In-beam measurement of the hydrogen hyperfine splitting: towards antihydrogen spectroscopy Martin Diermaier LEAP 2016 Kanazawa Japan Martin Diermaier Stefan-Meyer-Institute March th 2016
MOTIVATION Charge particle - antiparticle Parity spatial mirror Time reversal CPT symmetry Combined symmetry of charge parity and time reversal same properties for particles and antiparticles No violation observed to date slide 2
PRECISION -18-15 -12-9 -6 Mass [ev] -3 1 3 6 9 12 e - -e + absolute precision (left edge) = relative precision (length) measured quantity (right edge) n-n p-p maser atomic beam 0 0 K -K H-H ν 1s-2s H-H ν HFS -12-9 -6-3 3 6 1 Frequency Energy [GHz]] 9 12 15 GS-HFS of Hydrogen / Antihydrogen offers best test of CPT on absolute scale slide 3
HYDROGEN / ANTIHYDROGEN 1s-2s 2 photon transition λ = 243 nm Δν/ν = -14 ground state HFS ν = 1.42 GHz Δν/ν = -12 slide 4
GROUND STATE HYPERFINE SPLITTING OF ANTIHYDROGEN Breit-Rabi diagram 2.0 1.5 1.0 H π1 σ1 π 2 (F,M)=(1,-1) 1 2 e + p low-field seekers Coupling of angular momentum of proton and electron - spin spin Interaction Splits into Singlet state Triplet state (GHz) ν 0.5 0.0-0.5-1.0 3 (F,M)=(0,0) -1.5 4-2.0 0.00 0.02 0.04 0.06 0.08 0. B (T) (F,M)=(1,0) (F,M)=(1,1) high-field seekers slide 5
GROUND STATE HYPERFINE SPLITTING OF ANTIHYDROGEN Breit-Rabi diagram Zeeman effect: energy levels shifted in external field 2.0 1.5 1.0 H π1 σ1 π 2 (F,M)=(1,-1) 1 2 e + p low-field seekers In an inhomogeneous magnetic field states can be classified into (GHz) ν 0.5 0.0-0.5 (F,M)=(1,0) (F,M)=(1,1) ~F = r(~µ ~ ~B) / grad B Low field seekers move in direction lower magn. Field High field seekers move in direction higher magn. field -1.0 3 (F,M)=(0,0) -1.5 4-2.0 0.00 0.02 0.04 0.06 0.08 0. B (T) Achievable resolution: -6 for T< 0 K scan in reasonable time: 0 Hbar/s in 1s state into 4π needed event rate 1/min slide 6 high-field seekers
GROUND STATE HYPERFINE SPLITTING OF ANTIHYDROGEN 2.0 two transitions possible 1.5 H with cavity σ 1 transition σ 1 1.0 π1 σ1 π 2 (F,M)=(1,-1) 1 2 e + p low-field seekers ν (GHz) 0.5 0.0-0.5 (F,M)=(1,0) (F,M)=(1,1) -1.0 3 (F,M)=(0,0) -1.5 4-2.0 0.00 0.02 0.04 0.06 0.08 0. B (T) Achievable resolution: -6 for T< 0 K scan in reasonable time: 0 Hbar/s in 1s state into 4π needed event rate 1/min slide 7 high-field seekers
GROUND STATE HYPERFINE SPLITTING OF ANTIHYDROGEN two transitions possible with cavity σ 1 transition π 1 transition (GHz) ν 2.0 1.5 1.0 0.5 0.0-0.5 H π 1 π1 σ1 π 2 (F,M)=(1,-1) (F,M)=(1,0) (F,M)=(1,1) 1 2 e + p low-field seekers -1.0 3 (F,M)=(0,0) -1.5 4-2.0 0.00 0.02 0.04 0.06 0.08 0. B (T) Achievable resolution: -6 for T< 0 K scan in reasonable time: 0 Hbar/s in 1s state into 4π needed event rate 1/min slide 8 high-field seekers
