Posts Tagged ‘Geneva’

Faster Than Light Particles! So, Warp Speed Ahead, Right???

September 22, 2011 3 comments

The OPERA detector at Gran Sasso National Laboratory in Italy

I’ll have more to say about this story once I see the work on arXiv, but I feel I should comment now because this story is exploding.

The interwebs and blogospheres are abuzz with the news that researchers at CERN have measured the velocity of neutrinos which seem to be travelling faster than light.

Neutrinos are nearly massless  subatomic particles which have been known to travel near the speed of light. But, like all other things in the universe, they are not supposed to be able to travel faster than light.

Basically the experiment involves the creation of neutrinos at CERN in Geneva, Switzerland, and the neutrinos travelling 730 km to a laboratory 1,400 meters underground in Italy. There, an experiment called OPERA (Oscillation Project with Emulsion-tRacking Apparatus) detects those neutrinos and measures how quickly it took them to make the trip.

The neutrinos arrived 60 nanoseconds sooner than they should have. This means they were travelling at a speed of about 299 800 km/s, which is slightly higher than the speed of light, which is about 299 792 km/s.

This discovery will rock the very foundation upon which modern physics is built. Seriously, this is like the discovery that the world is round or wave-particle duality; it’s a complete game-changer.

If it’s true.

Like a lot of folks out there, I am quite skeptical of this discovery. Think of it this way: which of these two scenarios is more likely,

  1. Particles can travel faster than light, completely re-writing modern physics and decades of previous research. Or,
  2. These guys made an innocent mistake.

Now, it is certainly possible that this discovery will turn out to be genuine. However, it is much more likely that there was some kind of error or misinterpretation which has led to this result.

I would like to point out that the researchers have revealed their work in the proper way. They are excited, but very skeptical themselves and are asking the academic community to review their work and try to find a flaw. Antonio Ereditato, a physicist at the University of Bern in Switzerland and OPERA’s spokesman said in an interview

Whenever you are in these conditions, then you have to go to the community

THIS is science in action, folks! A group of physicists think they have discovered something awesome. But they haven’t started trumpeting their results like they have been absolutely confirmed, no emails were leaked suggesting the discovery, and they didn’t go to some rogue publication to get their work in print prior to peer-review.

Beautiful, isn’t it?

I am very hopeful this turns out to be a genuine discovery. I can’t wait to read the papers and hear the response from the scientific community.


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CERN Traps Anti-Matter For 1000 Seconds

May 4, 2011 8 comments

Antimatter is cool.

It lets us perform PET scans and powers the starship Enterprise. But it is extremely difficult to study.

That is because when anti-matter comes into contact with normal matter, they annihilate one another, emitting pure energy (photons). This is unfortunate for scientists because they would love to study anti-matter, but developing a trap for it is understandably tricky. The anti-matter particles can easily interact with background gases or the walls of the container.

But last year, researchers at CERN published a paper in Nature (which I also blogged about) describing how they managed to trap 38 atoms of anti-hydrogen (an antiproton orbited by a positron) for 172 ms.

They have not stopped working on improving their trap, however, and have now performed a study detailing how they were able to trap anti-hydrogen for 1000 seconds, an increase of nearly 4 orders of magnitude from their previous paper.

This is what they did:

First, CERN’s Antiproton Decelerator creates the antiprotons which will be used to create atoms of antihydrogen. The Anitproton Decelerator provides antiprotons in groups roughly 3 x 107 in number. Only anti-protons which have an energy less than a certain amount (< 3 keV) are trapped. Typically the number of antiprotons less than this energy threshold is ~6 x 104. These antiprotons are then cooled and compressed.

After this initial step, the antiprotons are then mixed with a cloud of positrons in an effort to get these two components to combine into atoms of antihydrogen. After mixing for about 1 second, the researchers end up with about 6 x 103 atoms of antihydrogen.

All this takes place inside a magnetic trap. The trap is cylindrical in shape and has a length of 270 mm and a diameter of 44.5 mm.

A schematic diagram of the anti-hydrogen trap (a). The other graphs in this figure show the strength of the magnetic field at different points in the trap.

In order to actually “trap” the anti-hydrogen atoms, a magnetic field is generated inside this cylinder. The field is shaped such that the magnetic field is weakest in the middle of the trap (~ 1 T), and stronger along the edges of the trap (~ 2 – 3 T). In this way, a type of “well” is created which keeps the antihydrogen atoms in the middle of the apparatus, which prevents them from interacting with the walls of the trap and annihilating themselves.

