Strong Force

Physicists have demonstrated their grasp of the strong force the binds 
the atomic nucleus by learning how to identify the exotic particles it
spawns, called glueballs

Quark is fanciful,  electron is classical.  Glueballs are made entirely 
of sticky stuff (gluons), particles that carry the strong force the 
binds quarks together to make up protons and neutrons.

QCD Quantum chromodynamics which predicts glueballs, is difficult to
determine the solutions to fundamental equations.  Thus it is 
difficult to predict what a glueball should look like.

Thanks to the convergence of two major lines of work :
  (1) a 20yr quest to extract accurate predictions from QCD by lattice
      calculations, which have given glueball hunters a picture of 
      their quarry
  (2) 25years of accelerator experiments which observed hundreds of 
      short-lived particles known as resonances, which can now be 
      compared with the theoretical predictions to identify any 
      glueballs lurking among them.

IBM Physicist Don Weingarten preseted lattice QCD predictions of 
glueball mass , lifetime and decay properties that seem to match the 
properties of a resonance at SLAC.  Theorists will also have the first 
confirmation t;hat they truly understand QCD and the strong interactions.  
That they can make meaningful predictions about the quark-gluons 
interactions.  QCD has always been the most troublesome of the theories 
of the Standard model of high-energy physics.  Gluons hold quarks (the 
fundamental building blocks of matter) together.  In QCD quarks are held 
together by their interaction with a chromoelectric field carried by 
gluons , just as the electromagnetic field is carried by photons.  QCD 
the force carried by the gluons is very weak when the quarks are close 
together, but gets stronger at larger distances.  So free quarks are 
never seen.  If you try to pull a quark free of a proton ,the charge 
gets bigger and bigger eventually the energy is the field is so big it 
spontaneously produces a quark-antiquark pair.  You get two hadrons 
instead of one.


    QCD is tough to use because of the quantum mechanical uncertainty 
principle, implies that any QCD calculation has to deal with the 
interacting particles themselves and with clouds of "virtual" gluons and 
quark-antiquark paris that appear unpreditable from the vacuum and 
vanish again.
    So physicists rely on approximate schemes (perturbation expansions) 
which provid esolutions to the equations of a quantum theory when the 
forces between particles are weak.  In QCD interactions are weak at 
high energies, > ~3bil eV and perturbation expansions have been used 
to predict the existence of phenomena seen in high energy collisions 
(gluon jets). At lower energies where the strong interactions are 
indeed strong, perturbation theory fails.
    At low energies, Steven Weinberg says are the big questions : Why 
the mass of a proton is what it is or why quarks interact the way they 
do.  It's also at these energies that glueballs should manifest themselves.
    Gluons can never exist as free particles.  They clump together, forming 
coherent superpositions like a little smoke ring made of the chromoelectric 
field.  It is difficult to distinguish glueballs from mundane hadrons are 
 (1) their quantum charges (neutral charged, flavorless and colorless) and 
 (2) mass and (3) decay properties  - quich are predicted accurately 
from the equations of QCD, which is where lattice QCD comes in.  1974 
Ken Wilson -> lattice QCD.
    Success came in 1993 Weingarten et al, predicted the masses of a 
dozen hadrons.  They also made their first mass prediction for the 
lightest possible glueball 1740 MeV.


    This coincides with a 1710MeV Particle known as the theta (1981 
SLAC), e-&e+ collider decay of J/Psi particles.  composed of a charm 
quark and antiquark ,their decay products were suspected to be 
glueballs.  After the quark and antiquark annihilate during decay the 
gluons linger for a moment.  The theta particle is observed.
    Weingarten claims the 1710MeV theta is a gluball.
    In Britain, massively parallel supercomputers for lattic QCD 
calculations have predicted a glueball mass of 1550MeV.  1993, Close 
and C. Amsler's experiment "the Crystal Barrel" at Low-Energy antiproton 
Ring (LEAR) at CERN.  Which has been running 5 years accumulating 
millions of events where neutral hadrons are created then decay into 
photons and (glueballs).  They had found a particle which matched at 1550MeV.
     The next heaviest gluball should weigh in at 2200MeV (according 
to both Weingarten and UK QCD) observed in the early 1980's at SLAC. 
Labeled eta.  The particle appeared during J/Psi decays into a photon 
and 2 hadrons.
     Also eta decays as QCD suggests a glueball should: into a parhir 
of pions (quark-antiquark pairs) as well as into proton and antiproton 
pairs.
   




    /*---------------------------------------------------------------------*/
 
Materials Scientists Make contact

Bringing futuristic materials a step closer to reality,
considered a wide array of topic
from superconductivity to nuclear waste storage.
Two intriguing presentations focused on efforts to simplify
computer chip manufacture patterning and
improve the electrical conductivity of thin films.

A new method of stamping copper patterns on a 
substract could simplify chipmaking

    /*---------------------------------------------------------------------*/
 

Supernova Maser Emission

Maser emission (microwave analog of laser light) from the
energy levels of an inverted population of interstellar molecules
was first discovered in 1965.  Cosmic maser emission
has been extensively used to probe dynamics and physical 
conditions of interstellar gas around galactic nuclei, protostars and 
evolved stars.  The high brightness and narrow spectral width
unique to maser radiation allows astronomers to detect 
unprecedented angular resolution compact gas clouds whose
size is as small as one astronomical unit
    /*---------------------------------------------------------------------*/
 
Polymer photovoltaic cells : enhanced efficiencies from network of internal donor - acceptor heterojunctions

The carrier collection efficiency (nc) and energy conversion efficiency (ne) of
polymer photovoltaic cells were improved by blending of the semiconducting polymer
with C60 .  Composite films of poly(2methoxy-5-(2'-ethy-hexyloxy)-1,4-phenylene vinylene ) (MEH-PPV)
and fullerenes exhibit nc of 29% electrons per photon and ne of 2.9% , efficiencies that are better by more than
two orders of magnitude than those that have been achieved
with devices made with pure MEH-PPV.  The efficient charge separation results from photoinduced
electron transfer from MEH-PPV (as donor) to C60 (as acceptor).  The high collection efficiency results
from a bicontinuous network of internal donor-acceptor heterojunctions.
    /*---------------------------------------------------------------------*/
 
Solution-Liquid-Solid Growth of Crystalline III-V Semiconductors: An analogy to Vapor-liquid-solid growth

Micrometer-scale or larger crystals of the III-V Semiconductors have not been grown
at low temperatures for lack of suitable mechanisms for covalent nonmolecular
solids.  A solution-liquid-solid mechanism for the growth of InP, InAs, and GaAs
is described that usese simple, low temperature (<203'C), solution-phase reactions.
The materials are produced as polycrystalline fibers or near-single-crystal
whiskers having widths of 10-150nanometers and length of micrometers.
Vapor-liquid-solid growth can operate at low temperatures; similar synthesis
routes for other covalent solids may be possible.
    /*---------------------------------------------------------------------*/
 

STM on Wet Insulators : Electrochemistry or Tunneling? 1849


--fin