We report on conductance measurements in carbon nanotube based double quantum dots connected to two normal electrodes and a central superconducting finger. By operating our devices as beam splitters, we provide evidence for Crossed Andreev Reflections tunable in situ. This opens an avenue to more sophisticated quantum optics-like experiments with spin entangled electrons.PACS numbers: 73.63.Fg Quantum optics has been an important source of inspiration for many recent experiments in nanoscale electric circuits [1,2]. One of the basic goals is the generation of entangled electronic states in solid state systems. Superconductors have been suggested as a natural source of spin entanglement, due to the singlet pairing state of Cooper pairs. One important building block required for the implementation of entanglement experiments using superconductors is a Cooper pair beam splitter which should split the singlet state into two different electronic orbitals [3,4].The basic mechanism for converting Cooper pairs into quasiparticles is the Andreev reflection in which an originally quantum coherent electron pair in the singlet spin state is produced at an interface between a superconductor and a normal conductor. Conventional Andreev Reflections (AR) are local and cannot readily be used to create bipartite states [5,6]. It has been suggested to make use of electron-electron interactions [6,7, 8,9,10,11,12,13], spin filtering [14] or anomalous scattering in graphene [15] to promote Cooper pair splitting i.e. the Crossed Andreev Reflection (CAR) process.In this letter, we show that Coulomb interactions as well as size quantization can favor the CAR processes in carbon nanotubes. We use a double quantum dot geometry where the nanotube is connected to two normal electrodes and a central superconducting finger. By operating our device as a beam splitter (i.e. biasing the central superconducting electrode), we find that there is a finite current flowing from the superconducting electrode to the left (L) arm and the right (R) arm for a bias voltage smaller than the energy gap of the superconductor, which demonstrates Cooper pair injection. This subgap current is enhanced when we tune the device to the degeneracy * To whom correspondence should be addressed: kontos@lpa.ens.fra. FIG. 1: a. SEM image of a typicalCooper pair splitter device in false colors with the two biasing schemes sketched. The bar is 1µm. A central superconducting electrode is connected to two quantum dots engineered in the same single wall carbon nanotube (in purple) which bridges between electrodes L and R. b. The elementary processes which carry current in the superconducting (S) state. In addition to the conventional local Andreev Reflection process, the Crossed Andreev Reflection can occur in which a Cooper pair is split in the two quantum dots. The relative probability of each of these processes can be inferred from the topology of the beam splitter.