Fundamental Physics with Antiprotons and Antihydrogen at Lowest Energies

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2 Fundamental Physics with Antiprotons and Antihydrogen at Lowest Energies Jochen Walz Univ. Mainz antimatter spectroscopy magnetic moments antimatter gravity

3 Why antihydrogen spectroscopy? CPT symmetry Greenberg 02 Pauli, Lüders, Bell 1954 charge conjugation parity inversion time reversal The Planck Scale at Gev / m: quantum gravity, grand unified theories, superstrings... Lorentz symmetry (rotations, boosts) mysteries: no antimatter in the universe, dark matter / dark energy, quantum theory of gravity The Standard Model: perfect symmetry. hydrogen frequencies: ν 1 S 2 S = (34) Hz ν HF = (1) Hz

4 Experimental tests of CPT symmetry m K 0 m K 0 /maverage < ( ) ge + g e /gaverage ( 0.5 ± 2.1) ( q p q ) p m p m p / q p m p ( 9 ± 9) ( ) ( mp m p /mp ) < gµ + g µ /gaverage ( 0.11 ± 0.12) 10 8 pdg.lbl.gov The Standard Model Extension Indiana group, Kostelecký et al., since 1997 modified Dirac equation for an electron in the proton Coulomb potential: ( iγ µ µ qγ µ A µ m e a e µγ µ b e µγ 5 γ µ }{{}}{{} standard Dirac equation CPT violating 1 2 He µνσ µν + ic e µνγ µ D ν + id e µνγ 5 γ µ D ν )Ψ = 0 } {{ } CPT preserving terms CPT-violating terms a and b have energy dimensions dimensionless comparison not meaningful H H ν1s 2S (b e 3 bp 3 )/π H H νhfs 2b p 3 /π ν 1 S 2 S = (34) Hz ν HF = (1) Hz (δm/m) K 0 / K benchmark: m 2 e M Planck = ev 3

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7 Antihydrogen physics progress at ATRAP background-free detection laser-controlled antihydrogen production next milestone: magnetic trapping Cs Cs (n=34) e + state distribution number of antihydrogens, N ρ is less than this value in µm F prestripping field F in V/cm PRL 89 (2002) N=bF -2 +c F -3/2 F-5/2 F -2 F antihydrogens / antiproton PRL 89 (2002) velocity measurement 1.2 no oscillating prestripping field laser excitation PRL 93 (2004) e e + Positronium (n 24) p H ( 24) thermal velocity of p well-defined n-states antihydrogen production in a Penning-Ioffe-trap _ H detection probability mev mev mev 1meV frequency of oscillating prestripping field in MHz PRL 93 (2004) PRL 98 (2007) , PRL 100 (2008) ATRAP collaboration: Harvard, FZ Jülich, MPQ Garching, York (Toronto), Mainz 6

8 Antihydrogen spectroscopy: Lyman-α source for laser-cooling 7

9 Laser-cooling and laser-spectroscopy of antihydrogen F=2, m F =2 "State-of-the-Art" spectroscopy of atomic hydrogen: atoms / s at < 8 K antihydrogen: 10 7 antiprotons at 5 MeV every 2 minutes 2 P 3/2 2 S 1/2 1.6 ns 122 ms F=1, m F =1 laser-cooling of antihydrogen at 1 K down to ~ mk using radiation at Lyman-α: velocity change per photon: 3.3 m/s -> need to scatter ~ 50 photons. 20 nw at 122 nm on 1 mm diameter -> excitation rate 100/s many, many oders of magnitude nm nm Lyman-α shelving spectroscopy 122 nm 243 nm 243 nm time 1S-2S spectroscopy of antihydrogen at 0.2 K (Zeeman-broadening 20 khz) 0.8 W power at 243 nm on 1 mm diameter -> excitation rate 0.3 / s 1 S 1/2 F=1, m F =1 time single 1S-2S excitation events in a single atom are detected using the strong Lyman-α transition. Radiation at Lyman-α will be essential for experiments with antihydrogen B in Tesla 0.4 Residual Zeeman-shift for 1 S 2 S transition (F = 1, m F = 1) (F = 1, m F = 1): 186 khz/t / 0.67 K/T = 278 khz/k laser cooling to mk-temperatures necessary for precise 1 S 2 S spectroscopy 8

