First evidence of a new decay mode of ... - Publico.es

International collaboration

ATLAS experiment of the Large Hadron Collider (LHC) just released the first evidence of the disintegration of the newly discovered two Higgs particles called tau, belonging to the family of particles that make up matter see in the universe. So far the LHC experiments had detected the Higgs particle by its disintegration into other particles called bosons, carriers of the forces acting in nature, while the decays into fermions evidence was inconclusive. This is the first clear evidence of this new decay mode of the Higgs boson, whose analysis in Spanish researchers have participated.

is the first time observed the Higgs boson decay into two tau

leptons

members of the ATLAS collaboration presented new results in a seminar at CERN on 26 November. They show for the first time with a level of certainty 4 sigma – best to proclaim a genuine observation is 5 – the Higgs boson decaying into two tau leptons (represented by the Greek letter ?). It is the first time this phenomenon has been measured in the Higgs boson.

Higgs boson is discovered in 2012 by the ATLAS and CMS LHC experiments revealed the existence of a new force field particle in nature. Also called the Brout-Englert mechanism-Higgs in honor physicists who proposed (two of them, Englert and Higgs, awarded the Nobel Prize in Physics and the Prince of Asturias Research). This force field is responsible for the origin of mass of elementary particles. Without this mechanism to generate mass, matter that makes up everything we see in the universe and ourselves could not form as we know it.

class=”despiece”> Compatible with standard Model

knew that the Higgs decays into one of two basic types of particles exist: bosons, responsible for interactions (forces) that occur in nature. The Brout-Englert mechanism-Higgs was proposed to explain the origin of the mass of these particles. However, the standard model of particle physics, the theory that describes the elementary particles and their interactions, postulated that the other basic type of particles, fermions, also acquired its mass by this mechanism.

Spanish scientists

IFIC, IFAE, IMB and UAM involved in the study

Now is the first time that scientists have clearly seen that the Higgs boson also decays into these particles, fermions, the ‘bricks’ that make up the visible matter in the universe (eg, electrons and the quarks that make up protons of an atom are fermions). In fact, the results obtained by scientists of the ATLAS experiment are consistent with the predictions of the standard model.

These results have been obtained with the data collected in 2012. Since its launch in 2015 after two years of maintenance, scientists hope to get many more LHC data, in addition to the energy function for which it was designed. Researchers at the Institute of Corpuscular Physics (IFIC, CSIC-UV) have been directly involved in this analysis, with an important role in the characterization of the background events, determination of statistical methods, multivariate technique definition and selection of the input variables , which have been crucial to achieve this result with a high level of statistical confidence.

Meanwhile, researchers at the Institute of High Energy Physics (IFAE) participants ATLAS experiment work on other channels to study the decay of the Higgs boson in other fermions (quarks top and bottom). In ATLAS also involved researchers from the Institute of Microelectronics of Barcelona (IMB-CNM-CSIC) and the Autonomous University of Madrid (UAM). In total, approximately 200 Spanish researchers involved in the LHC, grouped by the National Centre for Particle Physics, Astroparticle and Nuclear (CPAN).