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New Particle Discovered At CERN
New submitter ph4cr writes with news that a new particle has been discovered at CERN that confirms theoretical predictions. A pre-print of the academic paper is available at the arXiv (PDF). From the article:
"Physicists from the University of Zurich have discovered a previously unknown particle composed of three quarks in the Large Hadron Collider (LHC) particle accelerator. A new baryon could thus be detected for the first time at the LHC. The baryon known as Xi_b^* confirms fundamental assumptions of physics regarding the binding of quarks. ... In the course of proton collisions in the LHC at CERN, physicists Claude Amsler, Vincenzo Chiochia and Ernest Aguiló from the University of Zurich's Physics Institute managed to detect a baryon with one light and two heavy quarks. The particle Xi_b^* comprises one 'up,' one 'strange' and one 'bottom' quark (usb), is electrically neutral and has a spin of 3/2 (1.5). Its mass is comparable to that of a lithium atom. The new discovery means that two of the three baryons predicted in the usb composition by theory have now been observed."
Are all particles named so oddly?
Bring on the explanation for the lazy, science geeks.
I'm only just now using devices ready for usb 3.0, and here comes another one.
Don't disappoint your bird dog. Go to the range.
I just wish they had named it something pronounceable. "Chi b to the asterix" just doesn't flow off the tongue too well.. :)
-- Don't call me "Sir," I increase entropy for a living!
I don't understand much about particle physics, but perhaps someone could give a quick explanation of how a particle made of three quarks has a mass equivalent to an entire atom of atomic number 3 and atomic weight almost 7? Is it because a bottom quark is one of its constituents?
I can't claim to understand much about particle physics, but I would guess that this particular arrangement of quarks has a bigger interaction with the Higgs field, thus making it more massive.
Protons and neutrons are composed of strictly up and down quarks, in (uud) and (udd) combinations for protons and neutrons respectively. Up quarks weigh about 2.5 MeV and down quarks weigh about 5.0 MeV. A strange quark weighs about 100 MeV, and a bottom Quark weighs (very) roughly 4.2 GeV. It's because of the bottom quark that Xi_b^* weighs so much.
Source: http://pdglive.lbl.gov/Rsummary.brl?nodein=Q123
http://pdglive.lbl.gov/Rsummary.brl?nodein=Q005
It's pronounced "chi b star" and the discovery was by the CMS collaboration. The analysis was done by physicists from Zurich (apparently including one of my former postdocs) but they require data generated by the experiment so typically we credit the experiment. The discovery is of a new bound state of 3-quarks - not a new fundamental particle - so while interesting and definitely worthwhile it is not particularly exciting.
I find it funny that TFS talks about a Xi_b^* baryon with usb quarks, and goes on about its spin, as if it was common knowlegde, but has to precise that 3/2 is 1.5.
... and has a spin of 3/2 (1.5). ...
I don't know about the rest of the summary, but I can confirm that 3/2 is in fact 1.5.
Firstly, remember that mass != weight. Mass is all to do with energy (as in e=mc^2), and bottom quarks have lots of energy - just over 4GeV compared to the ~2.5MeV (up) and ~5MeV (down) of the quarks that protons and neutrons consist of.
UNIX? They're not even circumcised! Savages!
https://en.wikipedia.org/wiki/Quark_(TV_series)
yes, there are other quarks!
soylentnews.org Go there to enjoy the people!
Xi_b^* is actually the LaTeX code needed to generate the name of the particle. The particle's name is actually this (png image)
Indeed, without having that massive boondoggle at CERN we could have funded at least 1 more month of the Iraq war!
\Xi_b^*0 is part LaTeX for greek capital xi which gives the particle a Unicode identity of subscript b superscript * 0 - \Xi_b^{*0} ;)
It gets even more amusing when you consider that a proton has a mass of about 938MeV/c , whereas the three quarks it is made up doesn't even add up to 10MeV/c. The binding energy of protons and neutrons is immense compared to the particles they are composed of.
I know this is slightly in jest, but this paper is not the sum-total of all of the work at the LHC.
There are 6 projects, each with hundreds of scientists, all of whom are juggling many papers at once. This Xi stuff is completely independent from Higgs searches, and it is one of many particles already discovered or confirmed at the LHC. So this isn't a Higgs-worthy discovery, although I think it is pumped-up a bit because CERN has really good press, and it looks good that the LHC is finding new physics.
