Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom.
AHEP Group, Instituto de Física Corpuscular-C.S.I.C./Universitat de València Edificio de Institutos de Paterna, Apartado 22085, E-46071 València, Spain.
Phys Rev Lett. 2014 Jun 6;112(22):221601. doi: 10.1103/PhysRevLett.112.221601. Epub 2014 Jun 4.
Measuring a nonzero value for the cross section of any lepton number violating (LNV) process would put a strong lower limit on the washout factor for the effective lepton number density in the early Universe at times close to the electroweak phase transition and thus would lead to important constraints on any high-scale model for the generation of the observed baryon asymmetry based on LNV. In particular, for leptogenesis (LG) models with masses of the right-handed neutrinos heavier than the mass scale observed at the LHC, the implied large washout factors would lead to a violation of the out-of-equilibrium condition and exponentially suppress the net lepton number produced in such LG models. We thus demonstrate that the observation of LNV processes at the LHC results in the falsification of high-scale LG models. However, no conclusions about the viability of LG models can be drawn from the nonobservation of LNV processes.
测量任何违反轻子数守恒 (LNV) 过程的横截面积都将对早期宇宙中有效轻子数密度的洗出因子施加很强的下限，这将对任何基于 LNV 的高标度模型生成观测到的重子不对称性产生重要限制。特别是对于具有比 LHC 观测到的质量尺度更大的右手中微子质量的轻子生成 (LG) 模型，所隐含的大洗出因子将导致偏离非平衡条件，并使此类 LG 模型中产生的净轻子数呈指数级抑制。因此，我们证明了 LHC 对 LNV 过程的观测导致了对高标度 LG 模型的证伪。然而，从 LNV 过程的未观测到，不能得出 LG 模型的可行性的结论。
