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CERN Physicists discover new particle, Xi-cc++

K

KSweeley

Member
Link: https://www.nytimes.com/2017/07/06/science/cern-quarks-charm-baryon.html

JULY 6, 2017

Physicists have discovered a particle that is doubly charming.

Researchers reported on Thursday that in debris flying out from the collisions of protons at the CERN particle physics laboratory outside Geneva, they had spotted a particle that has long been predicted but not detected until now.

The new particle, awkwardly known as Xi-cc++ (pronounced ka-sigh-see-see-plus-plus), could provide new insight into how tiny, whimsically named particles known as quarks, the building blocks of protons and neutrons, interact with each other.

Protons and neutrons, which account for the bulk of ordinary matter, are made of two types of quarks: up and down. A proton consists of two up quarks and one down quark, while a neutron contains one up quark and two down quarks. These triplets of quarks are known as baryons.

There are also heavier quarks with even quirkier names — strange, charm, top, bottom — and baryons containing permutations of heavier quarks also exist.

An experiment at CERN, within the behemoth Large Hadron Collider, counted more 300 Xi-cc++ baryons, each consisting of two heavy charm quarks and one up quark.

“The existence of these particles has been predicted by the Standard Model,” said Patrick Spradlin, a physicist at the University of Glasgow who led the research. “Their properties have also been predicted.”

The mass of the Xi-cc++ is about 3.8 times that of a proton. The particle is not stable. Dr. Spradlin said the scientists had not yet figured out its lifetime precisely, but it falls apart after somewhere between 50 millionths of a billionth of a second and 1,000 millionths of a billionth of a second.
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S

somecrazymember

Banned
I'm too stupid to really understand all of this but it's fascinating! Could this help connect the dots between normal physics and quantum physics?
 
E

efyu_lemonardo

May I have a cookie?
scientists had not yet figured out its lifetime precisely, but it falls apart after somewhere between 50 millionths of a billionth of a second and 1,000 millionths of a billionth of a second.
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What exactly is the proper definition of a particle if something lasting 10^-14 seconds qualifies?
 
X

Xe4

Banned
Cool! I looked but couldn't find it. Does anyone know the sigma confidence of the discovery?
 
R

Reverend Funk

Comfy Penetration
So is this another one of those man created particles that don't really do anything or does this occur naturally at all?
 
W

WickedLaharl

Member
9f6a8c732bc5df60bb14da9da0dca174c491645f_hq.gif
 
L

Linkstrikesback

Member
Joeku said:
Fuck's sake, scientists.
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Looking at the name of the particle, that's not an actual name, but I think just a list of the properties it is expected to have. There are lots of particles they are currently looking for in accelerators and not much point naming them while they're still hypothetical!

Xi-cc++
Xi - is a greek letter, don't know what it represents in particle physics without checking. edit: from wikipedia: Xi baryons are baryons, (a particle containing three quarks) where they have contain one up or down quark plus two more massive quarks)
cc - double charmed particle (two charmed quarks)
++ electric charge of +2 (a charm quark has a charge of 2e, so of those plus one up quark is a charge equal to two electron charges).

They'll have been using this name specifically because there are lots of hypothetical particles and having the name explicitly be the properties makes it easier for everyone to remember which is which.
 
R

Rodney McKay

Member
efyu_lemonardo said:
What exactly is the proper definition of a particle if something lasting 10^-14 seconds qualifies?
Click to expand...

There are elements on the periodic table that decay in fractions of a second too.

I don't think the amount of time something exists is really related to whether something is, well, SOMETHING or not (element, particle, whatever). These are like particles that may have existed in nature during the Big Bang or might be in black holes or stuff like that.
 
K

KSweeley

Member
Xe4 said:
Cool! I looked but couldn't find it. Does anyone know the sigma confidence of the discovery?
Click to expand...

Over 7 sigma according to this: https://www.newscientist.com/articl...ew-particle-that-could-test-the-strong-force/

A firm discovery

All this extra mass means Xicc++ weighs in at around 3621 megaelectronvolts, four times heavier than the proton. That’s in line with theorists’ expectations, says LHCb member Sheldon Stone at Syracuse University, New York, unlike previous results.

In 2002, the SELEX experiment at US particle accelerator Fermilab found evidence for a similar particle, but with a different mass that puzzled theorists. “It had a very strange mass that looked suspicious,” says Stone. “It would have done chaos to our model of how things are put together. So this is going to be very comforting to the theorists.”

The result announced at the European Physical Society Conference on High Energy Physics in Venice, Italy, has a statistical significance of over 7 sigma – a measure of how confident the researchers are in the find. Traditionally, physicists treat anything over 5 sigma as a firm discovery. The SELEX result only reached 4.8 sigma.

Physicists hope studying the new particle will help them test quantum chromodynamics, the theory of the strong force, which is responsible for holding quarks together in baryons. As the Xicc++ is the first baryon to contain two heavy quarks, it will push the theory in a new direction. “It really tests the theory if you put two of them together with a light quark,” says Stone. “It’s a nice result.”
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T

TyrantII

Member
efyu_lemonardo said:
What exactly is the proper definition of a particle if something lasting 10^-14 seconds qualifies?
Click to expand...