10 Continuous four-wave mixing in mercury vapour 7 1 S 545 nm 408 nm 1,3 12 P 6 3 P Lyman-α is at nm in the vacuum-ultraviolet (VUV). lenses & windows: T=50% mirrors: R=85% max. beams in vacuum or He in this wavelength region: no tunable direct lasers no frequency doubling crystals use higher-order nonlinear optical processes nm nm 1st generation Lyman-α source: K. S. E. Eikema, J. W., and T. W. Hänsch Phys. Rev. Lett. 83 (1999) S Hg Phys. Rev. Lett. 86 (2001) nd generation Lyman-α source: solid-state laser systems 9

11 The Lyman-α team Thomas Diehl Andreas Müllers Daniel Kolbe Andreas Koglbauer Matthias Stappel Anna Beczkowiak Ruth Steinborn J. W. What is it all about? a laser-beam at 122 nm wavelength ( (Lyman-alpha) in the vacuum-ultraviolet λlyman-alpha 1 4 λ visible) 10

12 Solid-state laser system in the UV at 253 nm Yb:YAG disc laser (g max at 1030 nm) tuned from down to 1014 nm frequency doubling in LBO to 507 nm frequency doubling in BBO to 253 nm yield: up to 0.9 W in the UV mercury spectroscopy M. Scheid et al., Opt. Lett. 32 (2007)

13 Solid-state laser system in the blue at 408 nm Diode-pumped green pump-laser, 10.5 W at 533 nm Ti:Sapphire laser (Coherent 899), 1.3 W at 816 nm Frequency-doubling in Brewster-cut LBO crystal in an external enhancement cavity, 430 mw at 408 nm 12

14 Solid-state laser system in the yellow-green at 545 nm Yb fibre laser at 1091 nm frequency doubling in LBO to 545 nm 10 W 3.5 W iodine spectroscopy wave number in cm norm. transmission x signal in a.u frequency at 545.5nm in MHz F. Markert et al., Optics Express 15 (2007)

15 Solid-state continuous coherent Lyman-alpha generation Lyman-alpha: nonlin. polarization of different isotopes can interfere 7 1 S 545 nm 1,3 12 P 1014 nm nm 6 P nm 6 3 P nm nm 1 6 S Hg fluorescence: of different isotopes is independent M. Scheid et al., Opt. Expr. 17 (2009)

16 Phasematching of the four-wave mixing process = 100 GHz = 200 GHz = 400 GHz 7 1 S 545 nm 1,3 12 P 408 nm 6 3 P optimal phasematching expected at b k 4 k depends on the dispersion in the mercury scan the mercury temperature ( density) nm 1 6 S nm Hg 15

17 Velocity-selective double-resonance in a ladder system Two-photon resonance of 253 nm and 408 nm with the 7 1 S 0 state an essential part of Lyman-alpha generation. Fixed detuning of the UV beam, scan the blue beam. Observe the fluorescence out of the 7 1 S 0 state. far-resonant UV beam two-photon peaks near-resonant UV beam all types of peaks (a) UV resonant, stays (b) blue resonant, moves (c) two-photon resonance, moves (a) & (b) & (c) coincide for one velocity class δ 2 3 /k 2 3 = δ 1 3 /k 1 3 T. Beyer et al., Phys. Rev. A 80 (2009)

18 Amplified spontaneous emission after two-photon absorption 7 1 S 545 nm 1,3 12 P 1014 nm nm 6 P nm 6 3 P the fluorescence at 1014 nm is a beam at high power levels nm nm 1 6 S Hg 29.9 % abundance 6.9 % abundance the 1014 nm beam after passing an interferometer D. Kolbe et al., Opt. Lett. 36 (2010)

19 Magnetic moment of the Proton and the Antiproton 18

20 The magnetic moment of the Proton and the Antiproton Goal: ultra-precise measurements of µ p and µ p Present knowledge: µ p = ± µ N (hydrogen hyperfine splitting) µ p = ±0.008 µ N (x-rays of antiprotonic atoms) Leinweber GSI MPIK Heidelberg Univ. Mainz Wolfgang Quint Klaus Blaum Susanne Kreim Crícia de Carvalho Rodegheri Stefan Ulmer Stefan Stahl Andreas Mooser Holger Kracke J. W. Christian Mrozik 19

21 Double Penning trap for the magnetic moment measurement use a single proton drive spin-flip transition in precision trap move the proton detect spin-orientation in analysis trap repeat / step Larmor excitation frequency Detection of the spin state: magnetic bottle at the analysis trap - ferromagnetic ring (CoFe) with toroidal shape electrostatics: J. Verdú, S. Kreim, et al.: New. J. Phys. 10 (2008) cyclotron frequency of a particle in a Penning trap: ω c = q m B Larmor frequency of a spin in a magnetic field: ω L = µb 2 = g q p 2m B magnetic moment / µ N = g-factor: g p = 2 ω L ωc in a 1.9 T magnetic field at 4 K temperature 20

