Charged Particle Electric Dipole Moment Searches in Storage Rings

Transcription

1 1 / 87 Charged Particle Electric Dipole Moment Searches in Storage Rings J. Pretz RWTH Aachen & FZ Jülich for the JEDI collaboration Axions and the Low Energy Frontier, Bonn, März 2016

2 2 / 87 Outline Introduction: Electric Dipole Moments (EDMs): What is it? Why is it interesting? What do we know about EDMs? Experimental Method: How to measure charged particle EDMs? Recent Achievements: Spin- Coherence Time Tune Feedback Tracking

3 What is it? 3 / 87

4 4 / 87 Electric Dipoles Classical definition: r 1 d = q i r i i 0 + r 2

5 5 / 87 Order of magnitude charges r 1 r 2 EDM naive expectation observed atomic physics e 1 Å= 10 8 cm 10 8 e cm water molecule e cm hadron physics

6 6 / 87 Order of magnitude atomic physics hadron physics charges e e r 1 r 2 1 Å= 10 8 cm 1fm = cm EDM naive expectation 10 8 e cm e cm observed water molecule neutron e cm < e cm

7 7 / 87 Neutron EDM d r n cm neutron EDM of d n = e cm corresponds to separation of u from d quarks of cm

8 8 / 87 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 but if a = α P = + + β P = in general a d a 0 i.e. molecules

9 9 / 87 EDM of molecules x z N H H y H x z H H N H y Ψ 1 z Ψ 2 z ground state: mixture of Ψ s = 1 2 (Ψ 1 + Ψ 2 ), P = + Ψ a = 1 2 (Ψ 1 Ψ 2 ), P =

10 10 / 87 EDMs & symmetry breaking Molecules can have large EDM because of degenerated ground states with different parity

11 11 / 87 EDMs & symmetry breaking Molecules can have large EDM because of degenerated ground states with different parity Elementary particles (including hadrons) have a definite parity and cannot posses an EDM P had >= ±1 had >

12 12 / 87 EDMs & symmetry breaking Molecules can have large EDM because of degenerated ground states with different parity Elementary particles (including hadrons) have a definite parity and cannot posses an EDM P had >= ±1 had > unless P and time reversal T invariance are violated!

13 13 / 87 T and P violation of EDM d: EDM µ: magnetic moment both to spin H = µ σ B d σ E T : H = µ σ B+d σ E P : H = µ σ B+d σ E s d µ + P T + + EDM measurement tests violation of fundamental symmetries P and T ( CPT = CP)

14 14 / 87 Symmetry (Violations) in Standard Model electro-mag. weak strong C P ( ) T CPT CP ( ) ( ) C and P are maximally violated in weak interactions (Lee, Yang, Wu) CP violation discovered in kaon decays (Cronin,Fitch) described by CKM-matrix in Standard Model CP violation allowed in strong interaction but corresponding parameter θ QCD (strong CP-problem)

15 15 / 87 Sources of CP Violation and connection to EDMs Standard Model Weak interaction CKM matrix unobservably small EDMs Strong interaction θ QCD e.g. SUSY best limit from neutron EDM beyond Standard Model accessible by EDM measurements

16 Why is it interesting? 16 / 87

17 17 / 87 Matter-Antimatter Asymmetry Excess of matter in the universe: observed η = n B n B n γ SM prediction Sakharov (1967): CP violation needed for baryogenesis New CP violating sources beyond SM needed to explain this discrepancy They could manifest in EDMs of elementary particles

18 What do we know about EDMs? 18 / 87

19 History of Neutron EDM 19 / 87

20 20 / 87 EDM: Current Upper Limits cm edm/e SUSY ( α π <ϕ tau muon electron (YbF, ThO) <1) CP Λ 199 proton ( Hg) neutron Standard Model (θ QCD =0) deuteron

21 21 / 87 EDM: Current Upper Limits cm edm/e SUSY ( α π <ϕ tau muon electron (YbF, ThO) <1) CP Λ 199 proton ( Hg) neutron Standard Model (θ QCD =0) deuteron Goal exp. at -24 COSY (10 e cm) Goal dedicated -29 ring (10 e cm) FZ Jülich: EDMs of charged hadrons: p, d, 3 He

