Arthur T Knackerbracket has processed the following story:
There’s a newfound mismatch between matter and antimatter. And that could bring physicists one step closer to understanding how everything in the universe came to be.
For the most part, particles and their oppositely charged antiparticles are like perfect mirror images of one another. But some particles disobey this symmetry, a phenomenon known as charge-parity, or CP, violation. Now, researchers at the Large Hadron Collider near Geneva have spotted CP violation in a class of particles called baryons, where it’s never been confirmed before.
Baryons are particles that contain three smaller particles called quarks. The most famous examples of baryons are protons and neutrons. Previously, scientists had seen CP violation only in mesons, which are particles containing one quark and one antiquark.
For the new study, researchers with the LHCb collaboration studied particles called lambda-b baryons. The scientists looked at a decay of a lambda-b baryon into a proton and three lesser-known particles: a kaon and two pions. The rate of this decay is slightly different than that of its antimatter counterpart, the team found. This difference indicates CP violation, the researchers report in a paper submitted March 21 to arXiv.org and in a March 25 talk at the Rencontres de Moriond meeting in La Thuile, Italy.
Building on previous hints of CP violation in baryons, the study is the first to cross the statistical threshold for a discovery, known as five sigma.
A better understanding of CP violation could help explain how matter came to dominate over antimatter. In the Big Bang, matter and antimatter were made in equal measure. CP violation is thought to have given matter the upper hand. But known processes don’t violate CP enough to account for the matter-antimatter imbalance. The new study doesn’t solve that quandary, but it’s a step in the right direction.
(Score: 5, Interesting) by number6x on Friday April 11, @01:48PM (11 children)
This is great! CERN is just re-starting it's accelerator and has tested both beams at 6.8TeV earlier this morning. (Getting flooded by progress alerts).
Hopefully we can get more data and tweak the standard model. It's the most accurate scientific model ever developed, but nothing says we can't make it even better.
(Score: 3, Insightful) by JoeMerchant on Friday April 11, @03:38PM (9 children)
More matter-antimatter asymmetry is reassuring...
What I'm wondering is: what's the explanation for so much bayronic matter - it just seems... odd, that the universe is comprised of quarks at that level, and so much of what we interact with is baryons - the quarks are so stable as baryons, and yet they seem to fit in such a specific limited puzzle piece fashion.
Where are all the "heavy baryons" comprised of more quarks?
Where are all the free quarks?
What happens when you bombard a brick wall with free quarks?
Atoms have all these weird isotopes and things, where are the heavy protons?
🌻🌻🌻 [google.com]
(Score: 2) by Tork on Friday April 11, @04:44PM
Oh... he franchised his bar, no more free Quark's.
🏳️🌈 Proud Ally 🏳️🌈
(Score: 3, Informative) by pTamok on Friday April 11, @04:54PM (7 children)
Quarks interact with each other via the exchange of gluons, which are the force carrier for the strong nuclear force. Gluons have a property known as 'colour charge' which means their interactions have unusual properties: the quark-quark interaction resembles them being attached to each other by a nearly inextensible piece of string. If you supply energy to the quarks to make them move apart the 'string' eventually 'snaps', releasing enough energy to create a quark at the 'free end'. This means that at temperatures below a certain very high average energy, you cannot have 'free' quarks: they are always associated with at least one other.
https://en.wikipedia.org/wiki/Gluon [wikipedia.org]
https://en.wikipedia.org/wiki/Color_confinement [wikipedia.org]
(Score: 2) by JoeMerchant on Friday April 11, @06:47PM (6 children)
And that's just weird, when a proton finally is split into three quarks (by a very hot collision) - do those same three quarks always get back together? Aren't any ever just roaming around in search of a partner? This:
"attempts to isolate them would only lead to the creation of new quark-antiquark pairs, effectively preventing a single quark from existing freely."
Sounds like utter rubbish to me... created a new quark-antiquark pair from what? Do they suck the energy out of the surrounding space to do that? If we make enough heat why doesn't it instantly collapse into a bunch of new quark-antiquark pairs?
🌻🌻🌻 [google.com]
(Score: 3, Interesting) by pTamok on Friday April 11, @08:19PM
If you put in enough energy to 'snap the string', that's enough to create an entirely new quark at each 'free end' of the 'snapped string'.
