1. Michael Charlton -LAL Lecture 28-02-06 Physics With Low Energy Antiparticles LAL Lecture

2. Michael Charlton -LAL Lecture 28-02-06 ATHENA – circa 2004 Aarhus P.Bowe, J.S. Hangst, N. Madsen Brescia E. Lodi-Rizzini, L. Venturelli, N. Zurlo CERN G. Bonomi, M. Doser, A. Kellerbauer, R. Landua Genoa M. Amoretti, C. Canali C. Carraro, V. Lagomarsino, M. Macri, G. Manuzio, G. Testera, A. Variola Pavia A. Fontana, P. Genova P. Montagna, A. Rotondi Rio de Janeiro (URFJ) C. Lenz Cesar Swansea M. Charlton, L. Jørgensen, D. Mitchard, H.H. Telle, D.P. van der Werf Tokyo/Riken M. Fujiwara, R. Funakoshi, R. Hayano, Y. Yamazaki Zurich C. Amsler, H. Pruys, C. Regenfus, J Rochet Athena/AD-1 Collaboration

3. Michael Charlton -LAL Lecture 28-02-06 Overview of Talk Antihydrogen Motivation Formation by the ATHENA nested trap method, Results: antiproton cooling, temperature dependence, spatial distributions ALPHA and trapped antihydrogen Antihydrogen via positronium ASACUSA proposals Positronium Lifetimes, spectroscopy, many Ps physics, high field effects

4. Michael Charlton -LAL Lecture 28-02-06 PHYSICS GOALS | Antihydrogen | = | Hydrogen | ? CPT Gravity

5. Michael Charlton -LAL Lecture 28-02-06 Overview of the ATHENA Apparatus

6. Michael Charlton -LAL Lecture 28-02-06 Early Photograph- ATHENA

7. Michael Charlton -LAL Lecture 28-02-06 Antiprotons - Capture and Cooling Antiproton Capture Trap Scheme first demonstrated by the TRAP collaboration. See: Gabrielse et al, PRL 57 2504 (1986) and Gabrielse et al, PRL 63 1360 (1989) ATHENA

8. Michael Charlton -LAL Lecture 28-02-06 Positron Accumulation - ATHENA Buffer Gas Positron Accumulator – first developed by Surko group. See e.g. Murphy and Surko, PRA 46 5696 (1992) Surko and Greaves, Phys. Plasmas 11 2333 (2004) Surko, Greaves and Charlton, Hyp. Int. 109 181 (1997)

9. Michael Charlton -LAL Lecture 28-02-06 Positron Accumulation - ATHENA Open circles: no rotating electric field Closed circles: rotating field applied see e.g. Jorgensen et al, Non-neutral Plasma Physics, AIP Vol. 606 35 (2002) and van der Werf et al, Appl. Surf. Sci. 194 312 (2002)

10. Michael Charlton -LAL Lecture 28-02-06 Positron Transfer - ATHENA Transfer efficiency ~ 50 % Cold positrons for antihydrogen : 75 million / 5 min. Positron plasma : r ~ 2 mm, l ~ 32 mm, n ~ 2.5x10 8 cm -3 Lifetime ~ hours. Jorgensen et al, Phys. Rev. Lett. 95 025002 (2005) reports stacking and compression in 3 T, 15 K environment; 10 9 positrons, density more than 10 10 cm -3

11. Michael Charlton -LAL Lecture 28-02-06 Antihydrogen Production- ATHENA 1. Fill positron well in mixing region with 75·10 6 positrons; allow them to cool to ambient temperature (15 K) 2.Launch 10 4 antiprotons into mixing region 3.Mixing time 190 sec - continuous monitoring by detector 4.Repeat cycle every 5 minutes (data for 165 cycles) For comparison: “hot” mixing = continuous RF heating of positron cloud (suppression of formation) Nested Penning trap approach suggested by Gabrielse et al, Phys. Lett. A 129 38 (1988)

12. Michael Charlton -LAL Lecture 28-02-06 Antiproton Cooling by Positrons - ATHENA By lowering the voltages applied to the trap the antiprotons can escape and be counted. An estimate of their kinetic energy can be obtained as a function of the time spent in the positron cloud

