PHYSICS NEWS UPDATE -- Number 714 January 3, 2005 by Phillip F. Schewe, Ben Stein

From: Sam Wormley (swormley1_at_mchsi.com)
Date: 01/03/05 

Date: Mon, 03 Jan 2005 20:35:21 GMT

PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 714 January 3, 2005 by Phillip F. Schewe, Ben Stein

NEUTRINO SUPERFLUIDS aren't going to be observed any time soon, but
the mathematical proof that they could exist helps to augment the
catalog of possible physical reality. Superfluids are closely
related to superconductors. In both phenomena numerous
particles---whether boson particles such as helium-4 atoms or pairs
of fermion particles such as electrons or helium-3 atoms---can
coalesce into a single, all-encompassing quantum state; examples
include supercurrents, superfluids, and Bose-Einstein condensates
(BEC). Joe Kapusta, a physicist at the University of Minnesota, has
shown that neutrinos too can become a superfluid. First they must
pair up, as electrons do in superconductors. Two electrons with
opposite spins can form pairs by the exchange of slight
disturbances in the underlying matrix of atoms in the solid sample.
Analogously, neutrinos with opposite helicity (for a "left-handed"
neutrino, its intrinsic spin is oriented opposite to its direction
of motion; for "right-handed" neutrinos it's the other way around)
could pair up by exchanging a disturbance in the all-pervasive sea
of Higgs bosons in the universe. (The Higgs boson, in turn, is the
much-sought cornerstone of the current standard model of particle
physics; it is the particle whose presence confers mass on many of
the other known particles.) After pairing up, the nu pairs could
then form a superfluid condensate. Kapusta admits that the chances
of observing his superfluid are slim since, first, right-handed
neutrinos have never been observed (and might be even more elusive
or ghostly than their left-handed partners) and, second, because the
superfluid would only occur at temperatures far colder than the
2.7-K average-temperature of the current universe. Kapusta points
out that a superfluid of heavy neutrinos would make a great medium
for advanced civilizations to send messages over intergalactic
distances since the scattering length of pulses (the average
distance they go before scattering) moving through the neutrino
fluid would be much greater than for electromagnetic pulses.
(Physical Review Letters, 17 December 2004; kapusta@physics.umn.edu)
                                                                 
ANTI-HYDROGEN PRODUCTION UNDER LASER CONTROL has been achieved in an
experiment conducted at the CERN lab in Geneva. Cold anti-hydrogen
(Hbar) atoms are the antimatter counterparts of hydrogen atoms.
Previously antihydrogen was formed when positrons cooled antiprotons
within the carefully designed electric and magnetic fields of a
nested Penning trap. That the anti-atoms had formed at all was
verified, but they're not yet cold enough to be held in place. The
ultimate goal is to make a goodly supply of anti-atoms, store them,
and then probe their internal structure with laser light to
determine whether they have the same quantum behavior as ordinary
hydrogen.

An incremental step would be not just to make the anti-atoms but to
see to it that they are in specific internal energy states, and this
is what the ATRAP (http://hussle.harvard.edu/~atrap/ ) collaboration
has now done. To gain some extra control over anti-H production,
they have to make the production process a bit more complicated.
Where the lasers come into the picture is to initiate a three-step
process. First, laser light selectively excites cesium atoms into
special "Rydberg" states. Second, positrons collide with the Cs
atoms, an encounter which cedes one of the atom's electrons to the
positron; the positron-electron pair, which constitutes a sort of
atom-like entity of its own, known as positronium (abbreviated Ps),
inherits the cesium atom's excitation. (By the way, this excited Ps
is a thousand times bigger than plain Ps). Third, the positron part
of the Ps can occasionally be captured by an antiproton moving in
the same direction. In the process the anti-hydrogen atoms assumes
the same binding energy as the former Ps. The rate for producing
anti-H this way is still lower than with the older methods, but the
use of the intermediate cesium process and laser excitation offers
an extra measure of control over atomic conditions within the trap
(useful in experiments yet to come) and, furthermore, may have
resulted, in this case, in the coldest anti-atoms ever created in a
lab. (Storry et al., Physical Review Letters, 31 December 2004;
contact Gerald Gabrielse, 617-495-4381,
gabrielse@physics.harvard.edu)

***********
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