Tag Archives: antihydrogen

Physicists observe the light spectrum of antimatter for the first time

After two decades of experiments, scientists working at CERN‘s ALPHA experiment have finally visualized the light spectrum emitted by antimatter, fulfilling a long-standing goal of particle research.

Measuring the antihydrogen spectrum with high-precision offers an extraordinary new tool to test whether matter behaves differently from antimatter and thus to further test the robustness of the Standard Model (Image: Maximilien Brice/CERN)

“This represents a historic point in the decades-long efforts to create antimatter and compare its properties to those of matter,” theoretical physicist Alan Kostelecky from Indiana University, who was not involved in the study, told NPR.

“Using a laser to observe a transition in antihydrogen and comparing it to hydrogen to see if they obey the same laws of physics has always been a key goal of antimatter research,” said Jeffrey Hangst, Spokesperson of the ALPHA collaboration.

Antimatter is a strange thing. It is a material composed of anti-particles with the same mass as ordinary particles but opposite charges, lepton numbers, and baryon numbers (leptons and baryons are subatomic particles). As the name puts it, they are similar but exactly opposite to regular matter. A mirror reflection, so to speak. We know antimatter exists, we’ve seen it in the lab, but why the universe is filled with matter and virtually completely devoid of antimatter is anyone’s guess. The fact that antimatter is so hard and expensive to produce in a lab makes it even harder to study this mystery – and yet, modern particle theory predicts that every single particle in the universe has its own opposite antiparticle. This is one of the biggest unsolved problems in physics.

Antimatter spectrum

Atoms consist of electrons orbiting around a nucleus. When the electrons move, they emit and absorb light at different frequencies, representing the atom’s spectrum. Every element has its own unique spectrum, through which it could be identified, and the study of these spectra (called spectroscopy) has numerous applications in chemistry, physics, and astronomy. But what about antimatter?

The Antihydrogen Laser Physics Apparatus, or ALPHA experiment at CERN captured 14 or so antihydrogen atoms per trial and blasted them with a laser to see what kind of light they absorb. ALPHA is a unique experiment at CERN, able to produce antihydrogen atoms and hold them in a specially-designed magnetic trap, manipulating antiatoms a few at a time. Trapping antihydrogen atoms allows them to be studied using lasers or other radiation sources.

“Moving and trapping antiprotons or positrons is easy because they are charged particles,” said Hangst. “But when you combine the two you get neutral antihydrogen, which is far more difficult to trap, so we have designed a very special magnetic trap that relies on the fact that antihydrogen is a little bit magnetic.”

As expected (and hoped), the spectrum of anti-hydrogen was identical to that of hydrogen.

“It’s long been thought that antimatter is an exact reflection of matter, and we are gathering evidence to show that is indeed true,” Tim Tharp from ALPHA told Ryan F. Mandelbaum at Gizmodo.

I say “hoped” because if the spectra didn’t turn out to be identical, then it would mean that much of what we hold as true today – including the Big Bang theory and Einstein’s special relativity – wouldn’t hold up. Special relativity assumes that a single unified thing called spacetime splits differently into space and time for observers moving relative to each other. The spectra were identical, which means that the theory of relativity passed yet another difficult test. But researchers are already planning to create more antimatter and blast it with a different type of laser, to observe even more spectra.

Particle physics is a bizarre and complicated world and we are only now getting the chance to test theories proposed many decades ago.The fact that these theories are holding op, that researchers got so many things right only through theory is a testament to the brilliant mind which contributed to this field of science.

 

Antihydrogen and antimatter

Coldest antimatter yet might help scientists probe its secrets

A novel technique for cooling antimatter down to the point where it might become almost stationary might provide scientists with a better basis for studying one of the greatest modern mysteries today.

Antimatter, as it name implies, is the total opposite of matter and when the two meet they cancel each other out. For instance the opposite of an electron is a positron. It’s because of this fascinating behavior, however, that studying antimatter is extremely difficult, since we’re ubiquitously surrounded by matter. A great puzzling dilemma for physicists today is why is there so little antimatter present in the Universe compared to matter.

Antihydrogen and antimatter

It’s theorized that after the first Big Bang sparks, equal amounts of both matter and antimatter were spewed through out the early Universe, but for some yet unknown reason matter won out. Currently, the only instances antimatter has been observed naturally are those following radioactive decay or cosmic ray collisions, and though the existence of antimatter has been proven since the 1930s only recently could it be artificially produced, and in small quantities to top it over.

With this in mind, scientists have been looking to devise ways to ease antimatter research. A recent technique that has garnered quite a bit of attention was developed by Makoto Fujiwara, a research scientist at Canada’s particle physics lab TRIUMF and an adjunct professor at the University of Calgary, along with colleagues, and is called Doppler cooling. It implies chilling anti-hydrogen (with one positron and one anti-proton) to just a tad over absolute zero Kelvin – 25 times colder than ever attempted.

