On the possibility of tree-level leptogenesis from Kalb–Ramond torsion background M. de Cesare, Nick E. Mavromatos and Sarben Sarkar Eur. Phys. J. C, 75 10 (2015) 514 Published online: 29 October 2015 DOI: 10.1140/epjc/s10052-015-3731-z