Tag Archives: antimatter

Credit: The Reality Files.

Scientists make most precise measurements of antimatter — but only deepen mystery

Credit: The Reality Files.

Credit: The Reality Files.

Antimatter is, you’ve guessed it, the opposite of matter. When the two meet, they annihilate each other. According to the Big Bang theory, at the ‘T zero’, equal amounts of matter and antimatter were created in the early universe. But today, everything we see from the smallest life forms on Earth to the largest stellar objects is made almost entirely of matter. Why hasn’t all that early matter and antimatter annihilated each other, leaving behind a void as large as the universe itself?

While attempting to answer this very important scientific question, researchers found themselves opening a bigger, more philosophical one. Researchers part of the ALPHA collaboration at the European Organization for Nuclear Research (CERN) performed the most precise measurement of antihydrogen yet, looking for even the slightest differences from hydrogen that might explain the matter-antimatter disparity.

The researchers had to mix 90,000 antiprotons with 3 million positrons (electron anti-matter) to produce 50,000 antihydrogen atoms. The resulting antihydrogen atoms are held in a magnetic trap to prevent them from coming into contact with matter and self-annihilating.

The team led by Jeffrey Hangst, a physicist at Aarhus University in Denmark, studied the anti-matter by analyzing its reaction when it was probed with laser light. Atoms from different types of matter absorb different frequencies of light, and according to one prevailing theory, hydrogen and anti-hydrogen should absorb the same frequencies of light.

According to the latest measurements, the two types of matter indeed seem to absorb the same frequencies. The two types of measurements agreed with a precision of 2 parts per trillion, which marks a 100-fold improvement over the previous research.

Unfortunately, despite the impressive science involved, the new study doesn’t tell us anything more than we already knew. However, Ulmer says that perhaps a deviation at an even greater level of precision could have tipped the scale, which is why he and his team is shooting for even better precision for the next experiment.

“Although the precision still falls short for that of ordinary hydrogen, the rapid progress made by ALPHA suggests hydrogen-like precision in antihydrogen (measurements)… are now within reach,” said Hangst in a statement.

Scientific reference: M. Ahmadi et al. Characterization of the 1S–2S transition in antihydrogen, Nature (2018). DOI: 10.1038/s41586-018-0017-2. 

Credit: CERN.

There’s an abundance of antimatter in our atmosphere, and dark matter decay might be to blame

Credit: CERN.

Crab nebula. Credit: NASA.

In 2008, physicists found that the number of high-energy positrons — the antiparticle or the antimatter counterpart of the electron — hitting Earth was three times greater than the Standard Model predicted. Some scientists have suggested that nearby pulsars, which expel copious amounts of positrons as they spin erratically, could account for the extra positions. One new study, however, proposes that this antimatter may be the result of decaying particles of dark matter. 

Stranger than fiction

Dark matter is an elusive and hypothetical substance that is supposed to comprise roughly 5/6 of all matter in the universe. Scientists have never been able to directly observe dark matter, which seems to be invisible to current means of observation, but they do have good reasons to believe dark matter exists judging from the gravitational effects it exerts on ordinary matter.

Though not as weird as dark matter, antimatter is also another exotic physical quirk. You’ve likely heard a lot about antimatter in the science fiction universe. Star Trek’s starship Enterprise uses matter-antimatter annihilation propulsion for faster-than-light travel and in the famous book Angels and Demons, (spoiler alert) Professor Langdon tries to save Vatican City from an antimatter bomb. Unlike dark matter, though, we know for sure that antimatter is real.

Every particle of ordinary matter has an antimatter counterpart which is equal in mass but opposite in charge. When the two kinds of particles meet, they annihilate each other while releasing energetic photons called gamma rays.

There are many unsolved riddles surrounding antimatter. For instance, antimatter should have annihilated all ordinary matter during the Big Bang. Scientists think the reason why galaxies, stars, and eventually we exist in the first place is that there was one extra matter particle for every billion matter-antimatter pairs.

