Tag Archives: proton

Decade-old debate put to rest with new measurement of proton diameter

We now have an accurate measurement of how large protons are.

Image via Pixabay.

Back in 2010, a team of physicists set their field (figuratively) on fire. They measured the radius of a proton and found it to be 4% smaller than expected. Physicists are very passionate about this kind of stuff and it sparked a huge debate. Now, researchers from York University have put the debate to rest by taking a precise measurement of the size of the proton.

How big is something very small?

“The level of precision required to determine the proton size made this the most difficult measurement our laboratory has ever attempted,” said Distinguished Research Professor Eric Hessels, Department of Physics & Astronomy, who led the study.

The exact size of the proton is an important unsolved problem in fundamental physics today, one which the present study addresses. The team reports that protons measure 0.833 femtometers in diameter (a femtometer is one-trillionth of a millimeter). This measurement is roughly 5% percent smaller than the previously-accepted radius value.

“After eight years of working on this experiment, we are pleased to record such a high-precision measurement that helps to solve the elusive proton-radius puzzle,” said Hessels.

The exact measurement of the proton’s radius would have significant consequences for the understanding of the laws of physics, such as the theory of quantum electrodynamics, which describes how light and matter interact. Hessels says that the study didn’t exist in a vacuum — three previous studies were pivotal in attempting to resolve the discrepancy between electron-based and muon-based determinations of the proton size.

The 2010 study was the first to use muonic hydrogen to determine the proton size (whereas previous experiments used regular hydrogen). Hydrogen atoms are made up of one proton and one electron In the 2010 experiment, the team replaced the electron with a muon, a related (but heavier) particle.

While a 2017 study using simple hydrogen agreed with the 2010 muon-based result, a 2018 experiment, also using hydrogen, supported the pre-2010 value. Hessels and his team spent the last eight years trying to get to the bottom of the issue and understand why researchers were getting different results when measuring with muons rather than electrons.

The team carried out a high-precision measurement using a technique they developed for this purpose, the frequency-offset separated oscillatory fields technique (FOSOF). In essence, they used a fast beam of hydrogen atoms created by shooting protons through hydrogen molecules. Their result agrees with the value found in the 2010 study.

The paper “A measurement of the atomic hydrogen Lamb shift and the proton charge radius” has been published in the journal Science.

Pressure distribution.

Pressure in protons’ cores is over ten times greater that that in neutron stars

An experiment once thought to be impossible reveals that the protons have incredibly pressurized cores.

Pressure distribution.

Pressure distribution in the proton. The left end of the scale is the proton’s core, the right end corresponds to the proton’s edge.
Image credits V. D. Burkert et al., (2018), Nature.

Protons are the positively-charged elemental blocks of matter — only, they, in turn, consist of three smaller particles called quarks. Each is made up of two ‘up’ quarks and one ‘down’ quark bound by the strong nuclear force. However, beyond that, we simply don’t know much about the internal going-ons of protons. Given how hard it is to split one, it’s obvious that the three quarks are held tightly together.

But they’re bound together so strongly that, in the absence of something to push back, they would just collapse into a single point. To get to the bottom of things, one team of researchers reconciled two theoretical frameworks (one of which was actually considered impossible to implement directly) and then shot an electron through the proton. But the results were worth all the hassle.

“We have the medical 3D imaging technology that now allows the doctors to learn more in a non-invasive manner the structure of the heart,” study co-author Latifa Elouadrhiri from the Thomas Jefferson National Accelerator Facility told Nature. “And this is what we want to do with the new generation of experiments.”

Back in 1966, American physicist Heinz Pagels showed that the energy and momentum of a proton’s internal components can be gleaned from so-called gravitational form factors. However, Pagels himself pointed out that, because the gravitational forces involved would be ludicrously tiny, his findings wouldn’t actually ever be used in practice.

Since then, however, researchers have developed mathematical models that allow them to produce a 3D model of a proton’s structure by probing its electromagnetic force. These models are known as generalized parton distributions — or GDPs. It was these GDPs that the team used in lieu of the gravitational probe to turn Pagels’ work into something with practical applications.

“This is the beauty of it. You have this map that you think you will never get,” says Elouadrhiri. “But here we are, filling it in with this electromagnetic probe.”

The team used the Compton scattering effect, which describes the interaction between photons and a charged particle (such as an electron) to finally peer into the proton. The team accelerated an electron to massive speeds, in a bid to narrow its wavelength — then shot it at a proton. Then they analyzed the pattern of scattering for the photons produced int he collision to determine how the quarks fared in the impact.

