The discovery of a ‘left-handed’ magnetic field that pervades the universe could help explain a long standing mystery – the absence of cosmic antimatter. A group of scientists, led by Prof Tanmay Vachaspati from Arizona State University in the United States, with collaborators at the University of Washington and Nagoya University, announce their result in Monthly Notices of the Royal Astronomical Society.
Planets, stars, gas and dust are almost entirely made up of ‘normal’ matter of the kind we are familiar with on Earth. But theory predicts that there should be a similar amount of antimatter, like normal matter, but with the opposite charge. For example, an antielectron or positron has the same mass as its conventional counterpart, but a positive rather than negative charge.
In 2001 Prof Vachaspati published theoretical models to try to solve this puzzle, which predict that the entire universe is filled with helical (screw-like) magnetic fields. He and his team were inspired to search for evidence of these fields in data from the NASA Fermi Gamma ray Space Telescope (FGST).
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Geneva, 3 June 2014. In a paper published in the journal Nature Communications today, the ALPHA experiment at CERN1’s Antiproton Decelerator (AD) reports a measurement of the electric charge of antihydrogen atoms, finding it to be compatible with zero to eight decimal places. Although this result comes as no surprise, since hydrogen atoms are electrically neutral, it is the first time that the charge of an antiatom has been measured to high precision.
“This is the first time we have been able to study antihydrogen with some precision,” said ALPHA spokesperson Jeffrey Hangst. “We are optimistic that ALPHA’s trapping technique will yield many such insights in the future. We look forward to the restart of the AD program in August, so that we can continue to study antihydrogen with ever increasing accuracy.”
Antiparticles should be identical to matter particles except for the sign of their electric charge. So while the hydrogen atom is made up of a proton with charge +1 and an electron with charge -1, the antihydrogen atom consists of a charge -1 antiproton and a charge +1 positron. We know, however, that matter and antimatter are not exact opposites – nature seems to have a one-part in 10 billion preference for matter over antimatter, so it is important to measure the properties of antimatter to great precision: the principal goal of CERN’s AD experiments. ALPHA achieves this by using a complex system of particle traps that allow antihydrogen atoms to be produced and stored for long enough periods to study in detail. Understanding matter antimatter asymmetry is one of the greatest challenges in physics today. Any detectable difference between matter and antimatter could help solve the mystery and open a window to new physics.
While antiparticles can be created and then detected with costly and complex particle-accelerator experiments, such particles are otherwise very difficult to study. However, Fleishman and the two co-researchers have reported the first remote detection of relativistic antiparticles — positrons — produced in nuclear interactions of accelerated ions in solar flares through the analysis of readily available microwave and magnetic-field data obtained from solar-dedicated facilities and spacecraft. That such particles are created in solar flares is not a surprise, but this is the first time their immediate effects have been detected.
The results of this research have far-reaching implications for gaining valuable knowledge through remote detection of relativistic antiparticles at the Sun and, potentially, other astrophysical objects by means of radio-telescope observations. The ability to detect these antiparticles in an astrophysical source promises to enhance our understanding of the basic structure of matter and high-energy processes such as solar flares, which regularly have a widespread and disruptive terrestrial impact, but also offer a natural laboratory to address the most fundamental mysteries of the universe we live in.
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An international team of physicists has found the first direct evidence of pear shaped nuclei in exotic atoms.
The findings could advance the search for a new fundamental force in nature that could explain why the Big Bang created more matter than antimatter—a pivotal imbalance in the history of everything.
“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 Tim Chupp, a University of Michigan professor of physics and biomedical engineering and co-author of a paper on the work published in the May 9 issue of Nature.
Antimatter particles have the same mass but opposite charge from their matter counterparts. Antimatter is rare in the known universe, flitting briefly in and out of existence in cosmic rays, solar flares and particle accelerators like CERN’s Large Hadron Collider, for example. When they find each other, matter and antimatter particles mutually destruct or annihilate.
What caused the matter/antimatter imbalance is one of physics’ great mysteries. It’s not predicted by the Standard Model—the overarching theory that describes the laws of nature and the nature of matter.
Antimatter is strange stuff. It has the opposite electrical charge to matter and, when it meets its matter counterpart, the two annihilate in a flash of light. Four University of California, Berkeley, physicists are now asking whether matter and antimatter are affected differently by gravity as well. Could antimatter fall upward – that is, exhibit anti-gravity – or fall downward at a different rate?
Almost everyone, including the physicists, thinks that antimatter will likely fall at the same rate as normal matter, but no one has ever dropped antimatter to see if this is true, said Joel Fajans, UC Berkeley professor of physics.
And while there are many indirect indications that matter and antimatter weigh the same, they all rely on assumptions that might not be correct. A few theorists have argued that some cosmological conundrums, such as why there is more matter than antimatter in the universe, could be explained if antimatter did fall upward.
In a new paper published online on April 30 in Nature Communications, the UC Berkeley physicists and their colleagues with the ALPHA experiment at CERN, the European Organization for Nuclear Research in Geneva, Switzerland, report the first direct measurement of gravity’s effect on antimatter, specifically antihydrogen in free fall. Though far from definitive – the uncertainty is about 100 times the expected measurement – the UC Berkeley experiment points the way toward a definitive answer to the fundamental question of whether matter falls up or down.
The international team running the Alpha Magnetic Spectrometer (AMS1) today announced the first results in its search for dark matter. The results, presented by AMS spokesperson Professor Samuel Ting in a seminar at CERN2, are to be published in the journal Physical Review Letters. They report the observation of an excess of positrons in the cosmic ray flux.
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.
“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.”
A new discovery provides a crucial key to understanding how neutrinos – ghostly particles with multiple personalities – change identity and may help shed light on why matter exists in the universe.
In an announcement today (Thursday, March 8), members of the large international Daya Bay collaboration reported the last of three measurements that describe how the three types, or flavors, of neutrinos blend with one another, providing an explanation for their spooky morphing from one flavor to another, a phenomenon called neutrino oscillation.
The measurement makes possible new experiments that may help explain why the present universe is filled mostly with matter, and not equal parts of matter and antimatter that would have annihilated each other to leave behind nothing but energy. One theory is that a process shortly after the birth of the universe led to the asymmetry, but a necessary condition for this is the violation of charge-parity (or CP) symmetry. If neutrinos and their antimatter equivalent, antineutrinos, oscillate differently, this could provide the explanation.