1. 55. Jahrestagung der ÖPG, September 2005 Pionischer Wasserstoff: Präzisionsmessungen zur starken Wechselwirkung J. Marton Stefan Meyer Institut der ÖAW on behalf of the Pionic Hydrogen Collaboration

2. 55. Jahrestagung der ÖPG, September 2005 Physics Goals  N coupling constant (using Goldberger Miyazawa Oehme sum rule) pion-nucleon sigma term (measure of chiral symmetry breaking) High precision values for the hadronic shift and width of the 1s ground state of pionic hydrogen  pion-nucleon scattering lengths (isoscalar, isovector) with an accuracy at the percent level scattering lengths  basis for comparison of changes in the nuclear medium

3. 55. Jahrestagung der ÖPG, September 2005 Pion-Nucleon Scattering Lengths shift data from pionic hydrogen and deuterium, width from pionic hydrogen (Schröder et al.,2001) >>> W. Thirring 1954

4. 55. Jahrestagung der ÖPG, September 2005 Electromagnetic Cascade of  p 1 observables: shift and width 1s state Pion decay  ~10 -8 s slow compared to reaction rates  precise QED calculations  advanced cascade theory  p is not an isolated system  interaction with hydrogen

5. 55. Jahrestagung der ÖPG, September 2005 Principle of Set-Up high stop density  high X - ray line yields  bright X - ray source position & energy resolution  background reduction by analysis of CCD hit pattern spherically bent Bragg crystal ultimate energy resolution

6. 55. Jahrestagung der ÖPG, September 2005 SET-UP at PSI crystal spectrometer spherically bent crystals CCD X-ray detector 2  3 matrix X-ray tube cryogenic target cyclotron trap II

7. 55. Jahrestagung der ÖPG, September 2005 Experimental Method Bragg crystal CCD X-ray detector Target and cyclotron trap

8. 55. Jahrestagung der ÖPG, September 2005 Cyclotron Trap with Target and Degraders X - rays   beam    stop efficiency f stop  density  1% @  stp 10 9  /s super-conducting split coil magnet

9. 55. Jahrestagung der ÖPG, September 2005 Spherically curved Bragg crystal 100 mm 

10. 55. Jahrestagung der ÖPG, September 2005 Large - Area Focal Plane CCD Detector N. Nelms et al., Nucl. Instr. Meth 484 (2002) 419 2  3 CCD 22 array pixel size 40  m  40  m 600  600 pixels per chip operated at – 100°C   150 eV @ 4 keV  X  90% image area storage area flexible boards cooling (LN 2 )  

11. 55. Jahrestagung der ÖPG, September 2005  high pion flux in  E5 at PSI p  =112 MeV/c, ~ 10 9  - /s  cyclotron trap for small stop volume and high stopping efficiency  Light weight cryogenic target for wide density range  spherically bent Bragg crystals characterization by ECRIT X-ray source  position sensitive X-ray detection with CCD array: CCD-22 background reduction by shielding and pixel analysis of CCD data  calibration lines (pionic oxygen) measured in parallel Features of the Experiment

12. 55. Jahrestagung der ÖPG, September 2005 πp Hadronic Shift and Width e.m. transition without strong interaction attractive shift Goals: Shift 0.2% Width 1% Molecular effects Doppler broadening Coulomb deexcitation required resolution: 1:100000 careful study of small effects Stability & Calibration

13. 55. Jahrestagung der ÖPG, September 2005  extention of parameter space: measurements of shift and width with different  Doppler broadening of width to be measured with muonic hydrogen X-rays (no hadronic interaction) Experimental Procedure  densities  X-ray transitions (4p-1s, 3p-1s, 2p-1s)  Investigations on molecular effects Coulomb transitions effecting the width

14. 55. Jahrestagung der ÖPG, September 2005  H(3p-1s) energy no density dependence identified  1s = + 7.116  0.008  0.007 eV  E QED = ± 0.006 eV P. Indelicato, priv. comm.   previous experiment LH 2 previous experiment ETHZ-PSIH.-Ch.Schröder et al. Eur.Phys.J.C 1(2001)473 Density Effect ? Molecular formation ("Vesman“ mechanism)  p + H 2  [(  pp) p] ee

15. 55. Jahrestagung der ÖPG, September 2005 Electron Cyclotron Resonance Ion Trap cyclotron trap (4) + hexapole magnet (2) ( D. Hitz et al., Rev. Sci. Instr., 71 (2000) 1116)  large mirror ratio B max / B min ! argon / oxygen (1/9) 1.4  10 -6 mbar HF 6.4 Ghz Response Function H- and He-like electronic atoms T ion  5 eV "cold" plasma  narrow X-ray transitions  X = 10 - 40 meV  high X-ray intensity: short measuring time First plasma inside ECRIT

16. 55. Jahrestagung der ÖPG, September 2005 ECRIT and Crystal Spectrometer D.F.Anagnostopoulos et al., Nucl. Instr. Meth. B 205 (2003) 9 CCD detector aperture  6.4 GHz, 450 W  = 10 –8 s M1 transitions in He-like S, Cl and Ar  response function very well understood

17. 55. Jahrestagung der ÖPG, September 2005 previous experiment H.-Ch.Schröder et al. Eur.Phys.J.C 21 (2001) 473 not corrected for Coulomb de-excitation crystal resolution subtracted 15 3.5 3.5 28.5 LH 2 10 bar Line Width Analysis

18. 55. Jahrestagung der ÖPG, September 2005 Hadronic Width (preliminary) Hadronic width – corrected for Doppler effect due to Coulomb de-excitation Preliminary average value for the hadronic width  1s = 785 ± 27 meV

19. 55. Jahrestagung der ÖPG, September 2005 Coulomb de-excitation  low-energy component Coulomb de-excitation  high-energy components Muonic Hydrogen ----- Crystal response ECRIT 2004 µH R-98.01 December 2004

20. 55. Jahrestagung der ÖPG, September 2005 PSI Experiment R98-01 previous exp. 1. step goal  1s /  1s 0.5%   0.2% 0.2% reached  1s /  1s 7 %   3 % 1% Results on Pionic Hydrogen Work in progress:  H Coulomb de-excitation  analysis  Hhigh statistic run

21. 55. Jahrestagung der ÖPG, September 2005 Status of πp Experiment Density dependence studies of the  1s  no effect of molecular effects at our accuracy found  value consistent with result of previous experiment Measurement of transitions from 4p, 3p and 2p to 1s  influence of cascade processes on width (due to Coulomb de-excitation) visible  Doppler effect ECRIT  response function extracted Precision measurement of µp X-ray spectrum  study of the Doppler broadening due to Coulomb transitions

22. 55. Jahrestagung der ÖPG, September 2005 Outlook Analysis in progress High statistics measurement / high resolution crystal Thank you for your attention