22 22 / 87 Why Charged Particle EDMs? no direct measurements for charged hadrons exist potentially higher sensitivity (compared to neutrons): longer life time, more stored protons/deuterons complementary to neutron EDM:? d d = dp + d n access to θ QCD EDM of one particle alone not sufficient to identify CP violating source

23 23 / 87 Sources of CP Violation Neutron, Proton Nuclei: 2 H, 3 H, 3 He Diamagne?c atoms: Hg, Xe, Ra Paramagne?c atoms: Tl, Cs Molecules: YbF, ThO, HfF + atomic theory nuclear theory QCD (including θ- term) quark EDM quark chromo- EDM gluon chromo- EDM four- quark operators lepton- quark operators FUNDAMENTAL THEORY Leptons: muon lepton EDM J. de Vries

24 How to measure charged particle EDMs? 24 / 87

25 25 / 87 Experimental Method: Generic Idea For all EDM experiments (neutron, proton, atoms,... ): Interaction of d with electric field E For charged particles: apply electric field in a storage ring: d s dt d E s In general: s E d s dt = Ω s build-up of vertical polarization s d

26 26 / 87 Experimental Requirements high precision storage ring systematics ( alignment, stability, field homogeneity) high intensity beams (N = per fill) polarized hadron beams (P = 0.8) long spin coherence time (τ = 1000 s), large electric fields (E = 10 MV/m) polarimetry (analyzing power A = 0.6, acc. f = 0.005) σ stat 1 Nf τpae σ stat (1year) = e cm challenge: get σsys to the same level

27 27 / 87 Systematics 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 = e cm in a field of E r = 10MV/m This corresponds to a magnetic field: B r = de r ev = µ N ev/t T Solution: Use two beams running clockwise and counter clockwise, separation of the two beams is sensitive to B r

28 28 / 87 Systematics ee v evb r ee v mg evb r mg Sensitivity needed: 1.25 ft/ Hz for d = e cm (possible with SQUID technology)

29 29 / 87 Spin Precession: Thomas-BMT Equation d s dt = Ω ( ) s = e m [G B+ G 1 v E+ m γ 2 1 e s d( E+ v B)] s Ω: angular precession frequency d: electric dipole moment G: anomalous magnetic moment γ: Lorentz factor BMT: Bargmann, Michel, Telegdi

30 30 / 87 Spin Precession: Thomas-BMT Equation d s dt = Ω ( ) s = e m [G B+ G 1 v E+ m γ 2 1 e s d( E+ v B)] s Ω: angular precession frequency d: electric dipole moment G: anomalous magnetic moment γ: Lorentz factor dedicated ring: pure electric field, ( ) freeze horizontal spin motion G 1! = 0 γ 2 1 only possible if G > 0 (i.e. protons)

31 31 / 87 Spin Precession: Thomas-BMT Equation d s dt = Ω ( ) s = e m [G B+ G 1 v E+ m γ 2 1 e s d( E+ v B)] s Ω: angular precession frequency d: electric dipole moment G: anomalous magnetic moment γ: Lorentz factor dedicated ring: pure electric field, ( ) freeze horizontal spin motion G 1! = 0 γ 2 1 only possible if G > 0 (i.e. protons) combined E/B ring G B + (G 1 γ 2 1 ) v E! = 0

32 32 / 87 Spin Precession: Thomas-BMT Equation d s dt = Ω ( ) s = e m [G B+ G 1 v E+ m γ 2 1 e s d( E+ v B)] s Ω: angular precession frequency d: electric dipole moment G: anomalous magnetic moment γ: Lorentz factor COSY: pure magnetic ring access to EDM via motional electric field v B, requires additional radio-frequency E and B fields to suppress GB contribution

33 33 / 87 Spin Precession: Thomas-BMT Equation d s dt = Ω ( ) s = e m [G B+ G 1 v E+ m γ 2 1 e s d( E+ v B)] s Ω: angular precession frequency d: electric dipole moment G: anomalous magnetic moment γ: Lorentz factor COSY: pure magnetic ring access to EDM via motional electric field v B, requires additional radio-frequency E and B fields to suppress GB contribution neglecting EDM term spin tune: ν s Ω ω cyc = γg, ( ω cyc = e γm B)

