The mystery of the Higgs boson
Two experiments at CERN could confirm or contradict everything scientists theorise about the nature of the universe.
|Scientists at CERN use particle accelerators to understand the process of the creation of the universe [GALLO/GETTY]|
When you stare into the night sky, the planets, stars and galaxies you can see make up only a tiny four per cent of what’s actually out there.
That’s according to scientists who work in laboratories with particle accelerators to find out more about the rest. What’s more, two exciting experiments being carried out right now could confirm or contradict everything scientists believe they know about the nature of the universe.
First, the search for the Higgs boson particle, which could unlock secrets about the beginning of the universe, and secondly, the Opera experiment – in which certain particles appeared to travel faster than the speed of light – which is believed to be the limit of speed.
If the results from the Opera experiment are reproducible, it would mean a correction to Einstein’s theory of special relativity, proposed in 1905.
And physicists at CERN in Switzerland have recently announced that they may be closing in on a sighting of the Higgs boson particle – which would tell researchers about the origin of particle mass and shed light on the process of the creation of the universe.
What is the Higgs boson?
Scientists find signs of ‘God particle’
Embodying everything scientists theorise about the behaviour of fundamental particles – the 12 basic building blocks of the visible universe – is a theory called the Standard Model. The only problem with this theory is that it is missing the mechanism that gives rise to mass.
“The Standard Model has a table of particles with a hole in it: The Higgs Boson … the detection of a Higgs Boson would confirm parts of the Standard Model and would mean we don’t have to revise everything,” explained Robert Cailliau, formerly of CERN.
To resolve the problem, scientists hypothesised that all particles had no mass right after the Big Bang.
As the universe cooled, an invisible force-field (named the Higgs field) spread throughout the universe. When particles interacted with this field, they were given a mass corresponding to the amount of interaction via the Higgs boson particles that existed in the field.
Unfortunately, the Higgs boson has not been observed by scientists beyond statistical fluctuation in an experiment to confirm the theory. If they do detect the Higgs boson, it will help scientists understand why particles have certain mass and let them move on to develop their explanation of how the universe was created.
“Traces of something that might be the Higgs boson have been observed … but they may still be something else or just flukes,” continued Cailliau.
“The particle can only be seen by its tracks, like footprints in the snow. If you see a single print that looks like it was made by the paw of a cat, you should consider that it could have been something else that made the print: a falling leaf, the wind, whatever … It’s only after seeing many prints of cat paws one after the other in related circumstances that you would be justified to say ‘there was a cat here’,” said Cailliau.
In that way, if scientists are unable to find enough traces of the particle to confirm it beyond a reasonable doubt, physicists will have to drop the Standard Model and develop a completely new theory to explain where particle mass comes from.
Faster than the speed of light?
The second experiment that physicists at CERN are working on currently, the Opera experiment, came up with astonishing results – the resulting particles appeared to travel faster than the speed of light.
To carry out the experiment, a particle accelerator was used to create neutrinos – one of the 12 fundamental particles. Neutrinos differ from other particles, as they are electrically neutral and have very little mass, if any mass at all.
For this reason, neutrinos can pass through “solid” objects without interacting. This is how scientists were able to shoot a beam of neutrinos through the crust of the earth, 730km to the Gran Sasso laboratory in Italy.
“The measurement of the anomaly was a side measurement … we didn’t expect to find that result,” explained Antonio Ereditato, spokesperson of the Opera experiment at the INFN Gran Sasso Laboratory.
The results, which showed that the particles seemed to travel faster than the speed of light, came as a shock because scientists believed that the speed of light was the limit of speed.
“The speed of light is considered to be the top speed of anything with mass,” Ereditato continued.
These results sent a tremor through the global physics community.
If the results are accurate, they would contradict Einstein’s theory of special relativity, which would turn “modern physics upside down,” according to Chang Kee Jung, professor at SUNY at Stoneybrook, and T2K International Co-spokesperson.
“In particle physics, we live and eat and drink with special relativity – everything uses it,” Jung continued.
What could have gone wrong?
Scientists require results to be reproduced several times before they can be considered valid, yet many are thrilled by the prospect of this particle potentially breaking the speed of light. However, not everyone thinks neutrinos are “special” enough to shatter special relativity.
