A new particle discovery has heads spinning

Markus Schulze explains the new particle. It could be the most significant discovery in physics in half a century, but more research is needed to confirm this.
Written by Boonsri Dickinson, Contributing Editor

After running experiments on a particle accelerometer, scientists noticed a bump in the data. It was so unusual, in fact, that scientists think it could mean they've discovered a new particle.

“Nobody knows what this is,” Christopher Hill of Fermilab told The New York Times' Dennis Overbye. “If it is real, it would be the most significant discovery in physics in half a century."

Fermilab's Tevatron Collider Detector (CDF) was designed to study high energy particle collisions to identify particles and how they interact.

The CDF beams protons and antimatter particle around a ring through a vacuum pipe using 1,000 superconducting magnets. The particles accelerate at a speed that is nearly the speed of light. When the particles collide inside the two four-story detectors, showers of new particles are created. The collisions recreate the conditions of the early universe. By looking at how the particles behave after the collisions, scientists can tell if they've discovered something new by measuring properties such as the electric charge and momentum of the particles.

If it is indeed a new particle, it would challenge the Standard Model, the current theory of particle physics and their forces. Currently, the model provides the framework for low energy processes such as chemistry and nuclear physics - as well as high energy processes such as sub-nuclear physics and cosmology. So if this bump turns out to represent a new particle - it could re-frame physics.

I asked Markus Schulze, a physicist at Johns Hopkins University, about this new particle and its significance.

SmartPlanet: What is the big news about?

MS: Results of an analysis from the Tevatron collider suggest that there might be a new particle. The signal of this potentially new particle manifests itself as a "bump" in the data, where there should be none, according to the Standard Model of particle physics.

Have a look.

The red shaded line is the expected data and the blue bump corresponds to "something strange" and unexpected which could be a new particle.

SmartPlanet: I thought physicists really wanted to look for the Higgs boson. Why do we care about this new particle?

It is true, particle physicists are very much interested in finding or excluding the Higgs boson. The reason is that the Higgs boson is the last missing particle, out of 17 particles in the Standard Model.

This model has been extremely successful over almost the last 40 years. It allows us to describe interactions between elementary particles in hundreds of experiments with high precision.

On the other hand, one of the major ingredients that make this model a consistent theory is the yet undiscovered Higgs boson. This is why we all are very interested in the question whether the Higgs boson really exists.

The Large Hadron Collider (LHC) in Geneva will be able to answer that questions definitely.

It is already clear from the size of the bump that the potentially new particle that showed up at the Tevatron cannot be the standard model Higgs boson! It could be something completely new.

This would be very exciting because one cannot just add a single particle to the Standard Model without violating its mathematical consistency. What would be needed is a whole new framework, for example, a new force or new symmetry principles or a rethinking of space-time.

This is what we are actually looking for. Finding the Higgs boson alone would leave us with many questions unanswered. A whole new theory, however, would probably give us some hints about unsolved problems like dark matter, dark energy or the matter-antimatter asymmetry in the universe.

SmartPlanet: What is the significance of the finding at the Tevatron accelerator? What are the implications that it could mean for physics?

SM: It is important to emphasize that this recent measurement does not tell us much about the specific properties of the potentially new particle.

The location of the bump tells us that its mass might be in the range of 150 Giga-Electronvolt, 5/3 as heavy as a Z-boson (the heavy brother of the photon).

But this is all we know so far.

Hence, there are many viable theories and different particles that can explain the bump in the measurement.

SmartPlanet: What would this discovery mean for physics?

SM: Yes, it could be a new force actually in physics we say interaction because forces are described as particle exchange.

This new interaction would extend our model of particle physics and help answering other big questions in physics and cosmology.

SmartPlanet: Is there a chance this discovery was an error?

SM: Your question is very important: How reliable is the measurement? In principle, every measurement can be wrong at some level of precision. A typical way to describe our confidence in a measurement is to give a probability that the measured result is just a fluke. In our case, the question is how likely is it that the bump in the data is just a statistical fluctuation.

At present, there is about a 1% probability that the measurement is just a random fluctuation. Further improvements will either makes this probability become smaller or bigger. In physics, we claim a real discovery of a new particle when there is only a 1 out of 1 million chance (0.00006%) of a statistical fluctuation. This is why there is still some skepticism allowed.

In addition to all that, it can be that there is an error in the data analysis or a misjudgment of the uncertainties.

Therefore, it is very important that the other experimental group at Tevatron (DZero) performs a second independent measurement to cross check the result.

It will be very interesting to follow these results.

Photo: Fermilab

Fermilab Physicist May Have Found New Particle [New York Times]

This post was originally published on Smartplanet.com

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