Physics

A quasiparticle called the exciton is responsible for the transfer of energy within devices, such as solar cells, LEDs, and semiconductor circuits, and has been understood for decades, but exciton movement within materials has never been directly observed.


Below is a clip from a chapter of my book where I describe the story of the silicon microvertex detector of the CDF experiment. CDF collected proton-antiproton collisions from the Tevatron collider in 1985, 1987-88, 1992-96, and 2001-2011. Run 1A occurred in 1992, and it featured for the first time in a hadron collider a silicon strip detector, the SVX. The SVX would prove crucial for the discovery of the top quark.

The existence of exotic hadrons — a type of matter that cannot be classified within the traditional quark model - has been confirmed in a forthcoming article prepared by the Large Hadron Collider beauty (LHCb) Collaboration at CERN in Geneva, Switzerland.

Quarks are hard, point-like objects found within the nucleus of an atom. When quarks combine in threes, they form compound particles known as baryons. Protons are probably the best-known baryons. Sometimes, quarks interact with corresponding anti-particles (i.e., anti-quarks), which have the same mass but opposite charges. When this happens, they form mesons. These compounds often turn up in the decay of heavy man-made particles, such as those in particle accelerators, nuclear reactors, and cosmic rays.


U.C. Santa Barbara physicist Tarun Grover says he has definitive mathematical evidence for supersymmetry in a condensed matter system. Sought after in the realm of subatomic particles by physicists for several decades, supersymmetry describes a unique relationship between particles.

The fundamental constituents of matter — electrons, quarks and their relatives — are fermions. The particles associated with fundamental forces are called bosons. Several decades ago, physicists hypothesized that every type of particle in the Standard Model of particle physics, a theory that captures the dynamics of known subatomic particles, has one or more superpartners — other types of particles that share many of the same properties but differ in a crucial way.


Yesterday I was in Rome, at a workshop organized by the Italian National Institute for Nuclear Physics (INFN), titled "What Next". The event was meant to discuss the plan for basic research in fundamental physics and astrophysics beyond the next decade or so, given the input we have and the input we might collect in the next few years at accelerators and other facilities.

In February, the University of California, Los Angeles held its 11th Symposium on Sources and Detection of Dark Matter and Dark Energy in the Universe - "Dark Matter 2014" was aimed at discussing the latest progress in the quest to identify dark matter, the umbrella term for the unknown stuff that makes up more than a quarter of the universe yet remains a mystery.

So where does the hunt stand? Between sessions, three leading physicists at the conference spent an hour discussing the search for dark matter on several fronts.


If I look back at the first times I discussed the important graph of the top quark versus W boson mass, nine years ago, I am amazed at observing how much progress we have made since then. The top quark mass in 2005 was known with 2-3 GeV precision, the W boson mass with 35 MeV precision, and we did not know where the Higgs boson was, or if there was one.
The mass of the top quark is a very important parameter of the standard model: using its value together with other no less fundamental ones (the W boson mass, the Higgs mass, and many parameters describing the properties of Z bosons) it is possible to study in great detail the predictions of the theory. In particular, due to the way heavy particles influence the Higgs field, one may verify the consistence of the standard model by looking at a graph where the top quark mass is in the x axis and the W boson on the y axis: different hypotheses for the Higgs boson mass then lie on different parallel curves. One example of such a graph is shown below. It is too complex to discuss it in detail here, but if you are curious I can supply more information in the comments thread.
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Apr 02 2014 | 2 comment(s)

As I mentioned a few months ago, lately I have been writing a science book for laymen. The idea is to focus on the history of CDF, a particle physics experiment that collected data from 1985 to 2011 at the Fermilab laboratory near Chicago.

In a recent PNAS paper, scientists have described how they managed to achieve a quantum entanglement with a minimum of 103 dimensions with only two particles.

103 dimensions rather than 3? Is that a typo?

Elementary particles such as photons can produce superpositions - where they exist in many possible quantum states simultaneously. In addition, when two particles are entangled a connection is generated so measuring the state of one (whether they are in one place or another, or spinning one way or another, for example) affects the state of the other particle instantly, no matter how far away from each other they are.