For experts: Direct and Indirect Search

In the LHC accelerator, protons are accelerated to almost the speed of light and brought to collision. In the collision process, many unstable particles are created, including some that may not even be known yet. In the direct search, we look specifically for the decay products of a new unstable particles and reconstruct the its mass from their energy and angular distribution. This method allowed for example to discover the Higgs particle.

In the direct search the mass of the new particle is limited by the energy available in the collision.

This involves looking for deviations from measurements and theoretical predictions. For example, the planet Neptune was predicted by astronomers as early as 1948 by observing the orbit of Uranus as it showed deviations from the expectations of Kepler's laws.

Indirect measurements require both highly precise measurements and accurate predictions. Unlike direct searches, they can also be used to find particles that are so heavy that they cannot be produced directly in the collision.

According to the Heisenberg uncertainty principle, the conservation of energy can be violated for a short time. This means that for a short time very heavy new particles can be created, which have more energy than is present at all in the proton-proton collision. Since these particles exist only for a very short time, they cannot be detected directly, but their impact can be detected as small deviations in known processes.