34 34 / 87 Summary of different options 1.) pure magnetic ring existing (upgraded) COSY lower sensitivity ring can be used, shorter time scale 2.) pure electric ring no B field needed works only for p 3.) combined ring works for p, d, 3 He,... both E and B required

35 35 / 87 Ring Design with E/B elements B = 0.46 T, E = 12 MV/m Y. Senichev

36 Results of first test measurements 36 / 87

37 Cooler Synchrotron COSY COSY provides (polarized ) protons and deuterons with p = GeV/c Ideal starting point for charged particle EDM searches 37 / 87

38 38 / 87 RF E B dipole COSY RF solenoid Polarimeter sextupoles cooled beams: e-cooling, Polarized proton & deuterons stochastic cooling

39 39 / 87 R & D at COSY maximize spin coherence time (SCT) precise measurement of spin precession (spin tune) spin feed back spin tracking simulation tools rf- Wien filter design and construction tests of electro static deflectors (goal: field strength > 10 MV/m) development of high precision beam position monitors polarimeter development

40 40 / 87 Experimental Setup Inject and accelerate vertically polarized deuterons to p 1 GeV/c

41 41 / 87 Experimental Setup Inject and accelerate vertically polarized deuterons to p 1 GeV/c flip spin with help of solenoid into horizontal plane

42 42 / 87 Experimental Setup Inject and accelerate vertically polarized deuterons to p 1 GeV/c flip spin with help of solenoid into horizontal plane Extract beam slowly (in 100 s) on target Measure asymmetry and determine spin precession

43 43 / 87 Asymmetry Measurements Detector signal N up,dn (1 ± P A sin(γgω rev t)) A up,dn = Nup N dn N up + N dn = P A sin(γgω revt) A: analyzing power, P : polarization A up,dn = 0 spin p C A up,dn = PA spin p C

44 44 / 87 Polarimetry Cross Section & Analyzing Power for deuterons N up,dn (1 ± P A sin(ν s ω rev t)) A up,dn = Nup N dn N up + N dn = P A sin(ν s ω rev t) A : analyzing power P : beam polarization

45 45 / 87 Polarimeter elastic deuteron-carbon scattering Up/Down asymmetry horizontal polarization ν s = γg Left/Right asymmetry vertical polarization d spin N up,dn 1 ± PA sin(ν s ω rev t), f rev 750 khz

46 46 / 87 Up - dn asymmetry A up,dn A up,dn (t) = AP 0 e t/τ sin(ν s ω rev t + ϕ) τ spin decoherence ν s spin tune time scales: ν s f rev 120 khz τ in the range s

47 Polarization Flip Left-Right-Asymmetry P y time in s envelope of Up-Down-Asymmetry P x time in s 47 / 87

48 Polarization Flip Left-Right-Asymmetry P y time in s y envelope of Up-Down-Asymmetry P x time in s x z 48 / 87

49 Polarization Flip Left-Right-Asymmetry P y time in s y envelope of Up-Down-Asymmetry P x time in s x z 49 / 87

50 Results: Spin Coherence Time (SCT) Short Spin Coherence Time Horizontal Asymmetry Run: 2042 UD Asymmetry 0.25 χ 2 / ndf / Amplitude ± SCT ± time[s] unbunched beam p/p = 10 5 γ/γ = , T rev 10 6 s decoherence after < 1 s bunched beam eliminates 1st order effects in p/p SCT τ = 20 s 50 / 87

51 51 / 87 Results: Spin Coherence Time (SCT) Long Spin Coherence Time Horizontal Asymmetry Run: 2051 Asymmetry UD χ 2 / ndf 93.9 / Amplitude ± ± SCT time[s] SCT of τ =400 s, after correction with sextupoles (chromaticities ξ 0)