13. Michael Charlton -LAL Lecture 28-02-06 Antiproton Cooling by Positrons - ATHENA

14. Michael Charlton -LAL Lecture 28-02-06 Antiproton Cooling by Positrons - ATHENA Main results: [10 4 antiprotons launched at 30 eV into a 15 K positron plasma of density around 10 8 cm -3 ] Those antiprotons which overlap physically with the positron cloud cool quickly and antihydrogen formation begins after about 10-20 ms. Instantaneous antihydrogen rates over 400 s -1 have been recorded. Antihydrogen formation continues for many tens of seconds as the positron plasma slowly expands. Antiprotons appear in the side wells. This is attributed to field ionization of weakly-bound antihydrogen atoms. [See Amoretti et al, Phys. Letts. B 590 133 (2004)]

15. Michael Charlton -LAL Lecture 28-02-06 Analysis Procedure - ATHENA Reconstruct annihilation vertex Search for ‘clean’ 511 keV-photons: exclude crystals hit by charged particles + its 8 nearest neighbours ‘511 keV’ candidate = 400… 620 keV no hits in any adjacent crystals Select events with two ‘511 keV’ photons Reconstruction efficiency ≤ 0.25 %

16. Michael Charlton -LAL Lecture 28-02-06 Antihydrogen Cold Antihydrogen - ATHENA 10 4 antiprotons & 10 8 e + mixed in Penning trap 10 4 pbars 10 8 e + Si strips CsI crystals 2.5 cm 3T 10 8 e + Antihydrogen forms, annihilates on electrode cos(   ), opening angle of two 511keV  s, seen from the vertex  is plotted 10 4 pbars   Hbar Annihilation antiproton annihilates into charged pions e + annihilates into back-to-back  s Neutral pions give uncorrelated background Hbar Formation

17. Michael Charlton -LAL Lecture 28-02-06 ATHENA Observations - Signal Cold Mixing : 103270 vertices, 7125 2x511keV events Hot Mixing : Scaled (x1.6) to 165 mixing cycles. 131± 22 events Amoretti et al., Nature 419 456 (2002)

18. Michael Charlton -LAL Lecture 28-02-06 ATHENA Annihilation Distribution Cold Mixing Hot Mixing Amoretti et al., Nature 419 456 (2002)

19. Michael Charlton -LAL Lecture 28-02-06 Antihydrogen Emission Angles ATHENA Vertex Z Distribution Madsen et al, PRL 94 033403 (2005)

20. Michael Charlton -LAL Lecture 28-02-06 ATHENA Golden Events Very restrictive cuts: threw away >99.7% of events Can connection be made between Antihydrogen and Vertices? 131± 22 Golden Events Antihydrogen Charged Vertex Opening Angle (2  511 keV  ) Golden Events ~50% ~10% ~5% Total: ~0.25% approx. cut efficiency Golden Event Selection

21. Michael Charlton -LAL Lecture 28-02-06 ATHENA Fit Results  opening angle Vertex XY distribution Vertex R distribution Two  events  yield Charged trigger yield Antihydrogen fraction during mixing (averaged over 180 sec) ~65 ±10 % In 2002/3, we produced ~ Two Million Antihydrogen atoms ~700k reconstructed vertices  ~400k Antihydrogen atoms

22. Michael Charlton -LAL Lecture 28-02-06 Formation Processes RadiativeThree-body Rate T dependenceT -0.6 T -4.5 Final staten > 10 Stability ( re-ionization )highlow Expected rates~10s Hzfast ??? Radiative Three-body +

23. Michael Charlton -LAL Lecture 28-02-06  T=15+-15 meV (175K) Cold mixing  T=43+-17 meV (500K) 306+-30 meV (3500 K) (Hot mixing) Opening angle Trigger rate vs time Antihydrogen production temperature dependence (1) ATHENA

24. Michael Charlton -LAL Lecture 28-02-06 Proportional to the total number of detected antihydrogen in a mixing cycle T scaling not 3body 300-400 Hz initial rate : 10 times the expected rate for radiative recombination Scaling law Opening angle excess Tot. number of triggers in 180 sec Peak trigger rate From Amoretti et al. Phys. Letts B 583 (2004) 59 Antihydrogen production temperature dependence (2) No simple interpretation – antiprotons not in thermal equilibrium with positrons... ATHENA data

