In the context of particle collisions, the terms "observed" and "observer" can be used in different ways depending on the specific experimental setup and the information one is interested in gathering.
In particle physics experiments, collisions between particles are often studied by accelerating them to high energies and allowing them to collide inside particle accelerators or detectors. In this context, the observed particles are typically the ones produced as a result of the collision. Scientists use detectors to measure various properties of these particles, such as their momentum, energy, charge, and decay products. The detectors serve as tools to observe and collect data about the particles and their interactions.
The term "observer" can refer to the scientists or the experimental apparatus itself. The scientists design and conduct the experiments, analyze the data, and make interpretations based on the observations made by the detectors. The experimental apparatus, including the detectors and associated electronics, serves as the technological means to observe the particles and record their properties.
It's important to note that in the framework of quantum mechanics, the act of observation itself can have an effect on the observed system. This is often referred to as the observer effect or measurement problem. In the context of particle collisions, the act of measuring certain properties of particles can influence their behavior, for example, by collapsing their wave functions. This influence of measurement on the observed system is a fundamental aspect of quantum mechanics and is a subject of ongoing investigation and interpretation.