Slashdot Mirror
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.
WTF! This just bows me away. I know he is small, but how in the world did they manage to fit three Ferengi into a USB!?
Or maybe there are other Quarks out there?
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!
This is a bit of cool and all, but do we really need a /. post for every new particle over which the high-energy people trip?
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!
Tiny little particle; huge godlike pricetag.
Xi_b^* is actually the LaTeX code needed to generate the name of the particle. The particle's name is actually this (png image)
\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.
How does the peer review system come into play with something like this?
How do you do double-blind testing with CERN?
What does this say about the scientific method?
Someone's been looking at my coworker's variable names.
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.
.. before the particle could be identified, a janitor swept it up and dumped it in the dust-bin.
holly shit
unknown is not how I would call it. It has been expected, its description was already there, one knew where to search. if the higgs was discovered, one wouldn't call it unknown since it's in textbooks for a long time already. .... boring... what's interesting is having the entire / a large part of the spectrum.
Furthermore, be honest, another particle found in a spectroscopy study is
Making rumours on this particle is like making rumours on one single CKM-triangle angle. it's boring unless you have the other three and see either consistency or inconsistency.
Therefore, please find the other _sb baryons first and then tell us about the entire story.
PS: html also support superscript and greek letters, so please newspages call it & Xi ; sub b /sub sup *0 /sup
PPS: how do I get html tags through slashdot?
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!"
And where can I get one so I can try these experiments?
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."
So would the next stage of nuclear power after fusion be proton/neutron fission that extracts their binding energy?
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.
Yes its the bottom quark, up and down quark have very little mass, and baryons make of those, get most of the mass, from the
trapped energy of quark motion in the QCD glue (at any one time this will be part QCD potential energy (glue) and part kinetic equation (velocity)), but the bottom quark is quite massive itself around 4.6GeV and gets its mass directly from interacting with the Higg boson. So its the bottom quark that give the Xi_b star most of its mass. Another 150MeV comes from the strange quark which again gets its mass from the Higgs, but the star adds at least 200MeV, and come from the particle have all the quark spins in the same direction, its a chromomagnetic energy, (the spin of the particles making the color equilivent of a magnetic field).
So you are claiming the "mega" prefix is not from SI nor a metric unit?
Gram is a unit of mass. Electron Volts are a unit of energy directly comparable to a Jule.
You must be a product of the American educational system...
I already have just such a baryon!
He He....I wrote I already have such a baryon....if you ask anymore questions I will fart in your general direction!
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.
The gayon...
After all it is composed of up strange bottom quarks... :)
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
Particles of unusual size? I don't think they exist.
AAAAGGGHHHH!
...particular arrangement of quarks...
I see what you did there.