APS News

2002 April Meeting Features New SNO Data, CPU Study

More than 1200 physicists and astronomers attended the 2002 APS Spring Meeting, held April 20-23 in the beautiful southwest city of Albuquerque.

The principal subject areas were particle, nuclear, and astrophysics, including new data on neutrino oscillations (see page 3) and extreme hydrogen physics (see page 5). However, many other topics were covered as well, such as the final report of the NAS Committee on the Physics of the Universe (page 1), countering terrorism, women in physics, and the play "Copenhagen," about the wartime meeting between Werner Heisenberg and Niels Bohr.

The meeting was sponsored jointly by the APS and the high energy astrophysics division (HEAD) of the American Astronomical Society (AAS).

Next Linear Collider.
The panel of particle physicists (HEPAP) that advises both the US Department of Energy and the National Science Foundation has called for the construction, in the US or elsewhere, of a giant accelerator where beams of electrons and positrons would mutually annihilate in a burst of energy.

Moreover, an international steering committee has been set up to promote the project. What kind of machine is this "Next Linear Collider" and what are the physics goals? Speakers at a Monday session looked at the production of high energy beams at such a machine.

Other sessions featured talks about the specific physics experiments to be done, such as the detailed study of the Higgs boson, the elusive object thought to be responsible for the mass of other particles.

The Quest for Anti-Atoms.
Particle physicists are on the verge of creating cold anti-hydrogen atoms that can be manipulated and studied.

Gerald Gabrielse of Harvard University reported on his group's experiments at CERN that have combined antiprotons and positrons (antielectrons) in a trap. Obtaining definitive evidence for the existence of antihydrogen atoms in the trap is difficult and Gabrielse (a member of the ATRAP collaboration) discussed the status of the evidence for antihydrogen.

Another seeking to make anti-atoms at CERN (and a member of the ATHENA collaboration), Michael Holzscheiter of Los Alamos, examined how antihydrogen can be tested to see how closely it mirrors normal hydrogen, whether antimatter falls downward due to gravity and the implications for the most fundamental properties of the universe.

Gamma Rays: The Next Generation.
The orbiting Gamma Ray Large Area Space Telescope (GLAST), scheduled for launch in 2006, is to be the successor to the highly successful Compton Gamma Ray Observatory. GLAST will study the cosmos by looking at objects that emit high energy photons. For instance, one onboard detector, the Large Area Telescope (LAT), will look for gammas with energies as high as 300 GeV.

The results of a balloon test flight from August 2001 of some GLAST components were reported at a Saturday session of the April meeting. The scientific targets for GLAST include some of the most violent events in the cosmos-gamma-ray bursters, active galactic nuclei-as well as the effort to map dark energy and to search for supersymmetric particles. (See http://www-glast.stanford.edu/)

New Data on Proton and Neutron Structure.
Last year, physicists working at Jefferson Lab in Virginia reported experimental evidence that the proton's electric charge was spread out, or distributed, in a different way than its magnetization current density.

At the April Meeting, Vina Punjabi of Norfolk State University in Virginia discussed new Jefferson lab data on the proton electric charge and magnetization current density distributions.

Andrei Semenov of Kent State reported similar measurements on the structure of the neutron, while John Ralston of the University of Kansas presented a theoretical explanation of the proton's differing magnetization current density and electric charge distributions.

Finally, Gerald Miller of the University of Washington presented an alternative explanation for the different distributions.

Spooky Action at a Distance.
In 1935, Albert Einstein published a paper with graduate students Boris Podolsky and Nathan Rosen in which they described a paradox (dubbed the EPR paradox after the authors) that Einstein called "spooky action at a distance" whereby one particle seems to affect instantaneously another particle a large distance away. Arthur Fine of the University of Washington and Martin Jones of Oberlin College each discussed the history and development of the EPR paradox and quantum entanglement.

In 1982, landmark experiments by Alain Aspect of the Institut d'Optique, France, tested the consequences of the EPR concepts and how it changed our notion of quantum reality. Aspect discussed that work and more recent developments that take advantage of progress in quantum optics.

Anton Zeilinger of the University of Vienna closed the session with a demonstration of how the originally problematic paradox is now driving new schemes for transmitting and processing information through quantum communication, quantum cryptography, quantum teleportation and quantum computation.

Hunting for New Physics.
Even as Michael Green (Cambridge) and John Schwarz (Caltech) received the 2002 Dannie Heineman Prize for their early work on the theory of superstrings, one of the pillars of modern particle physics, other scientists look for cracks in the standard model. Examples presented at the April meeting included new results from the measurement of the magnetic moment of the muon at Brookhaven, the measurement at Fermilab's NuTeV experiment of the parameter that sets the mixing of the weak nuclear force and electromagnetic force, the study of CP violation (antimatter not behaving quite like matter) at SLAC's B factory, the first physics from Brookhaven's Relativistic Heavy Ion Collider, and the mysterious spectrum of the highest-energy cosmic rays.

The Secret Life of Black Holes.
Black holes not only drive the latest science fiction stories but also the research programs of physicists exploring the fundamental structures of the universe.

Chris Fragile of Lawrence Livermore National Laboratory described simulations of black holes "eating" nearby matter, stars and gas clouds and the dynamics of those accretion flows. When two black holes try to swallow each other, the fabric of space-time undergoes extreme stresses.

Richard Price and Robert Owen of the University of Utah have investigated the downward spiral of two black holes orbiting one another, finding that a higher dimensional analogue of the black hole is the black string. Past research has indicated that black strings can split in two.

Matthew Choptuik of the University of British Columbia reexamines this issue in light of some contradictory predictions and presents the results of numerical simulations. But when is a black hole not a black hole? When it's a gravastar (a gravitational condensate star), according to LANL's Emil Mottola.

Science Goes Underground.
The U.S. is considering the prospect of building a major new science laboratory in South Dakota, specifically at the site of the Homestake Gold Mine in Lead, South Dakota.

The Homestake Mine was the site where neutrino measurements were made for many years and it remains a highly desirable underground location, shielded from the effects of cosmic rays and other environmental disturbances that can otherwise upset sensitive measurements.

Wick Haxton of the University of Washington discussed the prospect of a National Underground Science Laboratory at the Homestake site. According to Haxton, "This site provides great depth (to 8000 ft.) and valuable infrastructure, including massive shafts, hoists, ventilation, air conditioning, and communications systems and the presence of a skilled staff of engineers, geologists, and miners." He believes that the science possibilities at NUSL-Homestake are rich, spanning important topics in neutrino physics, dark matter, nucleon stability, nuclear astrophysics, supernova physics, earth science, materials science, and geomicrobiology.

Haxton provided an up-to-date report on the political and scientific progress in realizing the National Underground Science Laboratory.

Philip F. Schewe, Ben Stein, and James Riordon of the American Institute of Physics, and David Harris of the APS contributed to the technical coverage in this issue.



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