CERN experiment discovers five new particles

http://www.stfc.ac.uk/news/cern-experiment-discovers-not-one-but-five-new-particles/

by musha68k • 9 years ago

299 85 9 years ago

stfc.ac.uk

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

gpderetta• 9 years ago

yes, and note that these are not fundamental particles (like the Higgs was for example), but composite particles of yet another combination of the fundamental quarks. The SM predicts the existence of hundreds (thousands?) of these.

inlineint3• 9 years ago

Actually it is even a one new particle (Omega_c baryon), but they observed five different excited energy states of it (like observing different excited states of a Hydrogen atom), so called resonances [1]. But the discovery is still exciting because it should have been really hard to find something that we don't really know how looks like in such large amount of noise.

The problem is that it is hard for us to predict masses/energies of new composite particles because although Standard Model provides hypothetical way to do it, it is infeasible computationally.

[1] http://physics.stackexchange.com/questions/64862/resonances-...

brutuscat2• 9 years ago

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 predicted, but never yet observed. Their discovery will help to address important unsolved questions about how hadrons are bound together by the strong interaction.”

So I would assume that yes they have been predicted and is opening the doors for further confirmations?

wolfgke2• 9 years ago

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)

jessaustin2• 9 years ago

Please take more care in quoting. What you've quoted does not describe the current work, but rather something they haven't demonstrated yet called "doubly heavy baryons". That sentence was immediately preceded by this one:

Professor Tim Gershon, Professor of Physics at University of Warwick and UK spokesperson for the LHCb experiment, explained what will come next 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.

grabcocque2• 9 years ago

There are a lot of baryons fyi:

https://en.wikipedia.org/wiki/List_of_baryons

guitarbill• 9 years ago

AFAIK, the experimentally determined rest masses of these excited states/particles (same thing, different was of looking at it) agree with the calculated ones well. So yes, they were predicted. No surprises sadly; of course it's still a huge achievement!

dukwon4• 9 years ago

The theory uncertainties are large. Any measurements within a broad range would also agree with some calculated masses. That doesn't tell you much.

See e.g. https://arxiv.org/abs/1311.4806

sidlls• 9 years ago

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 questioning and hypothesis up by really throwing into question some things.

M_Grey3• 9 years ago

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

ajross• 9 years ago

Yes. They're baryons (three-quark states). This is analogous to the discovery/synthesis of new isotopes in the middle of the last century. Technically they were "predicted", but it's still important to take the measurements. Occasionally there are surprises.

grabcocque2• 9 years ago

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.

bpicolo• 9 years ago

How'd it fail at it's primary task? Wasn't the Higgs a big part of that? Or is the argument that is hasn't found anything outside of the standard model?

shepardrtc• 9 years ago

It succeeded at its primary task, and the Higgs was a big part of it. Its still doing its job, so give it time. Finding nothing can often be just as important as finding something unexpected.

dkural4• 9 years ago

The physics community does not consider finding the Higgs new physics. Not finding Higgs would've been more exciting, or a more massive / lighter Higgs, etc. The Higgs showed up exactly as predicted with the predicted mass, so we're stuck with the Standard Model - i.e. no "new physics".

dukwon4• 9 years ago

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

shmageggy2• 9 years ago

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

Pharylon• 9 years ago

None of that makes any sense.

M_Grey3• 9 years ago

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.

ISL• 9 years ago

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

dave_ant• 9 years ago

Well, I don't know if the LHC is a vital instrument but it will certainly decide were the community of particle physics will go after the plug is pulled on it.

The little I know about is that the LHC is an hadron collider (of course, duh), which means the collisions are not as "clean" as they were with the LEP collider, because the energy is not "deposited" on elementary particles like electrons but on composite hadrons. Which apparently makes things more complicated when it comes to know exactly how the energy is distributed inside the hadrons when they collide...

I'm not sure, I'm not an expert :) I've read that the next collider should use electrons again for collisions, up to 1 TeV or more. Maybe using linear accelerators...

Even if the analogy is not very good it's a little bit like the James Web space telescope, it will open new horizons and open the way for more precise exploration with 50m-class optically stabilized terrestrial telescopes... Just like actual 10m-class telescopes have studied Hubble discoveries in more details.

I see the LHC the same way. The results they will gather from it will decide what to explore next, with more a "precise" collider using leptons and "clean" high energy collisions.

Maybe I'm wrong though. On the political side of thing, sure, it's a costly adventure but I'd rather see money spent on those big scientific project than throwing money at military spendings and engage in useless and illegal wars.

That doesn't mean we can't debate big scientific project. ITER is also a monstrous one when it comes to budget and is even more risky because of the disruptions problem when it comes to confined unstable plasmas in a Tokamak chamber. An apparently 70 years old unsolved problem. Some physicists have warned about powerful disruptions, because of the size of ITER and induced currents in it, potentially harmful for the installation and the people that will work on it if the Tritium breeding blankets are destroyed...

Still, it will be made. And an even bigger experimental reactor is planned, DEMO, that will cost even more. I'm more sceptic about ITER than the LHC...

dkural4• 9 years ago

Just to give a bit more context:

* These are not elementary particles. * It was predicted for a long time that these composite particles should exist. So it is not "new" in the sense that it was unexpected, but we finally have the resolution (energy, luminosity etc.) to detect these with statistical significance. * These belong to the same class as protons and neutrons - these are hadrons made with multiple quarks.

Here's a super simple overview of Quantum Field Theory & Particle Physics:

Everything is made of force fields and matter fields.

* We discovered that force fields (i.e. electromagnetism) is quantized, giving rise to quantum mechanics etc.

* Matter fields are also quantized, hence their excitations behave like discrete particles - the ones we observe at the atomic scale, for instance.

* In hindsight, we should've been able to predict this after E = mc^2 telling us energy <> matter, thus if energy is quantized so should matter.

wfunction2• 9 years ago

I've never heard the term "matter field"... Is that a thing?

danbruc5• 9 years ago

They are properly called fermionic fields [1] as opposed to bosonic fields. I also want to note that the »super simple overview of Quantum Field Theory & Particle Physics« really is super simple. As far as I can tell - I am not a physicist - none of the statements is actually correct.

[1] https://en.wikipedia.org/wiki/Fermionic_field

tbrownaw2• 9 years ago

I assume you've heard of particle/wave duality, or how really tiny things are never exactly in only one place.

There are a set of wave equations that describe how this works.

There are also two kinds of things. Some things can go thru eachother, like photons. Other things bounce off eachother, like neutrons (and other things considered matter).

The equations for the kind of things that bounce off eachother would be a matter field.

tedsanders• 9 years ago

Energy isn't necessarily quantized though. For instance, the spectrum of an unbound particle is continuous. So why does it follow that matter should be quantized from E = mc^2?

-A curious physicist

grkvlt• 9 years ago

For more in-depth information see the CERN press release "LHCb observes an exceptionally large group of particles" at https://home.cern/about/updates/2017/03/lhcb-observes-except...

Or, the paper "Observation of five new narrow Ω0c states decaying to Ξ+cK−" is available at https://arxiv.org/abs/1703.04639

And finally, the LHCb web site section on "Observation of five new narrow Ωc0 excited states" at http://lhcb-public.web.cern.ch/lhcb-public/Welcome.html#Omeg...

CERN experiment discovers five new particles

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