How big was the "particle zoo" prior to quark discovery

[the_emi_guy]

I am trying to sort out a discrepancy I see between historical accounts which suggest that there were "hundreds of strongly interacting particles (hadrons) believed to be fundamental..." (Wikipedia under "particle zoo" among other places), and my actual count of such particles.

Specifically, when the quark theory was confirmed with the discovery of the omega minus particle in 1964, particles containing up,down, and strange had been observed. Looking at table of particles (various sources), I see only 26 hadrons that contain these three quarks, 15 baryons and 11 mesons. Even if we double this to include anti-particles it seems way short of the "zoo".

 

[vanhees71]

A good account on the history of which particles were discovered at a given time is the Review of Particle Physics. All issues are online!

http://pdg.lbl.gov/rpp-archive/

 

[mfb]

Don't forget all their excited states. We know 40 light unflavored mesons - that is just up and down with reasonable evidence for their existence, not counting antiparticles.
Tens of additional states with weak evidence for them.
Nearly 30 with 1 strange quark

Similar for baryons. The current PDG list. Not all these states were found before the quark model was developed, of course.

 

[the_emi_guy]

Thanks folks,
Very helpful links.

 

[ohwilleke]

Specifically, when the quark theory was confirmed with the discovery of the omega minus particle in 1964, particles containing up,down, and strange had been observed. Looking at table of particles (various sources), I see only 26 hadrons that contain these three quarks, 15 baryons and 11 mesons. Even if we double this to include anti-particles it seems way short of the "zoo".

Part of what made it a "zoo" is that new hadrons kept being discovered at a rapid pace and nobody had any idea how many hadrons were out there to be discovered or how to categorize the ones that were discovered in a physically meaningful way. They didn't even know really, if hadrons with similar properties (e.g. spin, charge, parity, mass) were all one kind of hadron, or had subtypes discernible by some unknown means. The lack of order or sense in what was already discovered and what continued to be discovered at a rapid pace, contributed to the feeling that it was a "zoo".

Also, while you state that "quark theory was confirmed . . . in 1964", the entire scientific establishment doesn't just adopt a new theory instantaneously when a single experiment providing empirical evidence for it reports a result. A discovery like this may win over lots of people, especially those at the cutting edge of research, quickly, but it takes something like a decade for a discovery like that to be fully assimilated into the physics community to the point that it becomes scientific consensus (and a few die hards will inevitably cling to their own, since disproven pet theories with epicycle-like fixes, until they die).

For example, there are still people today who cling to Technicolor theories (which were designed to provide an alternative explanation for phenomena attributable to the Higgs boson in the Standard Model, in the event that no Higgs boson was discovered) despite the discovery of the Higgs boson.

Plenty of people of good will are going to doubt a particular experimental result until it has been robustly and precisely confirmed by multiple experiments using more than one methodology. Quark theory wasn't almost universally agreed to be correct until the very late 1960s or early 1970s, even though it was gaining converts very rapidly in that time period.

This is especially true across sub-disciplinary lines. Sub-disciplines adopt discoveries from other sub-disciplines investigating the same thing more slowly than those in the sub-discipline where the original discovery is made. For example, I see papers every month from HEP physicists at arXiv proposing dark matter candidates that haven't been ruled out using HEP methods even though astronomy data already rules out these candidates, without any mention (and probably without any knowledge) of the relevant data from another field investigating the same thing using different methods. Back in the early 1960s, for example, bubble chamber researchers might not have been on the same page of collider researchers who may not have been on the same page as "nuclear physicists" that worked with nuclear power plants.

 

[Vanadium 50]

For example, there are still people today who cling to Technicolor theories (which were designed to provide an alternative explanation for phenomena attributable to the Higgs boson in the Standard Model, in the event that no Higgs boson was discovered) despite the discovery of the Higgs boson.

Name them, please.

 

[ohwilleke]

Name them, please.

Examples of papers written backing technicolor in the year 2016 include (I've tried to avoid author overlap but Koichi Yamawaki links several otherwise non-overlapping author lists): https://arxiv.org/abs/1607.01440, https://arxiv.org/abs/1606.09469, https://arxiv.org/abs/1605.04667, https://arxiv.org/abs/1605.01951, https://arxiv.org/abs/1604.07085, https://arxiv.org/abs/1601.03302, and https://arxiv.org/abs/1601.02287

 

[Vanadium 50]

I took a look at one at random - 1606.09469, which is an attempt to write a theory that incorporates technicolor in addition to a SM-like Higgs boson. They say this in Sentence #4. They certainly aren't denying that EWSB doesn't involve a SM-like Higgs. You have misrepresented what they have said.