52 52 / 87 SCT: Longer Cycles preliminary

53 Spin tune: ν s = γg = s p Spin Tune ν s nb. of spin rotations nb. of particle revolutions 2πγG B deuterons: p d = 1 GeV/c ( γ = 1.13), G = (72) ν s = γg / 87

54 54 / 87 Results spin tune time [s] ϕ [rad] sin(ν s(t)ω revt + ϕ) = sin(ν 0 s ω revt + ϕ(t) ) number of particle turns [10 ]

55 Results spin tune time [s] ϕ [rad] sin(ν s(t)ω revt + ϕ) = sin(ν 0 s ω revt + ϕ(t) ) ] 9 ν s [ σ νs number of particle turns [10^6] 55 / 87

56 Results spin tune time [s] ϕ [rad] sin(ν s(t)ω revt + ϕ) = sin(ν 0 s ω revt + ϕ(t) ) ] 9 ν s [ σ νs 10 8 ] 9 ν s [ σ νs number of particle turns [10 ] 56 / 87

57 57 / 87 Spin Tune Measurement B P = s i f rev f s = ν s f rev precision in one cycle of 100 s (translated to angle, precision is 2 π = 0.6 nrad) spin tune measurement can now be used as tool to investigate systematic errors spin tune measurement allows for feedback system to keep polarisation aligned with momentum vector for dedicted ring or at a given phase with respect to radiofrequency Wien filter

58 58 / 87 Spin Feed back system polarisation rotation in horizontal plane at t = 85 s COSY rf changed during cycle in steps of 3.7 mhz (f rev = Hz) according to online ν s measurement to keep spin precession and solenoid RF constant solenoid (low amplitude) switched on at t = 115 s polarisation goes back to vertical direction

59 59 / 87 Simulations EDM signal is build-up of vertical polarisation radial magnetic fields (B r ) cause the same build-up misalignments of quadrupoles create for example unwanted B r Run simulations to understand systematic effects General problem: Track 10 9 particles for 10 9 turns! ( use transfer maps of magnet elements (code: COSY Infinity)) orbit RMS y RMS is measure of misalignments

60 60 / 87 Spin Tracking = 0) S y per turn (φ η -4 =10 EDM =10 EDM η η =0 EDM mm y in mm RMS Random Misalignments from 1µm to 1 mm η = 10 5 corresponds to edm of e cm M. Rosenthal

61 61 / 87 JEDI Collaboration JEDI = Jülich Electric Dipole Moment Investigations 100 members (Aachen, Bonn, Daejeon, Dubna, Ferrara, Grenoble, Indiana, Ithaca, Jülich, Krakow, Michigan, Minsk, Novosibirsk, St. Petersburg, Stockholm, Tbilisi,... ) 10 PhD students close collaboration with sredm collaboration in US/Korea

62 62 / 87 Summary & Outlook EDMs of elementary particles are of high interest to disentangle various sources of CP violation searched for to explain matter - antimatter asymmetry in the Universe EDM of charged particles can be measured in storage rings Experimentally very challenging because effect is tiny First promising results: spin coherence time: spin tune: feed back system simulations few hundred seconds in 100 s allows to control spin to understand systematics

63 Spare 63 / 87

64 64 / 87 Up - dn asymmetry A up,dn Long SCT τ allows now to observe ν s (t) γg, respectively ϕ(t) A up,dn (t) = AP 0 e t/τ sin(ν s (t)ω rev t + ϕ) = AP 0 e t/τ sin(ν 0 s ω rev t + ϕ(t))

65 Phase vs. turn number time [s] ν 0 s [rad] ϕ number of particle turns [10 ] ν s (t) = νs d ϕ ω rev dt ν s (38 s) = ( ± 9.7) /

66 Preliminary 66 / 87 Spin Tune for different cycles 10 5 P ξ up P ξ down ] 9 [10 ν s ν s = 10 8 p/p 10 7 time [s]

67 Spin Tune jumps 67 / 87

68 68 / 87 Event Distribution Time within turn in ns Turn 1 6

69 69 / 87 SCT Chromaticity I Chromaticities vs. tune giving maximal SCT according to simulation Chromaticity Chromaticity X Chromaticity Y Vertical Betatron Tune Q y

