From: Larry Klaes (lklaes@bbn.com)
Date: Fri Jul 30 1999 - 14:07:52 MDT
Date: Fri, 30 Jul 1999 09:02:31 -0400 (EDT)
From: AIP listserver <physnews@aip.org>
To: physnews-mailing@aip.org
Subject: update.441
PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 441 July 30, 1999 by Phillip F. Schewe and Ben Stein
THE CHANDRA X-RAY TELESCOPE is now installed in its
highly elliptical orbit, where the Earth itself, and not just its
atmosphere, will not interfere with x-ray reception. Named for
astrophysicist Subrahmanyan Chandrasekher, the 14-m-long
telescope is considered one of NASA's three "great observatories";
the other telescopes in this battleship class are the Hubble Space
Telescope and the Compton Gamma Ray Observatory. Chandra
will have superb angular resolution (half an arc-second, 8 times
better than previous x-ray telescopes), sensitivity to faint objects
(20 times better), and spectral resolution (1 eV). The object of the
mission is unflinchingly to explore graphic violence wherever it can
be found at x-ray wavelengths: quasars, black holes, pulsars,
supernovas, and intergalactic plasmas.
(http://www1.msfc.nasa.gov/NEWSROOM/background/facts/cxoqu
ick.htm)
BLOCH STATES: NOT FOR ELECTRONS ONLY. It is often
essential to consider an electron traveling through a solid as being a
wave that spreads out through the whole of the solid. The quantum
description of this spread-out electron was formulated by Felix
Bloch in the 1920s. Physicists have since sought to extend this idea
of a "Bloch state" to guest atoms in a crystal, but an atom's mass is
so large (and its equivalent wavelength so small) that a Bloch state
for an atom has been difficult to observe. Now, physicists from
Japan (Ryosuke Kadono, KEK, ryosuke.kadono@kek.jp) have seen
clear signs of a Bloch state for a muonium "atom," in effect a light
isotope of hydrogen whose proton is replaced by a positively
charged muon particle having 1/9 of the proton's mass. Performing
experiments at the Rutherford Appleton lab in England, the
researchers studied spin-polarized muonium (Mu) atoms in a KCl
crystal cooled down to 10 mK. Measuring how long it took the
atoms to lose their initial polarization in the presence of an external
magnetic field provided information on their energy state and
matched the predictions of a Bloch model. Further studies may
offer new insights into the energy bands of atoms in crystals.
(Kadono et al., Physical Review Letters, 2 August 1999.)
PARTICLE ACCELERATOR TURN-ONS. The concrete poured
and the magnets tuned, several important new machines are about to
take up important physics matters. The Main Injector at Fermilab,
dedicated in June, is an additional 2-mile racecourse for getting
protons up to speed in much greater numbers. What this means is
that the proton-antiproton collider run starting in 2000 will record in
one year as much data as was taken in the earlier 10-year era. This is
crucial since beam intensity is no less important than the energy of
collision when producing rare objects, such as supersymmetric
particles (hypothetical cousins of the known leptons and quarks) and
the much sought Higgs boson (playing a sort of midwife role in the
life of many other particles, the Higgs should also exist in its own
right). New theoretical estimates for the mass of the Higgs suggest
that Fermilab might just have enough energy to discover the Higgs
(Science, 25 June). Meanwhile, two accelerator schemes dedicated
to studying CP violation through the agency of B-meson decays, are
nearly ready. The Asymmetric B Factory at SLAC in California is
now smashing 9-GeV electrons into 3.1-GeV positrons to produce
pairs of Bs. The decay products are absorbed in a detector called
BaBar. A comparable setup at the KEK lab in Japan will soon
collide 8-GeV electrons with 3.5-GeV positrons inside a detector
called BELLE. By the way, the cost of these detectors is a not-
inconsiderable portion of the accelerators themselves. BaBar and
BELLE cost, respectively $80 million and $70 million (Physics
World, May 1999). Finally, at the DAFNE electron-positron
collider in Frascati, Italy, CP violation is also the subject matter, but
the approach is different. Here the collisions are dedicated to
making phi mesons, which then decay into a pair of K mesons,
which in turn break up (amid the KLOE detector) in a process that
violates charge-parity invariance (CERN Courier, June 1999.)
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