22 A single proton in the precision trap cyclotron motion at 29 MHz FFT of the induced current in a segmented ring electrode trap storage time > several weeks axial motion at 637 khz in thermal equilibrium with a superconducting tuned circuit Other important steps: transport: precision trap analysis trap detection of the spin state first detection of the orientation of a nuclear spin in a Penning trap 21

23 Superconducting radiofrequency resonator Need record quality factors for precision experiments with just one single proton. GaAs-FET amp 1 - lose wire not cold 2 - Cu loose wire 3 - polish 4 - better caps 5 - thermal anchoring S. Ulmer et al., Rev. Sci. Instrum. 80 (2009) Can use this for self-excitation and feedback cooling of one single proton. 22

24 Axial frequency drifts in the analysis trap analysis trap: electrostatic quadrupole + homogeneous magnetic field + magnetic bottle: B 2 [( z 2 ϱ 2 /2 ) e z z e ϱ ] magnetic moments couple to B 2 spin orientation can be measured via ν z a spin-flip corresponds to ν z = 0.2 Hz out of ν z = 674 khz long-term drifts 25 Hz non-technical, ν z in precision trap (w/o magnetic bottle) is stable sorted frequency values (taken during a quiet phase) cyclotron quanta? (n thermal 4000) QND-measurement of radial energy?... 23

25 Antimatter gravity 24

26 Antimatter gravity Equivalence Principle valid for antimatter? m inertial? = m gravitational well-known unknown for antimatter J. S. Bell (1986) exchangeable energy does not antigravitate Supersymmetry / Quantum Gravity: graviphotons (spin-1) and graviscalars (spin-0)? range v, charge a range s, charge b non-newtonian gravity V (r) = G m ( 1 m 2 r 1 ± a e r/v + b e r/s) a b Adelberger Eöt-Wash experiments with matter are sensitive to a b antimatter... a + b v s Experiments with charged particles (positrons / antiprotons) never got to the end. Antihydrogen is electrically neutral and stable ideal for experiments in antimatter gravity. 25

27 Temperature scales for antimatter gravity experiments vertical height kt/2 = mgh desirable range 1 km 1 m 1 mm temperature 1 K 1 mk 1 µk 3.4 m height for H at 8 mk vertical velocity 1 σ = kt/m 100 m/s 1 m/s 0.1 m/s 10 m/s current antiproton temperature 4.2 K 1S-2P laser cooling recoil limit 1.3 mk Doppler limit 2.4 mk H atoms in a trap 8 mk using pulsed Lyman-α I.D. Setija et al. PRL 70 (1993) 2257 cw Lyman-α source: K.S.E. Eikema, J. Walz, and T.W. Hänsch PRL 83 (1999) 3828, 86 (2001) 5679 (after G. Gabrielse, Hyp. Interact. 44 (1988) 349) need ultracold antihydrogen atoms 26

28 Ideas for antihydrogen cooling to ultracold temperatures positive antihydrogen ions sympathetic cooling photodetachment (J. W. and T. W. Hänsch, Gen. Rel. Grav. 36 (2004) 561) P. Perez, Saclay Linac (SELMA) & e + /e separator (SOPHI) laser-cooled Os sympathetic coling of p form ultracold antihydrogen (A. Kellerbauer and J. W., New J. Phys. 8 (2006) 1) ev A. Kellerbauer, MPI-K Os Emmy Noether Nachwuchsgruppe 0 5d 6 6s 2 6p 6 D 5.07 µm (15 % 6 F, 10 % 4 F) J = 7/2, 9/2, or 11/ µm 2.29 µm M 1 γ = 1/160 s F 3/2 F 5/2-0.5 M 1 γ = s 1 F 7/2 λ = nm M 1 γ = 2.17 s 1-1 5d 7 6s 2 4 F 9/2 Kellerbauer group: Phys. Rev. Lett. 102 (2009) , ibid 104 (2010)

29 Summary Good reasons to seriously test CPT & to measure antimatter gravity. Precision experiments with antiprotons and antihydrogen have a great potential. On the way:... spontaneous lasing... measurement of a single nuclear spin with superconducting electronics 28

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