According to the team, the scattering patterns suggest that the center of the proton is pressurized, preventing the particle from collapsing in on itself. An equal pressure from the outside keeps the quarks together. What was surprising, however, was just how immense these pressures were: 100 decillions (35 zeroes) Pascal. To put that into perspective, it’s ten times the pressure inside a neutron star.

Next up, the team plans to continue using this process to further explore the proton’s internal structure and mechanics.

The paper “The pressure distribution inside the proton” has been published in the journal Nature.

The proton and antiproton are incredibly similar — indicating that perhaps, our universe shouldn’t exist

Matter and antimatter violently annihilate each other. If they’re absolutely symmetrical, then maybe — just maybe — the universe shouldn’t exist.

We see matter around us every day. Unlike matter, antimatter is much more elusive. Researchers are now playing the world’s most complex ‘spot the difference’ game with matter and antimatter. (Depicted here, two nitrogen gasses Image credits: Greenhorn1)

Just like there is matter in the universe (pretty much everything that exists), there is also antimatter. Basically, all particles have a corresponding anti-particle — with the same mass, but opposite electric charge, and other differences in quantum parameters. The proton, for instance, has a positive charge, while the antiproton has a negative charge. When a proton and an antiproton collide, they annihilate each other in a violent outburst.

Researchers at CERN in Switzerland have made the most precise measurement ever of the magnetic moment of an antiproton. The magnetic moment determines how a particle reacts to an external magnetic force. They found that the two moments are absolutely identical but with an opposite sign. This is really problematic.

“All of our observations find a complete symmetry between matter and antimatter, which is why the universe should not actually exist,” says Christian Smorra, a physicist at CERN’s Baryon–Antibaryon Symmetry Experiment (BASE) collaboration. “An asymmetry must exist here somewhere but we simply do not understand where the difference is.”

“It is probably the first time that physicists get a more precise measurement for antimatter than for matter, which demonstrates the extraordinary progress accomplished at CERN’s Antiproton Decelerator,” added Smorra, who is first-author of the study.

Since matter and antimatter annihilate themselves and the universe exists and hasn’t annihilated itself (yet), there’s good reason to believe that there is much more matter than antimatter in the universe. But why? There must be some discrepancy in the parameters of these particles that allows matter to dominate, but researchers haven’t found it yet. It’s like playing spot the difference at a particle level.

The work of Smorra and his colleagues is an elegant design, a two-particle measurement method developed in Stefan Ulmer’s RIKEN laboratory. Researchers simultaneously capture and measure two separate antiprotons one at a high temperature (350 degrees Kelvin / 76 C / 170 F) and the other at a very cold temperature (0.15 K / -273 C / -459 F), very close to absolute zero. The first particle is used for calibration, while the colder one is used to measure a parameter called the Larmor frequency, which governs how a particle precesses (rotates and spins) under a magnetic influence. Even doing this for protons was a breakthrough (published in Nature in 2014), but doing it for antiprotons is a whole new ball game.

The BASE experiment at the CERN antiproton decelerator in Geneva. Image credits: Stefan Sellner, Fundamental Symmetries Laboratory, RIKEN, Japan.

With this method, they managed to keep an antiproton captured for inside a special chamber about as big as a tall pint. Measurements were incredibly accurate, indicating a value for the antiproton magnetic moment of −2.7928473441 μNN is a constant called the nuclear magneton). Precise to nine significant digits, this measurement is 350 times more accurate than the previous measurement. It’s the equivalent of measuring the Earth’s circumference to a few centimeters.

Their results are identical to those obtained for the proton, aside from the minus sign.

“It is probably the first time that physicists get a more precise measurement for antimatter than for matter, which demonstrates the extraordinary progress accomplished at CERN’s Antiproton Decelerator, ” added first-author of the study Christian Smorra.

However, for all these elegant improvements, they still couldn’t answer the fundamental question of why our universe exists — why matter and antimatter are so unevenly distributed through the universe, allowing us to exist. Still, Smorra says that they can still improve significantly.

“By upgrading the experiment with several new technical innovations, we feel that some further improvement can still be made, and in the future, following the CERN upgrade expected to finish in 2021, we will be able to achieve an at least ten-fold improvement.”

