Search for rare exclusive decays of the Higgs and $Z$ bosons to a meson and a photon with the ATLAS detector

In 2015 the ATLAS detector resumed data taking operations after the first long shutdown for the Large Hadron Collider at CERN. During this shutdown upgrades were made to the Level-1 Calorimeter trigger in order to maintain the physics performance in the anticipated Run-2 conditions. Changes to the hardware-based isolation were implemented and validated. These changes allowed for a low threshold Level-1 electromagnetic trigger to be maintained. During the first data-taking a measurement of the $W$ and $Z$ boson cross-sections was performed, which offered the first measurement at the new centre-of-mass energy and was used for the detector commissioning. One of the main goals of the LHC is to understand the nature of the Higgs boson which has been so far mainly observed in its decays to the electroweak bosons. A possible channel to observe the decays to the light quarks is in the final state including a meson and a photon which provides an easily triggerable signature compared to direct quark-antiquark production. The searches for the Higgs and $Z$ bosons decaying to a $\phi$ or $\rho^0$ meson and a photon are presented in detail.