Anti-hydrogen Article

Researchers say this graphic visualization shows the annihilation of an anti-hydrogen atom, captured by the ATHENA detector.  An annihilated antiproton throws off four charged pions (yellow tracks) that are detected by position-sensitive silicon microstrips (pink).  The positron annihilates into two gamma rays (red tracks) that are detected by cesium iodide crystals (red cubes).  The charged pions also deposit energy into cesium iodide crystals (yellow cubes).

European scientists say they have created enough anti-hydrogen, a type of the mirror-image, antimatter stuff that fictionally powers spaceships on “Star Trek” to test a widely held basic model of the universe.

While anti-hydrogen been made before, the more than 50,000 atoms created at the CERN particle accelerator in Geneva are “by far the most produced,” said Jeffrey Hangst, a leader of the ATHENA collaboration, one of two groups of physicists working on anti-hydrogen at CERN.  The quest to understand and manipulate antimatter is one of the most competitive pursuits in science.  Not all particle physicists — even within CERN — agree with the new findings.

A spokesman for the competing ATRAP Collaboration at CERN said he doubts that anti-hydrogen had been produced in the latest experiment.  The ATHENA group relied on indications of the simultaneous destruction of anti-hydrogen’s two atomic particles: the positron and the antiproton to show it had been produced, said Harvard physicist Gerald Gabrielse, spokesman for the ATRAP group.  “Our long experience with these very difficult experiments warns that observing simultaneous positron and anti-proton annihilation does not ensure that anti-hydrogen has been produced.”

ATHENA researchers plan to make more anti-hydrogen to test the "Standard Model" - equations that explain the nature of matter and energy.  If the anti-hydrogen doesn’t behave the same as normal hydrogen “the science textbooks will have to be rewritten,” said Hangst, who is a physicist at the University of Aarhus in Denmark, along with his CERN work.  “It would imply that we have overlooked something fundamental about how nature works,”  Hangst said.  “Such a discovery certainly wouldn’t help you to build a better computer or TV, but it might shed some light on why we have a universe that looks the way it does.”

Antimatter is the mirror image of conventional matter with opposite properties.  Antimatter is destroyed whenever it collides with matter, turning both into bursts of electromagnetic radiation.  Scientists believe this process was crucial to the fiery creation of the universe billions of years ago.  Why so little antimatter is made now in nature remains one of physics’ great dilemmas.  Only modest levels have been detected in cosmic ray showers and the nuclei of distant galaxies.  Antimatter is difficult to make in the lab.  Giant particle accelerators at CERN and Fermilab near Chicago specialize in the quest.  In the first antimatter experiments a few years ago, only dozens of short-lived antimatter particles were created.  Hydrogen, the most abundant element, consists of an electron orbiting a proton.  Anti-hydrogen is the exact opposite; a positron — an electron with a positive charge — orbiting an antiproton, or a proton with a negative charge.

In the latest experiments, ATHENA researchers used the CERN accelerator to create antiprotons and electromagnetically trapped them in a vacuum chamber.  A radioactive source, meanwhile, was used to create positrons, which were held in a separate trap.  The antiprotons were then fed into the pool of positrons, where the two combined to form anti-hydrogen.  The antimatter was short-lived.  Hangst said it was annihilated when it bumped into normal matter.  Detectors picked up the unique signatures of antimatter as it was destroyed, he said.  David Christian of Fermilab said the ATHENA group appears to have made antimatter in greater quantities.  “They’ve got a lot more big steps they need to make, but this one is a big step,” Christian said.

However, Gabrielse said upcoming publications by his group “will show how it is possible to be fooled.”  “Our initial understanding of the recent report makes it likely that we will present the case that the reported observations do not prove that any anti-hydrogen was observed,” he said.  ATHENA researchers plan several experiments to test the Standard Model by creating more anti-hydrogen, exciting it with lasers and observing what happens when the atom’s positron jumps from one orbit to another.  They also want to study gravity’s effect on anti-hydrogen.  Some speculate antimatter “falls up,” but most scientists don’t believe that is the case, Hangst said.

Using antimatter to power a starship or create a weapon, meanwhile, is still in the realm of science fiction, he said.  Making antiprotons requires 10 billion times more energy than it produces.  For example, the antimatter produced each year at CERN could power a 100-watt light bulb for 15 minutes, Hangst said.

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