

Two new subatomic particles discovered at CERN - pursuing
http://www.cbc.ca/news/technology/2-new-subatomic-particles-discovered-at-cern-1.2840199?cmp=rss

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cozzyd
In case people are wondering about the impact of this, it's not very
interesting (to non particle physcists) unless something unexpected about
these particles is found later, as these particles were predicted by the
Standard Model. The exact mass splittings, of course, are useful to validate
(and further improve) theoretical models of QCD.

What I find more interesting is that LHCb is licensing their eprint as CC-
BY-4.0. I wonder how PRL feels about this.

~~~
mkartic
Are the particles found first and retrofitted into the Standard Model? Or does
the model act as a map of sorts by telling us where to look? If latter, does
that mean we're not looking for particles outside of the standard model?

~~~
evanb
The Standard Model is a list of fundamental particles (electron, muon, tau,
their corresponding neutrinos, and 6 flavors of quarks: up, down, strange,
charm, top, and bottom) as well as their interactions (electroweak force &
strong nuclear force). The input to the SM are around 20 numbers controlling
the masses of these particles and the strengths of the interactions, as well
as a few Higgs parameters. After that, everything is fixed, so that the SM
makes definite predictions about where to look to find new baryons and mesons
(things made out of quarks). It's not quite so simple as "add up the masses of
the constituent quarks" because the strong interactions translate into mass
(essentially via E=mc^2)---exactly how big an effect the strong force has
requires calculation.

So the SM is a map telling you where to look, but a very sneaky kind of map.
In the sector where the strong force matters, it's as if someone encrypted a
map, and for every new destination you want to find out about, you have to
expend computational resources to decrypt it. In principle, you have all the
information, but in practice it is hard to extract predictions from the
theory. That is a very peculiar situation for scientists to be in: to have a
definite, precise theory, and the opportunity to do experiments, but to
struggle to compare the two!

Anyway, these particles are predicted by the SM, where "predicted by" means
after expending a lot of computation to understand the strong dynamics one
finds out that these particles (which are quarks held together by gluons)
should be there.

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Leszek
I suppose this is the particle physics equivalent of 'discovering' heavier and
heavier elements in the periodic table -- good evidence towards existing
theory, but effectively these are artificial constructions that exist only
briefly and never (?) outside lab conditions.

~~~
cozzyd
It's more akin to 'discovering' new nuclear isomers that are predicted but
have never been observed.

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krohling
More technical details here:
[http://home.web.cern.ch/about/updates/2014/11/lhcb-
observes-...](http://home.web.cern.ch/about/updates/2014/11/lhcb-observes-two-
new-baryon-particles)

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MrJagil
A bit off-topic, but I was recently recommended the documentary "Particle
Fever" by someone here on HN. I can now highly, highly recommend it as well.
Really puts this whole thing in perspective!

~~~
soci
I just finished watching it a few minutes ago. Great documentary,

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danbruc
Why does nobody include the particle name in the heading? Supersymmetry?!?
Click. Nope, some pseudo particle or a bunch of quarks.

~~~
pbhjpbhj
"0b" [that's a copy paste, the Xi doesn't appear, the super and subscript
letters do, the pi doesn't show] I'm going to guess that is why?

Though the OP does say "The discovery of the particles, known as Xi_b'\- and
Xi_b*-, were announced by CERN [...]"

𝛯′⁻ works in unicode, but I can't get the subscript b nor superscript asterisk
in there (cf.
[http://en.wikipedia.org/wiki/Unicode_subscripts_and_superscr...](http://en.wikipedia.org/wiki/Unicode_subscripts_and_superscripts)).

~~~
sp332
I don't see a subscript-b in Unicode anywhere.

~~~
pbhjpbhj
No, me neither, nor a superscript asterisk.

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hazz
Here's the paper in question:
[http://arxiv.org/abs/1411.4849](http://arxiv.org/abs/1411.4849)

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ezequiel-garzon
If I may, [http://xkcd.com/1437/](http://xkcd.com/1437/)

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LaneRendell
Must be good being a particle physicist these days. :)

