@staticmethod
def _shrink_transverse_emittance(beam, geo_emittance_factor):
    """Account for the transverse geometrical emittance shrinking
        due to acceleration cooling.
        """
    beam.x *= geo_emittance_factor
    beam.xp *= geo_emittance_factor
    beam.y *= geo_emittance_factor
    beam.yp *= geo_emittance_factor
