For this instance of my "Guess the plot" series I wish to go back to the basics. So I picked a graph which allows me to illustrate a general concept, something about particle physics (but we could say physics in general, and actually extending to other exact sciences) which is a source of endless awe for me: the fact that some functions exist, in the infinite-dimensional space of all real functions of a real variable, which describe some specific feature of our world.

The fact that the picture on the right -which is a clipped part of a larger graph- will be easily recognized by some readers is not surprising -they have certainly seen the whole graph dozens of times, or even plotted it on their own screen for their presentations, etcetera. In fact, I am here asking those "insiders" to abstain from spoiling the fun to all others: if you know what this figure represent, please consider yourself unqualified to participate -sorry, I will try to publish some harder riddle for you in the next edition of the "guess the plot".

What is surprising, instead, is that the functions shown here have "a life of their own": even if they might not describe any real physics after all, they certainly are uniquely determined (well, up to some uncertainty, but that's a detail) by the theoretical model we use to describe our knowledge of particle physics.

I stop here since I am saying too much... Can you guess what these functions represent, and what is the reason for their shapes ? There is even a little extra help, since I did not take the care of removing the "gg" label... I will post an answer here in a few days (I am about to leave on a ship which will bring me back to Venice, and the internet connectivity on the ship is close to zero). Have fun, and remember to write your thoughts down in the comments thread below!