Testing CPT Invariance with Antiprotonic Atoms

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1 Testing CPT Invariance with Antiprotonic Atoms Dezső Horváth KFKI Research Institute for Particle and Nuclear Physics, Budapest, Hungary & ATOMKI, Debrecen, Hungary

2 Outline CPT Invariance and its Tests The Antiproton Decelerator at CERN Antihydrogen: Why, What and How? Antihydrogen Production p-he Spectroscopy Charge and Mass of Antiproton Magnetic Moment of Antiproton Hyperfine Structure of Antihydrogen Outlook

3 CPT Invariance Charge conjugation: Space reflection: Time reversal: C p(r,t)> = p(r,t)> P p(r,t)> = p( r,t)> T p(r,t)> = p(r, t)> Basic assumption of field theory: CPT p(r,t)> = p( r, t)> = p(r,t)> meaning antiparticle particle going backwards in space and time. Giving up CPT one has to give up: locality of interactions causality, or unitarity conservation of matter, information,... or Lorentz invariance

4 CPT Invariance: violation? Theoreticians in general: CPT cannot be violated CPT -violating theories: (Alan Kostelecký, F.R. Klinkhamer, N.E. Mavromatos et al) Standard Model valid up to Planck scale ( GeV). Above Planck scale new physics Lorentz violation possible Quantum gravity: fluctuations Lorentz violation loss of information in black holes unitarity violation Motivation for testing CPT at low energy Quantitative expression of Lorentz and CPT invariance needs violating theory low-energy tests can limit possible high energy violation

5 How to test CPT? Particle = antiparticle? m(k 0 ) m(k 0 )/m(average) < proton antiproton? (compare m, q, µ) hydrogen antihydrogen? (2S 1S) ν ν mass, mixing (LSND data?)

6 Exception: antigravity? ATHENA home page ( CPT : particle Earth antiparticle anti-earth weak equivalence: particle Earth antiparticle Earth

7 1 2 3 Bohr Dirac Lamb HFS 1S 2P 1/2 1/2 2S 1/2 2P 3/2 ANTIHYDROGEN F=0 F=1 Antihydrogen: e + p atom HYDROGEN 3 2 2P 3/2 2S 1/2 2P1/2 1 1S1/2 F=1 F=0 Bohr Dirac Lamb HFS 2S 1S transition with 2-photon (Doppler-free) spectroscopy at precision M. Charlton, J. Eades, D. Horváth, R. J. Hughes, C. Zimmermann: Antihydrogen physics, Physics Reports 241 (1994) 65.

8 Accelerators at CERN Until 1996 From 2007?

9 Antihydrogen observation: CERN, 1996 Expt. PS-210 at LEAR Fast p in LEAR hits Xe jet e + e created co-moving p and e + can bind to make relativistic H Neutral H leaves ring, e + and p separated and identified 11 counts 2 bgrd = 9 H observed G. Baur et al., Phys.Lett. B 368 (1996) 251 Similar experiment at FERMILAB: G. Blanford et al., Phys.Rev.Lett. 80 (1998) 3037 Spectroscopy needs cold, confined, ground-state antihydrogen

10 The Antiproton Decelerator at CERN has been built to test CPT invariance Three experiments test CPT: ATRAP: q(p)/m(p) q(p)/m(p) H(2S 1S) H(2S 1S) ATHENA: H(2S 1S) H(2S 1S) ASACUSA: q(p) 2 m(p) q(p) 2 m(p) µ l (p) µ l (p) H H HF structure RED: done, GREEN: planned c Ryugo S. Hayano

11 Cold Antihydrogen: How? 1. Trap p and e + in nested Penning trap 2. Mix p with e + at high particle densities 3. In p+ e + +e + collisions excited H atoms form 4. Confine H in quadrupole field (e + spin) 5. Stimulate deexcitation with laser 6. Make two-photon spectroscopy 1 3 are done by ATHENA and ATRAP, rest is planned ATHENA: M. Amoretti et al., Nature 419 (2002) 456. ATRAP: G. Gabrielse et al., Phys. Rev. Lett. 89 (2002)

12 Empty trap electrons cool with sync radiation Trapping antiprotons To make antihydrogen cool p with positrons Trap opened 10 7 antiprotons in Trap closed electrons cool antiprotons Cold antiprotons trapped Trap opened another bunch of 10 7 antiprotons in

13 Production of Antihydrogen ATHENA experiment H annihilation event, 2002 ATHENA, ATRAP, 2003 > 10 5 cold H produced

14 Is it really antihydrogen? Antiprotons and positrons mix in nested trap In collisions neutral particles are produced which leave the trap and could be ionised to e + and p. e + cools p: if p is overcooled it sinks in its well and stops colliding no H. The particles can be heated with RF and the H production rate driven. When H production is on, most annihilations happen at the walls, with no H the p annihilate on residual gas. ATHENA: M. Amoretti et al., Phys. Lett. B 583 (2004) 59. ATRAP: G. Gabrielse et al., Phys. Rev. Lett. 89 (2002)

15 Mass and Charge of Antiproton Proton s well (?) known: m(p)/m(e) = (85) q(e) = (63) C Precision: and Relative measurements: proton vs. antiproton Cyclotron frequency in trap q/m TRAP ATRAP collaboration Harvard, Bonn, München, Seoul p and H together precision Atomic transitions: E n m red c 2 (Zα) 2 /(2n) m q 2 PS-205 ASACUSA collaboration Tokyo, Budapest, CERN, Debrecen, Vienna Atomic Spectroscopy And Collisions Using Slow Antiprotons Asakusa, Tokyo