70 70 / 87 SCT Chromaticity II Chromaticities vs. sextupole setting Chromaticity Chromaticity X Chromaticity Y MXS in m

71 71 / 87 SCT vs. sextupole setting SCT Chromaticity I Maximal SCT for predicted sextupole setting

72 72 / 87 SCT chromaticity chromaticity ξ = Q/( p/p) T = L β T 0 L 0 β 0... means time average for one particle because of bunched beam: T = 0 T 0 betatron oscillations leads to L 0 L 0 β β 0 0 ν s ν s 0 sextupole settings gives access to L L 0 x,y = π L 0 ɛ x,y ξ x,y

73 Spin Tune as tool to investigate systematics ν s = γg + imperfections kicks Create artificial imperfections with solenoids/steerers measure spin tune change ν s expectation ν s (y ± a ± ) 2 a ± : kicks due to imperfections, y ± : kicks due to solenoids 73 / 87

74 parabolic behavior expected from simulations y ± = χ 1 ± χ 2, χ 1,2 : solenoid strength 2 for perfect machine, minimum should be at y + = 0 74 / 87

75 parabolic behavior expected from simulations y ± = χ 1 ± χ 2, χ 1,2 : solenoid strength 2 for perfect machine, minimum should be at y + = 0 75 / 87

76 76 / 87 Electron and Neutron EDM J. M. Pendlebury & E.A. Hinds, NIMA 440(2000) 471

77 77 / 87 EDM: SUSY Limits electron: MSSM: ϕ 1 d = e cm ϕ α/π d = e cm neutron: MSSM: d = e cm sin φ CP 200GeV M SUSY

78 78 / 87 SM EDM values µ n = e ecm (CP & P conserving) 2m p d n = }{{} P violation 10 }{{ 3 } G F F }{{ π } = ecm CP violation no flavor change d n = O(g 4 wg 2 s ) = O(G 2 F g2 s ) (3loop) d e = O(g 6 wg 2 s ) = O(G 3 F g2 s ) (4loop)

79 79 / 87 Electrostatic Deflectors Electrostatic deflectors from Fermilab (±125kV at 5 cm ˆ= 5MV/m) large-grain Nb at plate separation of a few cm yields 20MV/m

80 Wien Filter Conventional design R. Gebel, S. Mey (FZ Jülich) stripline design D. Hölscher, J. Slim (IHF RWTH Aachen) 80 / 87

81 81 / 87 d s dt = Ω s = e m Pure Magnetic Ring ( GB + m es d v B ) s 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

82 d s dt = Ω s = e m Pure Magnetic Ring ( GB + m es d v B ) s 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 B E field in the particle rest frame tilts spin due to EDM up and down no net EDM effect Use resonant magic Wien-Filter in ring ( E W + v B W = 0): EW = 0 part. trajectory is not affected but BW 0 mag. mom. is influenced net EDM effect can be observed! 82 / 87

83 83 / 87 Spin Precession: Thomas-BMT Equation d s dt = Ω ( ) s = e m [G B+ G 1 v E+ m γ 2 1 e s d( E+ v B)] s Ω: angular precession frequency d: electric dipole moment G: anomalous magnetic moment γ: Lorentz factor COSY: pure magnetic ring access to EDM via motional electric field v B, requires additional radio-frequency E and B fields to suppress GB contribution neglecting EDM term spin tune: ν s Ω ω cyc = γg, ( ω cyc = e γm B)

84 84 / Pure Electric Ring Brookhaven National Laboratory (BNL) Proposal

85 85 / Combined E/ B ring Under discussion at Forschungszentrum Jülich (design: R. Talman)

86 86 / 87 EDM Activities Around the World K. Kirch

87 87 / 87 Systematics Splitting of beams: δy = ± βcr 0B r E r Qy 2 Q y 0.1: vertical tune = ± m Modulate Q y = Q 0 y (1 m cos(ω m t)), m 0.1 Splitting causes B field of ft in one year: 10 4 fills of 1000 s σ B = ft per fill needed Need sensitivity 1.25 ft/ Hz D. Kawall