According to Wikipedia, a Journal Club is a group of individuals who meet regularly to critically evaluate recent articles in the scientific literature. Since this is Universe Today if we occasionally stray into critically evaluating each other’s critical evaluations, that’s OK too.
And of course, the first rule of Journal Club is… don’t talk about Journal Club. So, without further ado – today’s journal article is about a new addition to the Standard Model of fundamental particles.
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The good folk at the CERN Large Hadron Collider finished off 2011 with some vague murmurings about the Higgs Boson – which might have been kind-of sort-of discovered in the data already, but due to the degree of statistical noise around it, no-one’s willing to call it really found yet.
Since there is probably a Nobel prize in it – this seems like a good decision. It is likely that a one-way-or-the-other conclusion will be possible around this time next year – either because collisions to be run over 2012 reveal some critical new data, or because someone sifting through the mountain of data already produced will finally nail it.
But in the meantime, they did find something in 2011. There is a confirmed Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at the ATLAS experiment – or, in a nutshell… we hit Bottomonium.
In the lexicon of sub-atomic particle physics, the term Quarkonium is used to describe a particle whose constituents comprise a quark and its own anti-quark. So for example you can have Charmonium (a charm quark and a charm anti-quark) and you can have Bottomonium (a bottom quark and a bottom anti-quark).
The new Chi b (3P) particle has been reported as a boson – which is technically correct, since it has integer spin, while fermions (hadrons and leptons) have half spins. But it’s not an elementary boson like photons, gluons or the (theoretical) Higgs – it’s a composite boson composed of quarks. So, it is perhaps less confusing to consider it a meson (which is a bosonic hadron). Like other mesons, Chi b (3P) is a hadron that would not be commonly found in nature. It just appears briefly in particle accelerator collisions before it decays.
So comments? Has the significance of this new finding been muted because the discoverers thought it would just prompt a lot of bottom jokes? Is Chi_b (3P) the ‘Claytons Higgs’ (the boson you have when you’re not having a Higgs?). Want to suggest an article for the next edition of Journal Club?
Otherwise, have a great 2012.
The ATLAS collaboration Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at the ATLAS experiment.
8 Replies to “Journal Club – This new Chi b (3P) thingy”
This new called ?_b (3P) occurs from radiative transitions of Y(1S) to Y(2S), where the Y is meant to mean “upsilon.” This particle is a quantum level of bottomonium, a quarkonium state composed of the b and anti-b quarks. This is the latest in a spectrum of such particles discovered, starting with the J/? meson c plus anti c quark meson found in 1974. This may be the most massive of the quarkonium states which may exist, for a t plus anti-top quark bound state (toponium) may not form due to the very short lifetime of the top quark. In technicolor theories the Higgs particle is a composite, and the T-T-bar system or toponium is a candidate for that. However, making this work is infernally difficult.
Is this the Higgs particle? It could be, or it could be related to it. There is a common structure. The electron-positron system is a form of hydrogen atom, which has an SO(4) symmetry of states. What is interesting is that this a euclideanized from of the Lorentz symmetry of spacetime SO(3,1). The potential for the hydrogen or e-e^+ “hydronium” is 1/r, while for a quark-antiquark system it is r^2. Hence the energy levels change, but their symmetry is preserved. It is worth noting that a meson with two quarks can be spun up, say by absorbing a photon, which results in a ladder of quantum states. The Higgs particle may have some correspondence to this by this relationship to spacetime physics. There is an isomorphism between the symmetries of and anti-de Sitter (AdS) spacetime and a conformal field theory on the boundary. So a five dimensional AdS has a four dimensional spacetime boundary, which has symmetries SO(3,1). The conformal field theory on the boundary is SU(4). This is a form of QCD, or gives QCD in the decomposition to SU(3)xU(1), and certain quarkonium states with SO(4) symmetry. If the occurrence of mass is involved with spacetime physics, there may then be some connection between this quarkonium state, the symmetries of spacetime and the Higgs field.
This is somewhat speculative, but given the low signal in the Higgs search so far it could be that what has been attributed to a scalar field, or the Higgs field, turns out to be more subtle than previously thought.
Surprised to hear the Higgs might be a composite particle (conflicts with its Wikipedia write-up). Wouldn’t that mean it could have mass itself – then leading to the question of what gives the Higgs its mass?
The Wikipedia article is focused on the standard Higgs. I don’t see that they claim it can’t be a composite, here in technicolor theories as suggested by lcrowell.
Sure, a composite bounded particle would get a mass from the interaction that binds it. However, in the standard model I understand it that three of the four different Higgs particles gets their mass from the interactions they have with other particles, bootstrapping the mass of themselves and W & Z particles into existence, while the fourth Higgs (“the” Higgs) gets it mass from spontaneous symmetry breaking of its vacuum expectation value.
The other particles gets their mass from Higgs via different mechanisms, depending on if they are matter particles or if they are force particles.
It’s a massive mess, but if anyone should guide us through it, I think Tanedo does a great job in his posts. And let’s face it, those particles of his are cute. You can’t touch that!
There are technicolor theories, first introduced in 1973 by Jackiw and Johnson, and then advanced into the extended form by Dimopolous and Susskind in 1979. The idea is that QCD at low energy is “self-breaking,” where condensates of quark-antiquark pairs which have an expectation value , which at the low energy symmetry breaking defines a mass. The condensate exhibits a breaking in a manner analogous to the Cooper pairing of electrons in superconductivity, which breaks the U(1) symmetry of QED.
I have not been a major upholder of this idea. The theory is infernally difficult to work with, for this “self-breaking” runs into what might be called a bootstrap problem: You are breaking QCD with a condensate of quarks and QCD which defines the breaking scale according to itself or its own amplitudes. However, of late prospects along these lines have become more plausible with the weak signal and data from the LHC on the Higgs particle. It was only a few years ago that finding the Higgs particle with the LHC was a “slam dunk,” where now we are being told the secondaries from the Higgs particle, W’s Z’s and photons, form a difficult signal and so forth
This bootstrap problem might be avoided if the condensate has some connection to spacetime physics. The universe may be the boundary of an anti-de Sitter spacetme, and where the symmetries of this spacetime is equivalent to a conformal field on that boundary. The physics of QCD may correspond to the symmetries of this spacetime, where the structure of the AdS and the dualism with QCD may provide the added information required to make this technicolor theory work. This is similar to the physics of using AdS ~ CFT physics to understand high temperature superconductivity with heavy metal composite materials.
Well, a Claytons reference does kinda open the door.
Previously the Bottom Quark was called the Beauty Quark.
So under that naming system, Bottomonium would have been comprised of a Beauty Quark and an Anti-Beauty or Ugly Quark.
As usual with Claytons, there is no upper limit you can drink before an Ugly Quark will start to look reasonable.
You know, it’s New Year’s morn – I already have a headache.
Liquour never gave me a headache like particle physics does. At least I understand Wild Turkey.
Happy New Year everyone, and I hope very much the new year will be as exciting for the science done as this past year was.
Boson my bottom, chi b. Bosonbottomonium.
Is astronomy without a telescope dead or you have 2 franchises? :d
I guess before things get better we’ll have to hit rock Bottomonium? Reading some of your posts are impressive and I admit to being a lightweight this arena.. Looks like I will have to tap-out… Happy Journal Clubbing…
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