1. FB18, Santos JZ / Aug. 25, 2006 Experimental Studies on Kaonic Atoms at DA  NE Johann Zmeskal Stefan Meyer Institute for subatomic Physics Austrian Academy of Sciences, Vienna, Austria for the DEAR/SIDDHARTA Collaborations 18th International IUPAP Conference on Few-Body Problems in Physics Aug. 21 – 26, 2006 - Santos, Brazil LNF - Italy SMI - Austria INFN Trieste - Italy IPNE - Romania Univ. Fribourg - Switzerland Univ. Neuchâtel - Switzerland RIKEN - Japan Univ. Tokyo - Japan Univ. Victoria - Canada UCB - USA

2. FB18, Santos JZ / Aug. 25, 2006 2 Content Motivation The DEAR experimental set-up Kaonic atom measurements with DEAR  Results on kaonic nitrogen  Results on kaonic hydrogen The SIDDHARTA project  New X-ray detectors  New setup  Physics goals Summary & Outlook

3. FB18, Santos JZ / Aug. 25, 2006 3 Experiments with exotic atoms, a broad research field K - p, K - d  - p,  - d ….

4. FB18, Santos JZ / Aug. 25, 2006 4 Motivations  K - p simplest exotic atom with strangeness  strong interaction shift ε 1s and width Γ 1s directly observable by X-ray spectroscopy  K - p: Information on Λ(1405) antikaon bound nuclear clusters  (A. Gal P24, Theory overview of antikaon bound state N.V. Shevchenko R1-26, Search for a K - pp bound state)  kaonic hydrogen, precision data missing  kaonic deuterium never measured before

5. FB18, Santos JZ / Aug. 25, 2006 5 Kaonic Hydrogen - Goals Measurement of strong interaction shift and width of kaonic hydrogen and kaonic deuterium with an accuracy of a few eV Determination of the isospin dependent scattering lengths near threshold no extrapolation to zero energy Testing chiral symmetry breaking in systems with strangeness

6. FB18, Santos JZ / Aug. 25, 2006 6 Review – results before DEAR K - p interaction attractive/repulsive ? Solution by KEK experiment width  1s  [eV] KpX -5005000 0 200 400 600 800 1000 shift  1s [eV] Davies et al, 1979 Izycki et al, 1980 Bird et al, 1983 repulsive attractive KpX (KEK) M. Iwasaki et al, 1997  = - 323 ± 63 ± 11 eV  = 407 ± 208 ± 100 eV

7. FB18, Santos JZ / Aug. 25, 2006 7 Strong Interaction in K - p  1s  1s s p d f E 1s } E 2p n 4 3 2 1 KK Due to the strong interaction kaon-proton the 1s level is shifted and broadened Shift and width of states n>1 negligible K   keV ε 1s = E 2p-1s (meas.) – E 2p-1s (e.m.)

8. FB18, Santos JZ / Aug. 25, 2006 8 Scattering Lengths Relation of strong interaction shift and width to the complex Kp scattering length a K - p For the determination of the isospin dependent scattering lengths a 0 and a 1 the hadronic shift and width of kaonic hydrogen and kaonic deuterium are necessary

9. FB18, Santos JZ / Aug. 25, 2006 9 Requirements Kaon Beam at DA  NE with unique performance Slow, nearly monochromatic kaons (E~16 MeV) Kaon pair emitted back-to-back Low hadronic background Target System Cryogenic gas target, pure hydrogen gas Thin windows, light-weight construction X-ray Detector Large active area Superior energy resolution Background suppression capability Calibration “online“ calbration – fluorescence lines

10. FB18, Santos JZ / Aug. 25, 2006 10 DA  NE (LNFrascati) electron – positron collider collision energy tuned to the Φ resonance at 1.02 GeV c.m. electron – positron collider collision energy tuned to the Φ resonance at 1.02 GeV c.m. DEAR

11. FB18, Santos JZ / Aug. 25, 2006 11 DEAR Setup at DAΦNE TMP CCD electronics Vacuum chamber APD Cryo-Cooler Target Cell CCD cooling CCD pre-amplifier CCD55-chips e + e - K-K-