The technique has yet to be proven, though an advanced prototype experimental setup is in the works, however a computer simulation showed extremely promising results.

“The ultimate goal of antihydrogen experiments is to compare its properties to those of hydrogen,” physicist Francis Robicheaux of Auburn University in Alabama said in a statement. “Colder antihydrogen will be an important step for achieving this.”

“By reducing the antihydrogen energy, it should be possible to perform more precise measurements of all of its parameters,” Robicheaux said. “Our proposed method could reduce the average energy of trapped antihydrogen by a factor of more than 10.”

Fujiwara led in 2011 a team of scientists at CERN that made the first direct measurement of antimatter’s energy and also held particles of anti-hydrogen stable for as long as 15 minutes, still a record. Comparing the properties of hydrogen and anti-hydrogen might allow scientists to explain why there is such a great quantitative gap between the two. If the two are indeed proven to exhibit totally opposite properties then a sounds basis for further study might be built.

The present technique uses precisely targeted lasers on antihydrogen in order to loose energy and chill it down. Remember, however, that antimatter and matter annihilate each other, so the key to their research is trapping antihydrogen – the scientists hope to achieve this through a system of magnetic fields.

“We want anti-hydrogen atoms as cold as possible in our trap, and by cold I mean not moving. In particular, to measure the gravitational properties, antihydrogen in our trap is still moving way too fast. So this paper has shown that the technique called laser cooling can be applied in our experimental set-up,” Mr. Fujiwara said.

The first immediate goals for Fujiwara and colleagues is to study basic properties of antihydrogen like colour, weight, how it reacts to light or gravity and so on. The laser cooling technique was described in a paper published in the Journal of Physics B.

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People find out that CERN trapped antimatter for over 15 minutes

It always baffles me to see how science news propagate; it seems whenever a study or a report is published, there are two waves of acknowledgement: the first one, science sites and magazines write about it, and the second one, the supermassive one, where the media picks it up. This is exactly the case here.

News and antinews

[Warning: there may be a little ranting in this part, so if you’re not interested in it, just jump to the next subtitle]

CERN announced that they held antimatter for approximately 1000 seconds over a month a go – I wrote about the antimatter trap here. Of course, I wasn’t the only one to do it – respectable sites, especially those who take the news directly from the source were all over it. But it wasn’t until yesterday that the study was picked up by major news agencies, which lead to the whole internet writing about how antihydrogen was trapped and all that. It saddens me to see even some of the big sites and magazines (be they science or popular science) have fallen into the trap of the easier path and pick up news from agencies instead of the real source, in this case, CERN.

The reason why it got picked up yesterday is that it was only then that the full study was officially published in Nature Physics (the study is free by the way, so you should really look at it if you are interested). So it would make perfect sense to go into additional details, at a higher scientific and even technical level, given the fact that you have a full study and not a report published by CERN. But this is not what happened – as you have probably noticed, if you are interested in science, the internet is full of general articles about antimatter, how it was trapped for the first time for such a long period, giving the impression that this happened just now.

Matter and antimatter

Antimatter raises probably the biggest unanswered questions in the world of physics; it is believed that in the first moments of the universe, both matter and antimatter existed in a brotherly fashion. Well, brotherly isn’t the word here, since they annihilate each other whenever they meet, but they existed in equal or at least comparable amounts. But look around you; there’s all this matter you see, and absolutely no antimatter, so where did it go ? This is the major question scientists are trying to answer, and of course, if you want to study something, you first have to ‘see’ it – in one way or another.

But capturing antimatter is extremely hard; up until this development, the record for capturing antimatter was only a few fractions of a second, so it’s easy to understand why 1000 seconds of antimatter is not something big – but something huge. Actually, on April 26, CERN announced that when fully operational, their facilities are capable of producing 10^7 antiprotons per minute. Thay may seem like an enormous amount, but it’s not; operating at this speed, it would take them 100 billion years to produce one gram of antiprotons. The costs are also huge: according to CERN, it cost over a few hundred million Swiss francs to produce about 1 billionth of a gram; in case you’re wondering a Swiss franc is more than one dollar.

Still, having antimatter at your disposal, even at these amazing efforts is worth it; in several minutes, you can study its properties, especially something called the charge-parity-time reversal (CPT) symmetry. In layman terms, what CPT says is that if you have a particle moving in one direction, and an antiparticle moving in the opposite direction in a mirror universe, they would be indistinguishable. So basically matter and antimatter have the same spectral profile. This is the reason why researchers have speculated that since our universe prefers matter over antimatter, it also prefers time moving forward and not backward.

Another thing which researchers are especially interested in are the gravitational effects; what gravitational effects does antimatter have ? Is it just like matter, totally different, or, as some speculate, does it produce antigravity ? Physicists hope to be able to trap antimatter again and apply extremely low temperatures to it, to better understand its gravitational properties.

