1 / 20

Measurements of Total π - -p Charge Exchange Cross Sections at Low Energies

Pion-nucleon scattering at low energies Johannes Breitschopf , Physikalisches Institut Universität Tübingen. Measurements of Total π - -p Charge Exchange Cross Sections at Low Energies. TRIUMF: differential cross sections at 20 – 68 MeV → Roman Tacik PSI:

ipo
Download Presentation

Measurements of Total π - -p Charge Exchange Cross Sections at Low Energies

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Pion-nucleon scattering at low energies Johannes Breitschopf , Physikalisches Institut Universität Tübingen Measurements of Total π--p Charge Exchange Cross Sections at Low Energies • TRIUMF: • differential cross sections • at 20 – 68 MeV • → Roman Tacik • PSI: • 1. Analyzing powers of • scattering at 45 – 90 MeV • 2. Total SCX cross sections • at 40 – 250 MeV Aim: Reliable data base for πp scattering below 100 MeV • σ-term •πNN coupling constant •strong isospin breaking

  2. A_y at PSI with LEPS p Detector s+ s- ±p Tp Q p Beam Polarized Proton Target Analyzing power measurement at PSI: Principle Background suppression: Active polarized target

  3. Active target Active polarized target B. van den Brandt et al., NIM A446 (2000) PM 3He/4He 4He BC 800 lightguide 800mm, Æ 12mm light- guide m wave- guide quarz- adapter scintillator Helmholtz coils beam 18 mm 5 mm targetcell / mixing chamber 18 mm

  4. Background suppression Active polarized target for background suppression Focal plane spectrum 1. without constraint 2.-4. with increasing size of active target signal. π+ scattering at Tπ = 68.6 MeV, θcm = 81.3°

  5. Results A_y pi+ LEPS/PSI Phys. Lett. B588 (2004) 155 Wieser et al., PRC54 (1995) KH80 SAID FA02 p+p

  6. KH80 SAID FA02 LEPS/PSI Phys. Lett. B588 (2004) 155 J. D. Patterson et al., Pys. Rev. C66 (2002) 025207 p-p

  7. Total cross section for π-p →π0n (SCX) Total SCX cross section Δ-resonance region Low energy region

  8. π p elastic scattering SCX ? Test of isospin breaking Test of isospin breaking

  9. ←10 cm → I =I0e-ασ I0 7mm → ← Principle of Measurement π- π- neutrals: SCX 4π scintillation detector Target ←20 cm → Principle of experiment 2 mm →← π- p  π0 n π- beam definition counters

  10. transmission 0.991398(12) 58 270 414 - 57 768 918 = 501 223 neutrals 57 768 918 pions seen in box Data acqusition? neutrals CH2 Data acquisition DAQ: All parameters (TDC, ADC, FADC) event-by-event (total of 3.5 TB) 58 270 414 pions Typical example:

  11. i = C, CH2 0 = empty target α = target thickness Typical target dimensions: 3.5 cm x 4.0 cm x 7.6 mm (CH2) 3.5 cm x 4.0 cm x 4.5 mm (C)

  12. Detector and corrections Modeling of the detector in GEANT3 • Corrections: • GEANT 3 and 4 • detection of • neutrals: • γ’s (5.5%), • n’s (2%), • π0-Dalitz (1.2%) • muons • In addition • π - – capture • randoms • efficiencies

  13. Corretions_all πM1 Corrections for detection of neutrals πE3 GEANT3

  14. Preliminary results from πM1 channel

  15. Percent deviation from SAID FA02

  16. Comparison with other data and predictions

  17. Percent deviation from SAID FA02 in comparison with other data

  18. @PSI: • Analyzing powers 45 – 90 MeV • R. Meier, M. Cröni et al.,Phys. Lett. B588 (2004) 155 Similar findings for @TRIUMF J. D. Patterson et al.,Phys. Rev. C66 (2002) 025207 Summary and outlook I Summary1 • No strong deviations from KH80 or SAID FA02. • Experimental data tend to be below predictions at • the lowest energies.

  19. Summary and outlook II Summary2 • SCX @PSI:Total SCX cross sections • Transmission on CH2 and C in event mode (3.5 TB) • πM1 channel: 60 – 250 MeV, ~ 2% statistical error • ~ 1 – 2% systematical error • Findings (preliminary): • Confirms Bugg et al. data • About 3% above Friedman et al. data • Excellent agreement with SAID SM95/FA02 • Below KH80 up to 170 MeV πE3 channel: 40 – 80 MeV • Of particular interest for isospin breaking • Analysis in progress

  20. Collaboration Analyzing powers R. Meier, M. Cröni,R. Bilger, J. Breitschopf, H. Clement, H. Denz, J. Pätzold, G. J. Wagner Physikalisches Institut, Univ. Tübingen, Tübingen, Germany B. van den Brandt, P. Hautle, J. A. Konter, S. Mango Paul Scherrer Institut, Villigen, Switzerland G. J. Hofman, M. Pavan TRIUMF, Vancouver, British Columbia, Canada J. Comfort Arizona State University, Tempe, Arizona, USA K. Föhl School of Physics, Univ. of Edinburgh, UK E. Friedman Racah Inst. of Physics, The Hebrew University, Jerusalem, Israel SCX J. Breitschopf,M. Bauer, H. Clement, M. Cröni, H. Denz, R. Meier, G.J. Wagner Physikalisches Institut, Univ. Tübingen, Tübingen, Germany E. Friedman Racah Inst. of Physics, The Hebrew University, Jerusalem, Israel E. Gibson California State University, Sacramento, USA Supported by BMBF (06Tü9871) and DFG (European Gradudate School Basel – Tübingen)

More Related