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Did the W-boson simply “break the usual mannequin”?

[This is a transcript of the video embedded below. Some of the explanations may not make sense without the animations in the video.]

Hey there’s yet one more anomaly in particle physics. You’ve got most likely seen the headlines, one thing with the mass of a type of particles referred to as a W-boson. And supersymmetry is as soon as once more the alleged rationalization. How critically must you take this? And why are particle physicists consistently speaking about supersymmetry, hasn’t that been dominated out? That’s what we’ll speak about right this moment.

Final time I talked about an anomaly in particle physics was a couple of months in the past and would you understand two weeks later it disappeared. Sure, it disappeared. Should you bear in mind there was one thing bizarre occurring with the neutrino oscillations in an experiment referred to as LSND, then a follow-up experiment referred to as Mini-Boone confirmed this, after which they improved the accuracy of the follow-up experiment and the anomaly was gone. Poof, finish of story. No extra neutrino anomaly.

You’d assume this is able to’ve taught me to not get enthusiastic about anomalies however, ha, know me higher. Now there’s one other experimental group that claims to have discovered an anomaly and naturally now we have to speak about this. This one really isn’t a brand new experiment, it’s a brand new evaluation of knowledge from an experiment that was discontinued greater than 10 years in the past, a particle collider referred to as the Tevatron at Fermilab in the USA. It reached collision energies of a few Tera electron volt, Tev for brief, therefore the title.

The information had been collected from 2002 to 2011 by the collaboration of the CDF experiment. Throughout that point they measured about 4 million occasions that contained a particle referred to as the W-boson.

The W-boson is without doubt one of the particles in the usual mannequin, it’s a type of that mediate the weak nuclear pressure. So it’s just like the photon, nevertheless it has a mass and it’s extraordinarily short-lived. It actually solely exhibits up in particle colliders. The worth of the mass of the W-boson is expounded to different parameters in the usual mannequin which have additionally been measured, so it isn’t an impartial parameter, it has to suit to the others.

The mass of the W-boson has been measured a couple of occasions beforehand, you possibly can see a abstract of these measurements on this determine. On the horizontal axis you might have the mass of the W-boson. The gray line is the expectation if the usual mannequin is right. The pink dots with the error bars are the outcomes from totally different experiments. The one on the backside is the consequence from the brand new evaluation.

One factor that pops into your eye immediately is that the imply worth of the brand new measurement isn’t so totally different from earlier knowledge analyses. The putting factor about this new evaluation is the small error bar. That the error bar is so small is the rationale why this consequence has such a excessive statistical significance. They quote a disagreement with the usual mannequin at 6.9 sigma. That’s nicely above the invention threshold in particle physics which is usually considerably arbitrarily put at 5 sigma.

What did they do to get the error bar so small? Nicely for one factor they’ve a number of knowledge. However additionally they did a number of calibration cross-checks with different measurements, which mainly means they know very exactly easy methods to extract the bodily parameters from the uncooked knowledge, or no less than they assume they do. Is that this cheap? Sure. Is it right? I don’t know. It might be. However in all honesty, I’m very skeptical that this consequence will maintain up. Extra possible, they’ve underestimated the error and their consequence is definitely appropriate with the opposite measurements.

But when it does maintain up, what does it imply? It could imply that the usual mannequin is fallacious as a result of there’d be a measurement that don’t match along with the predictions of the speculation. Then what? Nicely then we’d have to enhance the usual mannequin. Theoretical particle physicists have made many options for the way to do this, the most well-liked one has for a very long time been supersymmetry. It’s additionally one of many doable explanations for the brand new anomaly that the authors of the paper talk about.

What’s supersymmetry? Supersymmetry isn’t a idea, it’s a property of a category of fashions. And that class of fashions could be very giant. These fashions have all in frequent that they introduce a brand new accomplice particle for every particle in the usual mannequin. After which there are normally some extra new particles. So, in a nutshell, it’s much more particles.

What the predictions of a supersymmetric mannequin are relies upon strongly on the plenty of these new particles and the way they decay and work together. In follow this implies no matter anomaly you measure, you possibly can most likely discover some supersymmetric mannequin that may “clarify” it. I’m scare quoting “clarify” as a result of in case you can clarify every part you actually clarify nothing.

