Scientists at CERN observe three "exotic" particles for first time

[Mr. Sparkle]

Source: Reuters



GENEVA, July 5 (Reuters) - Scientists working with the Large Hadron Collider (LHC) have discovered three subatomic particles never seen before as they work to unlock the building blocks of the universe, the European nuclear research centre CERN said on Tuesday. Now scientists at CERN say they have observed a new kind of "pentaquark" and the first-ever pair of "tetraquarks", adding three members to the list of new hadrons found at the LHC.

They will help physicists better understand how quarks bind together into composite particles. Quarks are elementary particles that usually combine in groups of twos and threes to form hadrons such as the protons and neutrons that make up atomic nuclei. More rarely, however, they can also combine into four-quark and five-quark particles, or tetraquarks and pentaquarks.

"The more analyses we perform, the more kinds of exotic hadrons we find," physicist Niels Tuning said in a statement. "We're witnessing a period of discovery similar to the 1950s, when a 'particle zoo' of hadrons started being discovered and ultimately led to the quark model of conventional hadrons in the 1960s. We're creating 'particle zoo 2.0'."

Read more: https://www.reuters.com/lifestyle/science/scientists-cern-observe-three-exotic-particles-first-time-2022-07-05/

[Tetrachloride]

1. Story is insufficient. Doesn't say if from the latest upgrade

of the smasher or not

[Cheezoholic]

3. It had to be in the data from the last run

They just brought it up to full power today (highest power setting yet). No way they crunched any data gained today in a few hours.

[Tetrachloride]

4. So I surmised. Maybe the writer wasn't aware of new stuff

[BumRushDaShow]

2. My "elementary particle physics" learning is so obsolete now

And this -

We're creating 'particle zoo 2.0'.

LOL maybe 3-ring circus is a better analogy.

[xocetaceans]

11. FYI: Here's a recent three-volume, open-access reference from CERN and Springer Verlag...

which discusses all aspects of particle physics:

Particle physics reference library - Fabjan, Christian W et al


https://cds.cern.ch/record/2702370/files/

Also, here's the Particle Data Group's site at LBL:

Particle Data Group

https://pdg.lbl.gov/

[BumRushDaShow]

12. Oooo thanks! Bookmarked

Ever since they brought that CERN accelerator online, the particles discovered have obsoleted me.

I remember the buzz when Dan Brown's "Angels and Demons" came out, featuring the accelerator, including depictions in the film version -

[xocetaceans]

13. You're welcome.

Thanks also to you - I now have a movie to revisit!

[BumRushDaShow]

14. I've only seen part of that film

and it's on my watch list.

Back in college as a chem major, me and my buddies were thrown into 3 semesters of physics with physics & astronomy majors (along with some engineering majors). My professor for my "Electricity and Magnetism" course used to slap a transparency completely filled with handwritten scroll on an overhead projector and would whip it off the projector less than 30 seconds after putting it there, only to replace it with a new one filled with more writing. I literally had to bring a tape recorder to class to record the lectures because the guy (who was native Chinese) would talk too fast and I needed to listen again later to get the gist of what he was trying to say.

The professor I had for my first semester general physics and for my "Elementary Particle physics" classes (same guy for both) was a Brit who was a bit of a clown, and who would routinely do some "performances" (e.g., lying on a bed of nails) to demonstrate some concepts.

[xocetaceans]

15. This may sound a bit crazy, but...

Last edited Fri Jul 8, 2022, 03:22 PM - Edit history (1)

I think that there might be some value in combining undergraduate physics and chemistry degree programs a little bit more closely.