In the meantime, nature continues to consist of matter and we still don’t know why there’s not much antimatter around. Researchers continue to try and solve this mystery which could unlock one of the keys to understanding the universe.

New measurement of a proton leaves us with more questions than answers

Six years ago, physicists announced the results of a new measurement of the proton — and the particle turned out to be too short. Since then, a lot of effort has been put into checking their results — and again, the latest measurements have revealed smaller than expected results. Physicists are now left scratching their collective heads trying to pin down the elusive measurements of this particle.

Image via Pixabay

Protons are positively charged particles that, together with neutrons, form the nuclei of atoms. They’re really, really tiny — for years, the proton’s radius was set at about 0.877 femtometers. One femtometer being equal to 10−15 meters, slightly over a quadrillionth of a meter in diameter. This number, however, was changed in 2010, when Randolf Pohl from the Max Planck Institute of Quantum Optics in Germany used a novel measuring technique and got a better measurement for a proton’s size.

His team started from a simple hydrogen atom — which has one proton and one electron — and substituted its electron for a heavier particle called a muon. They then fired a laser at the altered atom, measuring the resulting change in its energy levels to calculate the size of the nucleus — which in the case of hydrogen is a single proton. They reported that their measurement of the particle came out 4% smaller than what other methods showed.

Measurements performed in 2013 confirmed the findings, setting the world of particle physics ablaze trying to find the answer to the “proton radius puzzle.”

Pohl also applied this technique to deuterium, a hydrogen isotope with one proton and one neutron — also known as a deutron in this case — in the nucleus. Accurately calculating the size of the deutron took plenty of time. Today, the team published the long-awaited result and, you’ll never guess it, it came up short again, this time by 0.8%.

Evangeline J. Downie at the George Washington University in Washington DC says that these numbers show the proton radius puzzle is here to stay.

“It tells us that there’s still a puzzle,” says Downie. “It’s still very open, and the only thing that’s going to allow us to solve it is new data.”

Several other similar experiments, both at Pohl’s and other labs around the world, are already underway. One such experiment will re-use the muon technique to measure the nucleus size of heavier atoms, such as helium.

Pohl believes the issue may not be with the proton itself, but rather with an incorrect measurement of the Rydberg constant which describes the wavelengths of light emitted by an excited atom. This constant’s value has been established very precisely in other experiments however, so something has to have gone really wrong for it to be inaccurate.

One other explanation proposes new particles that cause unexpected interactions between the proton and the muon, without changing its relationship with the electron. That could mean that the key to the puzzle lies beyond the standard model of particle physics.

“If at some point in the future, somebody will discover something beyond the standard model, it would be like this,” says Pohl.

A new measurement by RHIC's STAR collaboration reveals that the force between antiprotons (p with bar above it) is attractive and strong--just like the force that holds ordinary protons together within the nuclei of atoms. Credit: Brookhaven National Laboratory

Matter and antimatter have the same properties, experiment suggests

All models of particle physics are based on the mundane assumption that matter and anti-matter behave indistinguishably, but we can’t be sure. Luckily, an experiment at Brookhaven National Lab seems to confirm this basic caveat of particle physics after it found the attractive forces between antiprotons are the same as those seen in regular matter.

The quest for antimatter

A new measurement by RHIC's STAR collaboration reveals that the force between antiprotons (p with bar above it) is attractive and strong--just like the force that holds ordinary protons together within the nuclei of atoms. Credit: Brookhaven National Laboratory

A new measurement by RHIC’s STAR collaboration reveals that the force between antiprotons (p with bar above it) is attractive and strong–just like the force that holds ordinary protons together within the nuclei of atoms. Credit: Brookhaven National Laboratory

For every type of matter particle we’ve found, there also exists a corresponding antimatter particle, or antiparticle. These should look and behave just like their corresponding matter particles, except with opposite charge. A proton is naturally positively charged, as thought in any basic chemistry or physics class. The antiproton, however, is negatively charged. When matter and anti-matter these annihilate each other, releasing energy in the process.

During the Big Bang, matter and antimatter were created in equal amounts, but that’s clearly not what we’re seeing today. In fact, it’s difficult if not impossible to detect antimatter outside of a laboratory setting. For that matter, we wouldn’t have existed in the first place if antimatter and matter were still in equal proportion, given their tendency to annihilate each other. There has to be an explanation, but at this point opinions are mixed.

