It is called a pentaquark and it has been "photographed" by the LHCb experiment , in which Spanish scientists participate. As its name indicates, it is an exotic particle with the peculiarity of being made up of five quarks, the fundamental constituents of neutrons and protons. Something never seen in fifty years of research, as Guy Wilkinson, spokesperson for the LHCb, has underlined.
Scientists have known since 1964, when the North American physicist Murray Gell-Mann proposed the existence of these "bricks" of matter, that there are particles of three quarks (baryons) or two quarks (mesons), but the laws of physics do not prevent that there are other types of combinations , such as the one shown by the now discovered particle.
Specifically, the pentaquark is made up of four quarks and an antiquark (its antiparticle) , and although it does not call into question the standard model of physics, it can help to better understand the intimate structure of neutrons and protons. "To be precise, states are made up of two up quark (up), a down quark (down), a charm quark (charm) and its antiparticle, an anti-charm", details the physicist of LHCb Tomasz Skwarnicki, of the Syracuse University (USA).
Now it remains to be seen how these five ingredients are linked: "they could be strongly linked", explains the physicist of LHCb Liming Zhang, from Tsinghua University (China), "or more weakly, in a kind of meson-baryon molecule in which both experience a strong residual force , similar to that which holds protons and neutrons together to form the nucleus ”.
