Talk:Neutral particle oscillation

Which particles?

A list of those neutral particles for which this phenomenon can occur would be nice. Or is it possible for all of them? According to this article and my knowledge, it's possible for neutral kaons, B mesons and neutrinos. But what about neutrons, for example? --129.70.15.51 (talk) 22:10, 7 June 2010 (UTC)

Neutron anti-neutron oscillations would violate baryon number conservation. If observed, it would be evidence of physics beyond the Standard model. See for instance: http://arxiv.org/abs/0910.1877 --Tim314 (talk) 20:09, 3 July 2011 (UTC)

Improvement of the page

I plan to include the following as I go about improving the page:

• Rabi Oscillations as a general property of any oscillatory two state system
• Inferences about suitable length scales for the system from the above
• Flavor oscillations of neutral particles
• Types of CP violation in neutral Kaon systems as a consequence of oscillation
• Discuss about the symmetries in two state systems and their corresponding commutator relations
• A very brief discussion on generalization to three state systems and how the CKM/PMNS matrices arise as a result

I'll be editing this page over the span of a month or so. You might find certain incomplete or unexplained sections occasionally. So please bear with me till I complete editing.
Any query, suggestion or constructive criticism will be extremely appreciated.

— Soham92 (talk) 16:11, 16 October 2014 (UTC)

I read through the article. Very nice work! Compared to the March version of this article, a huge improvement. The mathematical modeling sections are pretty clear and the notation well-explained. Stepping back from the details, I think what this article could use now is some introductory explanation, motivation and impact near the start of the article. Why should a reader care about neutral particle oscillations? Are they useful or important scientifically? What is the history of these--how were they discovered? What impact does this theory have on our understanding of the world? Ideally it would be good to give a qualitative explanation of the phenomenon, say at the level of Scientific American, that someone without detailed knowledge of the mathematics of quantum mechanics could grasp. Talking about neutral oscillations in the context of the the solar neutrino problem or CP violation in kaons, for instance, would help indicate the importance of these oscillations. --Mark viking (talk) 20:05, 13 November 2014 (UTC)

Thank you. I'll include something about the motivation and history behind the study of neutral kaon and neutrino oscillation in a couple of weeks (since I'm a bit busy at the moment), and that'll include a qualitative description. Cheers!

— Soham92 (talk) 22:35, 13 November 2014 (UTC)

A simple-minded thought

Being interested but unable to follow the maths, I wonder how a particle with a given mass can oscillate into a different particle with a different mass. In a decay, spare mass is radiated away as some form of energy, but in an oscillation it has to hang around until it is needed again. Where does it go? — Cheers, Steelpillow (Talk) 20:38, 13 November 2014 (UTC)

That is a good question. It prompted me to add a couple of lines to the introduction to explicitly mention this subtle point. Please take a look.

In quantum mechanics, particles are described by wave functions (or state vectors). The wave function that propagates (i.e. evolves in time) is a linear combination of the energy (mass) eigenfunctions. On performing a measurement (detection) on the wave function, we obtain the energy (mass) corresponding to a particular eigenfunction, and that corresponds to a particle of that mass.

Simply put, particles A and B travel as a mixed state which on detection may yield particle A or particle B with probabilities P(A) and P(B) respectively. It is this probability that oscillates as a function of distance traveled by the mixed state.

— Soham92 (talk) 22:26, 13 November 2014 (UTC)

Thanks, that helps - a little. I am now puzzled how two different particles with different mass/energies can be alternative creations of the same energy-conserving event. Do they travel at different velocities, for example? — Cheers, Steelpillow (Talk) 22:42, 13 November 2014 (UTC)

Well, view it this way: A large number of parcels (each starting with a red ball in it) traveling at a constant velocity pass through a series of equidistant checkpoints. At each checkpoint 5 random parcels are opened (without altering the velocity of the parcels) and their balls replaced by balls of another other colour (say, blue; i.e. if the ball is red, it is replaced by a blue ball, and vice versa). Now, you are at the (n+1)^th checkpoint and want to open a certain number (say, N) of the parcels and inspect their contents. The fraction (out of N) of times (and hence the probability) you'll get a blue or a red ball then will obviously depend on the number of checkpoints the parcels have passed through before reaching you (and in this case that number is n). Instead of the (n+1)^th checkpoint, if you're at the (n+m+1)^th checkpoint, the probability of obtaining a ball of a particular colour will no longer be the same as at the (n+1)^th. Hence, the fraction (and hence the probability) is a function of the number of checkpoints the parcels have crossed.

