Outlook and Open Questions

Further studies of color transparency are expected during the next year or two. An experiment to measure the transparency in at BNL is ready to begin taking data. This new experiment will provide higher missing energy resolution as well as increased range. More detailed measurements of the reaction at CEBAF are to be performed in 1995. This experiment will yield higher statistical precision and better missing energy resolution (few MeV) in the range (GeV/c). In addition, it appears that the HERMES experiment can provide information on the reaction at (GeV/c) and lower energy transfer where the coherence length is of order the nuclear diameter.

Further studies of the inclusive nuclear response at will also be performed at CEBAF in the near future. This kinematic region, forbidden to the free nucleon, offers a unique window on the nuclear effects at high . Earlier data from SLAC indicate that scaling in the Nachtmann variable may be observed, suggesting that local duality may govern the structure function in this region. Exploring this phenomenon at higher at CEBAF will further elucidate this interesting behavior where both hadron and quark/gluon degrees of freedom may be exhibited.

The proposed upgrade of CEBAF to higher energy and possibility of further studies with higher energy electron beams (at SLAC and perhaps ELFE) and muon beams (Fermilab and CERN) can provide crucial new information in this field. The open questions to be addressed include:

• Color transparency: Higher energy at CEBAF ( GeV) will enable extending the range of this reaction. Even higher energies available at SLAC (and potentially ELFE) will allow studies at even higher (GeV/c).

• at : Higher energies at CEBAF (or ELFE) will allow exploration of this reaction up to (GeV/c).

• Hadronization: High duty factor electron facilities at high energy (upgraded CEBAF and/or ELFE) will allow study of hadronization in deep inelastic scattering where the formation length for final state hadrons is of order the nuclear radius. This will enable use of the nuclear medium as a filter to study the hadronization process.

• Shadowing: Further studies of shadowing will require more access to very high energy muon beams to reach the low region.

• Gluon distribution: New information on the nuclear binding effect on the gluon distribution could be obtained by using high luminosity, high duty factor beams at GeV to study charmonium production in nuclei.

Further progress in this field will require upgrading the CEBAF energy to at least 10 GeV and the availability of CEBAF quality beams in the higher energy range of 15-30 GeV. Access to higher energy GeV muon beams will be necessary for study of the lower region. In addition, one should anticipate that appropriate instrumentation (spectrometers, etc.) will be necessary to exploit new facilities such as a higher energy CEBAF.