Infrared polarimetry of Mrk 231: scattering off hot dust grains in the central core by Lopez-Rodriguez, E, Packham, C, Jones, T, Siebenmorgen, R, Roche, P, Levenson, N, Alonso-Herrero, A, Perlman, E, Ichikawa, K, Ramos Almeida, C, González-Martín, O, Nikutta, R, Martinez-Paredez, M, Shenoy, D, Gordon, M, Telesco, C