Same as it's always been. You could say the same about super heavy elements that decay and can only he made in labs and supernovae.

Not sure here, but with elements there some evidence of a stable island of suoer heavy elements that we haven't seen yet. Maybe something similar exists in the quantum level.
 
X

Xe4

Banned
KSweeley said:
Over 7 sigma according to this: https://www.newscientist.com/articl...ew-particle-that-could-test-the-strong-force/
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Wow, that's fucking crazy high. For anyone who doesn't know, there's only a 1 in 390,682,215,445 chance this was random noise.

LookAtMeGo said:
I see see.

Pretty neat stuff. So many god damn particles. Where the graviton at?
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lol. The scientist who discovers the graviton can enjoy their nobel prize good and well. It's not happening anytime soon. The level of engineering required to detect a graviton is so far beyond what we have it's insane.
 
E

efyu_lemonardo

May I have a cookie?
Rodney McKay said:
There are elements on the periodic table that decay in fractions of a second too.

I don't think the amount of time something exists is really related to whether something is, well, SOMETHING or not (element, particle, whatever). These are like particles that may have existed in nature during the Big Bang or might be in black holes or stuff like that.
Click to expand...

According to this list nothing on the periodic table comes even close unless you consider highly unstable isotopes which indeed can have much shorter half lifes.

http://www.periodictable.com/Properties/A/HalfLife.v.log.html

https://en.m.wikipedia.org/wiki/List_of_radioactive_isotopes_by_half-life
 
D

danthefan

Member
TyrantII said:
Same as it's always been. You could say the same about super heavy elements that decay and can only he made in labs and supernovae.

Not sure here, but with elements there some evidence of a stable island of suoer heavy elements that we haven't seen yet. Maybe something similar exists in the quantum level.
Click to expand...

Sorry to be a pedant but basically all metals, stable, unstable, natural etc come from supernovae. It's the only way they form.
 
X

Xe4

Banned
efyu_lemonardo said:
According to this list nothing on the periodic table comes even close unless you consider highly unstable isotopes which indeed can have much shorter half lifes.

http://www.periodictable.com/Properties/A/HalfLife.v.log.html

https://en.m.wikipedia.org/wiki/List_of_radioactive_isotopes_by_half-life
Click to expand...

Those are elements though. Unstable particles have very short lifetimes. Something like the Higgs Boson has a mean lifetime of 1.56*10^−22 s. It's pretty common for particle physics to find particles by looking at the decay products rather than the particle itself.
 
E

efyu_lemonardo

May I have a cookie?
Xe4 said:
Those are elements though. Unstable particles have very short lifetimes. Something like the Higgs Boson has a mean lifetime of 1.56*10^−22 s. It's pretty common for particle physics to find particles by looking at the decay products rather than the particle itself.
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Right, but I was responding to a reply claiming there are similarly unstable elements.

Regarding highly unstable particles, this brings me back to my original question: how is a particle defined in the first place?
 
M

Mindlog

Member
Fuck you standard model. So boring, correct and slightly incomplete.
Your day is coming, but you win this round. Again.
 
L

Linkyn

Member
Joeku said:
Fuck's sake, scientists.
Click to expand...

It's not as unwieldy as they make it out to be. Xi is a letter in the greek alphabet (which are frequently used to name families of particles). The cc is because it has two charm quarks, the ++ denotes its electric charge, in this case twice the charge of a proton.

Edit: To give a bit of context, consider eg the particles below (I've highlighted our culprit in red):

rpp377127f02_onlineegk60.jpg


This diagram shows a number of particles that are predicted by the standard model. In this case, they are all baryons, which means that they are made up of 3 quarks (which are smaller, more fundamental particles). Each point represents a type of particle. The particles here are evenly distributed, and each particle represents a distinct quark combination, and thus distinct properties. For instance, electric charge increases from bottom left to top right (denoted by the -, 0, +, or ++ superscripts), whereas the number of charm quarks increases from bottom to top (denoted by the empty, c, cc, or ccc subscripts).

Physicists really like symmetry, because it hints at a well-ordered basic structure of the universe. The neat thing about this is then that it confirms the existence of yet another predicted particle, and thus further serves to cement the standard model.
 
X

Xe4

Banned
efyu_lemonardo said:
Right, but I was responding to a reply claiming there are similarly unstable elements.

Regarding highly unstable particles, this brings me back to my original question: how is a particle defined in the first place?
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Decay products. The collide in an area that allows particle tracks to be mapped. Then they watch what decay products are created. If a particle creates the decay products predicted at the energy theorized, they can confirm that the particle does exist.

It's more complicated than that obviously, but that's the gist of it.
 
R

Rookhelm

Member
"but it falls apart after somewhere between 50 millionths of a billionth of a second and 1,000 millionths of a billionth of a second."




If you say so
 
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