Sometimes it is difficult to identify which kinds of particles that took part in a collision. The most common problem is that particles disappear into the beam pipe or a hole in the detector. If the particles that disappear carry much energy, a fake signal of neutrinos will be created.

Disappearing particles can also cause the picture of the collision to look different compared how it should look. For example, a quark jet going in the direction of the beam pipe may look like a mini-jet from a tau particle if some of the particles disappear into the beam pipe.

Tau particles are notoriously hard to identify since we only can see the particles they decay into. The signature with 1 or 3 charged decay particles could easily be destroyed if one of the charged particles is not detected (see above). It is also quite common that a tau particle decays into two neutrinos plus either an electron or a muon. Then it can be difficult to know if the electron/muon originates from a tau particle or if it were created initially in the collision.

The collisions have been analysed with a computer program that put colours on the tracks of the particles depending on which jet they belong. The number of jets can therefore be estimated by counting the number of colours of the tracks. However, sometimes the computer program makes a mistake and joins two jets into one, or splits one jet into two.

It can therefore be easy to make a mistake when analysing a single collision. This is however not such a big problem since one always should analyse many collisions to gather a lot of statistics. Then the errors made with singe collisions will disappear in the properties of the big number of collisions that are analysed. The exercises with WIRED should therefore be completed by analysing hundreds of collisions.