With photons, gamma rays have enough energy to be converted into an electron/anti-electron (positron) pair.
https://en.wikipedia.org/wiki/Pair_production [wikipedia.org]
Quantum electrodynamics (QED) (and subsequent quantum chromodynamics) is seriously weird, and your instincts formed from interactions with the 'classical world' are entirely misleading. I recommend reading Richard Feynman's book on QED: QED: The Strange Theory of Light and Matter [wikipedia.org], which he wrote for the 'interested layman'.
A copy is available online at the Internet Archive https://archive.org/download/richard-feynman-pdf-library/Feynman%2C%20Richard%20%2837%20books%29/QED/Feynman%2C%20Richard%20-%20QED%20%28Princeton%2C%202006%29.pdf [archive.org]
Your instincts might rebel: but we have no better description of the universe. This does not mean it is without fault: the 'Standard Model [wikipedia.org]' gets some predictions disastrously wrong, but it gets others extremely accurate (and precise). This tells us that we need new, more accurate descriptions, but we don't know what they look like, yet.
(Score: 2, Interesting) by pTamok on Friday April 11, @08:49PM (4 children)
A proton isn't 'split into three quarks'. A proton is three quarks. It is a bit like a pointillist painting of a still life: from a distance, it looks like a bowl of fruit, but close up, all you see are dots of colour. At a distance, the three quarks look like a proton, but close up, it is 'just' three quarks. The painting looks like a banana, but close up, it is 'just' yellow dots.
The quarks behave as though they are held together by floppy strings that pretty much cannot be stretched. If you put a lot of energy into the string, at the point at which it breaks, you have added enough energy to the system to create two entirely new quarks at the 'free ends' of the string. The 'breaking of the string' and creation of the quarks is all part of the same process.
At a high enough energy, with particles zipping around like crazy, the energy density of the gluons being exchanged between the quarks is the same as the energy density of the string when it breaks/creates new quarks, so you get a quark/gluon 'soup' where the individual quarks are in an environment that is equivalent to being at the end of a breaking string all the time. At this point you can say the quarks are 'free', but only because the environment they are 'free' in is the same as a breaking string.
In much the same way that gama rays (high energy photons) can produce electron-positron pairs, high energy gluons can produce quark-antiquark pairs: this theoretical paper goes into an analytical treatment of the fusion of two gluons generating a quark pair.
Two-loop leading colour QCD helicity amplitudes for top quark pair production in the gluon fusion channel [springer.com]
If you open it up, you'll see lots of Feynman diagrams (read his QED for laymen) - you are not expected to understand it, but the point is that gluons (at high enough energies) and quark pairs are, in a way, equivalent.
In a way, asking to have a 'free quark' is a bit like asking for a piece of string with only one end.
(Score: 2) by JoeMerchant on Friday April 11, @09:16PM (1 child)
>The 'breaking of the string' and creation of the quarks is all part of the same process.
That actually makes some sense...
>asking to have a 'free quark' is a bit like asking for a piece of string with only one end.
Which I now lay at the feet of every author who ever described a quark as a particle.
🌻🌻🌻 [google.com]
(Score: 1) by khallow on Friday April 11, @10:20PM
It will no doubt comfort you greatly to know that when physicists bombard quark-based baryons like protons and neutrons with high energy photons, the internal quarks act as point-like objects. Photons interact with quarks because those are charged (+/- 1/3 or +/- 2/3), but not gluons which have zero charge. So the authors are covered.
(Score: 0) by Anonymous Coward on Saturday April 12, @12:20AM (1 child)
At a quark level what is adding more energy to the string/system though? What is actually happening?
e.g. some high energy particle goes to location X and Y happens...
(Score: 1) by khallow on Saturday April 12, @07:40AM
(Score: 1) by khallow on Saturday April 12, @07:38AM
It covers neither relativity (no gravity) or high energy (including more complex Feynman diagrams - the number increases superexponentially). Nor quantifies decay rate of free neutrons versus neutrons captured in atomic nuclei (multi-particle models involving quark dynamics). But of course, nothing I wrote says you can't improve what has considerable room for improvement so agree on that last bit.