Some physicists think that after the Big Bang, fractions of a second in, all matter and antimatter canceled each other out but in the process created radiation. Out of this radiation new matter-antimatter pairs were formed, which again annihilated each other creating new radiation and so on. When the universe expanded and cooled to below the temperature where particle-antiparticle pair production could happen, all the antimatter and matter that were in equal proportions annihilated with each other, leaving only radiation. Here’s the kick though. It may be that matter and antimatter weren’t created equal. There is a tiny, *tiny* chance that you only get matter when you try to create matter and antimatter or one particle of matter for every billion annihilation event.  As the universe evolved after the Big Bang, these very small symmetry violations may have resulted in the abundance of matter and the dearth of antimatter we see today.

Zhengqiao Zhang, a graduate student from the Shanghai Institute of Applied Physics, with STAR physicist Aihong Tang at the STAR detector of the Relativistic Heavy Ion Collider (RHIC). Credit: Brookhaven National Laboratory antimatter.

Zhengqiao Zhang, a graduate student from the Shanghai Institute of Applied Physics, with STAR physicist Aihong Tang at the STAR detector of the Relativistic Heavy Ion Collider (RHIC). Credit: Brookhaven National Laboratory antimatter.

We can’t don’t this for certain yet. “Although this puzzle has been known for decades and little clues have emerged, it remains one of the big challenges of science. Anything we learn about the nature of antimatter can potentially contribute to solving this puzzle,” says  Aihong Tang, a Brookhaven physicist.

Tang was involved with  Relativistic Heavy Ion Collider where he and colleagues smashed accelerated gold ions together at high energy and relativistic speeds. When the gold ions smashed instead of forming new gold particles, the collision created mostly forms of hydrogen and helium, but also exotic particles like  heavy quarks or their antimatter counterparts.

“We see lots of protons, the basic building blocks of conventional atoms, coming out, and we see almost equal numbers of antiprotons,” said Zhengqiao Zhang, a graduate student in Professor Yu-Gang Ma’s group from the Shanghai Institute of Applied Physics of the Chinese Academy of Sciences, who works under the guidance of Tang when at Brookhaven. “The antiprotons look just like familiar protons, but because they are antimatter, they have a negative charge instead of positive, so they curve the opposite way in the magnetic field of the detector.”

“By looking at those that strike near one another on the detector, we can measure correlations in certain properties that give us insight into the force between pairs of antiprotons, including its strength and the range over which it acts,” he added.

Ultimately, the researchers were able to investigate the effective and scattering range of two antiprotons. The effective range between two particles is a measure of how close they have to be to influence each other with their electric charge, while the scattering range is a measure of how much these particles deviate as they travel from source to destination. During this experiment the  the scattering length was around 7.41 femtometers and the effective range was 2.14 femtometer, which is roughly the same as the those of a proton pair. Whether matter or antimatter, it seems these types of interactions are virtually indistinguishable.

“This discovery isn’t a surprise,” said Kefeng Xin, a graduate student at Rice. “We’ve been studying the interaction between nucleons (particles that make up an atom’s nucleus) for decades, and we’ve always thought the forces between antimatter particles are the same as for matter. But this is the first time we’ve been able to quantify it.”

“There are many ways to test for matter/antimatter asymmetry, and there are more precise tests, but in addition to precision, it’s important to test it in qualitatively different ways. This experiment was a qualitatively new test,” said Richard Lednický, a STAR scientist from the Joint Institute for Nuclear Research, Dubna, and the Institute of Physics, Czech Academy of Sciences, Prague.

“The successful implementation of the technique used in this analysis opens an exciting possibility for exploring details of the strong interaction between other abundantly produced particle species,” he said, noting that RHIC and the Large Hadron Collider (LHC) are ideally suited for these measurements, which are difficult to assess by other means.

We’ve yet to solve the puzzle. Namely, we still don’t know why there’s so little antimatter left in the universe, but at least we now know that it’s not due to some difference in how the two types of matter interact.

Perfection is overrated: Flawed graphene sheets may lead to better fuel cells

A rather surprising study found that graphene’s imperfections can actually be used to improve fuel cell efficiency. Researchers from Northwestern University worked together with scientists of five other institutes to show that defective graphene actually works as the world’s thinnest proton channel—only one atom thick.

Flawed graphene might actually lead to better fuel cells, and even hydrogen cars. Image via Phys.org


The applications of graphene seem virtually limitless – it seems like we’ve written countless articles detailing that. However, despite advancements, there still isn’t a cheap and effective method of actually producing it – or at least producing it flawlessly, that is. But perfection is really overrated, as this study has shown, and manufacturing flawed graphene is also rewarding.

