
LHCb experiment discovers a new pentaquark - ljdk
https://home.cern/news/news/physics/lhcb-experiment-discovers-new-pentaquark
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drilldrive
So, what is a pentaquark exactly? The article doesn't say.

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andrepd
Usually quarks are confined in composite particles of two (mesons) or three
(baryons) quarks. However they can also in certain conditions form particles
of 5 quarks (the pentaquarks).

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drilldrive
Oh, so quarks can only be composites of two, three, and five? Any reason that
could be stated in layman's terms?

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andrepd
Quantum chromodynamics (the theory which describes the strong interaction) has
a feature called colour confinement, which says that quarks will favour being
in colourless configuration (where colourless = zero colour charge). The two
easiest ways for this to happen are in mesons (two quarks: one quark and one
antiquark of the same colour, like red + antired = colourless), or in baryons
(three quarks: 1 red + 1 green + 1 blue = colourless) like the familiar proton
and neutron. However other configurations are possible, these are just the
simplest ones. In certain incredibly difficult to attain conditions, we can
avoid producing either a two- or three-quark composite particle but produce
instead a five-quark particle (e.g. 1 red + 1 green + 1 blue + 1 red + 1
antired = colourless).

This "colour" means colour charge, it doesn't have any relation to the regular
meaning of "colour of light".

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Ygg2
> This "colour" means colour charge.

Color charge is essentially as charge. I.e. instead of having +/\- you have
A/B/C. Except you also have Anti A/B/C.

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afraca
This is both entertainment and information, so to justify it I'll ask a
question about this:
[https://www.youtube.com/watch?v=j50ZssEojtM](https://www.youtube.com/watch?v=j50ZssEojtM)
(Large Hadron Rap)

Are these goals still accurate or has new knowledge and engineering changed
the goals of the detectors?

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sanxiyn
The rap is pretty bad. It lists four questions: dark matter, matter-antimatter
asymmetry (aka baryogenesis, related to CP violation), Higgs boson, and
hierarchy problem (why gravity is so weak; rap alludes extra dimension).

We found Higgs boson, which is great. We are no closer to answer other three
questions, and frankly, there was no reason to expect LHC to help there, it
was all wishful thinking. Sure, it was possible, LHC would do what has never
been done, but not very probable.

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sand500
As I see it, we are basically putting more and more energy into these particle
collisions and hoping something unexpected happens.

