http://www.theatlantic.com/technology/archive/2014/11/CERN-large-hadron-collider-finds-two-new-subatomic-particles-called-baryons/382968/

Using the same massive particle accelerator that found the elusive Higgs Boson in 2012, physicists at CERN’s Large Hadron Collider (LHC) announced that they discovered two new “heavy-weight” subatomic particles on Wednesday.

The LHC is a 17-mile long underground “racetrack” that accelerates two opposing beams of particles to speeds of 99.9999 percent the speed of light. The particles race around the LHC on a crash course, and when they collide, the temperatures soar to more than 100,000 times hotter than the center of the sun. At heats this extreme, the particles transform into a primordial form of matter known–in not-quite-technical terms–as a “subatomic soup.”
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There are maybe three-to-five such particles discovered each year,” Patrick Koppenburg, a CERN scientist from the Netherlands’ Nikhef Institute, said to The Wall Street Journal. “Here we have two in one go, which is quite extraordinary.”

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I found Koppenburg’s comments interesting. I would not have guess that more than twenty of these had been found in the last decade.

Sheldon will be thrilled.

that’s shaggadelic

Checks original ArXiv to discover which ones.

I see, quark content bds = bottom+down+strange (which is better than ‘down strange bottom’ I suppose: joke). Or to put it another way Xi-bottom resonances with a negative charge. Xi barions contain one light quark (up or down) and two heavy quarks (any of strange, charm, bottom or top). The lightest Xi barons with two strange quarks have a mass of 1300 MeV/c^2. The new ones have a mass of 5900 MeV/c^2.

There’s some more info on this CERN page:

LHCb observes two new baryon particles

[…] the new X_ib particles both contain one beauty (b), one strange (s), and one down (d) quark. Thanks to the heavyweight b quarks, they are more than six times as massive as the proton. But the particles are more than just the sum of their parts: their mass also depends on how they are configured. Each of the quarks has an attribute called “spin”. In the Xi_b’- state, the spins of the two lighter quarks point in the opposite direction to the b quark, whereas in the Xi_b*- state they are aligned.

“Nature was kind and gave us two particles for the price of one,” said Matthew Charles of the CNRS’s LPNHE laboratory at Paris VI University. “The Xi_b’- is very close in mass to the sum of its decay products: if it had been just a little lighter, we wouldn’t have seen it at all using the decay signature that we were looking for.”

[…]

The related Xi_b*0, found by the CMS experiment at CERN in 2012, has a quark content of usb.

These new Xi baryons both contain dsb, so I guess you could call them quark isomers. They are distinguishable because they have different spin, due to the different spin alignment of their component quarks. And since spin is conserved, it’s not possible for one to spontaneously convert to the other. OTOH, I assume these things have tiny mean lifetimes (much less than a picosecond), so they generally wouldn’t have time to inter-convert, even if that were possible. :)

The fact that the Xi_b’- is very close in mass to the sum of its decay products means that the effective binding energy between its component quarks is very low. So it’s not surprising that it hasn’t been discovered before.

See the abstract of the paper on arXiv at Observation of two new Ξ−b baryon resonances

PM 2Ring said:

There’s some more info on this CERN page:

LHCb observes two new baryon particles

[…] the new X_ib particles both contain one beauty (b), one strange (s), and one down (d) quark. Thanks to the heavyweight b quarks, they are more than six times as massive as the proton. But the particles are more than just the sum of their parts: their mass also depends on how they are configured. Each of the quarks has an attribute called “spin”. In the Xi_b’- state, the spins of the two lighter quarks point in the opposite direction to the b quark, whereas in the Xi_b*- state they are aligned.

“Nature was kind and gave us two particles for the price of one,” said Matthew Charles of the CNRS’s LPNHE laboratory at Paris VI University. “The Xi_b’- is very close in mass to the sum of its decay products: if it had been just a little lighter, we wouldn’t have seen it at all using the decay signature that we were looking for.”

[…]

The related Xi_b*0, found by the CMS experiment at CERN in 2012, has a quark content of usb.

These new Xi baryons both contain dsb, so I guess you could call them quark isomers. They are distinguishable because they have different spin, due to the different spin alignment of their component quarks. And since spin is conserved, it’s not possible for one to spontaneously convert to the other. OTOH, I assume these things have tiny mean lifetimes (much less than a picosecond), so they generally wouldn’t have time to inter-convert, even if that were possible. :)

The fact that the Xi_b’- is very close in mass to the sum of its decay products means that the effective binding energy between its component quarks is very low. So it’s not surprising that it hasn’t been discovered before.

See the abstract of the paper on arXiv at Observation of two new Ξ−b baryon resonances

PM, do you concur with his three-to-five per annum estimate? How many elementary particles are known, now?

Then again, I guess baryons are not elementary…

They really should have been called bruceons.

I’ll get me coat

dv said:

PM 2Ring said:

There’s some more info on this CERN page:

LHCb observes two new baryon particles
[…]

PM, do you concur with his three-to-five per annum estimate? How many elementary particles are known, now?

Then again, I guess baryons are not elementary…

I found it a little surprising. OTOH, there are lots of possible 3 quark combinations, and it’s not easy to make those containing the heavier quarks, and hard to prove that you’ve made them due to the tiny mean lifetimes. So I guess it’s really not so surprising that the total number of baryons has been gradually increasing as the collider power and detection technology improves.

Unfortunately, Wiki’s List of baryons doesn’t provide discovery dates. There’s also a Timeline of particle discoveries but it only mentions major milestones, it doesn’t give details for all the hadrons.

have we done the “keep calm and baryon” yet?

No

Dropbear said:

have we done the “keep calm and baryon” yet?

Are they natural or implant big baryons.

That could be a joke, that female scientist sure has a pair of big baryons

If they have such a tiny lifespan would they have any effect on anything?