16 Metastable hadronic atoms In matter (gas, liquid, solid) τ(hadron) 1 ps except X He: K, π : τ 0 ; p: 3 4 µs Metastable 3-body system

17 Principle of laser spectroscopy τ µ Wavelengths in nm Induce transition between long-lived and short-lived state Force prompt annihilation

18 ASACUSA: Spectroscopy Setup

19 aser spectroscopy of antiprotonic helium N. Morita et al, Phys. Rev. Lett. 72 (1994)

20 Transition frequencies in isolated phe + atoms Experimental precision limited by: collisional and Doppler broadening, laser bandwidth Most important: density effect : measured density dependence, extrapolated to zero : reduced collisional effects by stopping slow p from RFQ post-decelerator in low-pressure (< 1 mbar), cryogenic target Last published CPT-violation limit: 10 ppb (10 8 ) M. Hori et al., Phys. Rev. Lett. 91 (2003) M. Hori et al., Phys. Rev. Lett. 87 (2001)

21 Determination of m(p),q(p) Principal quantum number p _ 4 He phe LEAR δm M p p [10 6 ] Q p / M p n= p _ 3 He allowed region phe AD + δq Q p p [10 6 ] metastable states 32 short-lived states n=31 l = Orbital quantum number 1.5 2

22 Resolution development Limits on the antiproton charge and mass from a combination of ASACUSA and ATRAP experimental results First measurement at LEAR Relative precision First AD measurement Low densities with RFQD LEAR: Higher statistics, better lasers and wavelength calibration Femtosecond optical comb generator Continuous-wave pulse amplified laser Doppler-free two-photon spectroscopy? Known mass of proton (p/e ratio) Years

23 Resolution development Resonance profile of the (n,l) = (37,35) (38,34) transition at λ = nm

24 ;1 8 : <= 2 ; ! NQ P N WM T V XY N WM T T H Level splitting in phe + atoms Density effect (T = 6 K) F =L 1/2 f,#& "#%$ ν (n,l ) &#+ "#%$ F =L 1/2 J + =L ν HF 0 / / *#& "#%$ ν SHF J =L 1 9 / / 8/7 6 / &#) "#%$ (#& "#%$ (n,l) ν HF + ν HF F + =L +1/2 '#& "#%$ - - * - - ) - - ( - - ' - - # - - " ν HF f + J ++ = L+1 ν SHF + F + =L+1/2 J + =L + ν C >?@ CB C >?A@ Level scheme, frequency scan B CB >?A@ L K M NO J K ν HF 1.15 BCG >?A@ ν + HF U K K TKS R K FCB >?A@ 1.10 BCE >?A@ DCB >?A@ H H F H H E H H D I H H H H? H H > R ++ /R ++ off Magnetic moments 0.95 p p CPT OK ν MW (GHz) E. Widmann et al., Phys. Rev. Lett. 89 (2002)

25 Outlook: slow antiproton beam Monoenergetic Ultra Slow Antiproton Source for High precision Investigations 5.8 MeV p injected into RFQ 100 kev p injected into trap 10 6 p trapped and cooled (2002) Slow p extracted (2004) Aim: stopping power single ionization nuclear studies

26 Hyperfine structure of antihydrogen p antiproton and positron Trap / Recombination + e Sextupole I Microwave Cavity Possible CPT-violation predicted by R. Bluhm et al., Phys. Rev. Lett. 82 (1999) Sextupole II Antihydrogen Detector v(p) 350m/s, L(MW cavity) = 20 cm ν HF 3kHz ppm precision E. Widmann, R.S. Hayano, M. Hori, T. Yamazaki, Nucl. Instr. Meth. B 214 (2004) 31.

27 Summary So far no CPT violation detected CERN s Antiproton Decelerator stopped in 2005 for LHC construction In H spectroscopy expected MUSASHI starts working as a user facility New antiproton machine is planned: FLAIR at GSI (A Facility for Low-energy Antiproton and Ion Research) Nobody expects CPT violation, but it must be tested

28 Making antihydrogen: Paul trap Linear antiproton Paul trap Two-tone antihydrogen production Paul trap Commercial positron source (First Point Scientific Inc.) Beam profile monitor Radiofrequency quadrupole decelerator 1 m Beam profile monitor, differential pumping, conductance limiter Electromagnetic calorimeter ASACUSA Collaboration, Addendum to Proposal, CERN-SPSC

29 Making antihydrogen: cusp trap positron source focusing solenoid cusp trap sextupole magnet MR T electron emitter microwave cavity H detector p from RFQD MUSASHI Trap (catching & cooling of p) Cusp Trap H counts RF frequency p e + H LS H HS Microwave Cavity Sextupole Lens H Det. A. Mohri, Y. Yamazaki, Europhys. Lett. 63 (2003) 207.

30 Laser spectroscopy: LEAR vs AD counts / 10 ns analog amplitude (arb. units) event-by-event λ = nm Annihilation time (µs) analog method λ = nm Annihilation time (µs) LEAR: slow extraction 10 6 laser shot, 50 min AD: fast extraction 1 laser shot, 2 min Gated phototube: prompt annihilation (97% p) off (Hamamatsu)

31 Antiproton tunnelling in collisions Temperature dependence of the cross section of quenching the metastable phe state in collisions with (H 2, D 2 ): σ q = σ 0 exp ( ) E b kt + σ t Arrhenius type + quantum tunnelling. σ t depends on barrier height and width on isotope and state. (37,34) T (K) cm 2 ) -16 (10 σ q H 2 D /T (1/K) (38,37) T (K) cm 2 ) -16 (10 σ q 5 1 B. Juhász et al., Chem. Phys. Lett., 379 (2003) 91; B. Juhász, PhD Thesis, Debrecen, H 2 D /T (1/K)