GROUND STATE HYPERFINE SPLITTING OF ANTIHYDROGEN & MINIMAL SME ν 1 ΔB LIV 4 ν 0 2.0 1.5 1.0 H π1 σ1 π 2 (F,M)=(1,-1) 1 2 e + p low-field seekers 0 B ν (GHz) 0.5 0.0-0.5 (F,M)=(1,0) (F,M)=(1,1) in minimal SME HFS shows CPT violation HFS: Splitting of triplet even in zero field no effect on σ 1 1s-2s no effect -1.0 3 (F,M)=(0,0) -1.5 4-2.0 0.00 0.02 0.04 0.06 0.08 0. B (T) high-field seekers Kostelecký, V. A., & Vargas, A. J. Lorentz and CPT tests with hydrogen, antihydrogen, and related systems. Physical Review D, 92(5), 056002 (2015) slide 9
HISTORY OF HYDROGEN GS-HFS 1936 Simple atomic beams ~5% 1946 Atomic beams plus 4 x -6 microwave resonance 1955 4 x -8 1969-70 Hydrogen maser 6 x -13 Not possible for antimatter Molecular Beam Resonance Setup I.I.Rabi et al., Phys. Rev. 55, 526 (1939) slide
ASACUSA S APPROACH RABI BEAM EXPERIMENT spin flip analyser produc8on region detector cavity already reported by Y. Nagata (Monday) double cusp sextupole same for hydrogen slide 11
HYDROGEN BEAM LINE slide 12
DIFFERENCES H/HBAR beam production rate Hbar low ~ per min detection efficiency approximately ~0.9 B. Kolbinger (Poster) detection method background annihilation products, tracking cosmic radiation supressed by tracking H very high 19 per minute detector -8-9 + solid angle electron impact ionization and single ion counting residual gas background >> signal slide 13
ATOMIC HYDROGEN SOURCE plasma induced by microwaves with f = 2.45 GHz H cooled with coldhead H - α (n: 3è2) H β (n: 4è2) H γ (n: 5è2) R.W. McCullough, J. Geddes, A. Donnelly, M. Liehr and H.B. Gilbody NIM B79, 708-7 (1993) slide 14
POLARIZATION PERMANENT SEXTUPOLE MAGNETS polarization gained with a set of perm. sextupole magnets in Halbach array B max = 1.3 T, 6 cm long, 1 cm inner diameter each V too high low field seekers focused V accepted high field seekers defocused V too low changing the distance to each other selects velocity slide 15
CAVITY SPIN FLIP RESONATOR Rubidium frequency standard spectrum analyser 50 Ω signal generator CAVITY amplifier stub tuner Helmholtz coils for static magn. field ν = 1.42 GHz, Δν = few MHz ~ mw power homogeneity over x x cm3 at λ = 21 cm spin flip resonator strip line design Q ~ 0 50 Ω antenna& strip-lines& mesh& contact&springs& slide 16
SUPERCONDUCTING MAGNET superconducting sextupole magnet 400 A with max field strength of 3.5 T analyser of the spin state high field seekers defocused slide 17
DETECTION QMS crossed beam configuration no recombination of the atoms before detection single particle detection with channeltron tuning fork chopper modulation of the beam, velocity cross checks slide 18
SEXTUPOLE FOCUSING - DEFOCUSING when the sextupole magnet is turned off a beam with low intensity can be seen sexutpole turned on beam intensity increases due to focusing TOF (phase) shows that slower part of the beam is focused on the detector QMS warm comp. cold comp.