Graphene is basically a continuous one atom thick sheet of carbon with some remarkable properties; but flawed graphene may be just as interesting – researchers found using a single imperfect layer and water, they can let protons, and only protons, to move from one side to the other. This system can lead not only to better fuel cells, but also brings hydrogen cars one step closer to becoming a reality.

“Imagine an electric car that charges in the same time it takes to fill a car with gas and better yet — imagine an electric car that uses hydrogen as fuel, not fossil fuels or ethanol, and not electricity from the power grid, to charge a battery. Our surprising discovery provides an electrochemical mechanism that could make these things possible one day,” said chemist Franz M. Geiger, who led the research in a statement.”

According to the team, single layer one-atom thick graphene could produce the world’s thinnest and most efficient photon channel.

“We found if you just dial the graphene back a little on perfection, you will get the membrane you want. Everyone always strives to make really pristine graphene, but our data show if you want to get protons through, you need less perfect graphene,” said Geiger, a professor of chemistry in the Weinberg College of Arts and Sciences.

Initially, they tried to achieve similar results with graphene, but they failed – because graphene was simply too perfect, and didn’t act as an efficient channel.

What happens is that defects from one side of graphene generate a chemical merry-go-round where protons are transferred to the other side. Still, researchers stress that this is just a proof of concept, and not something that will lead to improved fuel cells overnight.

“Our results will not make a fuel cell tomorrow, but it provides a mechanism for engineers to design a proton separation membrane that is far less complicated than what people had thought before,” Geiger said. “All you need is slightly imperfect single-layer graphene.”

Journal Reference: Jennifer L. Achtyl, Raymond R. Unocic, Lijun Xu, Yu Cai, Muralikrishna Raju, Weiwei Zhang, Robert L. Sacci, Ivan V. Vlassiouk, Pasquale F. Fulvio, Panchapakesan Ganesh, David J. Wesolowski, Sheng Dai, Adri C. T. van Duin, Matthew Neurock & Franz M. Geiger. Aqueous proton transfer across single-layer graphene. doi:10.1038/ncomms7539


Record breaking energies achieved in a compact particle accelerator 3 million times smaller than the LHC

With the help of the most powerful laser in the world, scientists have achieved the highest energies yet in a compact particle accelerator. The tabletop-sized device accelerates electrons to high speeds by firing high power laser pulses in a controlled manner through a plasma tube only 9 centimeters in size. The accelerator ring at the Large Hadron Collider in CERN is 17 miles long . Admittedly, we’re comparing apples and oranges in a way, since the LHC accelerators hadrons (protons), while the Lawrence Berkeley National Laboratory accelerator only works for electrons. Nevertheless, it’s a breakthrough achievement one that might help miniaturize bulky medical devices and slash costs.

The most efficient particle accelerator in the world


A 9 cm-long capillary discharge waveguide used in BELLA experiments to generate multi-GeV electron beams. The plasma plume has been made more prominent with the use of HDR photography. Credit: Roy Kaltschmidt

In the laser-plasma accelerator setup, the BELLA (Berkeley Lab Laser Accelerator) was used to fire petawatt pulses (a million billion watts) onto a charged-particle gas called plasma to get the particles up to speed. When the laser pulse ripples through the plasma, it creates a channel in its path followed by waves that trap the free electrons and accelerate them to high energies, akin to how a surfer skims down the face of a wave to gain momentum. Thus, through the nine-centimeter-long plasma tube electrons were accelerated to a speed equivalent to 4.25 giga-electron volts. Considering the short distance, this means an energy gradient 1000 times greater than traditional particle accelerators and marks a world record energy for laser-plasma accelerators.

“This result requires exquisite control over the laser and the plasma,” says Dr. Wim Leemans, director of the Accelerator Technology and Applied Physics Division at Berkeley Lab and lead author on the paper. The results appear in the most recent issue of Physical Review Letters.

Particle accelerators transfer energy so that protons, electrons or positrons (anti-electron) can reach high energies. When these particles are collided at these tremendous speeds, funny things start to happen. If billions of collisions are made, chances have it that all sorts of elementary particles, some lasting only a fraction of a second, can be seen. This is how the famed Higgs boson was confirmed at CERN only a few years ago. In a way, a high-energy particle accelerator like the LHC at CERN is a time machine, because it replicates conditions similar to those in place mere moments following the Big Bang.

