How you search for the Higgs boson with a collider

Large Hadron Collider consists of an accelerator ring (magnetic system) length 26,659 m., injection complex, accelerating section, seven detectors designed to detect elementary particles and several other minor systems.$ Two of the collider detectors are used to find the Higgs boson: ATLAS and CMS. Abbriveatures of the same name are the experiments carried out on them, as well as the collaborations (groups) of scientists who work on these detectors. They are quite numerous, for example, about 2.5 thousand people are involved in CMS collaboration.

In order to detect new particles, proton-proton collisions are created in the collider, i.e., collisions of beams of protons. Each beam consists of 2808 clots, and in each of these clots, about 100 billion protons. Accelerating in the injection complex, protons are “injected” into the ring, where they accelerate using resonators and gain energy of 7 Tev, and then collide at the locations of detectors. The results of such collisions are a whole cascade of particles with different properties. Before the experiments began, it was expected that one of them would be the boson previously predicted by theoretical physicist Peter Higgs.

The Higgs boson is an unstable particle. Appearing, it immediately decays, so it was searched for decay products into other particles: gluons, muons, photons, electrons, etc. The decay process was fixed by ATLAS and CMS detectors, and the resulting information was sent to thousands of computers around the world. Previously, scientists have suggested that there may be several channels (decay variants), and have done research on each of these directions with varying success.

In the end, on July 4, 2012, at an open seminar at CERN, physicists provided the results of their work. Scientists from CMS Collaboration announced that they were analyzing data across five channels: the decay of the Higgs boson into Z-bosons, gamma photons, electrons, W-bosons and quarks. The cumulative statistical significance of the Higgs boson detection was 4.9 sigma (this is a term from statistics, the so-called “standard deviation”) for a mass of 125.3 Gav.

The scientists from ATLAS Collaboration then announced the decay data of the boson through two channels: by two photons and by four leptons. The total statistical significance for a mass of 126 Gav was 5 sigma, i.e. the probability that the cause of the observed effect is statistical fluctuation (random deviation) is 1 in 3.5 million This result made it possible to announce the discovery of a new particle, the Higgs boson, with a high probability.

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