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

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

Traditional nuclear physics calculations (Glauber calculations) predict transparency to be nearly energy independent. T Energy (GeV) Ingredients  h-N cross-section Glauber multiple scattering approximation Correlations & Final-State Interaction effects hN Physics of Nuclei: Color Transparency 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 QCDQCD A(e,e’h), h = hadron

Search for Color Transparency in Quasi-free A(e,e’p) Scattering Constant value line fits give good description:  2 /df = 1 Conventional Nuclear Physics Calculation by Pandharipande et al. (dashed) also gives good description  No sign of CT yet

A-dependence Studies 1)Fit to  =   A a or T = A  -1 2) Classical attenuation model with effective cross section  eff independent of 

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

T p’ [MeV}  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

A(e,e’  + ) 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)

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

Physics of Nuclei: Pion Transparency | A(e,e’  + ) Red: low-  points

Without Color Transparency With Color Transparency Physics of Nuclei: 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 Q 2 = 10) such that one can directly see QCD at Work Total pion-nucleus cross section slowly disappears, or … pion escape probability increases  Color Transparency? A(e,e’  + )

Physics of Nuclei: Color Transparency A(e,e’  + ) Total pion-nucleus cross section slowly disappears, or … pion escape probability increases  Color Transparency  Unique possibility to map out at 12 GeV (up to Q 2 = 10) such that one can directly see QCD at Work Total pion-nucleus cross section slowly disappears, or … pion escape probability increases  Color Transparency? Projections for 12 GeV

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

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

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

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

p  K

Physics of Nuclei: Color Transparency AGS A(p,2p) Glauber calculation P p (GeV/c) Results inconsistent with CT only. But can be explained by including additional mechanisms such as nuclear filtering or charm resonance states. 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.

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