The thrust of physics is essentially to get past the basics of Newtonian mechanics, statistical mechanics and EM theory and to extend this via Hamiltonian mechanics and Lagrangian mechanics: one picks up special relativity along the way and then one has a foundation for the quantum mechanics of the hydrogen atom. This gets extended to quantum field theory (which uses Lagrangian densities in action integrals and the idea of minimization of the action). In broadly talking about quantum field theory and particle physics, that's when gauge theory and symmetries end up out front as descriptions of what is being discussed. SU(3)xSU(2)xU(1) talks about groups, group representations, etc and describes the standard model in that SU(3) relates to quantum chromodynamics (the strong force; relating to quarks and gluons) and SU(2)xU(1) (the electroweak force; relating to W+,W-,Z0 bosons and photons). This is a terribly oversimplified, off-the-cuff summary, but it has been quite a while for me.

Physical chemistry for chemistry majors seems to be a really good course - which I regret never having taken. From the outside, it seems to give one closer contact to important experimental data relating to statistical mechanics - i.e., enthalpy, entropy, etc. Anyway, it seems like it would give one a firmer foundation (i.e., an experimental foundation) in the early parts of a physics degree - the ones that relate to thermodynamics and, say, the quantum mechanics that applies in chemical reactions.

Anyway, perhaps physical chemistry and the physical chemistry lab course would be good for undergraduate physicists. What do you think?

To elaborate slightly, my above description leaves out mentioning almost all the math that underpins everything. If you've never looked at the standard model from the point of view of applied mathematics, here is a seemingly good lecture course that I ran into the other day. I haven't watched it, but, from the lecture titles, the ones that most directly relate to particle physics are those after lecture #34:

&list=PLOzRYVm0a65dGef0BEA_CWbVCO6BtMZhE

That being said, it might not be safe to skip the earlier lectures, depending on what is already known.

Knowing aspects of group theory is very important to the standard model. Most math texts are quite far away from anything directly applicable to the physics and focus on establishing the mathematical theory of groups, rings and fields - i.e., Herstein's book on Abstract Algebra. However, there is a more efficient and more visualizable approach to understanding group theory which allows one to quickly get past the basics of discrete groups and get on to continuous groups (Lie groups). That approach is based on Cayley diagrams and is discussed online in these lectures, which I would highly recommend to anyone whether they have seen group theory before or not:

https://www.youtube.com/playlist?list=PLwV-9DG53NDxU337smpTwm6sef4x-SCLv

They are based on an approach taken in this book, Visual Group Theory, by Nathan Carter -- https://bookstore.ams.org/clrm-32/.

(While one is mentioning very interesting math books that are perhaps worth a look, there are also these, Visual Complex Analysis, by Tristan Needham -- https://www.amazon.com/Visual-Complex-Analysis-Tristan-Needham/dp/0198534469 , and also Visual Differential Geometry, also by Needham -- https://www.amazon.com/Visual-Differential-Geometry-Forms-Mathematical/dp/0691203709 .)

Of course, visualization can be a two-edge sword if one accidentally brings unrecognized assumptions into one's arguments. This was pointed out in a recent 3Blue1Brown episode:

Anyway, I'm writing this without knowing what you know or what exactly you are interested in - forgive me if I'm covering topics that are already well-known to you and for the extensive length of this reply. I just believe that modern physics is a beautiful thing that is worth knowing, so I hope that this reply is useful in that light.

[BumRushDaShow]

16. Not crazy at all

I expect you see that with those who go into astro-chemistry because you really need to know all sides.

And when you wrote -

Physical chemistry for chemistry majors seems to be a really good course - which I regret never having taken.

I had 2 semesters of it.

I always laugh about how "taking chemistry" to the average high schooler is like how "taking PChem" is to the average college chem major - something that is dreaded. The labs were cool though. I don't recall any Physics majors taking that - it was something that we took around junior year and they probably had enough of their own requirements to do by then.

And yes - all of those physics concepts were fundamental to understanding chemistry and its underlying reactions. We also had to take 3 semesters of calculus, sitting there with math and physics majors as well as the EEs (I think differential/integral/multivariable). One of the good applications of calculus, particularly to PChem, was multivariable because you are looking at "volumes" and rotating stuff around multiple axes and that could be used for fluids and gasses.

