Abstract. We present a real-time investigation of ultrafast carrier dynamics in single-wall carbon nanotube bundles using femtosecond time-resolved photoelectron spectroscopy. The experiments allow to study the processes governing the subpicosecond and the picosecond dynamics of non-equilibrium charge-carriers. On the subpicoseond timescale the dynamics are dominated by ultrafast electronelectron scattering processes which lead to internal thermalization of the laser excited electron gas. We find that quasiparticle lifetimes decrease strongly as a function of their energy up to 2.38 eV above the Fermi-level -the highest energy studied experimentally. The subsequent cooling of the laser heated electron gas down to the lattice temperature by electron-phonon interaction occurs on the picosecond time-scale and allows to determine the electronphonon mass enhancement parameter λ. The latter is found to be over an order of magnitude smaller if compared, for example, with that of a good conductor such as copper.PACS 78.47.+; 81.07.De; 78.67.Ch Carbon nanotubes (CNTs) and in particular single-wall carbon nanotubes (SWNTs) have attracted broad interest due to their unique electronic structure and properties. Among the most impressive demonstrations of their potential use in novel technologies are the fabrication of fieldeffect and single-electron transitors from individual or small bundles of SWNTs [ 1,2,3,4]. Other conceivable applications include the implementation of CNTs as emitters in field-emission displays [5,6], ultrastrong fibers [7,8], chemical sensors [9,10], super-capacitors [11] and more. As molecular field effect transistors they have already been implemented into simple logic devices with outstanding transport characteristics and promising scaling behavior [12]. As molecular wires, carbon nanotubes exhibit exceptional resilience with respect to current induced failure and sustain current densities exceeding 10 9 A/cm 2 before * Corresponding Author suffering fatal damage, as reported by various groups [13,14,15,16,17,18]. The carrier scattering processes governing linear and non-linear transport properties in these devices, such as electron-electron (e-e), electron-phonon (eph) or impurity scattering are most frequently investigated by conventional -i.e. time-independent -transport studies.Here we present a complementary time-domain study of carrier dynamics in bundles of single-wall carbon nanotubes using femtosecond time-resolved photoemission. This technique can probe carrier dynamics in real-time and allows to access a wider energy range than typical transport studies. Time-resolved photoemission was developed from twophoton-photoemission [19,20] and has become a powerful technique for studies of surface and bulk electron dynamics on the femtosecond time-scale [21,22,23,24,25,26,27,28]. It has been most frequently used to probe the relaxation of photoexcited electrons with energies ranging from a few hundred meV above the Fermi level up to the vacuum level. Here, we have extended the most commonly us...