The Standard Model of Particle Physics (SM) is a theory that unites three of the fundamental interactions of nature into an elegant solution. It describes the properties and interactions of spin 1⁄2 fermions and integer spin bosons. These fermions are further divided into quarks and leptons. In the SM, neutrinos are considered massless particles
but this characteristic was later disproved by oscillation experiments, showing they carry masses of up to 0.1eV. This means that the SM must be extended in order to provide masses to neutrinos. The Seesaw Mechanism is such an extension, allowing neutrino masses by introducing sterile, right handed, massive neutrinos.

In this work we extend the Seesaw model by adding dimension 5 effective operators, which mediate the production and decay of long-lived heavy neutrinos N with masses in the GeV scale. We explore N production through exotic Higgs decays by way of a neutrino-Higgs effective operator. The heavy neutrino then decays into a SM neutrino and a photon via a dipole operator, whose partial width is calculated analytically. We considered two Higgs production processes: gluon fusion (GF) and vector boson fusion (VBF). We evaluate the possible detection of N through displaced photon searches in the ATLAS detector for 13 TeV collision energy, simulated in MadGraph. These searches employed time-delay and non-pointing variables, tγ and |∆zγ |, respectively. We found that for both GF and VBF processes most signal events belong to the background and control regions rather than the signal region, implying the search developed in this work is not sensitive to the model at hand.

Autor(es):
DELGADO DADOR, F.
Institución:
Pontificia Universidad Católica del Perú
Año: 2022
Ciudad: Lima
Url: https://tesis.pucp.edu.pe/repositorio/handle/20.500.12404/24286