At that point, I was 1 math course short of getting a math minor (would have needed a statistics course), but there was no way I was able to fit it in because the 1 credit labs were each 4 hours and those went along with the 3 credit lectures/discussions. So for like 1/2 of my 8 semesters, I was already "overloading" (more than 15 credits per semester) just to get it all in plus get the other core stuff in (English/writing, foreign language, social sciences, humanities).

By the time I got to my last 2 semesters, I was able to just take 12 credits both semesters my senior year and still graduate with 124 credits. I ended up doing 2, 6-credit research projects (did them in organo-metallic chemistry) and finished up some humanities courses and an Advanced Inorganic chem class.

I distinctly remember taking my very last final of college and when I came out of the auditorium, I stood on the corner outside of the lecture hall, hopped a campus shuttle to the movie theater near the school (this was UMASS/Amherst and the theater was at the Hampshire Mall) and saw "Return of the Jedi" on opening day with $5 in my pocket and bought a ticket that had recently gone up to $4.50.

My freshman class started with 100 chem majors and ended up 4 years later graduating 30, with half of those transfers and others who took 5 - 6 years to finish (where we only had 15 of the original 100 start and finish at the same time). And this was out of a university class of about 5000.

[xocetaceans]

17. Overloading like that had to be a challenging but rewarding experience....

Physics can be pretty insular. No one I knew took physical chemistry. I'm not sure that anyone ever paid attention to the departments outside of physics with the exception of paying attention to the math department.

Several years ago, I just started looking at various books at a used book store and came across a few by Peter Atkins: one was a popular science text and the other was his physical chemistry text. The text looked like it would have been great to have studied before taking statistical mechanics. Experiencing that material in the lab would have been great, I think, specifically at enlivening the calculations of stat mech. (I'm not current on that material at all now, though, so I would have difficulty discussing it.)

It would probably be hubris to suggest that one could just drop into a third-year course like PChem. How dependent was that course on prerequisites? Would a one-year freshman chemistry sequence with laboratory be enough to take that course successfully? Or are there second-year courses that are needed also? (FYI: This is an idle wonder for me.)

My chemistry knowledge is severely limited, but I am curious about organo-metallic chemistry research. What does that apply to in the world around us? What size molecules exhibit properties that would fall under that sort of investigation? What phase is under consideration? (These could be very naive questions.... I'm guessing experiments would have to be done in solution, but maybe they could be carried out by mixing gases?)


One other thing about particle physics that ought to be mentioned is the topic of Feynman diagrams. They are important to doing calculations. I mentioned what I did before because that gives one a way to understand how modern particle physics is often described in public - the SU(3)xSU(2)xU(1) idea. To understand what comes out of scattering experiments (which is exactly what is being done at accelerators like the LHC), one needs Feynman diagrams, a good introductory book for that is:

Introduction to Elementary Particles by Griffiths

https://www.wiley.com/en-us/Introduction+to+Elementary+Particles%2C+2nd%2C+Revised+Edition-p-9783527406012

That book has been around for a while, so there should be plenty of allied material on the internet. It gives a general overview of how particle physics came about, briefly discusses special relativity and groups, and then gets into showing how to start to deal with Feynman diagrams in computations in simple "toy" theories. Complex analysis, group theory and tensor analysis (or tensor notation) sort of float around under the surface of what he is discussing. Anyway, I just wanted to throw that in to the discussion in case you ever want to pursue looking further into modern particle physics.

[ProfessorGAC]

18. Good Post!

My PhD is in physical organic chemistry. I wholeheartedly agree with your take on this.
Chemistry doesn't exist, absent fundamental physocs.

