In-beam measurement of the hydrogen hyperfine splitting: towards antihydrogen spectroscopy. Martin Diermaier LEAP 2016 Kanazawa Japan

Transcription

1 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

2 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

3 PRECISION Mass [ev] 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 Frequency Energy [GHz]] GS-HFS of Hydrogen / Antihydrogen offers best test of CPT on absolute scale slide 3

4 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

5 GROUND STATE HYPERFINE SPLITTING OF ANTIHYDROGEN Breit-Rabi diagram 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 (F,M)=(0,0) B (T) (F,M)=(1,0) (F,M)=(1,1) high-field seekers slide 5

6 GROUND STATE HYPERFINE SPLITTING OF ANTIHYDROGEN Breit-Rabi diagram Zeeman effect: energy levels shifted in external field 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 (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 (F,M)=(0,0) 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

7 GROUND STATE HYPERFINE SPLITTING OF ANTIHYDROGEN 2.0 two transitions possible 1.5 H with cavity σ 1 transition σ π1 σ1 π 2 (F,M)=(1,-1) 1 2 e + p low-field seekers ν (GHz) (F,M)=(1,0) (F,M)=(1,1) (F,M)=(0,0) 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

8 GROUND STATE HYPERFINE SPLITTING OF ANTIHYDROGEN two transitions possible with cavity σ 1 transition π 1 transition (GHz) ν 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 (F,M)=(0,0) 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

9 GROUND STATE HYPERFINE SPLITTING OF ANTIHYDROGEN & MINIMAL SME ν 1 ΔB LIV 4 ν H π1 σ1 π 2 (F,M)=(1,-1) 1 2 e + p low-field seekers 0 B ν (GHz) (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 (F,M)=(0,0) 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), (2015) slide 9

10 HISTORY OF HYDROGEN GS-HFS 1936 Simple atomic beams ~5% 1946 Atomic beams plus 4 x -6 microwave resonance x Hydrogen maser 6 x -13 Not possible for antimatter Molecular Beam Resonance Setup I.I.Rabi et al., Phys. Rev. 55, 526 (1939) slide

11 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

12 HYDROGEN BEAM LINE slide 12

13 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 solid angle electron impact ionization and single ion counting residual gas background >> signal slide 13

14 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, (1993) slide 14

15 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

16 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

17 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

18 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

19 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.

20 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

21 RESONANCE LINESHAPE σ 1 transition get ν c, v, σ v, B osc measure σ 1 transitions (ν c ) at different magn. fields (a) data fit rate at the detector (Hz) ma ν c count rate ( 3 ) (b) (c) f excite - f literature (khz) shift of resonances in magn. field (a) 0 ma (b) 300 ma (c) 500 ma F ( ; B osc, c,v, v, A, b) ν - ν lit (Hz) Fit parameters results Microwave amplitude (mg) 5.8± 0.4 ν c (Hz) ± 30 Velocity (m/s) 839 ± 6 σ v (m/s) 130± 7 χ 2 /d.o.f. 32.9/34 slide 21

22 ZERO FIELD EXTRAPOLATION th zero field extrapolation 8 set Best beam value up to date (khz) - ν lit ν c 15 5 = (5) MHz 8 =3.5 P. Kusch, Phys. Rev. 0, 4, (1955) One extrapolation this work I HC (A) slide 22

23 OTHER METHOD FOR EXTRAPOLATION Counts (Hz) 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 MW frequency - f_literature (Hz) rate at the detector (khz) σ 1 in earth magn. field 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 = ± 0.01 μt Measured: B = 37 ± 4.2 μt Extrapolation: ν 0 = (88) Hz à 6 8 M. Diermaier et al. Hyperfine Interact. 233, Issue 1, (2015)

24 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, (1989) slide 24

25 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

26 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), (2015) simulations: -7 precision with 00 Hbar B. Kolbinger et al. Hyperfine Interact. 233, Issue 1, (2015) looking forward to measure zero field GS-HFS with antihydrogen slide 26

27 Thank you for your attention