Antimatter trapped for 15 minutes at CERN

The team operating the Antihydrogen Laser Physics Apparatus (ALPHA) at the CERN laboratory in Geneva, Switzerland reported storing antimatter for approximately 1000 seconds, which might not seem like much of a big deal, but it is about 10.000 times longer than the previous record !

A cloud of antihydrogen

This study will hopefully reveal more about the elusive antimatter, and whether this is in fact the true mirror image of matter. With this thought in mind, the ALPHA team set out to find a way to capture antimatter for as long as possible; they devised an antimagnetic trap to help them capture a cloud of antihydrogen. The thing about antimatter is that it creates a bang whenever it comes in contact with matter, thus making it almost impossible to store for a long time.

In previous experiments, researchers would open the trap and observe the collisions between antimatter and the trace gases; the collisions either annihilated the antimatter or gave it enough energy to escape the trap. But this time, the people at CERN did things a little differently.

They waited much longer before opening the trap, and they cooled the antiprotons, which lowered the energy of antimatter, allowed more to be captured, thus raising the chance that some of it will be captured for a longer period of time.

Capturing antimatter for a longer time will allow further experiments to be conducted on it, such as checking if the energy levels of the antihydrogen and hydrogen are the same.

Elusive Antimatter

When introduced, antimatter was a revolutionary concept, and rejected by many physicists at the moment. In recent years, it has been shown that with the right process, it can be captured for a limited amount of time, which was generally restricted to a fraction of a second. CERN particle physicists shattered that ‘record’, capturing it for a much longer period, almost enough to perform some experiments on it.

In particle physics, antimatter is an extension of antiparticles to matter. If you have, say a hydrogen atom, which is made out of 1 proton (positively charged) and 1 electron (negatively charged), an antihydrogen atom will be made out of 1 antiproton and one positron.

It is theoretized that when the Universe was formed, matter and antimatter were created in equal amounts, but the question remains: where is all the antimatter ? We are all made out of matter (you, me, trees, planets, etc), but it is almost impossible to even get a glimpse of antimatter. This is why researchers hope to capture it for longer periods of time, thus allowing the possibility of experiments which would shed some light on some of the most important questions in physics at the moment.

Antimatter captured at CERN

For physicists, antimatter is probably the most valuable substance ever; the slightest bit of it could provide extremely valuable information that can help clear out some of the most stressing issues in modern physics. However, the thing is these little gifts are pretty hard to wrap. However, the ALPHA project at CERN achieved this remarkable feat and took a huge leap towards understanding one of the questions about the Universe: what’s the actual difference between matter and antimatter.

The team had 38 successful attempts to capture single antihydrogen atoms in a magnetic field for about 170 miliseconds.

“We’re ecstatic. This is five years of hard work,” says Jeffrey Hangst, spokesman for the ALPHA collaboration at CERN.

And they should be ! Since it restarted working, the Large Hadron Collider at CERN had quite a few good moments, but this is the best one so far. Antimatter (or the lakc of it) still poses one of the biggest mysteries ever; according to the theories up to date, at the Big Bang, matter and antimatter were produced in equal amounts, but somehow all the antimatter dissappeared, so now researchers are forced to turn to more and more advanced and delicate methods in order to find it and study it.

Artist depiction of hydrogen and anithydrogen

As you can guess by its name, antimatter is just like matter, only in reverse. So the antiprotons are just like normal protons, but they are negatively charged, while electrons have a positive charge. The main objective of this stage of the ALPHA project was to compare the relative energy of hydrogen and antihydrogen in order to confirm that antimatter and matter have the same electromagnetic properties, which is a key feature of the standard model.

This is not the first time antimatter was captured, the first time it was in 2002, with the ATHENA project; however, it lasted just several miliseconds, which made it impossible to analyze. What happens is that when you combine matter with antimatter, they vanish with a big boom, releasing high energy photons (gamma rays). In the ATHENA project, antihydrogen combined with hydrogen from the walls of the contained and annihilated each other.

To prevent this from happening, the ALPHA team used a totally different technique, which was way more difficult: capturing the antimatter in a magnetic trap. To capture the 38 atoms, they had to repeat the experiment no less than 335 times.

“This was ten thousand times more difficult” than creating untrapped antihydrogen atoms, says Hangst — ATHENA made an estimated 50,000 of them in one go in 2002. To do spectroscopic measurements, Surko estimates that up to 100 antihydrogen atoms may need to be trapped at once.

“The goal is to study antihydrogen and you can’t do it without trapping it,” says Cliff Surko, an antimatter researcher at the University of California, San Diego. “This is really a big deal.”

Of course, achieving these atoms was very costly, but the effort was definitely worth it. However, physicists are looking into other methods that could prove to be more effective in times to come.

“Rather than trying to demonstrate that we can confine 38 antihydrogen atoms for a small fraction of a second, we are working on new methods to produce and trap much larger numbers of colder atoms,” says Gerald Gabrielse, ATRAP’s spokesman. “We shall see which approach is more fruitful.”

via CERN