Antimatter is closer to us than most people think. Small amounts of antimatter — at a rate ranging from less than one per square meter to more than 100 per square meter — constantly rain down on the Earth in the form of cosmic rays, energetic particles from space. Antimatter can be found closer yet.  The average banana (rich in potassium) produces a positron roughly once every 75 minutes. That’s because potassium-40 will occasionally split out a positron in the process of radioactive decay.

When researchers working with the space-based instrument PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) detected an overabundance of positrons hitting Earth’s atmosphere, things got weird. For a long time, scientists have thought that all of this extra positrons are sourced from pulsars.

A pulsar is a rapidly rotating neutron star which emits electromagnetic signals. These objects are also very dense, concentrating the mass of the sun in a diameter comparable to that of a large city. Pulsars radiate two steady, narrow beams of light in opposite directions from their poles. Although the light from the beam is steady, pulsars appear to flicker because they also spin really fast, and so constantly spin these polar rays around. For this reason, pulsars have earned the nickname of ‘cosmic lighthouses’.

But now, writing in a recently published paper in the journal Science, a team of researchers claims these candidates —  a pair of pulsars less than a thousand light-years away — aren’t the likely culprit.

“When I started this work, I really believed it was pulsars,” lead author Rubén López Coto of the Max Planck Institute for Nuclear Physics told National Geographic. “But these two pulsars actually cannot provide enough positrons in order to account for this positron excess.”

A new suspect: dark matter

HAWC detector consisting of 300 large water tanks, each with four photodetectors

HAWC detector consisting of 300 large water tanks, each with four photodetectors. Credit: Jordan A. Goodman

Coto and colleagues refer to observations made at the High Altitude Water Cherenkov Gamma-Ray Observatory (HAWC), a science laboratory nestled at the base of a volcano four hours away from Mexico City. When gamma rays from annihilated positrons interact with the atmosphere, they generate showers of particles that hit the planet’s surface. Inside HAWC, scientists have placed 300 corrugated steel tanks filled with water. When the extremely high-energetic particles strike the tanks, they generate flashes of light which can be used to distinguish the signature and origin of the gamma rays that triggered the particle cascade.

By back-tracking from the gamma-ray observations, the HAWC team found that the pulsars’ positrons were not moving fast enough to arrive on Earth. This implies that the interstellar medium between the two pulsars and Earth is likely murky, preventing the positrons from reaching Earth.

“HAWC scans about one third of the sky overhead, giving us the first wide-angle view of high-energy light from the sky,” says study co-author Jordan Goodman, a particle astrophysicist at the University of Maryland, College Park. “Before HAWC there were observatories that were highly sensitive to high-energy gamma rays, but they had relatively limited fields of view. With HAWC, we can see how gamma rays are diffusing from these pulsars across wide regions of sky.”

If the two pulsars, called Geminga and Monogem, aren’t the source of positron overabundance in Earth’s atmosphere, then “other pulsars, other types of cosmic accelerators such as microquasars and supernova remnants, or the annihilation or decay of dark matter particles” must be considered.

Not everyone is convinced that dark matter could be the source, though. Since dark matter is literally everywhere, it follows that the signature generated by dark matter particles annihilating one another should be ubiquitous — but they’re not. It could be that the positrons are sourced from even more unconventional sources such as high-energy particles produced by black holes.

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.

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.

 

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.

An international team of researchers has found direct evidence of pear-shaped nuclei in atoms. (c) Liam Gaffney and Peter Butler, University of Liverpool)

Nucleus shaped like a pear challenges current understanding of physics

The nucleus of an atom is closely shaped like a sphere or rugby ball, signifying that mass is evenly distributed inside it. What happens when you encounter an atom whose nucleus stays away from this conventional shape? Well, this would be a good hint to start finding alternative theories, and wouldn’t you know it scientists at CERN have actually found an atom that doesn’t fit the Standard Model. It’s nucleus’ shape resembles that of a pear, but there’s nothing fruity about it.