The analogies are:

• parcel → wave function (or mixed state). The parcel travels with a fixed velocity. It is meaningless to talk about the colour of a ball before opening it. Similarly, the concept of a 'particle' makes sense only when you detect (perform a measurement on) the wave function. The rest of the time it is a wave (wave-particle duality). The Copenhagen interpretation of quantum mechanics says that the parcel is a 'linear superposition' of the two types of balls.
• velocity (and hence energy) of the parcel → velocity (group velocity) with which the wave function propagates. The colours of the balls do not affect the velocity of the parcel. Similarly, the difference in the masses of the two particles does not affect the velocity of the wave function.
• number of checkpoints the parcels have passed through → distance propagated by the wave function before detection.
• opening a parcel → intercepting the wave function with a detector.
• obtaining a red or a blue ball → detecting one of the two particles in the detector.

In short, before you detect, you cannot even talk about a 'particle'. And hence you don't have to bother about the energies (or masses) of the individual components (just as you aren't concerned about the colour of the ball until you actually open the parcel and check it). The concept of a 'particle' manifests itself only on detection.

— Soham92 (talk) 00:06, 14 November 2014 (UTC)

First of all, thank you for taking the time to reply to my ignorance. I believe I grasp the oscillation bit as such. But my understanding is also that say neutrinos were originally formulated to carry a specific energy say e, that was being lost in certain decays. OK what is in the parcel is undefined until we open it, but surely we must know that, whatever it is, it has the same energy that went missing in the decay that produced it? if we have red and blue neutrinos/eigenvectors of differing masses, and which travelled in a given parcel at a given velocity, then to my naive view they must have different net energies (mc^2 + half mv^2). And one of those will not match the amount lost from the original decay. Eigenvectors and Copenhagen admonitions are all very well, but they do not allow us to break the law of conservation of energy. Heisenberg uncertainty gives us a little wiggle room, is that relevant here? For my sins, I cannot even recall what is complementary to energy. — Cheers, Steelpillow (Talk) 09:33, 14 November 2014 (UTC)

That's not an issue at all. It's fun to explain. Cheers!

That's a very dangerous remark to make to someone like me — Cheers, Steelpillow (Talk) 18:32, 14 November 2014 (UTC)

Indeed it is the uncertainty principle! It is the spread in the energy that allows room for a difference in the masses. In fact, all that we are able to measure from neutrino oscillation experiments is the difference in the squares of the masses (neutrino mass splitting). Neutrinos are produced as flavor eigenstates. That means, they're produced as a superposition of the mass eigenstates. This gives them a spread in the mass which results in the phenomenon of oscillation.

— Soham92 (talk) 14:03, 14 November 2014 (UTC)

P.S. Time is complementary to energy.

That's a brilliant explanation, thank you! Can I suggest it should go in the article, somewhere near the top? — Cheers, Steelpillow (Talk) 18:32, 14 November 2014 (UTC)

It's great to know that I could explain it to you! And thanks for the question and the suggestion. In a couple of weeks or so I'll include a section where one will be able to get the gist of the matter without going through the mathematics.

— Soham92 (talk) 19:40, 14 November 2014 (UTC)

A question about history and credit

The first neutral particle oscillations seen were in K0-K0bar. Why is this given less historical importance in this page than the neutrino oscillations? After all, the effect was not known before the kaon puzzle. It is usually cited as the discovery experiment. The neutrino experiments are less important (in this context), since the discovery of the solar neutrino puzzle was immediately hypotesized to be due to flavour oscillations. In fact, the Nobel citation for Ray Davis reads "for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos". Particle oscillations was so well-established by then that it was not mentioned even in the Nobel press release; for example B0-B0bar oscillations (which are not mentioned) had already been seen earlier. — Preceding unsigned comment added by 158.144.51.19 (talk) 08:43, 27 November 2014 (UTC)

The section 'Neutral Kaon oscillation' deals with the phenomenon. The usual K0-K0bar oscillation is just using the results of the mathematical section in the article and putting some numbers in them. What I really wanted to show was that CP violation is a direct consequence of the phenomenon. Secondly, the fact the solution to the solar neutrino problem is basically the fact that neutrinos have mass - thereby making oscillation possible in the first place. Particle oscillation was well established. True. But that neutrinos can be studied using that model was shown by Pontecorvo.

