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Proton, Pion and Kaon Transparency Measurements

Overview of existing and new kaon transparency data, A-dependent analysis, and needed transparency data from 12 GeV. Total hadron-nucleus cross sections and physics of nuclei: color transparency.

andrewstokes
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Proton, Pion and Kaon Transparency Measurements

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  1. Proton, Pion and Kaon Transparency Measurements Rolf Ent INT/Seattle October 27, 2009 • Overview of existing (& new kaon!) transparency data • Questions: • A-dependent analysis – any improvements needed? • What transparency data is needed from 12 GeV?

  2. Total Hadron-Nucleus Cross Sections K Hadron– Nucleus total cross section p _ p a p Fit to Hadron momentum 60, 200, 250 GeV/c a = 0.72 – 0.78, for p, p, k a < 1 interpreted as due to the strongly interacting nature of the probe A. S. Carroll et al. Phys. Lett 80B 319 (1979)

  3. Physics of Nuclei: Color Transparency Traditional nuclear physics calculations (Glauber calculations) predict transparency to be nearly energy independent. Ingredients A(e,e’h), h = hadron 1.0 • sh-N cross-section • Glauber multiple • scattering approximation • Correlations & Final-State • Interaction effects hN T Energy (GeV) 5.0 QCD From fundamental considerations (quantum mechanics, relativity, nature of the strong interaction) it is predicted (Brodsky, Mueller) that fast protons scattered from the nucleus will have decreased final state interactions

  4. Search for Color Transparency in Quasi-free A(e,e’p) Scattering Constant value line fits give good description: c2/df = 1 Conventional Nuclear Physics Calculation by Pandharipande et al. (dashed) also gives good description  No sign of CT yet

  5. A-dependence Studies • Fit to s = soAa • or T = Aa-1 2) Classical attenuation model with effective cross section seff independent of r

  6. Search for Color Transparency in Quasi-free A(e,e’p) Scattering Fit to s = soAa a a = constant = 0.75 Close to proton-nucleus total cross section data! But slightly higher than 0.72-0.73 from free proton-nucleus data.

  7. Search for Color Transparency in Quasi-free A(e,e’p) Scattering Analyzed in terms of an effective cross section with classical attenuation model  follows general energy dependence from free N-N scattering, but at reduced values Tp’ [MeV} 

  8. A(e,e’p+) Missing Mass Spectra Dashed line: two-pion threshold Green: simulated multi-pion yield (following phase space) Solid line: Used cut in transparency analysis (but similar results with a two-pion threshold cut)

  9. Physics of Nuclei: Pion Transparency A(e,e’p+) With CT | W/O CT

  10. Physics of Nuclei: Pion Transparency A(e,e’p+) Red: low-e points |

  11. Physics of Nuclei: Color Transparency A(e,e’p+) With Color Transparency Without Color Transparency Total pion-nucleus cross section slowly disappears, or … pion escape probability increases  Color Transparency  Unique possibility to map out at 12 GeV (up to Q2 = 10) such that one can directly see QCDat Work Total pion-nucleus cross section slowly disappears, or … pion escape probability increases  Color Transparency?

  12. Physics of Nuclei: Color Transparency A(e,e’p+) Projections for 12 GeV 6 7 8 9 10 Total pion-nucleus cross section slowly disappears, or … pion escape probability increases  Color Transparency  Unique possibility to map out at 12 GeV (up to Q2 = 10) such that one can directly see QCDat Work Total pion-nucleus cross section slowly disappears, or … pion escape probability increases  Color Transparency?

  13. Physics of Nuclei: Kaon Transparency Transparency w.r.t. to hydrogen (BUT…) Preliminary

  14. Physics of Nuclei: Kaon Transparency Transparency better defined w.r.t. to deuterium, as L and S peaks close Preliminary

  15. Physics of Nuclei: Kaon Transparency Preliminary A(e,e’K+) data point to a = 0.85-0.90 Carroll et al. a ~ 0.78

  16. Physics of Nuclei: Hadron Transparency • Compare with free hadron-nucleon cross sections: • NN ~ 40 mB • pN ~ 24 mB • KN ~ 20 mB • All are lower (artefact of Glauber?) • but follow general energy dependence Preliminary (Pion data fit too high in this plot!)

  17. K Preliminary p p

  18. Physics of Nuclei: Color Transparency Results inconsistent with CT only. But can be explained by including additional mechanisms such as nuclear filtering or charm resonance states. AGS A(p,2p) Glauber calculation The A(e,e’p) measurements will extend up to ~10 GeV/c proton momentum, beyond the peak of the rise in transparency found in the BNL A(p,2p) experiments. Pp(GeV/c) 2.9 5.1 7.3 9.6

  19. Physics of Nuclei: Color Transparency A(e,e’r+) at 12 GeV (at fixed coherence length) 12 GeV

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