This is the reason supersymmetry is talked about in a single breath with each anomaly that you just hear of: as a result of you should use it to clarify just about every part in case you solely attempt laborious sufficient. For instance, it’s possible you’ll bear in mind the 4.2 sigma deviation from the usual mannequin within the magnetic second of the muon. Might or not it’s supersymmetry? Positive. Or what’s with this B-meson anomaly, that lingers round at 3 sigma and makes headlines a couple of times yr. Might that be supersymmetry? Positive.

Can we in any of those circumstances really *know that it must be supersymmetry? No. There are lots of different fashions you could possibly fumble collectively that might additionally match the invoice. Actually, the brand new CDF paper in regards to the mass of the W-boson additionally mentions a couple of different doable explanations: further scalar fields, a second Higgs, darkish photons, composite Higgs, and so forth.

There’s actually 1000’s of these fashions, none of which has any proof stepping into its favor. And instantly after the brand new outcomes appeared particle physicists have begun cooking up new “explanations”. Listed below are just some examples of these. By the point this video seems there’ll most likely be a couple of dozen extra.

However wait, it’s possible you’ll marvel now, hasn’t the Giant Hadron Collider dominated out supersymmetry? Good level. Earlier than the Giant Hadron Collider turned on, particle physicists claimed that it could both affirm or rule out supersymmetry. Supersymmetry was allegedly a straightforward to search out sign. If supersymmetric particles existed, they need to have proven up just about instantly within the first collisions. That didn’t occur. What did particle physicists do? Oh all of the sudden they claimed that in fact this didn’t rule out supersymmetry. It’d simply dominated out sure supersymmetric fashions. So which model is right? Did or didn’t the LHC rule out supersymmetry?

The reply is that the LHC certainly didn’t rule out supersymmetry, it by no means may. As I stated, supersymmetry isn’t a idea. It’s an enormous class of fashions that may be made to suit something. These physicists who stated in any other case had been both incompetent or mendacity or each, the remainder knew it however saved their mouth shut, and now they hope you’ll neglect about this and provides them cash for a much bigger collider.

As you possibly can most likely inform, I’m very not amused that the particle physics neighborhood by no means got here clear on that. They by no means admitted to having made false statements, by accident or intentionally, and so they by no means gave us any cause to assume it wouldn’t occur once more. I fairly merely don’t belief them.

Didn’t supersymmetry have one thing to do with string idea? Sure, certainly. So what does this all imply for string idea? The transient reply is: nothing by any means. String idea requires supersymmetry, however the reverse will not be true, supersymmetry doesn’t essentially require string idea. So even within the unlikely occasion that we might discover proof for supersymmetry, this wouldn’t inform us whether or not string idea is right. It could definitely increase confidence in string idea however finally wouldn’t assist a lot as a result of string theorists by no means managed to get the usual mannequin out of their idea, regardless of the occasional declare on the contrary.

I’m afraid all of this sounds relatively damaging. Nicely. There’s a cause I left particle physics. Particle physics has degenerated right into a paper manufacturing enterprise that’s of nearly no relevance for societal progress or for progress in every other self-discipline of science. The one cause we nonetheless hear a lot about it’s that a number of funding goes into it and so lots of people nonetheless work on it, most of them don’t like me. However the disciplines the place the foundations of physics at the moment make progress are cosmology and astrophysics, and every part quantum, quantum info, quantum computing, quantum metrology, and so forth, which is why that’s what I principally speak about as of late.

The LHC has simply been upgraded and began working once more a couple of days in the past. Within the coming years, they may gather much more knowledge than they’ve to date and this might result in new discoveries. However when the headlines are available in, remember that the extra knowledge you gather, the extra anomalies you’ll see, so it’s nearly assured they may see a number of bumps at low significance “that might break the usual mannequin” however then go away. It’s doable in fact that a type of is the actual factor, however to borrow a German idiom, don’t eat the headlines as sizzling as they’re cooked.



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