— Soham92 (talk) 19:09, 27 November 2014 (UTC)

I still think the history section sounds biased. The history starts with K0-K0bar oscillations (1950s), then comes the discovery of B0-B0bar oscillations (1980s), and then the discovery of neutrino oscillations (1990s). This is not the impression you get from the page. I think it needs editing. — Preceding unsigned comment added by 158.144.51.19 (talk) 12:45, 1 December 2014 (UTC)

I've made some changes. I think that should satisfy you. Cheers!

— Soham92 (talk) 19:09, 27 November 2014 (UTC)

Some notes...

@Soham92: I interact on the physics side of things rarely, and in general I find the greater collection of physics articles to be of poor quality. They are generally written using lots of jargon that isn't explained. Math articles are even worse, but that's little consolation. So with that in mind, I started reading this, and right off the bat:

"In particle physics, neutral particle oscillation is the transmutation of a particle with zero electric charge into another neutral particle due to a change of a non-zero internal quantum number via an interaction that does not conserve that quantum number."

Generally the lede should be written so anyone can read it and get a basic idea of what the article is about. This is a good example of a statement that cannot be understood unless you're already familiar with the topic. For instance, what is this "internal quantum number"? Why do I need to know that now? What does and does not conserve it? What is the difference between zero electric charge and neutral (note the way it's worded suggests they are not the same thing)? Here's a possible example of the same basic statement written in more general language...

"In particle physics, neutral particle oscillation refers to a number of possible quantum mechanical effects that convert one type of electrically neutral particle into another."

That really does capture the essence of the topic, no? Everything else in the lede, unless I'm mistaken, is a variation on that statement. For instance, "change of a non-zero internal quantum number" seems like a given, because that's the definition of "type" in this case - unless I'm missing what you're saying here. And then you add "For example, a neutron cannot transmute into an antineutron as that would violate the conservation of baryon number." but this is not an example, it's an example of something that doesn't happen, which just confuses things. So perhaps this is a clearer version with the same basic information and a concrete example:

"In particle physics, neutral particle oscillation refers to a number of possible (actions|events|hmmm???) that convert one type of electrically neutral particle into another. Perhaps the best known example is the oscillation from electron-neutrinos back and forth to muon-neutrinos, an oscillation who's experimental discovery in the 1990s solved a longstanding problem in physics known as the solar neutrino problem."

Now that's fine and all, but it's lacking in depth. Are these a common thing? Not common? Let's attack that...

"There are very few types of oscillations in comparison to the wide variety of (actions|events|hmmm???) that also cause the charge of the particle to change. [insert one or two examples of charge changing events here]. In contrast, there are only two common types of neutral oscillations:" [insert existing list here]

Now, how to conclude the lede? Well the rest of the stuff that's there now isn't really about this topic at all, and I recommend removing them entirely. But then what to add, if anything? Are there other possible cases that are not seen in nature? Some interesting physics that comes about because of them? Lots of possibilities here...

Maury Markowitz (talk) 19:30, 15 July 2016 (UTC)

CP eigenstates of the neutral Kaons, K_1 and K_2, are mixed up

I am currently studying for a flavor physics exam and thought about checking out the wikipedia page on the oscillations of neutral mesons. The definitions of the CP eigensates of the neutral Kaons, K_1 and K_2, are mixed up. By that I mean that K1 should be "K0 - K0bar" and K2 should be "K0 + K0bar". The "+" and "-" should change places. This should be evident when applying the CP operator, because the "K1" should have a CP eigenvalue of "+1" and for that you need the "-", because "CP |K0> = -|K0bar>". I have looked at textbooks for sources and some got it right, but even some modern textbooks have gotten it wrong (maybe they copied it from here ;)). My best source be would be my lecture this semester and my own application of the CP operator, but I don't know if this is sufficient for Wikipedia. — Preceding unsigned comment added by Elimik31 (talk • contribs) 18:20, 30 April 2017 (UTC)

For a general quark-flavour eigenstate $\psi$, you have $CP|\psi \rangle =e^{+i\phi }|{\overline {\psi }}\rangle$ and $CP|{\overline {\psi }}\rangle =e^{-i\phi }|\psi \rangle$ where $\phi$ is some arbitrary unobservable phase. The solutions to $e^{+i\phi }=-1$ and $e^{-i\phi }=-1$ are identical, so if $CP|{\overline {K}}^{0}\rangle =-|K^{0}\rangle$ then $CP|K^{0}\rangle =-|{\overline {K}}^{0}\rangle$ too. — dukwon (talk) (contribs) 18:13, 1 May 2017 (UTC)

Thank you. I asked my lecturer and he told me as well that the sign chosen for the charge Operator is conventional. Elimik31 (talk) 16:03, 2 May 2017 (UTC)

References