https://theconversation.com/evidence-of-brand-new-physics-at-cern-why-were-cautiously-optimistic-about-our-new-findings-157464
In: Physics
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Physicists have put together over the years the “Standard Model” which describes all of the sub-atomic particles and how they combine/decay into other particles (and how often). A recent paper from CERN describes how they *might* have evidence of an error in what the Standard Model predicts vs. experimental results.
This is important, because there is a pretty strong belief that the SM is incomplete and overly complicated, and that there’s a better model out there if we could figure it out. Finding specific flaws in the existing model is one of the best ways to come up with a better model (and know that it is likely more correct).
Additionally, we now believe that there are 4 “fundamental” forces in nature. It is a *possibility* that this experimental data is evidence of a new, unknown force that isn’t in the SM.
But the key word is *might*. The existing experimental evidence could just be a fluke. It’s kind of like flipping a coin, since it is based on probability.
We know that when we flip a fair coin, 50% of the time it should come up heads and 50% of the time tails. But when you run experiments, you don’t get exactly 50/50 every time. You need a lot of coin flips to get close enough to 50/50 to be statistically certain that you have a fair coin. There’s always a possibility that you get way too many heads or tails just as a function of chance.
The CERN data is pretty strong, but not yet strong enough. They need a lot more certainty before being able to say for sure that the Standard Model is broken in that particular manner. And it would be helpful if it was also replicated elsewhere, to reduce the odds of experimental error. These experiments are very difficult to run.
The simplest answer I can come up with is that at the subatomic particle level (as in the things that make up protons, neutrons, and electrons) our “standard model” doesn’t fit perfectly. These subatomic particles only sometimes act like we expect them to. So making accurate predictions has been difficult. Though the more we observe these particles with experiments like what’s happening at Cern, the more we understand.
One famous example is known as quantum entanglement. Certain subatomic particles have a “spin” to them. Sometimes those subatomic particles are considered “entangled” with another. Where if we change the “spin” of one, the other will react instantaneously. This happens regardless of distance. If we separated the entangled pair on two different sides of our galaxy, they would each change at the exact same moment. This defies the standard model’s understanding of the speed of light where no information can travel faster than light through a vacuum. If it did it would take as long as it would for a photon to travel from one particle to the other to change spin.
Does this have any kind of impact whatsoever in the value of universal constants (ex: speed of light)? Or not?
In the standard model, electrons belong to a family of particles called leptons, which also includes the mu and the tau. The three essentially behave identically – the only difference is their mass.
What was observed here is that b quarks decay into electrons more often than they decay into muons, which is odd because electrons and muons should behave essentially the same. Having such a discrepancy is not inherently a problem with SM, since we know a lot of reasons why particles would prefer to decay to one lepton over another. However, all such examples are relatively easy to explain by combining our understanding of the weak force with basic physics principles. For example, even though the tau largely behaves the same as the other two, it is the most massive, so it can only appear in high energy decays based on energy conservation arguments. A more sophisticated example would be that charged pions decay to muons more than electrons. This is because this decay occurs by the weak force, and the weak force has a preference for certain angular momentum configurations, so we can explain this based on angular momentum arguments. The main point is that all of this “lepton physics” is well understood and has been studied for a long time.
What’s different about this is that they ALSO tried to apply lepton physics to this, but it didn’t work. Hence, they were forced to conclude that the discrepancy is due to the b quark simply having a greater affinity for the electron than the muon. This is surprising because there’s no reason for the b quark to decide among the leptons which one it likes. After all, the b quark mostly follows quark physics, which doesn’t even interact with leptons. Moreover, since the b quark is over 40 times bigger than either particle, the mass difference (that is, the only difference) should be negligible. So, apparently something from quark physics can distinguish leptons, even though as far as we know leptons don’t even appear in quark physics. This is the idea of the contradiction, and it can’t be put to rest quite yet because there’s a lot of quark physics we don’t know.
tl;dr e and μ are similar particles called leptons, which follow lepton physics (easy). b is a large particle that follows quark physics (hard). Lepton and quark physics should be 100% independent. However, we suspect that b prefers e over μ. If correct, the discrepancy can’t be explained by lepton physics, so it lies in quark physics, which mean that leptons are appearing in quark physics when they shouldn’t. This makes quark physics harder, but also more interesting.
