Number 229, June 7, 1995 by Phillip F. Schewe and Ben Stein
A NEW MEASUREMENT OF THE MASS OF THE W BOSON has been carried out by
the CDF collaboration at the Fermilab collider. The data sample consists
of thousands of events in which the charged W's are produced in high energy
proton-antiproton collisions and then each decay into a neutrino plus either
an electron or muon. The W's, along with the Z boson, are the carriers
of the weak nuclear force. Now that the top quark has been discovered,
the next major quarry in particle physics is the Higgs boson, the particle
which supposedly endows other particles with mass. Theorists believe that
measurements of the top quark mass and the W mass can be used to constrain
estimates of the likely Higgs mass. This knowledge, in turn, tells scientists
whether they could hope actually to produce the Higgs at an accelerator,
assuming that the Higgs exists as a physical particle. The new W mass measurement
(80.410 GeV) has only half the uncertainty of the best previous mass measurement.
(F. Abe et al., 3 July 95, Physical Review Letters.)
COSMIC RAYS AND GAMMA RAY BURSTS MIGHT BE RELATED. Eli Waxman of the
Princeton Institute for Advanced Study suggests that the same physical
mechanism (as yet unknown) which can produce cosmic ray particles with
energies above 10**20 eV (several such cosmic ray showers have been recorded
in recent years) might also be producing the mysterious gamma-ray bursts
observed from orbiting detectors. Although some cosmic rays may come from
our galaxy, the highest energy cosmic rays are thought to be extra-galactic.
Many (but not all) astronomers believe gamma bursts also originate outside
our galaxy. In Waxman's scenario the gamma bursts are produced by internal
shocks in ultra-relativistic winds, which also accelerate the 10**20-eV
protons we later observe as cosmic rays. The amount of energy injected
into the universe as gammas and as high energy cosmic rays should be comparable.
(Eli Waxman, 17 July 95, Phys. Rev. Lett.)
WATER ON THE SUN. The presence of water molecules at the Sun has been
detected in infrared spectra recorded at Kitt Peak. The astronomers trained
their high-resolution telescope at the darkest part of a sunspot, one of
the coolest places on the Sun's surface. At a temperature of 3200 K this
relative oasis is cool enough for water molecules to predominate over OH
as the majority oxygen-containing molecule. (Lloyd Wallace et al., Science,
26 May 1995.)
BLUE LIGHT FROM A SURFACE-EMITTING LASER . A collaboration of scientists
from UC Santa Barbara, Notre Dame, Matsushita Electric Co. (Osaka, Japan),
and the University of Tsukuba (Japan) have combined two burgeoning technologies---(1)
the direct production of blue laser light in stacks of zinc-selenide layers
and (2) the emission of laser light not horizontally but vertically from
the surface of the laser medium---to develop the first blue-light vertical
cavity surface emitting laser, at a temperature of 30 K. At warmer temperatures
the laser output would shift from the blue (488 nm) to blue-green wavelengths.
So far the laser medium has been optically pumped; that is, the atoms in
the laser medium have been excited by light waves. However, at a meeting
to be held at the University of Virginia later this month the researchers
will announce the operation of a blue-green surface-emitting laser using
a much more practical and efficient electrical pumping system. (P.D. Floyd
et al., Applied Physics Letters, 29 May 1995.)
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