1 / 21

C x and C x for K + Λ and K + S o Photo-production

C x and C x for K + Λ and K + S o Photo-production. R. Bradford Department of Physics and Astronomy, University of Rochester R. Schumacher Department of Physics and Astronomy, Carnegie Mellon University for the CLAS Collaboration. Overview. What are C x and C z ?

juana
Download Presentation

C x and C x for K + Λ and K + S o Photo-production

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. Cx and Cx for K+Λ and K+So Photo-production R. Bradford Department of Physics and Astronomy, University of Rochester R. Schumacher Department of Physics and Astronomy, Carnegie Mellon University for the CLAS Collaboration

  2. Overview • What are Cx and Cz? • Experimental Setup/Jefferson Lab • Overview of measurement/analysis techniques • Results for K+Λ and K+So • comparison with available models

  3. K+  X KCM p y Z Y What are Cx and Cz? In CM frame: Measure polarization transfer from g to Y in the production plane, along “z” or “x”

  4. Our data came from Jlab... • Tagged g beam on LH2 target. • 2.4 and 3.1 GeV endpoint energies. • g Polarization ~ 65%.

  5. The CLAS Detector in Hall B CEBAF Large Acceptance Spectrometer Torus magnet 6 superconducting coils Electromagnetic calorimeters Lead/scintillator, 1296 photomultipliers Liquid H2 target + g start counter; e minitorus Drift chambers argon/CO2 gas, 35,000 cells Gas Cherenkov counters e/p separation, 256 PMTs Time-of-flight counters plastic scintillators, 684 photomultipliers

  6. An advertisement... This analysis has also produced differential cross section measurements. See nucl/ex0509033

  7. Analysis Strategy Extract Cx and Cz using beam helicity asymmetry, Ax/z: Nx/z± = helicity-dependent yield eff = Effective weak decay asymmetry = 0.642 for L, -0.165 for So.  = photon beam polarization No acceptance correction necessary!!

  8. L Beam Helicity Asymmetry S0 - cos(θp) Analysis Details • For both channels, detect K+p. • L or So hyperon recreated from p(g,K+)X missing mass. • Yield extracted with fit. • Construct helicity asymmetries • Extract slope from linear fit.

  9. Photon Polarization Determination • Polarization of e- beam measured with Moller Polarimeter. • Polarization of  beam calculated using the Maximon and Olson relation (See: L.C. Maximon and H. Olson, Phys Rev 114, 887 (1959). P/Pe Ratio

  10. L Results Models: F.X.Lee et al, Nucl Phys A 695, 237, 2001; S. Janssen, PhD Thesis, Univ. of Gent, 2001

  11. L: Mid-Angles

  12. L: Mid-Angles

  13. L: Mid-Forward

  14. L: Foward Angles

  15. So: Backward angles

  16. So: Mid angles

  17. So: Forward angles

  18. Summary... • We have made first measurements of Cx and Cz for gp→K+L and gp→K+So. • The recoil L is shown to be almost maximally polarized along the direction of the incident g polarization. • The recoiling So has nonzero polarization, but with no preferred direction. • A paper is in the works....

  19. Supplemental Slides

  20. L weak decay asymmetry parameter = 0.642 Dillution to decay of So. Correction related to reference frame A note about So: We study So through its decay to gL. This results to changes in the effective value of the weak decay asymmetry parameter.

  21. A note about So, cont’d: Source: R.A. Schumacher, et al. Proton angular distribution in the So rest frame. CLAS-Note 2005-013. Posted at: http://www1.jlab.org/ul/Physics/Hall%2DB/clas/analysisIndex.cfm?note_year=2005

More Related