We analyse a large class of superconducting beamsplitters for which the Bell
parameter (CHSH violation) is a simple function of the spin detector
efficiency. For these superconducting beamsplitters all necessary information
to compute the Bell parameter can be obtained in Y-junction setups for the
beamsplitter. Using the Bell parameter as an entanglement witness, we propose
an experiment which allows to verify the presence of entanglement in Cooper
pair splitters.Comment: 5 pages, 2 figures, accepted for publication in EP
