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RE: Charmonia, bottomonia & toponia - the fantastic beasts of particle physics

in StemSocial7 months ago

Hello @lemouth,
I found this essay easiest to follow since you started blogging again. That may be because this one builds on material already covered, or it may be because you explain the material better. I'm not sure. But I find it exciting that you and your colleagues have made a breakthrough that has roused interest in the theoretical physics community (even though it's not time to open the champagne yet).

As I read about the 'invisible' (because of its rapid decay) top quark and that the only proof of its existence is data (the effect), I thought of an every day event. What if I watched someone who was about to swing a bat to break a glass, but I turned away for an instant, and didn't actually see the bat touch the glass. I'd hear the crash, see the fragments on the ground. Though I hadn't actually seen it happen, I would believe the bat hit the glass. What if I did that over and over again with the same outcome? I would have no direct proof that the bat broke the glass, but the circumstance and the effect would convince me.

You return to the issue of data, and its lack of precision. This seems to be the area in which you have made your breakthrough.

In my publication, we have shown that if we focus on the right property of the top-antitop decay products and that if we consider a specific subset of recorded collisions in which a top-antitop pair is produced, then toponium effects could have an impact of about 10%.

As you say, 10% cannot be overlooked.

I think the most impressive line in your whole essay for me is this:

With only a few elementary particles, we can describe all matter around us

That is an amazing statement, almost mystical.

A great lesson, @lemouth. Thank you. I hope I haven't mischaracterized anything you wrote. :)

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Thanks a lot for the feedback. This is always appreciated! And what you wrote is fully correct!

But I find it exciting that you and your colleagues have made a breakthrough that has roused interest in the theoretical physics community (even though it's not time to open the champagne yet).

I find it super exciting too. This topic has led in fact to my first article on Standard Model physics, all the rest of my research work lying in the context of physics beyond the Standard Model and new phenomena in particle physics.

We now pursue this work and try to provide better predictions ready to be used by our experimental colleagues. In this way, they will be able to directly compare our predictions with data (and conclude). Hopefully, this will allow for the addition of missing theory bits in different measurements for which there is a slight disagreement with theory, and which are expected to be sensitive to toponium effects.

What we try to do in the currently on-going follow-up study is to get more control on the theory predictions, and thus more precision (as mentioned later in your comment). For now, the 10% effects can be seen as an order of magnitude. They result somehow from a back-of-the-envelope calculation. What we now aim to do is to calculate this as precisely as possible, to know what is the true number and to be able to compare meaningfully with data.

As I read about the 'invisible' (because of its rapid decay) top quark and that the only proof of its existence is data (the effect), I thought of an every day event. [...] I would have no direct proof that the bat broke the glass, but the circumstance and the effect would convince me.

It is actually an every day event. Pairs of top quark-antiquarks are produced with a very large rate at the Large Hadron Collider. During the previous run 2 (2015-2018), the LHC collected hence more than 100,000,000 top-antitop pairs. Although the top quarks decay instantaneously, their decay products leave tracks in a detector and can be reconstructed. From there, we can very certainly reconstruct the impact of intermediate top quarks and antiquarks.

The connection with the bat an the glass is a very good one.

Let's assume we take the Standard Model without the top quark. We can calculate how many times the glass gets broken, which produces glass fragments,. In other words, we can estimate how many times something could mimic the effect of a bat (i.e. of a top quark). Moreover, we can also analyse the configuration of the glass fragments, how they are relatively oriented, etc., and how many times we obtain a given configuration if we mentally reproduce the glass breaking experiment many many times.

But for now this was only the theory. Then come the measurements and the real experiment (let's break a few windows). We would find that there is no way to get the glass breaking observations and the rates with which each configuration of the fragment is occurring without having a bat (i.e. a top quark) in the process. Here is our proof (following the "sigma" convention we already discussed in an earlier blog).

To finish:

That is an amazing statement, almost mystical.

That is simply the Standard Model of particle physics, an extremely well-working framework but with room for decades of potential improvements. This is also the reason why I like this domain of physics so much :)

This topic has led in fact to my first article on Standard Model physics
🏆

It is actually an every day event

Of course it is...imprecise lay language. I really meant, more familiar to people who aren't scientists. More pedestrian. We gaze at the stars and wonder. You work with mysteries that may explain the universe.

Moreover, we can also analyse the configuration of the glass fragments, how they are relatively oriented, etc., and how many times we obtain a given configuration if we mentally reproduce the glass breaking experiment many many times.

I see! It's not just repeating the experiment, but calculating distinctions in outcome--data!

Thanks for a great, thoughtful response @lemouth.

You are very welcome!