 

[ohwilleke]

I took a look at one at random - 1606.09469, which is an attempt to write a theory that incorporates technicolor in addition to a SM-like Higgs boson. They say this in Sentence #4. They certainly aren't denying that EWSB doesn't involve a SM-like Higgs. You have misrepresented what they have said.

A SM-like composite Higgs boson is very different from a SM Higgs boson that is fundamental. It is an epicyclish way to cling to technicolor theories.

 

[Vanadium 50]

It's OK if their theory - one that is not excluded by any measurement - is not to your taste. But that's not what you objected to in message 5. You are misrepresenting what that paper said.

 

[ohwilleke]

It's OK if their theory - one that is not excluded by any measurement - is not to your taste. But that's not what you objected to in message 5. You are misrepresenting what that paper said.

Seems to me that my statement:

there are still people today who cling to Technicolor theories (which were designed to provide an alternative explanation for phenomena attributable to the Higgs boson in the Standard Model, in the event that no Higgs boson was discovered) despite the discovery of the Higgs boson.

Is true.

1. There are people who cling to Technicolor theories.

2. Technicolor was an alternative explanation for phenomena to attributable to the Higgs boson in the Standard Model, in the event that no Higgs boson was discovered.

3. The Higgs boson has been discovered.

 

[vanhees71]

Well, a resonance with the features of the Higgs boson has been discovered. Who tells you that it's really a fundamental boson and not a (quasi-) bound state of something else as the Technicolor Models assume?

 

[ohwilleke]

Well, a resonance with the features of the Higgs boson has been discovered. Who tells you that it's really a fundamental boson and not a (quasi-) bound state of something else as the Technicolor Models assume?

Which goes to illustrate the point I mentioned it for in the first place, which is that old theories die hard and just because there is a decisive experimental result that strongly favors a new theory, this doesn't mean that the entire physics community will abandon its pre-discovery theories even if they have become much less well motivated. Instead, lots of people will try to fit the new wine into old skins. So, just because 1964 was the tipping point for lots of people in terms of quark theory, that doesn't mean that quark theory was immediately and universally adopted by everyone.

 

[mfb]

Well, a resonance with the features of the Higgs boson has been discovered. Who tells you that it's really a fundamental boson and not a (quasi-) bound state of something else as the Technicolor Models assume?

You can ask the same question about quarks, or all other particles. There are people at the LHC looking for these things. The searches are called "exotic" for a good reason. Low probability to find something, but with a huge impact if they do.

 

[vanhees71]

Indeed, to make any progress in HEP physics we need a clear hint at "physics beyond the Standard Model". Although the Standard Model is the most successful model ever, describing all known matter in the universe with unprecedented precision, we know that it has some theoretical problems, one of which is the hierarchy problem related to the Higgs boson, described as an elementary scalar, with it's quadratically divergent mass.

 

[Vanadium 50]

1. There are people who cling to Technicolor theories.

2. Technicolor was an alternative explanation for phenomena to attributable to the Higgs boson in the Standard Model, in the event that no Higgs boson was discovered.

3. The Higgs boson has been discovered.

Again, you are being misleadig, and misrepresenting those papers. Your defense is to repeat your claims.

You are suggesting that the authors of 1606.09469 are "clinging" to TC despite the evidence of the Higgs, when in fact they are arguing that in a family of TC theories you get a particle that looks and acts very much like the Higgs. Those authors are not claiming - and probably would be shocked to hear - that they disbelieve the Higgs or think it doesn't play a role in EWSB. Models where you have TC and a scalar have been around for almost 40 years.

Either the authors of 1606.09469 accept the discovery of the Higgs, or they don't. If they do, which is what their papers suggest, they are not examples of "people today who cling to Technicolor theories...despite the discovery of the Higgs boson."

 

[nikkkom]

It's OK if their theory - one that is not excluded by any measurement - is not to your taste. But that's not what you objected to in message 5.

He did not object to anything. My reading is he is not against people publishing TC theories (or any theories at all).

 

[ohwilleke]

I am not against anybody publishing anything. But I do think it is well established that when a new experimental result comes out that some significant part of the physics community will not just accept it at face value and instead will try to fit it into old theories that would never have come into being had the data point existed before the old theories were formulated.