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Pionic Hydrogen – Precision Measurements at PSI

Pionic Hydrogen – Precision Measurements at PSI. J. Marton Stefan Meyer Institut (SMI) / ÖAW on behalf of the Pionic Hydrogen Collaboration @ PSI. a Ioannina – b Coimbra – c SMI – d Jülich – e Paris – f PSI. Physics Goals. High precision values for the hadronic shift

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Pionic Hydrogen – Precision Measurements at PSI

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  1. Pionic Hydrogen – Precision Measurements at PSI J. Marton Stefan Meyer Institut (SMI) / ÖAW on behalf of the Pionic Hydrogen Collaboration @ PSI aIoannina – bCoimbra – cSMI – dJülich – eParis – fPSI PANIC, October 24-28, 2005

  2. Physics Goals • 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 N coupling constant (using Goldberger Miyazawa Oehme sum rule) pion-nucleon sigma term (measure of chiral symmetry breaking) PANIC, October 24-28, 2005

  3. Pion-Nucleon Scattering Lengths For e.m. contributions see talk by T.E.O- Ericson at this conference (IV.7.) shift data from pionic hydrogen and deuterium, width from pionic hydrogen (Schröder et al.,2001) PANIC, October 24-28, 2005

  4. Electromagnetic Cascade of p 1 observables: shift and width 1s state p is not an isolated system  interaction with hydrogen • precise QED calculations • advanced cascade theory • Pion decay • ~10-8 s slow compared to reaction rates PANIC, October 24-28, 2005

  5. Principle of Set-Up ultimate energy resolution spherically bent Bragg crystal high stop density  high X - ray line yields  bright X - ray source • position & energy resolution • background reduction by analysis of CCD hit pattern PANIC, October 24-28, 2005

  6. SET-UP at PSI cyclotron trap II X-ray tube cryogenic target crystal spectrometer spherically bent crystals CCD X-ray detector 2  3 matrix PANIC, October 24-28, 2005

  7. Experimental Method Target and cyclotron trap Bragg crystal CCD X-ray detector PANIC, October 24-28, 2005

  8. Cyclotron Trap with Target and Degraders super-conducting split coil magnet  beam  109/s   stop efficiency fstop  density  1% @ stp  X - rays PANIC, October 24-28, 2005

  9. Spherically curved Bragg crystal 100 mm  PANIC, October 24-28, 2005

  10. Large - Area Focal Plane CCD Detector 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% cooling (LN2) storage area  flexible boards  image area N. Nelms et al., Nucl. Instr. Meth 484 (2002) 419 PANIC, October 24-28, 2005

  11. Features of the Experiment • highpion flux in E5 at PSI p=112 MeV/c, ~ 109 -/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 PANIC, October 24-28, 2005

  12. πp Hadronic Shift and Width Goals: Shift 0.2% Width 1% required resolution: 1:100000 attractive shift careful study of small effects e.m. transition without strong interaction Molecular effects Doppler broadening Coulomb deexcitation Stability & Calibration PANIC, October 24-28, 2005

  13. Experimental Procedure • 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) • densities • X-ray transitions (4p-1s, 3p-1s, 2p-1s) • Investigations on molecular effects Coulomb transitions effecting the width PANIC, October 24-28, 2005

  14. Density Effect ? Molecular formation ("Vesman“ mechanism) p + H2 [(pp)p] ee H(3p-1s) energy no density dependence identified 1s = + 7.116  0.008  0.007 eV LH2  EQED = ± 0.006 eV P. Indelicato, priv. comm. previous experiment previous experiment ETHZ-PSI H.-Ch.Schröder et al. Eur.Phys.J.C 1(2001)473 PANIC, October 24-28, 2005

  15. Response Function Electron Cyclotron Resonance Ion Trapcyclotron trap (4) + hexapole magnet (2)(D. Hitz et al., Rev. Sci. Instr., 71 (2000) 1116)  large mirror ratio Bmax / Bmin ! • H- and He-like electronic atoms • Tion 5 eV "cold" plasma • narrow X-ray transitions • X = 10 - 40 meV • high X-ray intensity: short measuring time First plasma inside ECRIT argon / oxygen (1/9) 1.410-6 mbar HF 6.4 Ghz PANIC, October 24-28, 2005

  16. M1 transitions in He-like S, Cl and Ar  = 10–8 s ECRIT and Crystal SpectrometerD.F.Anagnostopoulos et al., Nucl. Instr. Meth. B 205 (2003) 9 aperture  6.4 GHz, 450 W CCD detector  response function very well understood PANIC, October 24-28, 2005

  17. Line Width Analysis not corrected for Coulomb de-excitation crystal resolution subtracted 15 3.5 3.5 28.5 LH2 10 bar previous experiment H.-Ch.Schröder et al. Eur.Phys.J.C 21 (2001) 473 PANIC, October 24-28, 2005

  18. 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 PANIC, October 24-28, 2005

  19. Muonic Hydrogen Coulomb de-excitation • low-energy component Coulomb de-excitation • high-energy components ----- Crystal response ECRIT 2004 µH R-98.01 December 2004 PANIC, October 24-28, 2005

  20. Results on Pionic Hydrogen PSI Experiment R98-01 previous exp. 1. step goal 1s/1s0.5%  0.2%0.2% reached 1s/1s7 %3%1% Work in progress: HCoulomb de-excitation  analysis H high statistic measurement (presently running) PANIC, October 24-28, 2005

  21. 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 PANIC, October 24-28, 2005

  22. Outlook High statistic data  most precise width determination Thank you for your attention PANIC, October 24-28, 2005

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