The excitation spectrum of URu2Si2 in the superconducting state has been investigated by a precise neutron-scattering experiment. A weak but clear positive energy shift of ∼40 μeV has been detected in the superconducting phase (at T = 400 mK) for the resonance at Q0 = (1,0,0). For the resonance at Q1 = (0.6,0,0), a two times smaller shift is observed but with an incertitude of the same order than this shift. This result is in agreement with our previous results indicating that the wave-vector Q0 is connected with the order parameters of the hidden order and of superconductivity.
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