12. FB18, Santos JZ / Aug. 25, 2006 12 CCD X-ray Detection Array of 16 CCD55-30 -1242 x 1152 pixels / chip - pixel size 22.5 x 22.5 µm - total area per chip 7.24 cm 2 - depletion depth ~30 µm - read-out time per CCD 2 min. - energy resolution ~150 eV @ 6keV - temperature stabilized at 165 K Array of 16 CCD55-30 -1242 x 1152 pixels / chip - pixel size 22.5 x 22.5 µm - total area per chip 7.24 cm 2 - depletion depth ~30 µm - read-out time per CCD 2 min. - energy resolution ~150 eV @ 6keV - temperature stabilized at 165 K

13. FB18, Santos JZ / Aug. 25, 2006 13 DEAR Target Light-weight cylindrical target structure Diameter: 12.5 cm Height: 14 cm Volume: 1150 ccm Side wall: 75 µm Hostaphan Entrance window: 125 µm Hostaphan Grid structure: glass fiber reinforced epoxy Hydrogen filling: Temperature:25 K (hydrogen) Pressure: 2 bar Density: 2.1 g/l (3 % LHD) Light-weight cylindrical target structure Diameter: 12.5 cm Height: 14 cm Volume: 1150 ccm Side wall: 75 µm Hostaphan Entrance window: 125 µm Hostaphan Grid structure: glass fiber reinforced epoxy Hydrogen filling: Temperature:25 K (hydrogen) Pressure: 2 bar Density: 2.1 g/l (3 % LHD) kaon

14. FB18, Santos JZ / Aug. 25, 2006 14 Kaonic nitrogen published in : Phys. Lett. B 593 (2004) 48-54

15. FB18, Santos JZ / Aug. 25, 2006 15 Resulting K - p X-ray Spectrum X-ray energy spectrum with all background fit-components subtracted  1s = - 193 ± 37 (stat.) ± 6 (syst.) eV  1s = 249 ± 111 (stat.) ± 30 (syst.) eV  1s = - 193 ± 37 (stat.) ± 6 (syst.) eV  1s = 249 ± 111 (stat.) ± 30 (syst.) eV At lowest order: a K-p = (-0.468 ± 0.090stat± 0.015syst) + i(0.302± 0.135stat± 0.036syst) fm

16. FB18, Santos JZ / Aug. 25, 2006 16 DEAR Results width  1s  [eV] KpX -5005000 0 200 400 600 800 1000 shift  1s [eV] Davies et al, 1979 Izycki et al, 1980 Bird et al, 1983 repulsive attractive KpX (KEK) M. Iwasaki et al, 1997  = - 323 ± 63 ± 11 eV  = 407 ± 208 ± 100 eV DEAR

17. FB18, Santos JZ / Aug. 25, 2006 17 From DEAR to SIDDHARTA Precision of the DEAR result limited by high X-ray background (S/N~1:70) Next step: background reduction by using kaon – X-ray time correlation (expected background suppression ~ 3 orders of magnitude  S/N ~ 10:1 for kaonic hydrogen)  New X-ray detectors  SDDs  New dedicated target-detector set-up

18. FB18, Santos JZ / Aug. 25, 2006 18 New X-ray Detector - SDD New X-ray detectors with  timing capability  background suppression by using the kaon - X ray time correlation  excellent energy resolution  high intrinsic efficiency, large area  Development of large area SDD detectors JRA10 in I3HP (EU FP6)

19. FB18, Santos JZ / Aug. 25, 2006 19 Silicon Drift Detector SDD Large area SDD with 1 cm 2 active area 3 SDD on 1 chip  SDD has small capacitance  low noise  Good energy resolution, comparable with CCD  But: timing capability (  t < 0.5 µs) SDD with JFET

20. FB18, Santos JZ / Aug. 25, 2006 20 Performance of Large SDDs First application of large (1 cm 2 ) SDDs in K-He experiment at KEK (see talk by S. Okada at this Workshop)

