Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

CERN experiment discovers five new particles

stfc.ac.uk

Post reply on HN
Print view View original

11–20 of 127 posts

Re: CERN experiment discovers five new particles

#11

Post by inlineint »

gpderetta wrote: post #3
teddythetwig wrote: post #2

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

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.

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-...

Re: CERN experiment discovers five new particles

#12

Post by grabcocque »

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.

Re: CERN experiment discovers five new particles

#13

Post by nonbel »

inlineint wrote: post #11
gpderetta wrote: post #3

Earlier quoted context omitted.

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.

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…

>"it should have been really hard to find something that we don't really know how looks like in such large amount of noise."

But if there are thousands of different such "surprising-to find-particles" to possibly detect, is it actually surprising to observe one of them?

Edit:

Also, from the top answer at your link: "The first generation of elementary particles are by observation not composite and therefore not seen to decay...The Standard Model of elementary particles, with the three generations of matter, gauge bosons in the fourth column and the Higgs boson in the fifth."

From wikipedia: "In the Standard Model, the Higgs particle is a boson with no spin, electric charge, or colour charge. It is also very unstable, decaying into other particles almost immediately." https://en.wikipedia.org/wiki/Higgs_boson

So do elementary particles decay or not?

Re: CERN experiment discovers five new particles

#14

Post by grabcocque »

brutuscat wrote: post #4
teddythetwig wrote: post #2

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

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…

There are a lot of baryons fyi:

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

Re: CERN experiment discovers five new particles

#15

Post by inlineint »

wolfgke wrote: post #5
brutuscat wrote: post #4

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)

The standard model provides a set of postulates that could be used for prediction of possible composite particles, their masses, and decay times.

However it is computationally infeasible to calculate them directly, without using various approximations. Physicists try to solve these problems numerically (see for example about the field called lattice QCD), but it is not always possible and leads to introducing various approximations that produce errors and other artifacts in the numerical predictions.

So the particles were allowed by the standard model, but we didn't know for sure their properties. So this provides way to verify already done numerical predictions (I don't really know were they be done for this exact particles or not) and give us data about exact properties of these particles.

One could possibly draw an analogy with (quantum) chemistry here.

Re: CERN experiment discovers five new particles

#16

Post by bpicolo »

grabcocque wrote: post #12

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.

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?

Re: CERN experiment discovers five new particles

#17

Post by inlineint »

nonbel wrote: post #13
inlineint wrote: post #11

Earlier quoted context omitted.

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…

>"it should have been really hard to find something that we don't really know how looks like in such large amount of noise." But if there are thousands of different such "surprising-to find-particles" to possibly detect, is it actually surprising to observe one of them? Edit: Also, from the top answer at your link: "The first generation of elementary particles are by observation not composite and therefore not seen t…

> But if there are thousands of different such "surprising-to find-particles" to possibly detect, is it actually surprising to observe one of them?

It is hard to correctly identify what exactly particles from those possible thousands are observed in given data. The are two main problems: the properties of those not yet observed particles are not well known (because it is computationally hard to predict them from the standard model) and because the number of useful events is much much smaller than the number of events that correspond to already known events.

> So do elementary particles decay or not?

I don't see a contradiction here: the first generation of elementary particles does not decay (or has not been observed to decay yet), Higgs boson is not from then because the author of the answer are talking about the first generation of fermions and Higgs boson is not one of them.

Re: CERN experiment discovers five new particles

#18

Post by shepardrtc »

bpicolo wrote: post #16
grabcocque wrote: post #12

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.

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?

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.

Re: CERN experiment discovers five new particles

#19

Post by sidlls »

teddythetwig wrote: post #2

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

Re: CERN experiment discovers five new particles

#20

Post by wolfgke »

shepardrtc wrote: post #18
bpicolo wrote: post #16

Earlier quoted context omitted.

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?

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.

> Finding nothing can often be just as important as finding something unexpected.

From a scientific point you are right. From a political point or the point of securing further funding this statement is (unluckily) wrong.

Post reply on HN