Because of the tremendous energies involved, Leemans and colleagues first made a computer simulation using gear available at the National Energy Research Scientific Computing Center (NERSC) to test the setup before any shots were fired. This way, the researchers selected the optimal region of operation and the best way to control the accelerator. BELLA’s pin-point accuracy sure helped, too.

Computer simulation of the plasma wakefield as it evolves over the length of the 9-cm long channel. Credit: Berkeley Lab

Computer simulation of the plasma wakefield as it evolves over the length of the 9-cm long channel. Credit: Berkeley Lab

“We’re forcing this laser beam into a 500 micron hole about 14 meters away, “ Leemans says. “The BELLA laser beam has sufficiently high pointing stability to allow us to use it.” Moreover, Leemans says, the laser pulse, which fires once a second, is stable to within a fraction of a percent. “With a lot of lasers, this never could have happened,” he adds.

The plan is to accelerate electrons to even greater energies, with a near-future goal set to 10 giga-electron volts. Tweaking the plasma channel’s density through which the laser light flows is the first obvious step – they need to make the channel’s shape just in the right way to handle more-energetic electrons.

New exotic particle behaviour found at CERN

The Large Hadron Collider at CERN has started doing some serious business. This time, an extremely rare particle containing equal parts of matter and antimatter popped up during experiments at the world’s largest and hottest particle accelerator.

CREDIT: CERN/Maximilien Brice, Rachel Barbier


The particle, named a B meson is made out of one quark (the building blocks of protons and neutrons) and one antiquark (the building blocks of antiprotons and antineutrons). What are antiprotons and antineutrons ? Well, they are just like their positive brothers… only they are negative. They have the exact same properties, only opposite in signs. For example, an antiproton has the exact same charge a proton has, but it is negative instead of positive.

All normal particles are thought to have antimatter analogues, and when matter and antimatter meets, they destroy each other. Scientists believe that at first, matter and antimatter were created equally, but if this is the case, then where is all the antimatter ? The most plausible solution would be that a huge quantity of matter and antimatter annihilated each other, and the remaining matter is what we see in our universe today.

The particle in case, the B meson, is thought to have been common right after the Big Bang, but it is believed that at the moment, it doesn’t occure naturally in nature. They aren’t stable, and after created, quickly start decaying; this process, a B meson decay has long been theoretized, but never seen before.

“Our experiment is set up to measure the decays of B mesons,” sayd Sheldon Stone, physicist at Syracuse University. “We discovered some new and interesting decay modes of B mesons, which hadn’t ever been seen before.”

Studying this type of behaviour can provide the answer to the ultimate question of antimatter – why do we see all this matter around us today, and no antimatter. Meanwhile, the search for the elusive Higgs boson is continued.

“When the universe was created in the Big Bang about 14 billion years ago, the number of particles and antiparticles was the same,” Stone said. “One of the major questions that we really don’t know the answer to is why are there particles around now and not antiparticles. By studying the differences we can learn maybe what the physics is behind that difference.”

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

LHC produces first results

Since the Large Hadron Collider went back in business, all sort of rumors have been circling the scientific circles (and not only). However, until these rumors are proven wrong or right, the first official paper on proton collisions from the Large Hadron Collider has been published in this week’s edition of Springer’s European Physical Journal C. .


Designed to reach the highest energy ever explored in particle accelerators, it features a circular tunnel with the circumference of 27 km. Since it’s been recommissioned, a total of 284 collisions have been recorded, all of which have been analyzed and interpreted. The researchers have been able to determine what is called ‘pseudorapidity density’ (the average number of charged particles that are emitted perpendicular to the beam direction. The goal of this was to compare the results with those obtained in the case of proton-antiproton collisions that took place in the same conditions.

The paper was published by ALICE (a Large Ion Collider Experiment that brings together authors from 113 institutions). As well as the actual results, the paper also explains how their detecting and analyzing system works. The results are not only consistent with earlier measurements, but they also fit the theoretical model produced by researchers.

Dr. Jürgen Schukraft from CERN and ALICE spokesperson said: “This important benchmark test illustrates the excellent functioning and rapid progress of the LHC accelerator, and of both the hardware and software of the ALICE experiment, in this early start-up phase. LHC and its experiments have finally entered the phase of physics exploitation.”