Neutrinos and Collider Physics

Abstract: We review the collider phenomenology of neutrino physics and the synergetic aspects at energy, intensity and cosmic frontiers to test the new physics behind the neutrino mass mechanism. In particular, we focus on seesaw models within the minimal setup as well as with extended gauge and/or Higgs sectors, and on supersymmetric neutrino mass models with seesaw mechanism and with $R$-parity violation. In the simplest Type-I seesaw scenario with sterile neutrinos, we summarize and update the current experimental constraints on the sterile neutrino mass and its mixing with the active neutrinos. We also discuss the future experimental prospects of testing the seesaw mechanism at colliders and in related low-energy searches for rare processes, such as lepton flavor violation and neutrinoless double beta decay. The implications of the discovery of lepton number violation at the LHC for leptogenesis are also studied.

• The paper demonstrates that collider experiments can probe seesaw mechanisms, testing extensions to the Standard Model for neutrino mass generation.
• It provides a detailed analysis of Type-I, Type-II, and Type-III seesaw models, incorporating numerical constraints from both high-energy and low-energy experiments.
• The study highlights that future discoveries of lepton number violation at colliders could offer key insights into matter-antimatter asymmetry and new physics.

Overview of "Neutrinos and Collider Physics"

The research paper "Neutrinos and Collider Physics" authored by Frank F. Deppisch, P. S. Bhupal Dev, and Apostolos Pilaftsis provides an in-depth examination of the intersection between neutrino physics and collider experiments. The paper emphasizes the role of collider phenomenology in probing new physics underlying the mechanisms of neutrino mass. It primarily focuses on the theoretical and experimental aspects of various seesaw models and the implications of potential future discoveries.

Theoretical Framework

The study begins by addressing the gap in the Standard Model (SM) concerning neutrino masses. Neutrino oscillations, long-observed in various experiments, necessitate non-zero neutrino masses—a phenomenon not explained within the SM framework. The paper explores the possible extensions to the SM that could account for these masses, particularly through the seesaw mechanism. The seesaw models—Type-I, Type-II, and Type-III—are explored extensively:

1. Type-I Seesaw: Involves heavy sterile neutrinos and provides a natural explanation for small active neutrino masses but requires a high-energy scale, typically around the GUT scale, challenging to probe experimentally.
2. Type-II Seesaw: Utilizes scalar triplets and accommodates electroweak scale physics, making it potentially accessible at colliders.
3. Type-III Seesaw: Involves fermion triplets and, similar to Type-I, can explore beyond SM physics through collider experiments.

Additionally, supersymmetric models incorporating R-parity violation are considered viable mechanisms for neutrino mass generation.

Phenomenology at Colliders

The paper highlights how collider experiments, such as those conducted at the Large Hadron Collider (LHC), can probe the seesaw mechanism and potentially discover new heavy neutrinos. The authors discuss various channels and signatures, including lepton number violation and rare decay processes, that are indicative of heavy neutrinos.

Key conclusions from collider experiments and relevant constraints on neutrino mixing parameters and masses of the heavy particles involved in seesaw mechanisms are presented. Despite the challenges posed by large backgrounds and complex signal identification, significant progress is anticipated in this domain.

Numerical Constraints and Experimental Challenges

The authors provide a thorough analysis of the current constraints on the parameters of seesaw models, synthesizing results from neutrinoless double beta decay experiments, meson decay studies, and EW precision data. These constraints guide future experimental searches by excluding certain parameter spaces.

Broader Implications and Future Prospects

The discovery of lepton number violation at colliders could have profound implications for understanding the matter-antimatter asymmetry in the universe via leptogenesis. The interplay between collider physics and cosmological observations is crucial, especially in constraining and validating these theoretical models.

The study emphasizes the complementary roles of high-energy and intensity frontier experiments. While colliders can probe high-energy scales directly, low-energy experiments and cosmological observations provide indirect constraints on the same parameters.

Conclusion

The paper concludes with a call for a robust and multi-faceted exploration of neutrino physics across various experimental settings. The complementarity between different approaches is critical to unraveling the mysteries surrounding neutrino masses and potentially discovering new physics beyond the SM. Looking forward, proposed high-energy colliders and next-generation neutrino experiments will likely provide deeper insights and perhaps even direct detections of new physics signatures predicted by the framework explored in this study.