After holding the antihydrogen atoms for a certain period of time, the researchers would shut down the magnets and wait for the atoms to annihilate themselves by hitting the walls of the trap. A special detector counts these annihilation events and allows them to detect the number of anithydrogen atoms remaining after the experiment.

Why don’t all the antihydrogen atoms remain? Most of them are lost through interactions with gases inside the trap, such as helium and molecular hydrogen.

They varied the experiment time from 0.4 seconds to 2000 seconds, and did several attempts for all time lengths. As you might expect, they detected more annihilation events per attempt for the short time lengths (e.g. 1.13 ± 0.13 events/attempt for 0.4 second time length) than the longer time lengths (0.77 ± 0.29 events/attempt for 1000 second time length).

Ah but now you are thinking, “but they did some experiments at 2000 seconds, why aren’t we hearing about that?”

The reason is that they only did  3 experiments at the 2000 second time scale, and while they did detect a few events, the results were not strong enough to say for sure that they were able to trap antihydrogen at that time scale.

The paper also discusses some of their computer simulations and how they compare to the actual experiment results, but I will leave that to the interested reader. 

So what are the implications of this work?

Being able to trap anti-matter for this period of time will allow for much easier ability to perform spectroscopy, since the density of atoms and intensity of radiation needed are dramatically reduced in the anti-matter can be held for a long period of time.

In addition, trapping anti-hydrogen for this long time scale will allow researchers to cool the anti-matter to very low levels, allowing them to probe the effect of gravity on anti-matter.

This post was chosen as an Editor's Selection for

ALPHA Collaboration, G. B. Andresen, M. D. Ashkezari, M. Baquero-Ruiz, W. Bertsche, E. Butler, C. L. Cesar, A. Deller, S. Eriksson, J. Fajans, T. Friesen, M. C. Fujiwara, D. R. Gill, A. Gutierrez, J. S. Hangst, W. N. Hardy, R. S. Hayano, M. E. Hayden, A. J. Humphries, R. Hydomako, S. Jonsell, S. Kemp, L. Kurchaninov, N. Madsen, S. Menary, P. Nolan, K. Olchanski, A. Olin, P. Pusa, C. Ø. Rasmussen, F. Robicheaux, E. Sarid, D. M. Silveira, C. So, J. W. Storey, R. I. Thompson, D. P. van der Werf, J. S. Wurtele, & Y. Yamazaki (2011). Confinement of antihydrogen for 1000 seconds arXiv arXiv: 1104.4982v1

Dan Brown Novel Coming True? Antimatter Captured at CERN

November 17, 2010 1 comment

In Dan Brown’s novel ‘Angels and Demons’, a supposed terrorist group steals a sample of anti-matter from CERN in Geneva. They rig it up like a bomb in an attempt to destroy the Vatican.

Anti-matter is the bizzarro-counterpart to regular matter. For example, regular matter is made up of protons, neutrons and electrons. A positron, which is the anti-matter counterpart to the electron, has the exact same mass as an electron but has an opposite electric charge (positive instead of negative, hence ‘positron’).

When anti-matter comes into contact with regular matter, they annihilate each other, and get converted entirely to energy. This is what makes anti-matter so difficult to handle, because most of our universe is made of regular matter, so anti-matter never hangs around for too long before it gets converted to energy. It is also why Dan Brown uses it in his novel, as an anti-matter bomb can be much more powerful than a nuclear weapon.

For example, half a gram of anti-matter could release as much energy as the atomic bomb dropped on Nagasaki in 1945.

Mushroom Cloud Over Nagasaki, August 9 1945. From Wikipedia.

This isn’t very realistic, however, since anti-matter is so difficult to trap.

But now science fiction has once again turned into science, and researchers at CERN today published a paper in Nature, stating that they had successfully trapped 38 anti-hydrogen atoms (a positron and an anti-proton) in a magnetic field at one time for 170 milliseconds.

This is an important experiment because scientists have always wished they could study anti-matter more closely, but it’s extremely difficult to get under the microscope (so to speak). Studying anti-matter will give us insight into the origins of the universe. It is believed that matter and anti-matter should have been created in equal proportions at the big bang, so one of the greatest mysteries in science is what happened to all the anti-matter?

 The scientists at CERN hope that they will be able to trap larger amounts of anti-matter in the future for longer periods of time in order to facilitate some real studies of the stuff.

So should we be worried about an anti-matter bomb? Well remember 0.5 grams of anti-matter roughly makes a Nagasaki. These guys trapped 38 atoms which is about 0.000000000000000000000000063 grams.

So no, you don’t have to worry :)