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Lead-proton collision at CERN’s Large Hadron Collider may have yielded a new form of matter

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A proton collides with a lead nucleus, sending a shower of particles through the ALICE detector

Researchers at CERN’s Large Hadron Collider (LHC) are reporting an unusual finding in collisions between protons and lead ions – their observations suggest that the collisions may have produced a new form of matter known as color-glass condensate.  Normally when these collisions between particles occur they yield hundreds of new particles which fly away from the point of collision at near light speeds.  However, the LHC team noted that some particles were moving together with their directions mysteriously correlated.

MIT physics professor Gunther Roland noted:

“Somehow they fly at the same direction even though it’s not clear how they can communicate their direction with one another. That has surprised many people, including us.”

It has been theorized that proton-proton collisions may produce a liquid-like wave of gluons, known as color-glass condensate. MIT explained that they had seen similar behavior before:

“The same flight pattern is also seen when ions of lead or other heavy metals, such as gold and copper, collide with each other. Those heavy-ion collisions produce a wave of quark gluon plasma, the hot soup of particles that existed for the first few millionths of a second after the Big Bang. In the collider, this wave sweeps some of the resulting particles in the same direction, accounting for the correlation in their flight paths.

While protons at normal energy levels consist of three quarks, they tend to gain an accompanying cluster of gluons at higher energy levels. These gluons exist as both particles and waves, and their wave functions can be correlated with each other. This “quantum entanglement” explains how the particles that fly away from the collision can share information such as direction of flight path. The correlation is “a very tiny effect, but it’s pointing to something very fundamental about how quarks and gluons are arranged spatially within a proton.”

The run lasted only a few hours.  In January the team intends to run several weeks of lead-proton collisions. A paper describing the unexpected findings will appear in an upcoming issue of the journal Physical Review B and is now available on arXiv.

Sources: MIT
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