25. Michael Charlton -LAL Lecture 28-02-06 Summary – results from ATHENA ATHENA Antihydrogen Apparatus –High rate, High duty cycle (5 min -1 ), Versatile [Amoretti et al NIM A 518 679 (2004)] First production and detection of cold antihydrogen [Amoretti et al, Nature 456 419 (2002)] Main results since then –In 2002/3 we produced ~2 Million Antihydrogen atoms –High initial rate production > 400 Hz [ Amoretti et al, Phys Lett B 578 23 (2004)] –Temperature dependence ~ T – (0.7 +/- 0.2) [Amoretti et al.,Phys Lett B 583 59 (2004)] [Needs extra work for interpretation – see e.g. Robicheaux, PRA 70 022510 (2004); arrested nature of 3-body process in finite positron plasmas]

26. Michael Charlton -LAL Lecture 28-02-06 Summary – results from ATHENA Main results since then … continued –Many measurements of antiproton cooling upon mixing with a positron plasma – shed light on dynamics of antihydrogen formation [Amoretti et al, Phys. Lett. B 590 133 (2004)] –Emission angles; points to epithermal antihydrogen emission [Madsen et al, PRL 94 033403 (2005)] –More to come … sideband cooling of ions in a non-neutral buffer gas [with PRA] modulation of antihydrogen formation [in preparation] attempt to laser stimulate antihydrogen formation [in preparation]

27. Michael Charlton -LAL Lecture 28-02-06 Trapping Neutral Anti-atoms - ALPHA quadrupole winding mirror coils Solenoid field is the minimum in B Well depth ~ 0.7 K/T Ioffe-Pritchard Geometry Based on Berkeley/Swansea results: not a good idea … field gradient across charged plasmas is too great; see Fajans et al., Phys. Rev. Lett. 95 155001 (2005)

28. Michael Charlton -LAL Lecture 28-02-06 Trapping Neutral Anti-atoms - ALPHA quadrupole octupole

29. Michael Charlton -LAL Lecture 28-02-06 (Anti)Hydrogen from Positronium

30. Michael Charlton -LAL Lecture 28-02-06 Antihydrogen from Positronium Ps* from Cs*; Hbar* from Ps*

31. Michael Charlton -LAL Lecture 28-02-06 ASACUSA – Antihydrogen proposal From ASACUSA SPSC presentation 2005

32. Michael Charlton -LAL Lecture 28-02-06 ASACUSA – Antihydrogen proposal From ASACUSA SPSC presentation 2005

33. Michael Charlton -LAL Lecture 28-02-06 ASACUSA – Antihydrogen proposal From ASACUSA SPSC presentation 2005

34. Michael Charlton -LAL Lecture 28-02-06 ASACUSA – Antihydrogen proposal From ASACUSA SPSC presentation 2005

35. Michael Charlton -LAL Lecture 28-02-06 ASACUSA – Antihydrogen proposal From ASACUSA SPSC presentation 2005

36. Michael Charlton -LAL Lecture 28-02-06 Positronium – o-Ps lifetime Vallery et al., PRL 90 203402 (2003) experiment Time Tagged Correction for “backscattered” Ps using a non-porous sample Same intercept

37. Michael Charlton -LAL Lecture 28-02-06 Positronium - Spectroscopy Fee et al., PRL 70 1397 (1993)

38. Michael Charlton -LAL Lecture 28-02-06 Positronium - Spectroscopy Fee et al., PRL 70 1397 (1993) More recent theory- Pachucki and Karshenboim, PRA 60 2792 (1999)

39. Michael Charlton -LAL Lecture 28-02-06 Positronium- Rydberg States

40. Michael Charlton -LAL Lecture 28-02-06 Positronium – Magnetised Rydberg States Work of Estrada et al., PRL 84 859 (2000) Positrons Electrons Effect of laser heating

41. Michael Charlton -LAL Lecture 28-02-06 Positronium – Many Ps effects Start with 2! Cassidy et al., PRL 95 195006 (2005)

42. Michael Charlton -LAL Lecture 28-02-06 Positronium – Many Ps effects Start with 2! Cassidy et al., PRL 95 195006 (2005) Q is the quenching signal – the difference between the lifetime spectra for compressed and expanded beams. Q is attributed to Ps-Ps interactions

43. Michael Charlton -LAL Lecture 28-02-06 Positronium – misc. Ground state and n = 2 hyperfine intervals Ps negative ion lifetime p-Ps lifetime