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X 0 , X 0 Polarization at 800 GeV/c. g. p 0. g. X 0 /. X 0. p/ p. L/ L. p - / p +. Theo Alexopoulos. National Technical University of Athens. HEP2003. Athens, Greece. Outline. KTeV Experiment. Description of Polarization. Method of Measurement. KTeV Polarization Results.

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  1. X0, X0 Polarization at 800 GeV/c g p0 g X0 / X0 p/p L/L p-/p+ Theo Alexopoulos National Technical University of Athens HEP2003 Athens, Greece

  2. Outline • KTeV Experiment • Description of Polarization • Method of Measurement • KTeV Polarization Results • Summary

  3. KTeV Experiment Ran for a year in 97 E832 E799II e’/e to 10-4 Rare decays to 10-11 KS p0 L,X0,S0 KL Rare decays Hyperons Rare decays KTeV99 ran in 99-00

  4. CP Violation 50m decay volume under vacuum K-Physics Exp. rare Kaon/hyperon decays

  5. Highlights of the KTeV Detector • Pure CsI EM Calorimeter • Drift Chambers Position resolution < 1mm Position resolution ~ 100mm Energy resolution < 1.0% • Photon Veto system • m-system e- from Ke3 DE/E 1% 0.4% P E/P

  6. What Do We Know about Hyperon Polarization(1)? Polarization depends on Pp, production angle/targeting angle, and material of the target. • Polarization reverses sign with production angle/targeting angle, and is zero at production angle q=0. Polarization is expressed as a function of transverse momentum pt =pXsinq, & momentum fraction of produced X, xF=pX/800 pp target q pX q=4.8 mrad pt

  7. What Do We Know about Hyperon Polarization(2)? • Anti-Hyperons have not been observed to be produced polarized, except for X+ and S- in E756, E761, both with incident protons at 800 GeV/c. • Anti-Hyperons were produced with the same sign and magnitude as their hyperon counterparts. QCD/PQCD can’t predict anything at small pt . Only prediction: P=0 for pt>4GeV/c

  8. X0, X0 Reconstruction g p0 g X0 / X0 p/p L/L p-/p+ zlampi0 Analysis cuts zppi A) ppr>120GeV/c B) zppi-zlampi0>1m C) 95m<zlampi0<150m D) d>25cm E) pt2<0.001(GeV/c)2 F) (M(ppi)-1.116)<0.010GeV/c2 G) Fiducial cuts; zlampi0 in the beam holes H) proton to be confined in the beam hole I) E/P (for pion) <0.8

  9. Mass peaks Ξο Λ πο before cuts after cuts

  10. Analysis Method x qx qz z polarization qy y Method I: Method II:

  11. Hyperon production at KTeV protons 800GeV/c y z x pbeam pX q n

  12. Polarization Precession from sweeper Magnets PX PX PX B target B B x NM3S NM2S1 NM2S2 NM2S3 NM2SR z y Where m in nuclear magnetons, for X is -1.250 and for L -0.613

  13. Asymmetry measurement Ξο Λ πο Ξο Λ πο

  14. Polarization Results

  15. Conclusions • X0 polarization at KTeV: Average Polarization: • X0 polarization at KTeV: Average Polarization: This result is valid for:

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