def map_l2dist_gaussianmech_zCDP(sensitivity, scale):
    """map an L2 distance `sensitivity` through the gaussian mechanism with parameter `scale` to rho-zCDP
    Lemma 2.4 https://arxiv.org/pdf/1605.02065.pdf#subsubsection.1.2.2
    
    :param sensitivity: maximum L2 distance perturbation of a query
    :param scale: standard deviation of gaussian noise
    :returns rho"""
    return (sensitivity / scale) ** 2 / 2