Otherwise, this would just be a normal story. New Baryons or Mesons (like this one) are found a few times a year.
Someone's been looking at my coworker's variable names.
There aren't that many of them.
It's news for nerds, and whatever kind of stuff it is, baryons comprise matter.
So you think particle detectors are susceptible to the placebo effect?
What a fool believes, he sees, no wise man has the power to reason away.
I just want to provide a little context to this announcement. As shown in the article, this is a Baryon, made up of 3 quarks. With 6 possible types of quarks, and 3 spots, this makes for many possible combinations of Baryons, a lot that have been found. Here is a current list of baryons:
PDG Baryon List
The proton and neutron are the p and n in the top left. The new Cascade (Xi_b) will be in the bottom right, in the "Bottom quark" section.
So this is neat and all, but hyped up a bit because its the LHC. A couple of these new Baryon (and also Mesons) are confirmed every year.
It's worth noting that the composite particle's masses are generally due primarily to the massless gluons who's immense energy contributes to the bound particle
Proton (uud): ~10MeV/c^2 in quarks , 938MeV total
Neutron (udd): ~12.5MeV in quarks, 940MeV total
Xi_b^* (usb): ~4293MeV in quarks, ~6517MeV total (7amu * 931 MeV/amu)
So not only is Xi_b^* composed of much higher mass quarks, but it would appear to have roughly twice the binding energy as well.
But why mention mass != weight? In a uniform gravitational field mass and weight are directly proportional to each other and can be used interchangeably using the gravitational acceleration as the conversion factor. The distinction is only relevant if you're either
1) operating within a non-constant gravitational field (i.e. in space) or comparing weights of different planets
or
2) You've discovered the first matter ever detected with different gravitational mass and inertial mass
Since (1) doesn't apply, and (2) almost certainly doesn't the distinction seems irrelevant
--- Most topics have many sides worth arguing, allow me to take one opposite you.
You're asking a couple distinct, and reasonable, questions. About "blind testing" -- I don't know the details for this particular result, but particle physicists put quite a bit of effort into making sure that they aren't fooling themselves. One of the best ways of doing it is so-called "blind analysis". The idea there is to define your entire data analysis strategy based solely on simulated data. There are pretty good simulations available of both the expected backgrounds, and of the process you are trying to actually find (the signal). So you define all of the methods you are going to use using these simulations before you look at the data. This ensures that you don't bias yourself into "finding something" in the data that isn't really there. (I don't know if a strict blinding procedure was used for this analysis, but likely something similar was done.)
The formal peer review system will come into effect now that the result is submitted to a journal. The paper will be distributed to some anonymous referees who will try to judge the merits of the physics and decide whether it merits publication. But I should note that the peer review process in modern particle physics actually starts long before the result is made public. Although there are only 3 or 4 main analysts, the paper is signed by the entire 3000 person CMS Collaboration (of which I am a member). So we have a very stringent internal review process to ensure that the result is sound before we release it with 3000 names taking responsibility. That doesn't mean that particle physics collaborations never make mistakes, but it does mean that results are scrutinized by a number of more or less unbiased eyes before they are made public.
I know this is slightly in jest, but this paper is not the sum-total of all of the work at the LHC.
There are 6 projects, each with hundreds of scientists, all of whom are juggling many papers at once. This Xi stuff is completely independent from Higgs searches, and it is one of many particles already discovered or confirmed at the LHC. So this isn't a Higgs-worthy discovery, although I think it is pumped-up a bit because CERN has really good press, and it looks good that the LHC is finding new physics.
Otherwise, this would just be a normal story. New Baryons or Mesons (like this one) are found a few times a year.
I know this is slightly in jest, but this paper is not the sum-total of all of the work at the LHC.
There are 6 projects, each with hundreds of scientists, all of whom are juggling many papers at once. This Xi stuff is completely independent from Higgs searches, and it is one of many particles already discovered or confirmed at the LHC. So this isn't a Higgs-worthy discovery, although I think it is pumped-up a bit because CERN has really good press, and it looks good that the LHC is finding new physics.
Otherwise, this would just be a normal story. New Baryons or Mesons (like this one) are found a few times a year.
