<div style="color: #959595;"> <div> <p>The word quark itself denotes in english a dairy product. This term was first used by the physicist Murray Gell-Mann to refer to the&nbsp; constituents of the nucleon in 1963. In his book, &quot;The quark and the Jaguar&quot;, Gell-Mann explains that he came across this nonsense word in James Joyce&#39;s novel &quot;Finnegans Wake&quot;:</p> <p>&nbsp;</p> </div> <div style="margin-left: 10px;"> <blockquote class="rl-bq-switcher"> <em>&quot;Three quarks for Muster Mark! <br/> Sure he has not got much of a bark <br/> And sure any he has it&rsquo;s all beside the mark.&quot; &nbsp; </em></blockquote> </div> <div> <p>This rhyme (quark, mark and bark) got his attention since quarks come in triplets in baryons. He adopted this term which has been used ever since. Gell-Mann later received the Nobel prize in 1969 &quot;for his contributions and discoveries concerning the classification of elementary particles and their interactions.&quot;</p> </div> </div>

<p>Protons are made of gluons and quarks (two up and one down quark). However, the sum of quark masses amount to a tiny fraction of the proton mass, while gluons are massless particles. Where does the rest of its mass come from? The key to this mystery is the strong interaction. It is the strong force, carried by gluons, that glues protons together, producing most of the proton mass. The same is true for other hadrons, such as the neutron and the recently discovered pentaquarks.</p>

<p>When some massive stars collapse they may produce pentaquarks before forming black holes. Such rare particles can be produced in these environments due to high density and temperature induced in the star core collapse, which make their production more likely. Studying these exotic particles might then be an important step to better understand the structure and formation of stars.</p>

<p>In the traditional quark model, hadrons can be made of three quarks (making baryons, such as protons and neutrons) or a pair between a quark and an anti-quark (making mesons, such as the pion). The exotic tetraquarks and pentaquarks have been first theorized in 1964 by the physicists Murray Gell-Mann and George Zweig. The first evidence of tetraquarks came from the Belle experiment in Japan in 2012, while pentaquarks have been observed at the LHC only in 2015.</p>