“What this would mean if it were correct is that relativity is wrong, but only for this particle … and we know that neutrinos are related to other particles by our theory – so how could relativity be right for one and not the other?” questioned Michael Peskin, a theoretical particle physicist at SLAC National Accelerator Laboratory at Stanford University.
“No one has put forward a good explanation yet … the easiest explanation is that there was a mistake,” Peskin continued.
With the huge number of measurements and calculations required by this experiment, it’s not hard to imagine that a mistake could have been made.
|The Large Hadron Collider, one of CERN’s particle accelerators, is 27km in circumference [GALLO/GETTY]|
Each step of the experiment, from CERN to Gran Sasso, must be painstakingly and precisely measured: from the time it took the original proton beam in the particle accelerator at CERN to produce the neutrinos through the process of radioactive decay, to the length and even temperature of the cables that the electronic signals of the devices and detectors used in the experiment travelled through.
Along with the measurements and calculations scientists needed to make, the detectors and equipment used in the experiment must be checked for their level of accuracy. One example of this is the GPS system used in the experiment.
“Most of the public don’t realise that GPS timing is not always accurate if it’s a cheaper model. You can get a very good one for tens of thousands of dollars which records down to nanoseconds of accuracy,” Jung explained.
And in this experiment, everything must be painstakingly accurate in order to prove these unexpected results.
The Opera experiment team has already begun making additional tests and so far, “they brought the same result. It was a different neutrino beam, but came up with the same result. This is not enough though – we are very demanding towards our results,” Ereditato said.
“If another test finds the same result, I would say we need another one. I will not be satisfied because this is really a result that could potentially be of very high impact on science,” Ereditato emphasised.
A physics revolution?
If the results are reproducible in further tests, the impact on physics would be equivalent to that of Einstein’s theory of special relativity on Newton’s laws. Einstein showed that Newton’s laws could not be applied in certain circumstances – such as at very high speeds or in very strong gravitational fields.
“We’re not just smashing things together and seeing what comes out, we are creating new particles.“
– James Gillies, head of communications and lab spokesperson for CERN
“Newton’s laws are good enough to put a rocket on the moon without making a mistake, as long as you don’t travel too fast. If you start travelling too fast, really fast, you will find Newton’s laws are not precise enough. You then have to add a correction – which is Einstein’s relativity,” explained Cailliau.
“This doesn’t mean Newton was wrong, only that it was an approximation. If the neutrinos did indeed go faster than the speed of light, then we will have to make another correction … and our ideas of how nature operates would have to change,” Cailliau continued.
Already, two other laboratories have begun planning experiments in an attempt to reproduce the Opera experiment: T2K in Japan and Fermilab in Chicago, Illinois.
It’s not the first time the travel speed of neutrinos has been measured, however. In 1987, there was a supernova close to our galaxy that allowed scientists to measure the travel speed of neutrinos – which was measured at the speed of light to one part in 10 million.
“So the mystery is how the neutrinos in this experiment travelled faster than that,” Peskin questioned.
CERN and particle accelerators in general
CERN’s largest (of several) particle accelerators is called the Large Hadron Collider (LHC) – which is situated 100 metres underground and is 27km in circumference. It is the machine they use to observe the behaviour of fundamental particles.
“Particle accelerators take tiny pieces of matter – fundamental particles from which we are all made – and accelerate them to high speeds [which can] reach above 99 per cent of the speed of light. When the beams collide, scientists can investigate some fundamental processes in nature,” explained James Gillies, head of communications and lab spokesperson for CERN.
“You can generate new particles that weren’t there before. We’re not just smashing things together and seeing what comes out, we are creating new particles,” said Gillies.
The particle accelerator at CERN is circular, so that scientists can send two proton beams in opposite directions, making it possible for the beams to continue travelling around in circles for hours – colliding a few particles every time.
The accelerated particles are electrically charged and are pushed using electromagnetic fields. The particles are confined using very powerful magnets made of superconducting coils carrying very large electric currents covering the entire 27km. The accelerated particles are confined as their path is restricted along the magnetic field lines.
But why are these particles important to understand?
“The science of the small is intricately linked to the science of the big. Small particles can tell you about the entire universe,” Gillies emphasised.