

Quarks Know Their Left From Their Right - engassa
http://news.sciencemag.org/physics/2014/02/quarks-know-their-left-their-right

======
kartikkumar
Awesome result. I think it's vitally important to acknowledge achievements
that happen in parallel with research at the LHC because otherwise we're going
to miss a lot of very neat results. I don't know enough about particle physics
to be able to comment on the techniques involved unfortunately, but I love
reading about the progress that's being made.

For someone that Wikipedia's a lot of this stuff, does someone know if this
type of spin asymmetry is in any sense related to CP violation? [1] As soon as
I read the article I thought of CP violation and I'm assuming this is
basically the "P" violation.

Finally, reading this article actually triggered a totally different question:

"Using the electron accelerator at Thomas Jefferson National Accelerator
Facility in Newport News, Virginia, the researchers shined 170 billion
electrons on a target of liquid deuterium over 2 months in 2009."

Shined or shone? Turns out to be quite the discussion topic (e.g., [2][3][4])!

[1]
[http://en.wikipedia.org/wiki/CP_violation](http://en.wikipedia.org/wiki/CP_violation)

[2]
[http://public.wsu.edu/~brians/errors/shined.html](http://public.wsu.edu/~brians/errors/shined.html)

[3] [http://grammarist.com/usage/shined-
shone/](http://grammarist.com/usage/shined-shone/)

[4] [http://motivatedgrammar.wordpress.com/2010/10/18/has-the-
sun...](http://motivatedgrammar.wordpress.com/2010/10/18/has-the-sun-shined-
or-shone/)

~~~
alxprc
As it says in the article, this is the discovery of parity, P, violation in a
system where it's not been seen before. In a "nice" universe, one might expect
mirror images to behave the same, but here they've discovered that
interactions between electrons and quarks are different depending on the spin
of the electron.

So, it's related to CP violation in the sense that it something "violates CP
symmetry" if it's behaviour changes when you flip the charge _and_ the parity
of the system simultaneous. Here, they only flip the parity.

------
milliams
For a science magazine, this article does a terrible job of talking about
spin. Saying "spinning as it zips along—to the right like a football thrown by
a right-handed quarterback or the left like a pigskin thrown by a lefty" is
immensely confusing to anyone who actually wants to understand what's going
on.

~~~
jpeterson
Can someone explain what's wrong with the spinning ball analogy? From my
understanding, it's a pretty good first approximation of the physical
interpretation of particle spin.

~~~
adobriyan
Elementary particles are dots for all intents and purposes. But dots can't
spin. Spinning requires internal structure to notice spinning, but elementary
particles don't have it.

Basically you don't need analogy at all.

Spin is inherent property of a particle like mass, charge, etc. It's quantum
like charge. If lagrangian of interaction includes particle's spin, spin
effects will be noticeable in scattering and everywhere.

Analogy is only needed to not mix spin with angular momentum.

Funny how in media spin is left and right, but in science spin is always "up"
or "down". :-)

~~~
jpeterson
Agreed, but you will also agree that you've gone well beyond the level of
first approximation here, right?

~~~
adobriyan
Maybe. :-)

This analogy has quite a lot of problems which arguably can confuse more than
explain.

First thing my physics professor said in uni was "forget everything you've
learned in school". This is applicable to spinning balls.

------
gnaritas
Quarks don't know anything and they don't spin like a football, bad science
reporting is bad science reporting.

