First measurement of the fragmentation fraction ratio f s / f d with tree level hadronic decays at 7 TeV pp collisions

Curiosity is an intrinsic characteristic of the human nature. One puzzle that philosophers and physicists have pondered for centuries is the question “what is matter?”. The Greek philosopher Democritus proposed it is made of indivisible elements, that he called “atoms”. Incredibly, this first intuition from 400 a.C. was closer to our present description than he might imagined. The long tale of physics brings us to particle physics where matter is depicted through theories describing the existence and interactions of particles using a mathematical language. A scientific theory has to be able to describe the known observations but at the same time to predict new observables that can be measured with experiments. In the 70s a great revolution in particle physics happened: a theory, called Standard Model (SM), was developed. This theory accounts for three of the four fundamental interactions between elementary particles, missing to describe only the role of gravity. This theory was confirmed by a wealth of experimental results over the last decades. Despite its success, the SM is not considered to be the conclusive theory of elementary particles. The presence of a large number of parameters leaves the physicists unsatisfied. Moreover looking to the sky, it turnes out there is much more material than we would expect. Most of this matter is invisible: it cannot be detected by telescope, but it can be only inferred through gravitational effects like gravitational lensing or rotation curves. None of the known particles is a satisfactory candidate to build up