It has been a while since the last time I posted the last riddle of this series. It was fun though, so upon seeing the graph below I immediately decided I would use it here, to let you guess what it is about. Please use the comments thread to provide your input: what does the graph represent ? What are the different coloured lines ? Why the funny behaviour ? What is on the x axis ? And on the y axis ?

Of course it is virtually impossible to answer all the above without being given some hint. I can tell you it has to do with LHC searches, and that is all the help I am going to give you!