It's interesting that it's yet another confirmation of the standard model. Calling it "new physics" is probably a little bit of an overstatement, since everybody expected that this particle was one of the ones that they would be able to prove out. It's a new and confirming result. I would go so far as to say something is "new physics" if it was weird enough to call the standard model into doubt, or if a neutrino really did travel faster than the speed of light, or if it looked like confirmation of a new theory.
As for the fact that it employs hundreds of scientists, that's really irrelevant. Since when do we do science as a jobs program for the very smart?
Science is for two things:
This is an example of the former.
Additionally, if the results are real, they can be replicated. LHC collides particles not only in the heart of the CMS detector, but there is also (among others) the ATLAS detector. This detector has more or less the same goals as CMS, but is built and operated by different people using a different detector design (both on the level of individual electronic chips and sensors, and on overall design choices), as well as different and mostly independently written software.
So I guess someone with access to ATLAS data should now write up the analysis and see if they can find it too.
--- Physicist who did his master thesis with sensors for ATLAS tracker, now doing a PhD on accelerator cavities for the CLIC future high-energy electron-positron collider.
And that only cost a $1-2 Trillion and about 150,000 to 600,00 lives. How long would it have taken Saddam and his psychopathic sons to kill that many people?
I'll have to change my online banking password now...
"Wait. Something's happening. It's opening up! My God, it's full of apricots!"
The "hundreds of scientists" bit wasn't an argument for the LHC producing jobs, but just that there are hundreds of scientists each working on several papers that are all producing interesting results. So the fact that we see "New particle at LHC" articles everywhere after several months of running is misleading, as several LHC-related papers are put on the arxiv each week.
And where can I get one so I can try these experiments?
Additionally, if the results are real, they can be replicated."
Replicated, definitely. That is what I used to live for.
The use of a rapidly depreciating, OK, OK, I'll use the current popular term, deprecating, LaTex phraseology is most irritating. Name it properly. Just look up _why_ the little wigglies are named Quarks in the first place. Early Physicists actually had a sense of humor. And they drank beer. And one even put a glass of beer in a particle beam to observe the formation of bubbles. At CERN.
Name the God-Damned thing, (See origin of the name God Particle), Ghiorsoroni. He deserves at least that much.
In fact this particle is pretty massive already, as TFA notes (around the mass of a lithium atom). So presumably a Xi_b^obelix would mass as much as a menhir.
From scarped cliff or quarried stone she cries "A thousand types are gone, I care for nothing, no not one."
Whenever new particles are discovered I always think of this comment regarding the Muon
Plan My Week for iPhone
bah humbug g'me an event horizon to bewonderlment at
Meh. They could make it spin twice as fast just by using usb2.
It's not so much the binding energy as the number of gluons in the proton that give it its mass. Binding energy would *decrease* the mass of the proton.
PS I can't believe "gluons" isn't in the Firefox spelling dictionary.
Expected time to finish is 1 hour and 60 minutes.
It's not just about curiosity. Even thought a discovery might not have practical uses today, it might in the future.
Clever signature text goes here.
The gayon...
After all it is composed of up strange bottom quarks... :)
right, because the people that dies fighting in a war always do it voluntarily/consentfully ????
Perhaps a better explanation is to say that a proton consists of dozens of quarks and gluons of various flavour, colour, and anti-ness, however it has an excess of two more up quark than up antiquarks, and one more down quark than down antiquarks. The evidence for this is that when the LHC collides protons, the vast majority of observed interactions are gluon-gluon, or low energy quarks (as evinced by the energy of the products).
For more info see http://profmattstrassler.com/articles-and-posts/largehadroncolliderfaq/whats-a-proton-anyway/ plus followup articles
It's turtles all the way down.
So long, and thanks for all the Phish
I want one!
Yes! Protons and Neutrons are straight up & down particles - not like the ones that are strange or have charm... :-)
..." two of the three baryons predicted in the usb composition by theory have now been discovered."
Does this mean that CERN is usb compatible?
Defining Statistics and Social Research
It's not just about curiosity. Even thought a discovery might not have practical uses today, it might in the future.
If there's no specific intent to use the information, it's basic research and we really do that to satisfy our curiosity. In particle physics, we are probably far past the point where there's any reasonable expectation that the results of the experiments will have any practical application.
...particular arrangement of quarks...
I see what you did there.