An international team of researchers has found direct evidence of pear-shaped nuclei in atoms. (c)  Liam Gaffney and Peter Butler, University of Liverpool)

An international team of researchers has found direct evidence of pear-shaped nuclei in atoms. (c) Liam Gaffney and Peter Butler, University of Liverpool)

The shape of nuclei is governed by the strong nuclear force that keeps them together and acts against the electrostatic repulsion that pushes protons apart. Many models and assumptions, based on empirical data, have been made to describe nuclei structure, suggesting most atoms’ nuclei are spherical in shape, however some models suggest some atypical shapes as well, like the now proven pear or the yet to be encountered pyramid or banana shaped nuclei.

Researchers at CERN found the pear-shaped nuclei after they  fired a high-energy proton beam at a piece of uranium carbide in the ISOLDE isotope mass separator facility at CERN. The pear shape was observed in two sort-lived isotopes, 220Rn and 224Ra, after using the particle accelerator to blast the atoms at eight percent of the speed of light. The data show that while 224Ra is pear-shaped, 220Rn does not assume the fixed shape of a pear but rather vibrates about this shape.

With two confirmed pear-shaped nuclei, scientists now have their work cut out for them since they need to tease apart current theoretical models that didn’t leave room for such nuclei shapes.  In fact, the finding could also poke holes in the Standard Model of physics itself, which  describes the strong and weak nuclear forces and the electromagnetic force.  One of the biggest dilemmas left unanswered by the SM is the matter/anti-matter discrepancy. We’re still to arrive to a sensible explanation as to why there is more matter than anti-matter in the Universe, even though they’ve been created in equal share once with the Big Bang. If matter and antimatter behaved in the same way, they would have almost entirely annihilated one another during the first few seconds of the Big Bang, leaving little but radiation behind.

“If equal amounts of matter and antimatter were created at the Big Bang, everything would have annihilated, and there would be no galaxies, stars, planets or people,” said University of Michigan physicist Tim Chupp, who co-authored the paper on the find., in a UM news release.

Some alternate models predict  some nuclei should generate a weak electric dipole field, similar to the magnetic field of a bar magnet. The Standard Model of particle physics predicts that the value of the EDM is so small that it cannot be observed. However there are many theories that suggest that there is a way to measure the EDM. The pear-shaped atom gives physicists the best known example to test these theories and get closer to obtaining observable measurements of the EDM.

“Our findings contradict some nuclear theories and will help refine others. The measurements will also help direct the searches for atomic EDMs currently being carried out in North America and in Europe, where new techniques are being developed to exploit the special properties of radon and radium isotopes,” said Peter Butler, the physicist from the University of Liverpool who carried out the measurements and led the research.

“Our expectation is that the data from our nuclear physics experiments can be combined with the results from atomic trapping experiments measuring EDMs to make the most stringent tests of the Standard Model, the best theory we have for understanding the nature of the building blocks of the universe,” Butler said in a release from University of Liverpool.

The findings were reported in the journal Nature.

AMS_on_ISS_700k_Small

Antimatter excess in space hints of tangible evidence of dark matter

A $1.6 billion cosmic ray experiment on the International Space Station has come across evidence of antimatter in space, a remarkable finding that was recently presented during a seminar at CERN and which might help probe the mysteries of dark matter – one of the major components that make up the Universe.

AMS_on_ISS_700k_Small

The AMS-02 experiment is a state-of-the-art particle physics detector that is constructed, tested and operated by an international team composed of 56 institutes from 16 countries and organized under United States Department of Energy (DOE) sponsorship. Seen here as the round instrument labeled as “AMS”. (c) NASA

The find was made using the Alpha Magnetic Spectrometer (AMS), an instrument mounted on the International Space Station which has been likened by many as an LHC in space. AMS job is that of  surveying the sky for high-energy particles, or cosmic rays and has so far recorded 25 billion events. It’s main mission is that of identifying and describing dark matter, a mysterious component which we can not see, unlike regular matter, but which we know for sure exists because of the gravitational effects it holds on regular matter.

