Much Rests On The Enhanced Large Hadron Collider

Mar 18, 2015
Originally published on March 18, 2015 1:11 pm

Get ready to look at the universe through a new window.

Later this month, the Large Hadron Collider, or LHC, the behemoth particle accelerator operated by the European Organization for Nuclear Research (CERN), will be back in action after a two-year hiatus. The pause was intentional, giving technicians and engineers time to ramp up the collision energy by almost a factor of two. In particle collisions, the higher the energy, the bigger the payoff, as the energy of the colliding particles gets translated into the masses of the debris, following the E=mc2 prescription.

As particles collide, their energy morphs into a shower of new particles that come flying off from the collision point. To see this, physicists use highly sophisticated detectors, essentially modern versions of ultrasensitive microscopes that can track each individual particle produced during the collision. The process is very complex, as there are literally trillions of collisions to sift through — most of them created by well-known events of little interest for new science.

Physicists, though, are nervously awaiting the unleashing of the bolder LHC; the payoff could be huge, leading, for example, to the discovery of the so-called supersymmetric particles that could possibly solve the mystery of dark matter in the universe. Dark matter is a strange material that attracts normal matter gravitationally, but doesn't emit any kind of radiation. And, if you are an optimist, you are waiting to hear whether the "new" LHC can find evidence of extra spatial dimensions called for by theories that attempt to unify all forces of nature.

Or, the whole thing could be a bust. That's the nature of research: If you don't look you won't find.

The LHC operation is truly of biblical proportions. First, the machine itself is essentially a circular pipe with a 27 km circumference (about 16.8 miles) buried 100 meters (328 feet) underground. Two beams of protons fly along the pipes in circles in opposite directions controlled by superconducting magnets placed outside the pipes that must be cooled down to only 1.9 K (-456.25 degrees Fahrenheit). For comparison, the temperature in outer space is a balmy 2.7 K (-454.81 degrees Fahrenheit). To keep the protons running around in circles, currents of 11,850 amps must run through the magnets to produce the required huge magnetic fields. Everything must work with absolute precision to obtain the desired collision energy and rate.

In July 2012, scientists at CERN announced the discovery of the Higgs boson, the particle needed to complete the so-called Standard Model, the sum-total of our understanding of how particles of matter interact with one another. Discoveries of new particles in modern physics are not your everyday affair. Statements are based on statistical analysis, given the huge number of collisions and decay pathways for the particles. In particle physics, a discovery is identified with a 5-sigma event, equivalent to a one-in-3.5-million chance that what was observed is not a new particle. In other words, it would be a total fluke if the bump they see in the data is not due to the existence of a new particle. Not impossible, but ridiculously perverse.

The new run, apart from throwing some much needed light on the existence, or not, of supersymmetry, will narrow down the properties of the Higgs, which are still somewhat vague. A particle's decay products, the offspring from its demise, depend uniquely on its properties. The higher energy from the LHC will allow physicists to study the Higgs decay in finer detail, for example, clarifying whether the Higgs is a fundamental particle or if it is a composite, made of other particles.

The future of high-energy physics hangs in the balance.

Science at this level needs constant stimulation, exciting discoveries, to be justified to taxpayers. If the new LHC finds nothing out of the ordinary, no hint of new physics, it will be hard to convince people that we need a bigger, bolder machine.

Yet, if we get unlucky, convince we must. Apart from all the technological spinoffs from basic research (the World Wide Web was created at CERN) and the many open questions we have (What is dark matter? How does the Higgs get its mass? Are the forces of nature unified at high energies?), to know the material composition of the cosmos is to know ourselves, our origins. If we stop probing nature at higher and higher energies, we will be closing the doors to the oldest line of inquiry in philosophy and science: the material composition of the world. We would be giving up on 25 centuries of intellectual inquiry that defined, to a large extent, the way we live today. The road that started with Thales of Miletus, around the year 650 B.C., continues today with the digital and Internet revolutions. Do we really want to be the generation that gives up?

Maybe we will get lucky, and amazing new discoveries are just around the corner. But in the event that the LHC comes out empty-handed, consider it nature's big tease. Consider it not as an obstacle but as a trigger for our creativity, a trigger that will force us to keep finding new ways to extend our reach into the deepest confines of reality.

Marcelo Gleiser is a theoretical physicist and cosmologist — and professor of natural philosophy, physics and astronomy at Dartmouth College. He is the co-founder of 13.7, a prolific author of papers and essays, and active promoter of science to the general public. His latest book is The Island of Knowledge: The Limits of Science and the Search for Meaning. You can keep up with Marcelo on Facebook and Twitter: @mgleiser.

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