Search For Charmed Particle Production In Proton Proton Collisions At The Cern Isr PDF Download

There has been much recent discussion of the possibility of the existence of 'charmed' particles, hadrons which possess non-zero values of 'charm', a further additive quantum number. These particles may be generated either in the three triplet model of Han and Nambu or by the postulate of a fourth, charm-bearing quark. On the assumption that charm, like strangeness, is conserved in strong and electromagnetic interactions (the opposite assumption would necessitate charmed particles coupling strongly to ordinary hadrons and the existence of yet undiscovered states, e.g. Z*s) but not conserved in weak interactions one might expect their production either singly in neutrino interactions or in pairs in associated production in high energy hadron collisions, to be followed by their subsequent, relatively slow, decay into 'uncharmed' particles. Various estimates as to mass, lifetime, production cross-sections and decay modes have been made for these particles. However their failure to appear as di-lepton events among the neutrino interactions of the Brookhaven A.G.S. and CERN P.S. experiments might suggest that their masses are in excess of 2 GeV/c2 the other hand, such particles would have been expected to have been observed directly in bubble chamber studies at FNAL had their lifetimes been greater than 10−11s as suggested by some authors. This proposal, which may be thought of as complementary to that of Burhop et al, is for a straightforward exposure of a stack of emulsions to a 400 GeV/c proton beam to look for evidence of the pair production of charmed particles. The spatial resolution of the emulsion technique is about one micron with the consequence that the decays of particles of mean lives in the range 10−11 to 10−14 s should be readily observable.