Inverse Seesaw Neutrino Signatures at LHC and ILC
The study conducted by Arindam Das and Nobuchika Okada investigates the collider signatures of pseudo-Dirac heavy neutrinos within the context of the inverse seesaw mechanism. This research proposes a theoretical framework where heavy neutrinos, possessing mass at the electroweak scale, exhibit significant mixing with the Standard Model (SM) neutrinos. This condition is pivotal as it enables the production of tiny light neutrino masses via the inverse seesaw mechanism and facilitates the potential observation of heavy neutrinos at high-energy colliders such as the Large Hadron Collider (LHC) and the International Linear Collider (ILC).
Theoretical Framework and Model
The inverse seesaw mechanism diverges from the conventional seesaw model by generating small neutrino masses through tiny lepton-number-violating parameters, rather than the suppression by a large neutrino mass scale. In this model, heavy neutrinos are treated as pseudo-Dirac particles capable of coupling with SM neutrinos through sizable Dirac Yukawa interactions. The research utilizes the next-to-minimal supersymmetric standard model (NMSSM) framework, extending it to integrate seesaw physics effectively.
The study explores two distinct flavor structure models for heavy neutrinos: the Flavor Non-Diagonal (FND) case, where the flavor structure arises from Dirac Yukawa interactions, and the Flavor Diagonal (FD) case, where it emerges from lepton-number-violating parameters. The authors assess these models under the conditions provided by SM constraints, neutrino oscillation data, and the stability of the electroweak scale.
Collider Signatures and Experimental Viability
The analysis entails scanning the parameter space to derive allowable configurations that conform with experimental constraints on the mixing matrices. Using fixed parameters, the authors perform a detailed examination of potential signals from heavy neutrino decays at the LHC and ILC. At the LHC, the prospect of observing heavy neutrino signals is investigated through tri-lepton final states and at the ILC through single lepton plus di-jet final states.
For the LHC, results indicate that while the FD flavor structure allows for significant signal observation, the FND structure results in negligible event rates. Signal events for the tri-lepton final states are calculated for both cases, yielding varying statistical significances that indicate the readiness for discovery under specific conditions.
At the ILC, studies demonstrate the potential for observing heavy neutrinos through alternative decay modes, utilizing detailed suppression techniques of SM backgrounds. The findings suggest that the inverse seesaw mechanism's predictions are observable given the assumed experimental collaboration conditions.
Future Prospects and Implications
The paper concludes that should heavy neutrinos be discovered through these proposed mechanisms, it could imply a deviation from conventional seesaw theories of neutrino mass generation. Such findings would provide new insights into the flavor structure of models for neutrino mass generation. Further research could delve deeper into optimizing detection methodologies at these colliders, potentially increasing the signal significance and exploring broader parameter space beyond the limits of this study.
The implications of this research extend into further understanding the fundamental nature of neutrinos and their interaction with SM particles. Future exploration could also focus on integrating similar mechanisms into other extensions of the standard model, thereby enhancing the scope and viability of detecting such neutrino signatures in various experimental setups.