Appears at CERN, a strange particle never seen until now


José Manuel NievesSEGUIR Updated: Save Send news by mail electrónicoTu name *

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A team of researchers of the project, LHCb, one of the four large detectors of the European Centre for Nuclear Research ( CERN ), have just announced the discovery of a strange particle composed by four quarks “charm” and never observed up to now. The discovery was presented during a recent seminar in the own CERN and described in an article that appears today in the server prepublicaciones ArXiv. The researchers believe that this is the first of a class of particles that is totally new and unknown to date.

The finding will help to better understand the quarks , which are fundamental components of all matter. The quarks, in effect, join together to form other particles, hadrons , which include protons and neutrons. The new discovery will assist scientists to better understand the ways in which the quarks are bound together to give way to the reality that surrounds us.

For the moment, you know six types of quarks are different , which scientists have classified by their “flavors”: quark bottom quark down quark up, quark top quark strange quark charm . The combinations between quarks of various flavors, give as a result of the different particles that make up matter.

Generally, the quarks are combined in the groups of two and three to form hadrons . For decades, however, theorists have predicted the existence of hadrons formed by four-and five-quark ( tetraquarks and pentaquarks ) and during the last years several experiments, including the LHCb, have confirmed the existence of several of these hadrons exotic.

This class of strange particles made up of combinations little currents of quarks are a authentic gift for the researchers, put to the test in them the four fundamental forces of Nature: electromagnetism, gravity, strong interaction (responsible for the cohesion of the atomic nuclei) and weak interaction (responsible for radioactivity). In particular, a detailed knowledge of the strong interaction, it is essential to determine if processes are new and unexpected, as this particle, are part of the physical standard or whether, on the contrary, they are the hint of a physical completely new, something that scientists are desperately looking for.

“The particles formed by four quarks are already alien -explains Giovanni Passaleva , spokesperson for the outgoing of the LHCb-. And that we have just discovered is the first formed by four heavy quark of the same type, namely two quark charm and two antiquarks charm. Until now, the LHCb and other experiments had only observed tetraquarks with two heavy quark as a maximum, and none with more than two quarks of the same type”.

Chris Perkes , of the University of Manchester and spokesman for the incoming of the collaboration LHCb, “the discovery of today opens an exciting chapter in this book is scientific, allowing us to study our theories about the particles that make up matter in a extreme case. This new particle is an extreme case: a hadron exotic, which contains four quarks rather than the two or three usual, and the first that contains a heavy quark. Consider an end system, as this allows scientists to test the strength of our theories. Through the study of this particle, and with the hope of discovering more particles of this kind in the future, we will test our theory of how to combine the quarks, which also governs the proton and neutron “.

The team of the LHCb found the new tetraquark using the technique of searching for an excess of events of collision in the accelerator, a “peak” on the plain background of events. By examining the sets of data of the LHCb obtained during two stages of activity, between 2009 and 2013, and between 2015 and 2018, the researchers detected an increase in the mass distribution of particles that was consistent with a quark charm, and a anti-charm.

The detected peak has a statistical significance exceeding five sigma , the threshold of certainty from which they can officially announce the discovery of a new particle, and corresponds to a mass that has predicted the existence of particles composed of four quarks charm.

in spite of everything, as happens with the discovery of tetraquarks, it is not yet clear whether the new particle is really a ” new tetraquark “, that is to say, a system of four quarks tightly bound, or whether on the contrary it is a question of two particles formed by two quarks each, and united weaker form, in a structure similar to that of a molecule.

If we are in the first case, we could be at the gates of a New Physics , beyond everything known.