It’s believed that whenever dark matter collides, it forms antimatter as a result of what’s called annihilation. Antimatter is, naturally, the reverse of matter and every particle in the Universe has its corresponding antiparticle. For instance, the electron’s antiparticle is the antielectron, known as a positron. The electron and the antielectron have exactly the same masses, but they have exactly opposite electrical charges. Scientists believe that in the wake of the Big Bang an equal amount of matter and antimatter was ejected through out the Universe, however why they didn’t cancel each other out or why there seems to be more matter than anti-matter is a subject that’s giving physicists really big headaches.

Normal matter contributes just 4.9% of the mass/energy density of the Universe, dark matter is believed to range somewhere in the 26.8% margin, while dark energy – the force thought to be accelerating the expansion of the Universe – sits atop a comfortable majority of 68.3%.

Anyway, the AMS instrument shines by counting the numbers of electrons and their anti-matter counterparts from space – positrons – falling on an array of detectors. At the CERN seminar, completed just mere hours ago, AMS spokesperson and lead scientist Professor Samuel Ting unveiled some spectacular results. According to Ting, a slight excess of positrons in the positron-electron count was experienced, something expected in the aftermath of dark matter annihilation.

Evidence of dark matter finally found? Don’t get too excited…

This positron count excess could have come from pulsars, the spinning remnants of dead stars that throw off wild winds of radiation. Analysis has shown however that the positrons fall on the AMS from all directions, rather than a specific signal direction like one given off by a pulsar, suggesting what the researchers have come across are actually dark matter decay remnants. What this also suggests is that we may be on the brink of a monumental discovery in physics. According to the CERN press release:

“The AMS results are based on some 25 billion recorded events, including 400,000 positrons with energies between 0.5 GeV and 350 GeV, recorded over a year and a half. This represents the largest collection of antimatter particles recorded in space. The positron fraction increases from 10 GeV to 250 GeV, with the data showing the slope of the increase reducing by an order of magnitude over the range 20-250 GeV. The data also show no significant variation over time, or any preferred incoming direction. These results are consistent with the positrons originating from the annihilation of dark matter particles in space, but not yet sufficiently conclusive to rule out other explanations.”

CERN scientists, as they should be, are cautious and don’t mean to make bold statements as of yet.

“As the most precise measurement of the cosmic ray positron flux to date, these results show clearly the power and capabilities of the AMS detector,” said AMS spokesperson, Samuel Ting. “Over the coming months, AMS will be able to tell us conclusively whether these positrons are a signal for dark matter, or whether they have some other origin.”

If the more positrons than expected at higher energies can be attributed to dark matter remains to be seen, as we anxiously await new findings from AMS and CERN in the coming months. What’s certain is that only two years in its ten year mission, the AMS has already shown us a great deal, so expect much more from its behalf.

The findings are slated for publishing in the journal Physical Review Letters.

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.

[source]

Antimatter mystery gets a hint

Physics is still not sure what to make of antimatter; theoretically speaking, after the Big Bang, matter and antimatter were created in equal amounts. But if this is the case, then where is all the antimatter ?

Matter vs antimatter

An antiparticle has exactly the same mass as a particle, but a opposite electrical charge,  and thus, if you would take an electron, for example, it is negatively charged. But if you take its counterpart, the antielectron (or positron), it would have the same properties, but a positive charge.

Given that pretty much everything we can see today is made out of matter, one can only ask where all the antimatter is. This is one of the biggest mysteries physics has to solve.

In 2010, researchers at the Tevatron accelerator claimed some extremely interesting results, reporting a small excess of matter over antimatter as particles decayed. Given the fact that each particle has a cousin antiparticle, and when the two meet, they annihilate each other with a blast, this small excess could prove crucial in the understanding of the situation.

New physics?

