Physics

By changing the material medium through which x-rays pass, physicists at Lawrence Berkeley National Laboratory have used laser light to control x-ray beams.

As a new generation of powerful light sources comes online, intense x-ray beams may be able to control matter directly and allow one beam of x-rays to control another, the new Nature Physics study suggests.

Using the Lawrence Berkeley National Laboratory's Advanced Light Source femtosecond spectroscopy beamline 6.0.2, researchers sent ultrashort pulses of laser light and higher-frequency x-rays together through a gas cell filled with pressurized neon. Excited by the laser pulses, the gas, which normally absorbs x-rays, became transparent to the x-ray pulses during their quick passage.
It makes me very happy when I see new precise results on the mass of the top quark being produced by the CDF collaboration (to which I still proudly belong). CDF, one of the two hadron collider experiments operating at the 2-TeV Tevatron proton-antiproton synchrotron in Batavia, IL, has been measuring the top quark mass since 1994, one year prior to its discovery. The figure with the top candidates (histogram) from which the mass measurement of 174+-12 GeV was obtained in 1994 is shown on the right below; backgrounds and top expectation are shown by hatched lines.
The American Chemical Society's Spring 2010 National Meeting and Exposition includes numerous research findings in the field of cold fusion, also known as Low Energy Nuclear Reactions (LENR). Here is the video of the live press conference that gives a broad introduction to the people involved and their views on this controversial part of science.



Blocking Temperature
1. Superparamagnetism
Quasicrystals

Quasicrystals

Mar 19 2010 | 0 comment(s)

Quasicrysstals

A brand new result in Higgs boson physics has been presented by my old-time CDF colleague Wei-Ming Yao at the Moriond QCD conference two days ago. It is the combination of CDF and DZERO limits on the Higgs boson, and it constitutes a significant advancement in our knowledge of the standard model.

The result is simple to state in a single sentence, although it will take me several pages to explain it acceptably. The Higgs boson is excluded at 95% confidence level in the 130-210 GeV mass range, if there are four generations of matter fields.
In 1950 Immanuel Velikovsky published his bestselling Worlds in Collision, where he proposed that Venus was once a satellite of Jupiter that went AWOL and caused catastrophes on Earth as it flew past. Nobody believes this now, and few believed it then either, but you can see how it would work using a solar system simulation designed by PheT.
How to explain resonance to a non-scientist? A few years back I heard a guest speaker on BBC Radio 4 trying to explain the resonance effects of pulsed microwave radiation on the brain in contrast to the thermal effects of the carrier frequency: sadly he failed miserably. What is it about resonance that makes it so hard to explain?

I have taught it to A-level students and to undergraduate engineers. Electrical engineers, in particular, need to be thoroughly familiar with the phenomenon and yet, I could see that its significance eluded them. There are few, if any, good visible examples in real life. The Tacoma Narrows Bridge is one famous example, where strong winds set the bridge oscillating. Eventually it hit its resonant frequency and collapsed.
I was delighted to receive news this afternoon of three new interesting results produced by the DZERO collaboration in the analysis of Quantum Chromodynamics (QCD) processes.

QCD, the theory of strong interactions between quarks and gluons, is the "boring" part of the physics of high-energy hadron-hadron collisions. It used to be more more exciting twenty years ago, when the theoretical calculations were not as refined as they are now, and there was still a lot to understand in the physics of strong interactions between quarks and gluons. But nowadays, things are much more clear.
The CDF collaboration, which runs one of the two proton-antiproton collider experiments at the Fermi National Accelerator Laboratory since the early eighties, has published hundreds of scienticif papers in the course of its 25 years of operation. I believe the number has abundantly surpassed the half-thousand mark, but I am unaware of its exact entity.