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  • For the first time, scientists have spotted a bizarre “X” particle

  • in a recreation of the primordial soup that existed just moments after the Big Bang.

  • By smashing billions of lead ions together using the Large Hadron Collider,

  • researchers were able to find just about 100 of these mysterious particles,

  • but that could be the start of figuring out what exactly this “X” particle is made of.

  • That’s why it’s just called the “X” particle; it’s not like it broke up with a physicist.

  • There are a few different ideas on what it could be but no one is sure yet.

  • Figuring it out could tell us more about what the universe was like a split second after it formed

  • and help us better understand the protons and neutrons that make up the nuclei of atoms.

  • You know, life’s little questions.

  • To understand the mystery, were going to have to talk about fundamental particles called quarks.

  • Don’t panic, itll be easy.

  • Some particles like protons and neutrons are made up of three quarks.

  • It’s also possible to have particles made of just two quarks, or more specifically a quark and antiquark pair.

  • These particles are called mesons.

  • Binding quarks together inside mesons, protons, and neutrons are gluons, which carry the strong force.

  • And here’s some shocking news: The strong force is really strong.

  • So strong that an isolated quark has never been observed because they seem to be locked inside protons and neutrons

  • in all but the most extreme conditions.

  • Now we come to the mystery of the “X” particle:

  • We think it’s made up of four quarks but nobody has been able to figure out yet how theyre arranged.

  • The two leading ideas suggest either the four quarks are tightly bound up in a teeny space

  • less than a third of a femtometer across,

  • or they could be paired up in two mesons that form something like a molecule that's loosely bound

  • and as large as five femtometers.

  • For reference, we think a proton has a radius of about 0.84 femtometers.

  • This is where the Large Hadron Collider comes in.

  • The LHC was not the first particle accelerator to spot the “X” particle;

  • it was actually first spotted almost two decades ago by the BELLE collaboration in Japan.

  • But until now, all the experiments that have spotted it were either smashing together electrons and positrons,

  • protons and antiprotons, or protons and protons.

  • Scientists think the key to unraveling the “X” particle’s secrets could be recreating conditions like those just after the Big Bang.

  • That isn’t easy to do by smashing protons together, even at very high energies.

  • Now you may be wondering why the LHC is different because as you may know, the LHC also smashes protons together.

  • That is famously how it found the Higgs Boson, often known asthe God Particle,”

  • but don’t call it that in front of a physicist because it turns out most of them hate that name.

  • However, for part of each year, the LHC stops smashing protons together and instead sends something much heavier

  • hurtling around it’s enormous ring: lead.

  • When two lead ions collide inside the LHC, hundreds of protons and neutrons are slammed together in an instant

  • and heat up to over 2 trillion degrees.

  • That’s 100,000 times the temperature inside the core of the Sun.

  • That’s so hot I didn’t have to say if it’s Celsius, Kelvin, or Fahrenheit because it doesn’t really matter.

  • Above that threshold, the quarks and gluons normally bound up inside the protons and neutrons

  • can break their bonds and create what’s called a quark-gluon plasma.

  • We think the entire universe was in a quark-gluon plasma state for a few millionths of a second after the Big Bang,

  • allowing exotic matter like “X” particles to form and decay again until things started cooling down

  • and particles like protons and neutrons formed.

  • When researchers at the LHC started looking for “X” particles produced by lead ion collisions,

  • they weren’t sure if recreating this primeval particle soup would help them or hinder them

  • because it would also generate tons of other particles that might mask their presence.

  • There’s also the problem that “X” particles decay so fast that the particle itself can’t be detected,

  • only what it decays into.

  • Using machine learning algorithms to sniff out the telltale signs of decaying “X” particles,

  • they were able to identify about 100.

  • Just 100 from more than 13 billion collisions.

  • Doesn’t sound like very many, and it isn’t,

  • but with this method “X” particles were detected about 10 times more frequently than in proton-proton collisions.

  • Spotting more “X” particles in conditions similar to how they formed in nature can finally tell us what theyre made of.

  • If they decay very quickly, that would point to them being loosely bound meson molecules.

  • If they decay still really quickly but slightly less so, then theyre probably made of four tightly bound quarks.

  • Unfortunately, the 100 seen by the LHC aren’t enough to definitively point to one possibility or the other.

  • But now that we know how to spot them in a quark-gluon plasma,

  • scientists are ready to hunt for a lot more.

  • The LHC has been undergoing upgrades since 2018 but it’s gearing up for another run.

  • Heavy ion smashing is scheduled for November of 2022, and after scientists have a chance to sift through the data,

  • they may see enough “X” particles to finally solve the mystery of their makeup

  • and give them a name once and for all.

  • I hope they name it Julian. That’s a good name.

  • If you enjoyed this quick dip into the warm waters of fundamental particles, I’ve got great news.

  • I just made a three-part deep dive on our other channel Seeker+ all about the Higgs Boson.

  • I think it makes understanding particle physics surprisingly approachable and I’m so proud of it,

  • so do me a favor and go check it out.

  • In the meantime though, place your bets. So do you think this “X” particle is a tetraquark or two mesons?

  • Let us know in the comments section and be sure to subscribe to Seeker.

  • Until next time, thank you so much for watching!

For the first time, scientists have spotted a bizarre “X” particle

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Scientists Found Particle 'X,' Now What?!

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    Summer 發佈於 2022 年 01 月 31 日
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