And now everyone: Noooo, not again.
(Explanation: it's well-known that the Standard Model can't be completely correct but again and again physicists fail to find an experiment contradicting its predictions, see https://en.wikipedia.org/wiki/Physics_beyond_the_Standard_Mo... for example)
I forgot the numbers, but they have severals layers of filtering between sensors and long-term storage. First there are FPGA-based real-time filters, next to the sensors, which throw away most of the data as "noise." Then there are local CPUs which throw away most of the remaining data, again classified as "noise" or uninteresting. Finally, what remains (30,000 TB/year) is stored long-term to be later analyzed by physicists.
All levels of filtering and analysis, from the FPGA to the physicist's algorithms, make use of the Standard Model itself and the rest of known physics to figure out what's "interesting" and what's "noise."
One big problem is thus: how can we find new things if we are only looking for what we already know? Hence the need for machine learning and automatic pattern discovery.
It is full of unexplained hadcoded parameters, indeed, which need an explanation from outside of the SM.
https://en.wikipedia.org/wiki/Magic_number_(programming)#Unn...
> The term magic number or magic constant refers to the anti-pattern of using numbers directly in source code
You have to run `git format-patch` and email the results to Him.
edit: thanks for the explanation
For any experts reading this: what are plausible-looking extensions of the standard model which can probably be challenged/"proved" by current generation accelerators (in particular the LHC) and would lead to interesting extensions of the standard model?
As far as I am aware, the LHC could e.g. find no sign of lots of variants of supersymmetry, which was a plausible candiate for this in the past:
> https://www.scientificamerican.com/article/supersymmetry-fai...
> https://www.quantamagazine.org/complications-in-physics-lend...
Until recently they were mostly looking for specific deviations predicted by extensions. They only recently announced that they're now going for a broader search.
They'll write down a model that describes it, which is all theorists' job to begin with.
We can add an extra parameter to general relativity (known as the "cosmological constant") to describe "dark energy" observations via a kind of 'anti gravity'; although we still don't fully understand what that means, or whether it's a correct description. It's also unclear whether this would have anything to do with quantum theories (like the standard model).
General relativity can explain "dark matter" observations by assuming there is more mass/matter than we can see (i.e. it's electrically neutral and doesn't interact with light). Since the standard model tries to describe all of the fundamental constituents of matter, and forces including electromagnetism (light), having nothing to say about such a seemingly large amount of stuff is a rather large discrepancy in the standard model.
AFAIK the standard model also says that neutrinos have zero mass; yet we've observed them undergoing radioactive decay ("neutrino oscillation", where each sort of neutrino can decay into the others). Particles which decay require some amount of time to do so. Particles with zero mass always travel at the speed of light (like photons, and hypothetical gravitons) and hence don't experience any time passing (this sentence is a consequence of special relativity). So particles with zero mass can't decay, so neutrinos can't have zero mass. I don't think we've measured their mass very accurately yet; we know it's very small, but it cannot be zero.
[1] https://en.wikipedia.org/wiki/Solar_neutrino_problem
OOPS: I see a sibling comment also covers this. Oh well, I'll keep this one up since it's slightly more eye-catching.
As the cosmologist Sean Carroll said in his podcast, particle physicists haven't really been surprised by an observation since the 1970s. Presumably many were hoping for a surprise.
If we have a conversation and you reveal that my assumptions are wrong, I can go back, rethink everything, and come out with a stronger world view.
Basically, this experiment didn't tell scientists anything they didn't already know, or didn't prove them wrong--which might lead to newer, more interesting models that reveal more about the universe.
The error bars are ±20%, so there's quite a lot of wiggle room for new physics.
With the improved understanding of the Higgs that we have now, an e+/e- machine can be custom-built to study it in great detail. The Higgs is the newest fundamental particle to physics, and the first/only known scalar. We should expect that it has more to tell us than simply its own existence.
Even when the LHC was being planned, LHC was the discovery machine, and precision experiments were to follow. In my opinion, only when those measurements are complete should we consider a huge leap toward higher energy, unless new accelerator technology emerges.
A question to physicists: Is there (strong) evidence that there might exist other scalars (if yes: at which energy level?). If not: Do there exist attempts of theories that predict why there is only one scalar?
At some level, it is something of a surprise to have found that there is just one particle responsible for the Higgs mechanism, and it is indeed spin-0, as Nature hasn't given us one of those before. Prior to the discovery of the Higgs, perhaps the majority of physicists were betting on something Higgs-like, but not quite the pure vanilla Standard Model Higgs.
I would not bet any money on it, but if one were looking for another scalar, one might find it in whatever mechanism underlies dark energy. Many theoretical models for dark energy use scalars, again, because they are easier...
Improved colliders, and improved experiments generally, tend to increase the number of ways in which we can search for a departure from the plan.
What we may need, at least as much as new colliders, is the right insight to open a new way forward. The standard model is large and complicated -- there aren't that many people who really understand its complexity enough to find something analogous to Gell-Mann's eightfold way.
