Register for an account

X

Enter your name and email address below.

Your email address is used to log in and will not be shared or sold. Read our privacy policy.

X

Website access code

Enter your access code into the form field below.

If you are a Zinio, Nook, Kindle, Apple, or Google Play subscriber, you can enter your website access code to gain subscriber access. Your website access code is located in the upper right corner of the Table of Contents page of your digital edition.

The Sciences

Chirality and the Positron's Mustache

Cosmic VarianceBy Sean CarrollJune 20, 2011 6:09 PM

Newsletter

Sign up for our email newsletter for the latest science news

6a00d8341c562c53ef0154330d829c970c-800wi.jpeg

Woke up this morning to the happy news that my post "The Fine Structure Constant is Probably Constant" walked away with the Charm Quark (i.e., tied for third place) in this year's 3QuarksDaily science blogging prizes. Many thanks to Lisa Randall for judging and Abbas Raza and the 3QD crew for hosting. And of course congrats to the other winners:

  1. Top Quark: SciCurious, Serotonin and Sexual Preference: Is It Really That Simple?

  2. Strange Quark: Anne Jefferson, Levees and the Illusion of Flood Control

  3. Charm Quark: Ethan Siegel, Where Is Everybody?

I already have a great nominee for next year's contest. One of the most confusing things in particle physics is the notion of "chirality." The related notion of a particle's "helicity" is relatively easy to explain -- is the particle spinning in a left-handed or right-handed sense when compared to its direction of motion? But a massive particle need not have a direction of motion, it can just be sitting there, so the helicity is not defined. Chirality is the same as helicity -- left-handed or right-handed -- for massless particles moving at the speed of light, but it's always defined no matter how the particle is moving. It had better be, since the weak interactions couple to particles with left-handed chirality but not ones with right-handed chirality! (And the opposite for antiparticles.) It all gets a bit heady, and you can't give a real explanation without going beyond simple pictures and actually talking about the quantum wave function. But Flip Tanedo at Quantum Diaries has given it an heroic effort, which I insist you go read right now. I don't want to reproduce the whole thing -- Flip was more careful and thorough than I ever would have been, anyway -- but I will tease you with this one picture.

impositron.png

Isn't that the cutest pair of elementary particles you've ever seen? I smell a Quark in this lepton's future.

    2 Free Articles Left

    Want it all? Get unlimited access when you subscribe.

    Subscribe

    Already a subscriber? Register or Log In

    Want unlimited access?

    Subscribe today and save 70%

    Subscribe

    Already a subscriber? Register or Log In