Journal of High Energy Physics Journal of High Energy Physics, Springer, 2011, 03, pp.136. ⟨10.1007/JHEP03(2011)136⟩ Journal of high energy physics 2011, 136 (2011). doi:10.1007/JHEP03(2011)136 Journal of High Energy Physics, 2011, 03, pp.136. ⟨10.1007/JHEP03(2011)136⟩