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CERN experiment discovers five new particles

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Re: CERN experiment discovers five new particles

#31

I have to admit, I rather admire their putting a brave face on things, with their mildly-too-insistent claim that the LHC is vital for finding new physics despite the increasing likelihood it's not going to find any. In that sense the LHC is a political failure, because it has failed at its primary political job, which is to make the argument for an even bigger collider.

You know, it's ok not understand much about high energy physics, it's a complicated and somewhat obscure field. It's ok not to understand about what's already been achieved at the LHC, and what might still be over the decades.

What's not ok is to pontificate from that seat of ignorance.

Re: CERN experiment discovers five new particles

#32
post #24

Earlier quoted context omitted.

You're jumping the gun a bit there. The general purpose experiments have only collected O(1%) of their eventual datasets.

I know what you intended, but technically O(1%) == O(100%) == O(5000%)

It's common in particle physics to express base-10 order of magnitude using this notation. I'm unfamiliar with how it's used elsewhere.

Re: CERN experiment discovers five new particles

#33
post #19

I assume these particles were already predicted as part of the Standard Model?

Yes, but these experiments serve at least three purposes. One, to verify the Model (after all, if its predictions fail in some part it will have to be revised). Another, to verify the characteristics of the predicted particles (there might be some differences from the prediction that are important, but not hypothesis-breaking). Finally, however unlikely and yet most excitingly (to me at least), to open new avenues of…

It's worth remembering that the Higgs particle was also predicted by the standard model, and no one underestimates the importance of that confirmation.

Re: CERN experiment discovers five new particles

#34

I have to admit, I rather admire their putting a brave face on things, with their mildly-too-insistent claim that the LHC is vital for finding new physics despite the increasing likelihood it's not going to find any. In that sense the LHC is a political failure, because it has failed at its primary political job, which is to make the argument for an even bigger collider.

LHC is a science experiment. Its job is to, first, check older results [1], and second, put nature to the test in a well-motivated and important way. In particular, LHC is the Higgs hunter, a messy [2] pathfinder before a precision Higgs-studying tool. It succeeded at that job [3].

That LHC has found no new physics beyond the standard model is not a failure. Finding nothing where you thought you might find something is as useful as finding something. If anything, it is more interesting, as it means there is still far more to be learned.

Politics are about people. The science case is a driver for the political case, but it generally takes a backseat to other goals when funding is at hand. First, science keeps us sharp. It pushes harder on materials and technology than anything ever done. An investment in science is also an investment in the entire science supply chain. The recent explosion of quantum-computing hardware investment has only been possible because scientists have built and sustained the tooling and companies that manufacture the necessary subcomponents at a reasonable cost.

More important, it teaches us how to learn; our most important product as scientists is our students. Students keep the field alive, yes, but most students take their new skills, knowledge, and curiosity with them to share outside of academia. Furthermore, governments support scientists to retain the skills for when they are needed by the populace in general; when the Fukushima accident occurred, our laboratory dropped everything it was doing in order to focus on atmospheric monitoring [4].

Finally, the fundamental knowledge we glean from each halting step forward moves us forward as a species. The device on which you are reading this text is the aggregate product of millennia of fundamental research and refinement.

LHC, at least from my outside perspective (I would benefit personally if less money were directed to colliders), has been well-run, successful, and worth the price, both scientifically and politically.

Where we go next is an interesting question -- I'd place my money on exotic accelerator technology. The detectors are wonderful, and linear accelerators are the century-scale path forward. The trick is finding a revolutionary new accelerator idea.

[1] Which it did beautifully. Really beautifully, and really fast. Look at Figure 3: http://lss.fnal.gov/archive/test-fn/0000/fermilab-fn-0923-cm...

[2] Protons are full of quarks and gluons, so when they collide, it's difficult to know which component hit which other component. Lepton-antilepton colliders, on the other hand, are harder to build, but extremely clean.

[3] There is one Higgs. Its mass is 125.09 ± 0.24 GeV. Its width is less than 1.7 GeV. It is the first fundamental scalar particle known to man. http://pdg.lbl.gov/2016/tables/rpp2016-sum-gauge-higgs-boson...

[4] https://arxiv.org/abs/1103.4853 , https://www.npl.washington.edu/monitoring/node/1

Re: CERN experiment discovers five new particles

#36

you forgot to beg for more funding

People who just want funding don't work on things like the LHC. If you want to solve a problem while someone is throwing money at you, then you work in defense. You shouldn't be so quick to harshly judge people who are making the choice to explore the edges of what we can achieve rather than make a quick buck developing the best new way to kill someone.

