Elementary particles are mysterious and unfathomable, and it takes giant accelerators and incredibly complex devices to study them. In the last 100 years we have made great strides in the investigations of the properties of quarks, leptons, and vector bosons, but I would lie if I said we know half of what we would like to. In science, the opening of a door reveals others, closed by more complicated locks - and no clearer example of this is the investigation of subatomic matter. 

Decision trees are one of the many players in the booming field of supervised machine learning. They can be used to classify elements into two or more classes, depending on their characteristics. Their interest in particle physics applications is large, as we always need to try and decide on a statistical basis what kind of physics process originated the particle collision we see in our detector.

Today I would like to mention that my book "Anomaly! Collider Physics and the Quest for New Phenomena at Fermilab" is now available for purchase as E-Book at its World Scientific site.

I would like to use this space to advertise a couple of blogs you might be interesting to know about. Many of you who erratically read this blog may probably have already bumped into those sites, but I figured that as the readership of a site varies continuously, there is always the need to do some periodic evangelization.

Every year, at about this time, the level of activity of physicists working in experimental collaborations at high-energy colliders and elsewhere increases dramatically. We are approaching the time of "winter conferences", so called in order to distinguish them from "summer conferences". 
During winter conferences, which take place between mid-February and the end of March in La Thuile, Lake Louise, and other fashionable places close to ski resorts, experimentalists gather to show off their latest results. The same ritual repeats during the summer in a few more varied locations around the world. 

The so-called Lambda_b baryon is a well-studied particle nowadays, with several experiments having measured its main production properties and decay modes in the course of the past two decades. It is a particle made of quarks: three of them, like the proton and the neutron. Being electrically neutral, it is easily likened to the neutron, which has a quark composition "udd". In the space of quark configurations, the Lambda_b is in fact obtained by exchanging a down-type quark of the neutron with a bottom quark, getting the "udb" combination.