21. FB18, Santos JZ / Aug. 25, 2006 21 Triple coincidence: SDD X * Scint K * Scint K Scintillator hydrogen gas SDD e+e+ e-e-  K+K+ K-K- X-ray Background suppression

22. FB18, Santos JZ / Aug. 25, 2006 22 Energy (keV) No timing SDD ‚single‘ coinc. SDD * Scint * Scint Background suppression to < 10 -3 Kaonic deuterium KK K  Ag K fluorescence lines (calibration) Kaonic Deuterium (MC)

23. FB18, Santos JZ / Aug. 25, 2006 23 SIDDHARTA Setup Cryogenic setup SDD array (~200 cm 2 SDDs)

24. FB18, Santos JZ / Aug. 25, 2006 24 SDD unit (2x3x3 SDDs)

25. FB18, Santos JZ / Aug. 25, 2006 25 SIDDHARTA Setup cont‘d Cryogenic target cell Target cell – SDD array assembly Cryogenic target cell 75 µm Kapton within a pure aluminum grid P max. ~ 5 bar

26. FB18, Santos JZ / Aug. 25, 2006 26 SIDDHARTA Setup – side view SDD Array Gas target Beam pipe Kaon Detector

27. FB18, Santos JZ / Aug. 25, 2006 27 Material Analysis by PIXE Carefully selected structure materials analyzed by PIXE@VERA: Avoiding iron content

28. FB18, Santos JZ / Aug. 25, 2006 28 Monte Carlo Results Counts Energy [keV] K-pK-pK-dK-d KαKα KβKβ KγKγ K high Monte Carlo simulated X-ray spectra (data taking 30 days). Measurement with SDD array and kaon trigger. K - p: ε 1s = 193 eV, Γ 1s = 249 eV, Y(K α )=2%  ε 1s = 2eV,  Γ 1s = 4eV K - d: ε 1s = 325 eV, Γ 1s = 630 eV, Y(K α )=0.2%  ε 1s = 18eV,  Γ 1s = 45eV

29. FB18, Santos JZ / Aug. 25, 2006 29 SIDDHARTA - Outlook width  1s  [eV] KpX -5005000 0 200 400 600 800 1000 shift  1s [eV] Davies et al, 1979 Izycki et al, 1980 Bird et al, 1983 KpX (KEK) M. Iwasaki et al, 1997  = - 323 ± 63 ± 11 eV  = 407 ± 208 ± 100 eV DEAR SIDDHARTA

30. FB18, Santos JZ / Aug. 25, 2006 30 Outlook Future physics program at DAΦNE Measurement of kaonic deuterium (first measurement ever) Precision measurement of kaonic hydrogen (at the percent level). Further perspectives: Kaonic helium studies with 3 He and 4 He targets Precision measurement of charged kaon mass

31. FB18, Santos JZ / Aug. 25, 2006 31 SUMMARY First production of exotic atoms at DAΦNE, Successful measurements on kaonic hydrogen New X-ray detector (SDD array) and setup in preparation, Installation at DAΦNE 2007  repulsive shift in K - p verified  smaller shift and width values, higher precision

32. FB18, Santos JZ / Aug. 25, 2006 32 Spare

33. FB18, Santos JZ / Aug. 25, 2006 33 Results on kaonic nitrogen 3 X-ray transitions - first measured extraction of the transition yields for 7-6, 6-5, 5-4

34. FB18, Santos JZ / Aug. 25, 2006 34 K - p and K - d Atoms Kaonic AtomKaonic HydrogenKaonic Deuterium e.m. position of K  line (eV) 64807810  1s (eV) ~200 (DEAR)*) theory  1s (eV) ~250 (DEAR)*) theory X-ray Yield (K  )1-3 %~0.2% (estimate) *) new studies: c.f. A.N. Ivanov et al., Eur.Phys.J. A 23 (2005) 79, U.-G. Meißner, U. Raha and A. Rusetsky, arXiv:nucl-th/0603029, 2006 K - p (K - d) e.m. bound kaonic atoms, Bohr radius ~80 fm