Are proposal estimating new efforts at 100's of km? 1000s?
Rather than trying to rule out a hypothesis completely, it's easier to place limits outside of which a hypothesis is essentially useless. IIUC, if the LHC didn't spot the Higgs mechanism below 14TeV then that wouldn't work as an explanation of other particles' mass. At that point there might have still been a Higgs mechanism at higher energies, but we wouldn't really care either way since the whole point of coming up with the Higgs mechanism was to explain the mass of other particles: if it can't do that, it becomes inconsequential. That's why the LHC was so important for the Higgs: we would either find it, and hence have a better explanation of particles' mass; or we would know that particle mass doesn't follow the Higgs mechanism.
At the moment we have a bunch of hypotheses which predict effects that larger colliders might see, but I don't think we have (feasible) limits which let us discard these hypotheses. Hence new colliders don't have a goal to aim at: it's just a case of going as big as possible to have the highest chance of seeing new effects. Yet we might see nothing, and that wouldn't actually tell us much, since the predictions could just be tweaked again.
Edit: Nope I'm wrong.
Yeah, that was the splice consolidation.
> but the luminosity was increased in 2016 and 2017 as well.
From what I know, that's through conditioning, repairs and improved techniques (BCMS, ATS, anti-levelling). The increase from 2015 to 2016 was because they didn't finish the intensity ramp in 2015 as the scrubbing campaign lasted so long. 2016 had the TIDVG dump problem as well as outgassing from the injection kickers. 2017 was marred by 16L2.
Context: at 10^16 TeV you start probing the planck energy scale, where gravity becomes strong enough to influence particle interactions. In nature, these energies are reached only inside black holes and just after the big bang. The standard model does not describe gravity, so it has no predictive power at this scale, which is why the above phenomena are a complete mystery to us.
The standard model gets away with this at LHC energy scale because gravity is so weak it can literally be neglected in the calculations.
It's of course possible we'd see some new physics before then, but it's not guaranteed, building a collider 10 times would be a bit of a stab in the dark.
If a model of the universe was completely correct, wouldn't it have equivalent complexity to the universe and hence not be a model?
So when you go from particle physics to chemistry, new complexities emerge that can't be explained in the realm of particle physics alone (iirc).
sadly certain "sciences" still cling to the idea that they can simply aggregate the results from multiple of their "particles" and get a solution for larger systems.
Correct me if I'm misunderstanding, but I think you're confusing general theory vs practical applicable models here maybe? Yes, fundamental principles of interaction can combine at scale to create new large scale effects, but that doesn't change the fact that they came out of fundamental principles nor that they can't be "explained" via those principles. There is no magic that pops into existence up the chain. The asymmetry of water molecules and the way their electron clouds distribute create all sorts of fascinating effects in bulk water, but they're still directly coming out of physics of course.
The issue in practice however is that the level of computing necessary to accurately model reality at scale from fundamentals matches or exceeds actually doing it in reality, and for us rapidly becomes absolutely, utterly infeasible for anything but the simplest systems. "New emergent complexities" absolutely "can be explained" from a correct lower level set of principles, but that doesn't mean we can actually crunch the math at any scale we want. So we need higher level bulk models too, at many levels all the way up, which are good enough to be effective approximations to a given level of accuracy in practical computing time. The low level fundamentals often at bulk average out due to random variance in sufficient quantity and are irrelevant to whatever we care about, so there is no need to do it that expensively (even if we could). But that isn't the same thing as the fundamentals being wrong somehow or not being at the root of everything above.
This is false both due to the nature of mathematical modelling in physics, and the ad-hoc nature of the term "complexity" when comparing the universe and the science we use to understand (or, perhaps, only model it).
To elaborate on the first point: No measurement can be perfect enough for their to be no uncertainty on it. It is therefore impossible for a model to be completely correct, although it can (obviously) agree with experiment to within current experimental uncertainties - like the standard model is now, so far.
For example, we had Newtonian Mechanics and that looked good for a couple of centuries, but then it turned out that it was too simple and we needed to add more laws.
We would have to settle for merely being able to explain every single phenomena in the observable universe at every scale.
Then see a recent essay at Quanta Magazine that explains that physics has long looked to some largely esthetic concerns especially about symmetry to pick and choose among alternate theoretical explanations -- again my rough summary from my rough memory.
https://www.quantamagazine.org/there-are-no-laws-of-physics-...
Sabine Hossenfelder, Lost in Math: How Beauty Leads Physics Astray
at
https://www.basicbooks.com/titles/sabine-hossenfelder/lost-i...
and is an excerpt from her book of the same name.
I was led to that excerpt by page
https://www.quantamagazine.org/authors/sabine-hossenfelder/
from page
Sabine Hossenfelder, "The End of Theoretical Physics As We Know It", August 27, 2018.
at
https://www.quantamagazine.org/the-end-of-theoretical-physic...
It's not currently (maybe ever?) possible to know when you're 'done' with an experimental science. With newtonian mechanics, we didn't know we needed something better until we did.
But why would a non-reducible universe be so predictable?