Backward angle (u-channel) scattering provides complementary information for studies of hadron spectroscopy and structure, but has been less comprehensively studied than the corresponding forward ...angle case. As a result, the physics of u-channel scattering poses a range of new experimental and theoretical opportunities and questions. We summarize recent progress in measuring and understanding high energy reactions with baryon charge exchange in the u-channel, as discussed in the first backward angle (u-channel) Physics Workshop. In particular, we discuss backward angle measurements and their theoretical description via both hadronic models and the collinear factorization approach, and discuss planned future measurements of u-channel physics. Finally, we propose outstanding questions and challenges for u-channel physics.
The 1.1 kton Soudan 2 calorimetric drift-chamber detector is read out by 16K anode wires and 32K cathode strips. Preamps from each wire or strip are bussed together in groups of 8 to reduce the ...number of ADC channels. The resulting 6144 channels of ionization signal are flash-digitized every 200 ns and stored in RAM. The raw data hit patterns are continually compared with programmable trigger multiplicity and adjacency conditions. The data acquisition process is managed in a system of 24 parallel crates each containing an Intel 80C86 microprocessor, which supervises a pipe-lined data compactor, and allows transfer of the compacted data via CAMAC to the host computer. The 80C86's also manage the local trigger conditions and can perform some parallel processing of the data. Due to the scale of the system and multiplicity of identical channels, semi-custom gate array chips are used for much of the logic, utilizing 2.5 micron CMOS technology.
The 1.1 kton Soudan 2 detector is read out by 16K anode wires and 32K cathode strips. Preamps from each wire or strip are bussed together in groups of 8 to reduce the number of ADC channels. The ...resulting 6144 channels of ionization signal are flash-digitized every 150 ns and stored in RAM. The raw data hit patterns are continually compared with programmable trigger multiplicity and adjacency conditions. The data acquisition process is managed in a system of 24 parallel crates each containing an Intel 8086 microprocessors, which supervises a pipe-lined data compactors, and allows transfer of the compacted data via CAMAC to the host computer. The 8086's also manage the local trigger conditions and can perform some parallel processing of the data. Due to the scale of the system and multiplicity of identical channels, semi-custom gate array chips are used for much of the logic, utilizing 2.5 micron CMOS technology.
We measured the high-momentum transfer
Q
2=4.8 and 6.2 (GeV/c)
2 quasi-elastic
12
C(p,2p) reaction at
θ
cm≃90° for 6 and 7.5 GeV/c incident protons. The momentum components of both outgoing protons ...and the missing energy and momentum of the proton in the nucleus were measured. We verified the validity of the quasi-elastic picture for ground state momenta up to about 0.5 GeV/c. Transverse and longitudinal momentum distributions of the target proton were measured. They have the same shape with a large momentum tail which is not consistent with independent particle models. We observed that the transverse distribution gets wider as the longitudinal component increases in the beam direction.
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