[xocetaceans]

25. Thanks for the positive feedback....

As was pointed out further up the thread by BumRushDaShow, physical chemistry would be a third-year sequence. Do you think it would be possible (hypothetically) for third-year physics students to step into that sequence or would those students have missed a critical prerequisite course or course sequence in the chemistry department? I'm going on the assumption that all the physics students would have taken a basic, first-year, two-semester chemistry sequence, but that is all. So, I'm just wondering how realistic it might be for something like physical chemistry (hypothetically) to be integrated into such a degree program.


Lastly, here is a potentially amusing story from the history of (experimental) physics (of which you may already know):

APS News
January 1998 (Volume 7, Number 1)
The Sad Story of Heisenberg's Doctoral Oral Exam
By David Cassidy

In May 1923 Werner Heisenberg returned to Munich from Gottingen, where he had been a visiting student, to finish out his last semester while writing his doctoral dissertation. Knowing Heisenberg's reputation for controversial solutions to problems in quantum theory, his Munich mentor, Arnold Sommerfeld, suggested that he write his dissertation in the more traditional field of hydrodynamics.

Heisenberg also had to take the four-hour laboratory course in experimental physics offered by Prof. Willy Wien. Wien insisted that any physicist, including Sommerfeld's brilliant theorists, must be fully prepared in experimental physics. Wien and Sommerfeld both sat on the candidate's final oral exam and both had to agree on a single grade in physics.

While Heisenberg struggled through Wien's lab course (much to Wien's displeasure at the results), Heisenberg prepared his dissertation. He submitted his dissertation, a 59-page calculation titled "On the Stability and Turbulence of Liquid Currents," to the Munich faculty on July 10, 1923. The topic arose from an earlier research contract Sommerfeld had received from a company channeling the Isar River through Munich. The problem was to determine the precise transition of a smoothly flowing liquid (laminar flow) to turbulent flow. It was an extremely difficult mathematical problem; in fact, it was so difficult that Heisenberg offered only an approximate solution. "I would not have proposed a topic of this difficulty as a dissertation to any of my other pupils," wrote Sommerfeld. The faculty accepted the thesis and Wien accepted it for publication in the physics journal he edited, but when the mathematician Fritz Noether raised objections in 1926, the results remained in doubt for nearly a quarter century until they were finally confirmed.

Acceptance of the dissertation brought admission of the candidate to the final orals, where in this case trouble began. The examining committee consisted of Sommerfeld and Wien, along with representatives in Heisenberg's two minor subjects, mathematics and astronomy. Much was at stake, for the only grades a candidate received were those based on the dissertation and final oral: one grade for each subject and one for overall performance. The grades ranged from I (equivalent to an A) to V (an F).

As the 21-year-old Heisenberg appeared before the four professors on July 23, 1923, he easily handled Sommerfeld's questions and those in mathematics, but he began to stumble on astronomy and fell flat on his face on experimental physics. In his laboratory work Heisenberg had to use a Fabry-Perot interferometer, a device for observing the interference of light waves, on which Wien had lectured extensively. But Heisenberg had no idea how to derive the resolving power of the interferometer nor, to Wien's surprise, could he derive the resolving power of such common instruments as the telescope and the microscope. When an angry Wien asked how a storage battery works, the candidate was still lost. Wien saw no reason to pass the young man, no matter how brilliant he was in other fields.

An argument broke out between Sommerfeld and Wien over the relative importance of theory and experiment. The result was that Heisenberg received the lowest of three passing grades in physics and the same overall grade (cum laude) for his doctorate, both of which were an average between Sommerfeld's highest grade and Wien's lowest grade.

Sommerfeld was shocked. Heisenberg was mortified. Accustomed to being always at the top of his class, Heisenberg found it hard to accept the lowest of three passing grades for his doctorate. Sommerfeld held a small party at his home later that evening for the new Dr. Heisenberg, but Heisenberg excused himself early, packed his bag, and took the midnight train to Gottingen, showing up in Max Born's office the next morning. Born had already hired Heisenberg as his teaching assistant for the coming school year. After informing Born of the debacle of his orals, Heisenberg asked sheepishly, "I wonder if you still want to have me."

