Particle Physicists Put the Squeeze on the Higgs Boson; Look for Conclusive Results in 2012

by Nancy Atkinson on December 13, 2011

Scientists gather as the ATLAS and CMS experiments present the status of their searches for the Standard Model Higgs boson. Credit: CERN

With “freshly squeezed” plots from the latest data garnered by two particle physics experiments, teams of scientists from the Large Hadron Collider at CERN, the European Center for Nuclear Research, said Tuesday they had recorded “tantalizing hints” of the elusive subatomic particle known as the Higgs Boson, but cannot conclusively say it exists … yet. However, they predict that 2012 collider runs should bring enough data to make the determination.

“The very fact that we are able to show the results of very sophisticated analysis just one month after the last bit of data we used has been recorded is very reassuring,” Dr. Greg Landsberg, physics coordinator for the Compact Muon Solenoid (CMS) detector at the LHC told Universe Today. “It tells you how quick the turnaround time is. This is truly unprecedented in the history of particle physics, with such large and complex experiments producing so much data, and it’s very exciting.”

For now, the main conclusion of over 6,000 scientists on the combined teams from CMS and the ATLAS particle detectors is that they were able to constrain the mass range of the Standard Model Higgs boson — if it exists — to be in the range of 116-130 GeV by the ATLAS experiment, and 115-127 GeV by CMS.

The Standard Model is the theory that explains the interactions of subatomic particles – which describes ordinary matter that the Universe is made of — and on the whole works very well. But it doesn’t explain why some particles have mass and others don’t, and it also doesn’t describe the 96% of the Universe that is invisible.

In 1964, physicist Peter Higgs and colleagues proposed the existence of a mysterious energy field that interacts with some subatomic particles more than others, resulting in varying values for particle mass. That field is known as the Higgs field, and the Higgs Boson is the smallest particle of the Higgs field. But the Higgs Boson hasn’t been discovered yet, and one of the main reasons the LHC was built was to try to find it.

To look for these tiny particles, the LHC smashes high-energy protons together, converting some energy to mass. This produces a spray of particles which are picked up by the detectors. However, the discovery of the Higgs relies on observing the particles these protons decay into rather than the Higgs itself. If they do exist, they are very short lived and can decay in many different ways. The problem is that many other processes can also produce the same results.

How can scientists tell the difference? A short answer is that if they can figure out all the other things that can produce a Higgs-like signal and the typical frequency at which they will occur, then if they see more of these signals than current theories suggest, that gives them a place to look for the Higgs.

The experiments have seen excesses in similar ranges. And as the CERN press release noted, “Taken individually, none of these excesses is any more statistically significant than rolling a die and coming up with two sixes in a row. What is interesting is that there are multiple independent measurements pointing to the region of 124 to 126 GeV.”

“This is very promising,” said Landsberg, who is also a professor at Brown University. “This shows that both experiments understand what is going on with their detectors very, very well. Both calibrations saw excesses at low masses. But unfortunately the nature of our process is statistical and statistics is known to play funny tricks once in a while. So we don’t really know — we don’t have enough evidence to know — if what we saw is a glimpse of the Higgs Boson or these are just statistical fluctuations of the Standand Model process which mimic the same type of signatures as would come if the Higgs Boson is produced.”

Landsberg said the only way to cope with statistics is to get more data, and the scientists need to increase the size of the data samples considerably in order to definitely answer the question on whether the Higgs Boson exists at the mass of 125 GeV or any mass range which hasn’t been excluded yet.

The good news is that loads of data are coming in 2012.

“We hope to quadruple the data sample collected this year,” Landsberg said. “And that should give us enough statistical confidence to essentially solve this puzzle and tell the world whether we saw the first glimpses of the Higgs Boson. As the team showed today, we will keep increasing until we reach a level of statistical significance which is considered to be sufficient for discovery in our field.”

Landsberg said that within this small range, there is not much room for the Higgs to hide. “This is very exciting, and it tells you that we are almost there. We have enough sensitivity and beautiful detectors; we need just a little bit more time and a little more data. I am very hopeful we should be able to say something definitive by sometime next year.”

So the suspense is building and 2012 could be the year of the Higgs.

More info: CERN press release, ArsTechnica

About 

Nancy Atkinson is Universe Today's Senior Editor. She also works with Astronomy Cast, and is a NASA/JPL Solar System Ambassador.

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