The calculation of high-energy hadron cascades in extended materials induced by electron beams in the GeV energy range is reconsidered. In particular, we estimate the contribution from hadronic interactions of high-energy electrons on nuclei as compared to hadron production by photons.Our estimate relies on the equivalent photon approximation . The interaction of the resulting quasireal photons with nuclei is described by the vector-meson dominance model and a Monte Carlo realization of the multistring fragmentation model, as discussed in ref . [1). For thin targets (as compared to the radiation length), hadronic interactions of the incident high-energy electrons on nuclei dominate the generation of high-energy hadrons.
l. IntroductionSo far, hadroproduction by leptons was of no importance for many practical applications in shielding and calorimetry : For example, due to the smallness of the corresponding hadronic cross sections, properties of electromagnetic calorimeters are well understood from the Monte Carlo calculation of purely electromagnetic showers in the detector geometry . However, with the construction of high-energy and/or high-current electron machines, like LEP at CERN, SLC at SLAC or CEBAF, hadron-production processes induced by energetic electrons and photons become important, at least for shielding: The large attenuation length of hadrons as compared to leptons may compensate their small production cross sections .For this reason, Ranft and Nelson [1] introduced a method to estimate the importance of hadron production by energetic photons in the development of electromagnetic showers. This method combines the idea of the vector-meson dominance (VMD) model with a Monte Carlo model based on the dual multistring fragmentation model . It has been included into the coupled hadron-electromagnetic cascade code FLUK.A-EGS [2] îor ;.z-urp'.i^ation in Monte Carlo shower simulations . Note that, due to the restrictions in applicability of both the VMD and the multistring fragmentation models, the method should not be applied to photon energies below 1-2 GeV . As a consequence, reliable results are to be * Permanent address : Sektion Physik, Karl-Marx-Universität, Leipzig, GDR . A292 (1990) 482-486 North-Holland expected only for the production of hadrons with energies above about 1 GeV. A careful comparison of calculations using the FLU KA code, with SLAC data on hadroproduction by 18 GeV electrons on a beryllium target shows a systematic underestimation of hadron yields at high momenta (above 2 GeV) by a factor of order two [3] . This disagreement rises the question for other important hadron-generating mechanisms in electron-photon showers . At least for high-energy electron beams direct electron-induced hadron production on nuclei might be such a process : Although suppressed by a factor of order a/,ir as compared to photoproduction mechanisms, the latter ones represent two-step processes for electron beams -the energetic photons have to be generated via hard bremsstrahlung first .In this note we es...