CAVITY RESONANCE SHAPE W-shape of resonance curves: à consequence of MW field in cavity Fit routine derived from numerical calculation of the Bloch equations for strip line cavity slide 20
RESONANCE LINESHAPE σ 1 transition get ν c, v, σ v, B osc measure σ 1 transitions (ν c ) at different magn. fields 26.6 26.4 26.2 26 25.8 25.6 25.4 (a) data fit rate at the detector (Hz) 26200 26000 25800 25600 25400 25200 450 ma ν c count rate ( 3 ) 26.8 26.6 26.4 26.2 26 25.8 27.4 27.2 27 26.8 26.6 26.4 (b) (c) -15 - -5 0 5 15 20 25 30 f excite - f literature (khz) shift of resonances in magn. field (a) 0 ma (b) 300 ma (c) 500 ma 25000 F ( ; B osc, c,v, v, A, b) 24800 000 0 000 20000 30000 ν - ν lit (Hz) Fit parameters results Microwave amplitude (mg) 5.8± 0.4 ν c (Hz) 1 420 417 482 ± 30 Velocity (m/s) 839 ± 6 σ v (m/s) 130± 7 χ 2 /d.o.f. 32.9/34 slide 21
ZERO FIELD EXTRAPOLATION th zero field extrapolation 8 set Best beam value up to date (khz) - ν lit ν c 15 5 = 1420.40573(5) MHz 8 =3.5 P. Kusch, Phys. Rev. 0, 4, (1955) One extrapolation this work 0 0.5 0.0 0.5 I HC (A) slide 22
OTHER METHOD FOR EXTRAPOLATION Counts (Hz) 2700 2600 2500 2400 2300 2200 20 Other method to obtain zero field HFS Up to now σ 1 measured at different magn. fields and then zero field extrapolated with Breit-Rabi formula Measure π 1 + σ 1 π 1 linear dependence on magn. Field σ 1 second order dependence Measurements depend on angle between oscillating and static magnetic field for σ 1 transition B-field parallel for π 1 transition B-field orthogonal pi1 transition in earth magn. field 440 460 480 500 520 MW frequency - f_literature (Hz) rate at the detector (khz) 3 27.5 27.0 26.5 σ 1 in earth magn. field 30 20 0 20 30 ν - ν lit (khz) H π 1 σ 1 (F,M) = (1,1) (F,M) = (1,0) (F,M) = (1,-1) (F,M) = (0,0) Magnetic field from Rabi eq. + meas.: σ 1 : B = 34.9 ± 5.8 μt π 1 : B = 33.78 ± 0.01 μt Measured: B = 37 ± 4.2 μt Extrapolation: ν 0 = 1 420 405 776(88) Hz à 6 8 M. Diermaier et al. Hyperfine Interact. 233, Issue 1, 35-40 (2015)
PRECISION LIMITS cusp trap microwave cavity D sextupole 1 L D antihydrogen detector antihydrogen detector Rabi method: line width ~ 1/T v in RF field Hbar àδν/ν ~ -7 Ramsey separated oscillatory fields: line width reduced by D/L cusp trap microwave cavity 1 microwave cavity 2 sextupole 2 Atomic fountain - trapped Hbar needs trapping and laser cooling outside of formation magnet slow beam & capture in measurement trap Ramsey method: with d=1m à Δν ~3 Hz, Δν/ν ~ 2x 9 M. Kasevich, E. Riis, S. Chu, R. DeVoe, PRL 63, 612 615 (1989) slide 24
SUMMARY & CONCLUSION cold atomic hydrogen beam line has been developed and constructed showed that the sextupole magnet works and focuses atomic hydrogen spin flip resonator has been characterised we could observe σ 1 and π 1 transitions for atomic hydrogen slide 25
OUTLOOK measurement of π 1 transitions with modified H-setup à need more homogeneous B field for Zeeman splitting different Helmholtz coils (poster M.C. Simon) π 1 à sidereal variations: first measurements of many SME parameters (direction dependent) Kostelecký, V. A., & Vargas, A. J. Lorentz and CPT tests with hydrogen, antihydrogen, and related systems. Physical Review D, 92(5), 056002 (2015) simulations: -7 precision with 00 Hbar B. Kolbinger et al. Hyperfine Interact. 233, Issue 1, 47-51 (2015) looking forward to measure zero field GS-HFS with antihydrogen slide 26
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