SLAC Today is
available online at:
In this issue:
symmetry: Explain it in 60 Seconds - W Boson
Science Today: Controlling the Wave
SLAC Employee Helps Create Benefit Concert
Retirement Savings Check Up
Thursday - April 3, 2008
symmetry: Explain it in 60 Seconds
The W boson is one of five particles that transmit the fundamental forces of nature. It is responsible for two of the most surprising discoveries of the 20th century—that nature has a "handedness" and that the physics of antimatter is subtly different from the physics of the matter-based world we see around us.
The W boson comes in positively and negatively charged varieties. They collaborate with another particle, the electrically neutral Z boson, to cause the force known as the weak interaction, which is responsible for some forms of nuclear decay, among other phenomena.
The W is very massive, which means its effects are very short range and very weak at everyday energies. Hence, the effects of these particles are subtle—but important! For example, the W can change the very nature of an interacting particle, turning an electron into a neutrino or a down quark into an up quark. This is important in the fusion reactions that power the sun, which involve protons turning into neutrons. Finally, the W provides the only established mechanism for allowing matter and antimatter to evolve in different ways. Read more in symmetry...
Controlling the Wave
Stanford University researchers working in part at the Stanford Synchrotron Radiation Laboratory have discovered a novel set of properties pertaining to a compound of materials called tritellurides. These compounds, composed of three atoms of tellurium and a single atom of one of the rare earth elements, demonstrate unique electronic properties that can be controlled by altering the temperature of the material.
The tritellurides display phenomena known as charge density waves (CDW). In a normal conductive metal, electrons persist in a "sea" wherein they are evenly distributed and equally available, or conductive. A CDW occurs under certain circumstances and causes the electrons to clump together, lowering their availability, and thereby lowering the compound's conductivity. Tellurium, when crystallized into quasi-two-dimensional planes and combined with rare earth elements, produces a material with CDWs that can be manipulated and controlled.
Using electrical conductance tests at Stanford and X-ray diffraction measurements at SSRL Beamlines 11-3 and 7-2, the group found that, when tellurium is combined with rare earth elements—in this case erbium and terbium—the CDW can be induced by manipulating the temperature of the compound. This "threshold temperature" is different for each rare earth element, and in some cases is room temperature. In the case of erbium, the group found that the compound actually has two threshold temperatures, which induce CDWs that occur at 90 degrees to one another. These results could reveal clues to how superconductors, which can also demonstrate CDWs, could be further exploited to create novel materials with unique electronic properties. More information about this research can be found in the full SSRL Headlines science highlight.
SLAC Employee Helps Create Benefit Concert
Late last year, SLAC Today profiled Rich Talley, who works as a SLAC technician by day and a rock musician by night. When he's not tending klystrons for the linac, Talley plays lead guitar and sings with Rumors, a three-year-old, Tracy-based band. Now, Talley and his band have created a new benefit concert for the fight against ALS-Lou Gehrig's disease and would like to invite the SLAC community to attend the upcoming event.
Two members of Rumors have lost members of their families to ALS-Lou Gehrig's disease and have pledged to raise money and awareness through their love of music by creating the 1st Annual Ten Grand At The Grand ALS Benefit Concert. The show will be hosted by local celebrities with live performances by recording artist and Tracy native Megan Slankard, the Motown cover group Prestige and, of course, Rumors.
The event will take place at 7 p.m. on Saturday, April 12th, at the newly renovated Grand Theatre in Tracy. Tickets are available at www.atthegrand.org or at the Grand theatre box office.
Retirement Savings Check-up
Have you checked your retirement savings lately? Make sure your contributions to the Tax-Deferred Annuity (TDA) or the Stanford Contributory Retirement Plan (SCRP) are working for you. Make an individual appointment with an investment counselor from Fidelity, TIAA-CREF or Vanguard for a retirement checkup. The counseling sessions are free and usually last an hour.
A representative from each investment company is at SLAC once a month. To see dates and how to make an appointment click here.
Access (see all)
Community Bulletin Board
View online at http://today.slac.stanford.edu/.