Topic: New Particle Discovered!!!!!!

[Lancezh]

http://nanopatentsandinnovations.blogspot.com/2012/04/new-particle-xib-discovered-at-cern-by.html

In german, swiss news:

http://www.tagesschau.sf.tv/Nachrichten/Archiv/2012/04/27/Vermischtes/Cern-entdeckt-unbekanntes-Teilchen-aus-Quarks

The calculations are based on data from proton-proton collisions at an energy of seven Tera electron volts (TeV) collected by the CMS detector between April and November 2011. A total of 21 Xi_b^* baryon decays were discovered – statistically sufficient to rule out a statistical fluctuation.

The discovery of the new particle confirms the theory of how quarks bind and therefore helps to understand the strong interaction, one of the four basic forces of physics which determines the structure of matter.

Direct Source from University of Zurich (german):

http://www.uzh.ch/news/articles/2012/erfolgreiche-spurensuche-im-teilchenzoo.html

Submitted Report (eng):

http://arxiv.org/abs/1204.5955v1

[Lancezh]

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[Shadow Of A Doubt]

Particle physics question!

Ξ^0 is made of up, strange, strange quark; charge 0 (already found)
Ξ^(-1) is down, strange, strange quarks; charge -1 (already found)
Ξ_b^* is up, strange, bottom - replacing one strange quark with a heavier bottom quark and presumably having charge 0 (new particle)

Idk what the * means, does anyone else have any idea?

[lukebourassa]

 

[Hanes]

Particle physics question!

Ξ^0 is made of up, strange, strange quark; charge 0 (already found)
Ξ^(-1) is down, strange, strange quarks; charge -1 (already found)
Ξ_b^* is up, strange, bottom - replacing one strange quark with a heavier bottom quark and presumably having charge 0 (new particle)

Idk what the * means, does anyone else have any idea?

I don't know that notation, but I do know about a neat table!
http://en.wikipedia.org/wiki/Xi_baryon

[341gerbig]

Fawk, im never going to memorise the particle zoo!

[Citizen Skeptic]

Whoever coded the simulation software that we're all a part of did a fabulous job of attention to detail. Software guys are god.

[Caffiene]

Whoever coded the simulation software that we're all a part of did a fabulous job of attention to detail. Software guys are god.

Nah. When someone spots an error they just patch the error and rewind the simulation to go from just before that point.

[Jim S]

Whoever coded the simulation software that we're all a part of did a fabulous job of attention to detail. Software guys are god.

Nah. When someone spots an error they just patch the error and rewind the simulation to go from just before that point.


ETA:  Holy crap, that wasn't supposed to happen.

 

[Hanes]

Fawk, im never going to memorise the particle zoo!

You don't have to! 

That would be like memorizing all of the elements; it's better to just understand what makes them up.

Baryons like these Xi's are just groups of three quarks.  If there are only two quarks, they are called Mesons.  These are composite particles, and their properties are basically just the sum of the quarks that make them up.

There are also Leptons (for example electrons and neutrinos).  Quarks and leptons have "spin" in increments of 1/2, 3/2, etc.  Collectively they are called Fermions.

There are other particles that have "spin" in increments of 1, 2, etc.  Due to [math], this allows them to behave differently, and transmit force between particles.  These are called Bosons, and include things like the photon and the Higgs.

It takes energy to be massive, so things that are heavy tend to decay into lighter particles.  This is for the same reason that balls roll down hills; lower energy state.  Particles can only decay in in ways that don't change some of their values--for example the total electrical charge of the system can't be different after it decays.



So this new particle they're talking about is made of an Up, a Strange, and a Bottom.  Ok, so its total electric charge is 2/3 + -1/3 + -1/3 = 0; it's electrically neutral.  Memorize shmemorize!

Obviously there are interesting subtleties (for example, those mesons I mentioned earlier can also transmit force), but the basics aren't too bad to wrap your mind around.

http://en.wikipedia.org/wiki/Standard_model

[Citizen Skeptic]

Is this going to be particle bonanza like when they started discovering elements that don't exist in nature?

[Hanes]

It already is.  How many different ways can you put six quarks into groups of two and three?

http://en.wikipedia.org/wiki/List_of_baryons
http://en.wikipedia.org/wiki/List_of_mesons

Really only baryons that exist in abundance nature (since after the universe expanded and cooled) are protons and neutrons. 

There are a few mesons of note.  For example the pion that transmits the strong force between neucleons in an atom. 

Some more exotic fermions show up in things like cosmic ray collisions with the atmosphere, and probably in exotic places like in the superheated dust swirling around a black hole's event horizon, but in general it takes too much energy to stop something from decaying into something lighter (keeping the ball from rolling down the hill).  The reason we can find these particles now is that the LHC has enough energy to kick the ball way up the hill.  Like they said in the article, the Xi they observed is as massive as six protons, for the same number of quarks!

[drizz]

Particle physics question!

Ξ^0 is made of up, strange, strange quark; charge 0 (already found)
Ξ^(-1) is down, strange, strange quarks; charge -1 (already found)
Ξ_b^* is up, strange, bottom - replacing one strange quark with a heavier bottom quark and presumably having charge 0 (new particle)

Idk what the * means, does anyone else have any idea?

I believe the * indicates a spin 3/2 particle. The Xi comes in many varieties of differing charge; some are spin 1/2 and some are spin 3/2. The ones with the asterisk are spin 3/2.

[Shadow Of A Doubt]

Particle physics question!

Ξ^0 is made of up, strange, strange quark; charge 0 (already found)
Ξ^(-1) is down, strange, strange quarks; charge -1 (already found)
Ξ_b^* is up, strange, bottom - replacing one strange quark with a heavier bottom quark and presumably having charge 0 (new particle)

Idk what the * means, does anyone else have any idea?

I believe the * indicates a spin 3/2 particle. The Xi comes in many varieties of differing charge; some are spin 1/2 and some are spin 3/2. The ones with the asterisk are spin 3/2.

Yes, thanks! Because the baryons are made of 3 quarks (spin 1/2 particles) they can exist at spin 1/2 or spin 3/2.

Do the spin 3/2 baryons decay into the the spin 1/2 baryons?

[drizz]

Yes, thanks! Because the baryons are made of 3 quarks (spin 1/2 particles) they can exist at spin 1/2 or spin 3/2.

Do the spin 3/2 baryons decay into the the spin 1/2 baryons?

They sure do! The principal decays for spin 3/2 baryons are into a spin 1/2 baryon and either a pion or a kaon which are both spin 0 mesons.

For example, a spin 3/2 Xi particle will most often decay into a spin 1/2 Xi particle and pion.