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Measurements of fragment-production cross sections have been made with 18 0 projectiles of 1.7 GeV/nucleon incident upon targets of Be, C, Al, Ti, Cu, Sn, W, Pb, and U at the LBL Bevalac. We have found that the enhancement with high-Z targets of cross sections for certain fragments agrees both in magnitude and ZT dependence with the predictions of the electromagnetic-dissociation process, which are based upon the known photonuclear cross sections and classical rel?tivistic virtual-photon theory. We have found as well that factorization of the cross sections for nuclear processes is valid to an accuracy of better than 4~.

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We report the first results of a Bevatron heavy-ion experiment on the inclusive spectra of isotopically identified nuclei, 3^ Z^ 7, produced by the fragmentation of 29-GeV 14 N ions in carbon and hydrogen. The preliminary values of the partial differential cross sections at 0° give evidence that the modes of fragmentation of 14 N projectiles are independent of the target nucleus.We report in this Letter the results of a Bevatron experiment on the single-particle inclusive spectra of secondary nuclei, A ^6, Z ^ 3, produced at 0° by the fragmentation of 29-GeV (2.1-GeV/nucleon) 14 N ions in carbon and polyethylene (CH 2 ) targets. 1 ' 2 Isotopic identification of the nuclear fragments was obtained by measurements of magnetic rigidity, rate of energy loss, and velocity. The external beam transport system was used as a rudimentary magnetic spectrometer to analyze the rigidity of the fragments. An on-line computer-controlled counter telescope 3 consisting of nine 500-mm 2 lithium-drifted silicon detectors, 3 and 5 mm thick, yielded dE/dx and, hence, charge information. The time-of-flight measurements were made over the 40-m distance between the target and the counter telescope, which were located at the first and second focal points of the beam transport system, respectively. Salient properties of the spectrometer-detector system were (a) rigidity resolution o(R)/R «1 to 2% for R ^6.7 GV/c; (b) absolute charge resolution o(Z) = ±0.12e; (c) time-of-flight resolution o(t) = ±0.5x10" 9 sec; and (d) acceptance cone angle of the spectrometer, 4 mrad, estimated from conventional beam-trace methods. The thicknesses of the carbon and polyethylene targets were 4.36 and 3.76 gm cm" 2 , respectively.Our initial observations demonstrated that the 0° fragments heavier than He (Z= 2) have velocities that differ little from the velocity of the primary 14 N beam. 2 Hence, the rigidity R (in GV/c) at which a secondary fragment is transmitted by the magnetic spectrometer is R =Mj3yc/ Ze, where M is the mass of the fragment in GeV/ c 2 , Z is its atomic number, and 0y frag = py^m = 3.1 for the 29-GeV 14 N beam. In the present experiment, the rigidity spectra of the 0° fragments were examined in the range 4.1 ^R ^6.7 GV/c