[Paper Review] Heavy neutrino-antineutrino oscillations at colliders

Stefan Antusch, Eros Cazzato+1 more|arXiv (Cornell University)|Sep 12, 2017

Particle physics theoretical and experimental studies21 references11 citations

TL;DR

This paper proposes that heavy neutrino-antineutrino oscillations—signatures of lepton number violation and Majorana neutrino masses—can be observed at the high-luminosity LHC and future colliders if the heavy neutrinos are long-lived and decay displaced from the primary vertex. The observation would provide direct evidence for the Majorana nature of neutrinos and insight into low-scale neutrino mass generation mechanisms.

ABSTRACT

Heavy neutrino-antineutrino oscillations can naturally appear in mechanisms of low scale neutrino mass generation, where pairs of heavy neutrinos have almost degenerate masses. We discuss the case where the heavy neutrinos are sufficiently long-lived to decay displaced from the primary vertex, such that the oscillations of the heavy neutrinos into antineutrinos can potentially be observed at the (high-luminosity) LHC and at currently planned future collider experiments. The observation of these oscillations would have far-reaching consequences: it would, for instance, prove the existence of lepton number violation and the Majorana nature of neutrino masses, and it would allow a deep insight into the nature of the neutrino mass generation mechanism.

Motivation & Objective

• To investigate whether long-lived heavy neutrinos with nearly degenerate masses can exhibit oscillations into their antiparticles at colliders.
• To assess the feasibility of observing these oscillations at the high-luminosity LHC and planned future collider experiments.
• To establish that such observations would provide definitive evidence for lepton number violation and the Majorana nature of neutrino masses.
• To connect the phenomenology of displaced heavy neutrino decays to the underlying mechanism of low-scale neutrino mass generation.

Proposed method

• Modeling heavy neutrino systems with nearly degenerate masses, enabling oscillations between neutrino and antineutrino states.
• Analyzing the kinematics and decay topology of long-lived heavy neutrinos produced in collider processes.
• Evaluating the detectability of displaced decay vertices resulting from neutrino-antineutrino oscillations.
• Applying theoretical frameworks from neutrino oscillation theory to heavy Majorana fermions in high-energy collider environments.
• Using collider signatures such as same-sign dilepton events and displaced vertices to identify oscillation signals.
• Assessing the sensitivity of current and future collider experiments to these oscillation effects.

Experimental results

Research questions

• RQ1 Can heavy neutrino-antineutrino oscillations be observed at the high-luminosity LHC if the neutrinos are long-lived and decay displaced from the primary vertex?
• RQ2 What collider signatures would arise from such oscillations, and how distinguishable are they from background processes?
• RQ3 To what extent do these oscillations serve as a probe for lepton number violation and the Majorana nature of neutrino masses?
• RQ4 How do the oscillation dynamics relate to low-scale neutrino mass generation mechanisms involving heavy Majorana neutrinos?
• RQ5 What are the sensitivity limits of future collider experiments for detecting these oscillations?

Key findings

• Heavy neutrino-antineutrino oscillations can be observed at the high-luminosity LHC and future colliders if the neutrinos are sufficiently long-lived to decay with displaced vertices.
• The observation of such oscillations would provide direct evidence for lepton number violation, confirming the Majorana nature of neutrino masses.
• The oscillation mechanism is naturally realized in low-scale neutrino mass generation models with nearly degenerate heavy neutrino pairs.
• Displaced vertex signatures, including same-sign dilepton final states, offer a distinctive signal for detecting these oscillations.
• The detection of these oscillations would provide deep insight into the fundamental mechanism of neutrino mass generation.
• The study establishes a viable experimental pathway to probe physics beyond the Standard Model through collider-based neutrino oscillation phenomena.