LHC Collides Lead Ions at Record-Shattering Energy Levels

November 30, 2015 | Joanne Kennell

Lead ions collide in the CMS detector
Photo credit: CMS © CERN

And it may be able to detect more Higgs particles.

The Large Hadron Collider (LHC) is moving into a new phase.  After being shut down for two years for important upgrades, researchers at LHC collided lead-ions on November 17, at an energy level twice that of any other previous experiment.

The scientists will continue to collide charged lead ions — lead atoms stripped of their electrons — for one month, in order to study the state of matter that existed shortly after the Big Bang.  “It is a tradition to collide ions over one month every year as part of our diverse research program at the LHC,” said CERN chief Rolf Heuer. “This year however is special, as we reach a new energy and will explore matter at an even earlier stage of our Universe.”

To study the state of matter directly after the Big Bang, scientists have to recreate a moment that existed for only a few millionths of a second — a time when extremely hot and dense matter existed, made up of fundamental particles called quarks and gluons.

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“There are many very dense and very hot questions to be addressed with the ion run for which our experiment was specifically designed and further improved during the shutdown,” said one of the team, Paolo Giubellino, a spokesperson for the ALICE collaboration.

When lead ions are crashed together, the lead ions turn into quark-gluon plasma, which is the Universe’s most perfect superfluid.  Thought to have formed just seconds after the Big Bang, quark-gluon plasma is the oldest form of matter in the Universe.  This quark-gluon plasma was recorded by the LHC and ALICE, a heavy ion detector, during the collision.  

The collision also generated a temperature of a few trillion degrees, a quarter of a million times hotter than the temperature of the core of the sun.  Researchers believe that studying the quark-gluon plasma will yield insight about the physical laws of matter within the Universe.

“The whole collaboration is enthusiastically preparing for a new journey of discovery,” added Giubellino.

The Higgs boson was discovered by scientists at LHC back in 2012, and physicists believe they can find even more Higgs particles.  Current theory suggests there are five types of Higgs, some much heavier than Higgs found in 2012, meaning LHC was not powerful enough to create them.  Until now.

Physicists hope to study what happens when two Higgs collide in the particle accelerator.  Theory suggests that when Higgs’ interacted with itself after the Big Bang, it resulted in an imbalance of matter and antimatter.  This imbalance favored a Universe composed of much more matter than antimatter.  

Researchers also believe Higgs may play a role in another unobservable particle — dark matter.  They suggest that it is possible that Higgs likes to turn into dark matter, or at least play a role in the behavior of it.  Detecting the energies of larger particles never before seen in LHC may give a glimpse of the particles that make up dark matter, especially if some of the energy created after the collision disappears.

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