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Does Antimatter Fall Up or Down?

Theory and observations support the view that antimatter experiences gravity just as ordinary matter does, but the evidence so far has been indirect. Indeed, some theorists speculate that antimatter is antigravitational, that it may fall “up” instead of “down.” Led by Berkeley Lab physicists, the ALPHA Collaboration at CERN has made direct measurements of the gravitational mass of atoms of antihydrogen, testing how they fall and in what direction.

BOSS Quasars Unveil a New Era in the Expansion History of the Universe

By collecting tens of thousands of quasar spectra, the Baryon Oscillation Spectroscopic Survey (BOSS) has measured the large-scale structure of the early universe for the first time. Like backlights in the fog, the quasars illuminate clouds of hydrogen gas along the line of sight. No other technique can reach back over 10 billion years to probe structure at a time when the expansion of the universe was still decelerating and dark energy was yet to turn on.

Understanding What’s Up With the Higgs Boson

On July 4 CERN released the latest results in the search for the Higgs boson. Members of the ATLAS and CMS experiments who are leading the search announced the observation of a new particle “consistent with the Higgs” at a very high level of confidence. Berkeley Lab has a large contingent of physicists in the ATLAS collaboration, some in key posts. They explain what’s involved in the Higgs search and what happens next, now that the news has broken.

MAJORANA, the Search for the Most Elusive Neutrino of All

Neutrinos may be even stranger than they seem, if indeed they are the only fermions (particles of matter) that are their own antiparticles. Proof would be a rare form of radioactive decay called neutrinoless double-beta decay, which could only be seen if there’s virtually no background interference. The MAJORANA DEMONSTRATOR now under construction at the Sanford Underground Research Facility in the Black Hills of South Dakota aims to prove these near-perfect conditions can be met.

The First Spectroscopic Measurement of an Anti-Atom

Scientists at Lawrence Berkeley National Laboratory have played leading roles in designing and operating ALPHA, the CERN experiment that was the first to capture and hold atoms of antihydrogen, a single antiproton orbited by a single positron. Now, by measuring antihydrogen’s hyperfine structure, ALPHA has achieved another first in antimatter science with the very first measurements of the energy spectrum of an anti-atom.

ALPHA Stores Antimatter Atoms Over a Quarter of an Hour – and Still Counting

Physicists in Berkeley Lab’s Accelerator and Fusion Research Division are key members of the international ALPHA Collaboration at CERN in Geneva, which has succeeded in storing a total of 309 antihydrogen atoms, many of them for as long as 1,000 seconds (almost 17 minutes) and some for much longer — more than enough time to perform meaningful scientific experiments on confined anti-atoms.

Anti-Helium Discovered in the Heart of STAR

Antimatter nuclei of helium-4, the heaviest antiparticles ever found, have been created by the STAR experiment at Brookhaven’s Relativistic Heavy Ion Collider. Eighteen examples of the antihelium particles were detected by STAR’s Time Projection Chamber, designed and built at Berkeley Lab, in debris from a billion high-energy collisions of gold nuclei.

A Flow of Heavy-Ion Results from the LHC

CERN’s Large Hadron Collider collides protons most of the year but switches to massive lead nuclei for a month. Collisions of these heavy ions reproduce the quark-gluon plasma that filled the universe millionths of a second after the big bang. Much of the program for quark-gluon plasma studies is shaped by theoretical and experimental contributions from Berkeley Lab’s Nuclear Science Division, as shown by results from ALICE and other experiments during the LHC’s first lead-lead run just concluded.

Antimatter Atoms Successfully Stored for the First Time

Atoms of antimatter have been trapped and stored for the first time by the ALPHA collaboration, an international team of scientists working at CERN in Switzerland. Berkeley Lab researchers made key contributions to the effort, including the design of the trap’s crucial component—an octupole magnet—and computer simulations needed to identify real antihydrogen annihilation events against a noisy background.

Large Hadron Collider Pauses Protons; Looks Ahead to Lead

The Large Hadron Collider has completed many successful months of colliding protons (hydrogen ions) at record-breaking energies and now begins four weeks of colliding much more massive lead ions, giving access to different physical phenomena. Berkeley Lab hosts U.S. participation in the ALICE experiment, designed specifically to study the heavy-ion collisions that give rise to a unique phase of matter, the quark-gluon plasma. Berkeley Lab is also a major participant in the ATLAS experiment, one of the other LHC experiments that will study lead-lead collisions.