Charged-hadron production in e+e- collisions at PEP with the TPC

We have studied hadron production in e+e- annihilation at 29 GeV center of mass energy. We have measured the particle fractions and particle separated differential cross sections using the PEP-4 (Time Projection Chamber) detector. The particles were identified by measuring their ionization energy loss (dE/dx). The pion fraction decreases from above 90% at 400 MeV/c to 55% at 6 GeV/c. Our results for kaon production require that a large number of kaons are produced by strange quarks pulled from the vacuum. We have also measured R, the ratio of the total hadronic cross section to the mu pair cross section. Our value for R is 3.7 with an uncertainty of 10%. This value is in agreement with the results of other experiments and with the predictions of the quark-parton model