Born did not answer until he had gone over the questions Heisenberg had missed. Convincing himself that the questions were "rather tricky," Born let his employment offer stand. But that fall Heisenberg's worried father wrote to the famed Gottingen experimentalist James Franck, asking Franck to teach his boy some experimental physics. Franck did his best, but could not overcome Heisenberg's complete lack of interest and gave up the effort. If Heisenberg was going to survive at all in physics it would be purely as a theorist.

There is an interesting epilogue to this story. When Heisenberg derived the uncertainty relations several years later, he used the resolving power of the microscope to derive the uncertainty relations-and he still had difficulty with it! And again, when Bohr pointed out the error, it led to emotional difficulties for Heisenberg. Likewise, this time a positive result came of the affair: Heisenberg's reaction induced Bohr to formulate his own views on the subject, which ultimately led to the so-called Copenhagen Interpretation of quantum mechanics.

David Cassidy (Hofstra College) is Secretary-Treasurer of the Forum on History of Physics. This article is excerpted from his book, Uncertainty, pp. 149-154, and may also be viewed at web site along with addition material on Heisenberg.

©1995 - 2022, AMERICAN PHYSICAL SOCIETY

APS encourages the redistribution of the materials included in this newspaper provided that attribution to the source is noted and the materials are not truncated or changed.

Editor: Barrett H. Ripin

https://www.aps.org/publications/apsnews/199801/heisenberg.cfm

To some extent, it illustrates how important experiment can be.

Lastly, I would not normally post an entire story - however, the APS seems to allow for exactly that as long as there is no truncation and proper attribution is given.

[ProfessorGAC]

26. To Your Question

I'm the wrong person to ask.
I got my B.S. in 3 years. I took organic & PChem at the same time, so the sequence wasn't normal.
However, the physics majors took the same 300 class, except it was listed as Thermodynamics (at least 351; i don't recall if 352 had an alternate name, but probably so as it much more focused on mass transfsr, probabilities, and surface effects). But, it was the same class, as there were physics majors in that class with me.
So, i guess your idea is logical since at least one school was doing it 47 years ago.

[xocetaceans]

27. Cool. That sounds like a fairly strenuous program.

From what I've heard of it, organic chemistry is reputed to be a bear with respect to its nomenclature alone, and I know quantum mechanics is initially, at least, a bit exotic until one gets used to calculating with it.

Thanks for the reply.

[Xoan]

5. Are we sure this isn't The Onion?

"The more analyses we perform, the more kinds of exotic hadrons we find,"

[SeattleVet]

7. Read it a little more closely...

it's 'hadrons', not 'hardons'.

[Effete Snob]

10. Large, Exotic, Hardons

[LudwigPastorius]

6. I'm telling ya,...

we all didn't start heading down this darkest-of-all timelines until they turned that sucker on.

Trump, COVID, Putin threatening WWIII...

Those eggheads might want to go back and see where things bifurcated, and try and get us back on the right track!

[C Moon]

8. I'm with you on that!

[electric_blue68]

21. Hooo, boy, you got THAT right

😄 😭

[KS Toronado]

9. Wish they would hurry up and discover "Warp Speed"

I'd like to start a taxi service going to Mars in under an hour.

[ProfessorGAC]

19. Depending Oh Where Mars Is In Its Orbit...

...at Warp 1, it would only take about 3 minutes
At worst it would take 20, including going around the sun.
Way under a hour!
BTW: I'll call your taxi service the minute you open for business.

[KS Toronado]

22. For that info you get a free round trip.

[ProfessorGAC]

23. Outstanding!

And, i accept.
Now, if can just get that warp speed thing soon.

[LudwigPastorius]

24. You could call it the Special Relativity Special.

...and guarantee that all passengers would arrive before they leave.

(Their luggage, though, might take longer.)

[henbuck]

20. At what point will any of this knowledge have an practical value that would influence

an average person's life?