Re: CERN experiment discovers five new particles

#37
post #5

Earlier quoted context omitted.

Professor Tim Gershon, Professor of Physics at University of Warwick and UK spokesperson for the LHCb experiment: “After the LHCb experiment is upgraded in the next long shutdown of the LHC (during 2019-20), it will be able to move to the next stage in the search for new particles: namely, doubly heavy baryons. These states – which contain two charm quarks or two beauty quarks or one of each – have long been predicte…

> Their discovery will help to address important unsolved questions about how hadrons are bound together by the strong interaction. If the particles were already predicted by the standard model, what kind of unsolved questions are to address here, besides validating the predictions of the standard model even further? (serious question)

I'm not sure about this particular one, but a general idea is that the properties you are measuring in a particle depends on a lot of virtual particles.

It's difficult to find an easy example. After some searches in Google I found this unrelated example: http://www.strings.ph.qmul.ac.uk/~bigdraw/feynman/slide3.htm...

It has 9 Feynman diagrams. If you look at the top left diagram, there is an electron that enters from the bottom right corner, then it emits a photon that go out thought the top left corner, then the electron goes out through the top left corner.

The following two diagrams show the case were the electron emits a second (and third) photon and reabsorbs it, so the second (and third) photons are not visible for the experimenter, they are virtual photons. These additional photons are only important because the change slight the properties of the electron.

In the next three diagrams the photon is so strong that it can spontaneously split in another electron and a positron. It looks like a loop/circle, because positrons are like electrons traveling backward in time. They are virtual electrons, and again they are not visible in the lab, they are only important to make a tiny correction to the result of the experiment.

The other three diagrams have two virtual electrons, than makes even smaller corrections.

And in addition of the virtual electrons, there can be virtual muons and tauons. They are like electrons but with more mass. So the probability of having one of them is smaller, so the correction is smaller. In this case, I think that the correction is so small that it's impossible to measure it.

And you can have another virtual particles, like virtual quarks and virtual W, anything that has a charge. Moreover you can have virtual unknown particles (with charge) because nature doesn't care if we know the particle yet or not. But they are heavier, so the correction is negligible.

If you change the experiment, and for example make a electron collide with a positron, then the calculations are very similar, but there is more energy laying around, and the corrections from heavy particles are more important, so this variation is more useful to discover new particles.

Back to your question ...

The new particles are composed by three quarks, but actually they are composed by a lot of gluons and virtual quarks and antiquarks. To do any calculations you have to include a lot of diagrams like in the figure linked above, and a lot more, many many more.

IIRC the calculation is so complex that it's not possible to compare the experimental results with theoretical calculations. Perhaps they have some heuristic to compare the results with the results of similar particles.

This was probably part of a bigger experiment that produces a lot of particles, and they are trying to classify them in families. And perhaps in the classifications they can spot some strange pattern that may provide a hit that there is a new elementary particle.

Re: CERN experiment discovers five new particles

#38

you forgot to beg for more funding

Your comment is being downvoted for a number of reasons. I'd like to use it as soapbox for a moment.

One reason I left academia was the constant cycle of grant funding proposals followed by a flurry of publication followed by more proposals. These proposals often carried some requirement for language that, in my view, was a direct response to a certain kind of taxpayer, in order to justify on some tangible level the "need" for the research to be funded.

Basic science, and theoretical research alike deserve far more funding than they get. That a significant portion of our country views the funding model we have for scientific discovery as "beg[ging]" is one of the greatest failures we have as a culture.

Re: CERN experiment discovers five new particles

#39

Earlier quoted context omitted.

There are a lot of baryons fyi: https://en.wikipedia.org/wiki/List_of_baryons

Math tells me there must be 216, no? 3 quarks make a baryon, there are 6 types of quarks, so 6^3? Idk if up up up baryons are allowed though, or any other baryon made of 3 equal quarks.

Pentaquarks are also theorized to exist: https://en.wikipedia.org/wiki/Pentaquark

Re: CERN experiment discovers five new particles

#40
post #33
post #19

Earlier quoted context omitted.

Yes, but these experiments serve at least three purposes. One, to verify the Model (after all, if its predictions fail in some part it will have to be revised). Another, to verify the characteristics of the predicted particles (there might be some differences from the prediction that are important, but not hypothesis-breaking). Finally, however unlikely and yet most excitingly (to me at least), to open new avenues of…

It's worth remembering that the Higgs particle was also predicted by the standard model, and no one underestimates the importance of that confirmation.

Not in the same way. There was no experimental evidence for the Higgs field before the Higgs was observed. These new particles arise naturally out of parts of the Standard Model that are already experimentally tested.
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