The results at Tevatron come as a result of collision between protons and antiprotons. The created shower also produced a number of different particles, and the team operating the Tevatron’s DZero detector first noticed a discrepancy in the decay of particles called B mesons. When they drew the line, they noticed a 1% excess of matter particles.

However, the thing is that there is always a certain level of uncertainty when conducting this kind of measurements, so it’s still too early to say that they were dealing with revolutionary results back then. However, this time they have much more data to work with, and they reduced the uncertainty to level of 3.9 sigma – equivalent to a 0.005%. But even so, this is not enough. Particle physics is extremely strict when it comes to what can be called a discovery – the “five sigma” level of certainty, or about a 0.00003% level of uncertainty.

Still, the results are quite convincing, and they will probably pass that margin of error pretty sure, thus giving one of today’s most desired scientific answers.

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.

For one tiny instant, physicists break a law of nature

The LHC isn’t the only particle accelerator doing serious business these days; scientists at Brook­haven National Laboratory on Long Island working at the Relativistic Heavy Ion Collider (RHIC) have managed to achieve something that was previously thought to be impossible. In that way, the title is a bit misleading – you cannot really break a law of nature, because that isn’t possible by definition, but you can expand our knowledge and understanding of the world by doing something that was believed to be impossible – and that’s what they did.

The general belief is that you cannot break parity, which means that the Universe is neither right or left handed, if you take a system and inverse its coordinates, you will get exactly the same thing, but inversed. But the so-called weak force, which is responsible for radioactivity breaks the parity law, at least according to research performed by a dozen particle physicists, including Jack Sandweiss, Yale’s Donner Professor of Physics.

The team created a “quark-gluon plasma”, which has a temperature of over four trillion degrees Celsius (!), and is believed to have existed just after the Big Bang. They smashed together nuclei traveling at 99.999% the speed of light, and the plasma that resulted was so incredibly powerful that a tiny cube of it with sides measuring about a quarter of the width of a human hair has enough energy to power the whole United States for an entire year.

“A very interesting thing happened in these extreme conditions,” Sandweiss says. “Parity violation is very difficult to detect, but the magnetic field in conjunction with parity violation gave rise to a secondary effect that we could detect.”

The results were so unexpected, that they took an entire year to study them before publishing; even so, the results only suggest a break of parity, they don’t prove it beyond the point of doubt.

“I think it’s a real effect, but we’ll know more in the upcoming years,” Sandweiss says.

Hopefully, understanding this will increase our understanding of the Universe even further, as well as answer some questions that have been puzzling scientists for years, including why we don’t see any antimatter.

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

Milky Way Has Mysterious Lopsided Cloud Of Antimatter: Clue To Origin Of Antimatter

dark matter
Antimatter is a fascinating story; basically nobody knows for sure what it could do and scientists have been trying to understand it for years. The artificial production of atoms of antimatter (specifically antihydrogen) first became a reality in the early 1990s. For example an atom of antihydrogen is composed of a negatively-charged antiproton being orbited by a positively-charged positron. But still the clue that our old Milky Way galaxy gave us is relevant and important.

The thing is that the proton traveling at relativistic speeds and passing close to the nucleus of an atom has the potential to force the creation of an electron-positron pair. The shape of the mysterious cloud of antimatter in the central regions of the Milky Way has been revealed by ESA’s orbiting gamma-ray observatory Integral.

These observations almost eliminated the idea that the chances that the antimatter is coming from the annihilation or decay of astronomical dark matter. Georg Weidenspointner at the Max Planck Institute for Extraterrestrial Physics and an international team of astronomers made the discovery using four-years-worth of data from Integral.

“Simple estimates suggest that about half and possibly all of the antimatter is coming from the X-ray binaries,” says Weidenspointner. The other half could be coming from a similar process around the galaxy’s central black hole and the various exploding stars there. He points out that the lopsided distribution of hard LMXBs is unexpected, as stars are distributed more or less evenly around the galaxy. More investigations are needed to determine whether the observed distribution is real.