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ATHENA: a High Performance detector for Low Energy physics

ATHENA: a High Performance detector for Low Energy physics. Univ. of Tokyo Ryo FUNAKOSHI ATHENA collaboration. Out Line. Introduction - antiproton facility at CERN ATHENA experiment (focused on detector) - setup (trap + detector), electronics, feature Detection of antihydrogen

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ATHENA: a High Performance detector for Low Energy physics

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  1. ATHENA: a High Performance detector for Low Energy physics Univ. of Tokyo Ryo FUNAKOSHI ATHENA collaboration

  2. Out Line • Introduction - antiproton facility at CERN • ATHENA experiment(focused on detector) - setup (trap + detector), electronics, feature • Detection of antihydrogen - detection scheme • Future experiment - antihydrogen trap (just idea)

  3. Slow Antiproton Facilityat CERN

  4. Introduction:Antiproton Decelerator (AD) • Low energy antiproton source (only one) • Stochastic & electron cooling • Antiproton: 3.5 GeV/c -> 100 MeV/c • Pulse beam, every 85 s （~2 x 107 antiprotons）

  5. Introduction:Antiproton facility at CERN ATRAP ATHENA ASACUSA AD 1999- LEAR 1986-1996 Three experiments in AD hall: Athena --- Antihydrogen Asacusa --- Pbar He, etc. Atrap --- Antihydrogen • 1992 Proposed by Munger et al.: • pbar + Z → hbar • 1996 9 events antihydrogen • (however life time ~40 ns)

  6. ATHENA experiment

  7. Introduction:ATHENA collaboration Univ. of Aarhus, Denmark Univ. of Brescia, Italy Univ. of Genova, Italy CERN, Geneva, Suisse Univ. of Pavia, Italy Univ. of Rio, Brazil Univ. of Swansee, Wales (UK) Univ. of Tokyo, Japan Univ. of Zurich, Suisse INFN, Italy LANL, USA

  8. ATHENA experiment:Basic shame

  9. ATHENA experiment:Motivations

  10. ATHENA Instruments ATHENA apparatus Features • strong e+ source • high performance detector • plasma manipulation

  11. ATHENA experiment:Overview of apparatus Antiproton catching trap Positron accumulator Mixing trap Antihydrogen detector

  12. ATHENA experiment:Main detector ・ compact, operation under strong B field ・ large solid angle > 80% ・ high granularity； Si : 2 layers, ~8000ch. -> charged particles CsI : 192ch. -> 511keV photons

  13. ATHENA experiment:Silicon module Thickness: 380mm • Double sided sensors • Read out VA2_TA chip (manufacture)

  14. ATHENA experiment:CsI crystals Resolution FWHM ~ 18% Efficiency ~ 20 % VA2_TA chip

  15. ATHENA experiment:Installation <Trap> P<10-12mbar, T~15K Cold nose <Detector> P~10-9mbar, T~130K

  16. ATHENA experiment:Antiproton catching Segmented Si (67 µ) beam counter Antiproton Capture Trap ～10000 antiprotons per AD shot

  17. ATHENA experiment :Imaging by Silicon detector non-destructive monitoring system YZ-projection Event display 3D image of antiproton annihilations XY-projection

  18. ATHENA experiment :Imaging by Silicon detector M. C. Fujiwara et al., Phys. Rev. Lett. 92, 065005 (2004) non-destructive 3D image of antiproton annihilations

  19. Detection of Cold Antihydrogenwith High-performance detector

  20. Cold antihydrogen:Production scheme qgg 104 pbars 108 e+ qgg • mixing 104 antiprotons + 108 e+ • annihilation of produced antihydrogen -> escape from B confinement -> charged particles from p annihilations -> two 511keV photons from e+ annihilations （back-to-back） • Vertex reconstruction by trace of charged particle paths • (Si-strip) Si-strip annihilation • Extrapolation of two 511keVphotons to the vertex (CsI crystals) Antihydrogen production 2.5 cm 3T Antihydrogen event Opening angle between two photons; cosqgg = -1 CsI crystals

  21. Cold antihydrogen:Detection efficiency Detection scheme Antihydrogen annihilation ~50% Vertex reconstruction ~10% Opening angle selection （ 2 x 511keV photons） ~5% Antihydrogen events Total efficiency ~ 0.25% 50,000 antihydrogen

  22. Cold antihydrogen:Cold antihydrogen I Antiproton annihilation distribution `Cold mixing’ `Hot mixing’

  23. Cold antihydrogen:Cold antihydrogen II 131± 22 GoldenEvents • Antiprotons only • Displaced 511keV energy window 1. `Hot mixing’  suppress antihydrogen production

  24. For the future :Estimated temperature Isolated hbar spatial distribution (“Cold mix.” – “Hot mix.”) Model • Hbar formation before thermal equilibrium • Including the plasma rotating (80kHz) • Two-temperature Gaussian distribution No Te+ dependence Best fit with Taxial = 10 x Tradial N. Madsenet al., Phys. Rev. Lett. 94, 033403 (2005) Temperature of antihydrogen > 150K (ATHENA experiment)

  25. For the future next experiment

  26. For the future:Motivation High precision tests for CPT (e/m) (matter)(antimatter) same mass & life time, same & opposite charge 2005 Impossible to do with ATHENA type equipment; Once antihydrogen has been trapped, any type of precision measurement can be contemplated

  27. For the future :Antihydrogen trap I Idea -neutral atom trap - Well depth ~ 0.7 K/T Aside: high n-states could have higher m

  28. For the future :Antihydrogen trap II + ATHENA type (trap + detector) amulipole trap +

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