Elucidating the Nature of Neutrinos Using Collider Probes


Jason Diao


Sebastián Urrutia Quiroga (email:


The project will require getting involved with different software. While coding skills are not required (but certainly desired and highly appreciated), students must be comfortable working with a computer, especially for programming tasks.

What Students Will Do

Students are expected to get familiar with the big picture of the project to rapidly move forward to utilizing some standard computer tools in particle physics [4], such as Madgraph or Delphes, for event simulation and analysis. These tools are open-source, and there is a large, dedicated community to help solve installation and compatibility problems.

Expected Project Length

One year

Figure for INTURN 24-2a

Image Description and Credits: Neutrinos may behave differently from their “mirror” antiparticle counterparts. Credit: APS/Carin Cain

Project Description

Exploring lepton number violation (LNV) at colliders is crucial for a deeper understanding of particle physics. This search is not merely a quest for a rare phenomenon; it holds the key to understanding the intrinsic nature of neutrinos—their masses and fundamental properties. Observing LNV could provide conclusive evidence that neutrinos are Majorana particles, a type of particle that is its own antiparticle, offering a plausible explanation for their tiny masses through the seesaw mechanism [1]. This would not only revolutionize our understanding of the neutrino’s identity—whether it is a Dirac or Majorana particle—but also shed light on the asymmetry between matter and antimatter in the universe [2]. The potential discovery of LNV processes is a critical step that guides us toward a more complete theory of fundamental particles and interactions, underpinning the very structure of matter and the evolution of the cosmos itself.

Long-lived particles (LLPs) are new, beyond the SM (BSM) states that travel a substantial distance between creation and decay in collider systems, presenting distinct experimental signatures. The experimental signatures of LLPs are particularly interesting. In contrast to promptly decaying particles, LLPs can decay after flying some distance from the primary interaction point. This produces a displaced vertex, with decay products including charged and neutral SM particles (e.g., charged leptons, light neutrinos, and pions). This kind of displaced signature is most commonly associated with LLPs and is very different from the usual SM processes studied at colliders; if observed, constitutes a striking “smoking gun” of new physics.

The primary objective of this project is the study of the potential observation of LNV in displaced vertex searches for
heavy neutral leptons (HNLs) at future lepton colliders, as performed in Ref. [3].


[1]    Lepton Number Violation: Seesaw Models and Their Collider Tests, Y. Cai et al [1711.02180]
[2]    Falsifying High-Scale Leptogenesis at the LHC, F. Deppisch, J. Harz, M. Hirsch [1312.4447]
[3]    Distinguishing Dirac and Majorana Heavy Neutrinos at Lepton Colliders, M. Drewes [2210.17110]
[4]    Computer Tools in Particle Physics, A. Vicente [1507.06349]

In collaboration with Vincenzo Cirigliano (