(edited for typos, some sentence structure, and the tldr)
Imagine you’re throwing rocks in a pond.
You throw a rock, and make a few ripples.
You throw a different rock but harder, and it makes larger ripples.
You take a really heavy rock and throw it, and the ripples are really big even tough you couldn’t throw the rock as hard.
Year passes, and you think this is all there is, but then you go to summer camp and a kid who is older shows you a secret way to throw rocks: You want flat stones, and you want to throw them really fast but ” rotating sideways” and “away from you”. You don’t know what that means so the next time you go to a pond, you try and try and try and suddenly it happens: The rock doesn’t sink and makes ripples, but instead it skips along the water and makes a lot more ripples than the past rocks ever could.
Kind of the same thing, but instead of throwing rocks at ponds we are taking the smallest things we know of (protons), making them go really, *really* fast and watching what happens when they crash into each other.
**Background / The basics:** Scientists in Cern use a large machine called a particle collider because this is all it does: collide very small (smaller than an atom) particles or parts of atoms together in a continuous beam. Having recorded trillions of these collisions the scientists and their computers have learned a great deal about how these particles usually behave when they collide, so they have made many predictions and combined all their knowledge into a big unified theory they call The Standard Model. (SM) The SM is not perfect because it cant explain everything we observe in the universe or even in the big collider, so more work is needed and the scientists comes up with new ideas to explain what is really happening. When these ideas are tested, sometimes they see a result that surprises them. And at Cern surprises like these can be good because they indicate new things in nature we dont know about yet.
**This experiment specifically:** I this case , the Standard Model predicted a certain result, but they saw something else. Imagine you are shooting two new strawberries at each other over and over and you photograph the collision with lots of fast photos. Each time you expect to see the same certain things: lots of strawberry juice droplets, some small some bigger, you expect seeds and so on , but now you see something new: you see some of these small seeds suddenly behaving like they are super heavy and big and going really far. The question the scientists are asking is why are they behaving like this? Why are they going so far? is it a new force of nature acting on them or is it something else?
To answer this, more tests are needed.
A lot of science isn’t “eureka!” but… is more “hmm… that’s odd”. Spotting the weirdness vs what’s already known produces theories… some of those produce new science.
In this case the CERN data seems to be pointing at weirdness in what we know of how the “Standard Model” works. This is likely to eventually produce new understandings as the weirdness is worked out, test and better understandings of it affect our existing knowledge.
You were given a standard LEGO set on your birthday years ago. For a whole year you played with it and made everything in the universe you could think of. You asked for more next year, but just got the same types of pieces, maybe with different colors and subtle variations in shapes, sometimes with a funny little figure that’s different than the rest but still considered part of the standard set. There was nothing more. Your life was complete.
Then this year, you got a LEGO Technic set.
Just some misconceptions I’d like to clarify:
– Gravity is a force
Einstein’s general relativity says otherwise. Gravity is described by Einstein to be the warped space-time around heavy objects. This is why even light’s path is bent by gravity. Someone not in a gravity well will age more than someone in a gravity well. In theory, if you can survive falling into a black hole and look back at the universe, you can see the whole future of the universe happening very quickly.
So far this is the most widely accepted theory of gravity.
– Why can’t we add Gravity to the SM
Because of a very simple reason. Gravity seems to disappear when we get to small things. The SM deals with extremely small things, so to “add” gravity to it, means to describe gravity in the very small things. It’s very hard to create a theory of something when you can’t even measure it.
General relativity describes the physics of the big things. Quantum physics describes the very tiny things. These 2 theories are not compatible with each other. However, they are the best theories we have. This is why the world is waiting for a unification of general relativity and quantum physics. If we have a theory that describes everything, it would also describe gravity in the very small things too.
– How can we consider Earth a closed system when there are other things out there?
It’s just for practical reasons. For things such as thermal activities, it is good enough to consider the Earth a closed system. The medium between the Earth and the other things do transfer some heat, but extremely tiny to have a meaningful impact on anything. Simply dismissing it will simplify our lifes a lot.
It’s the same thing when you consider Newton’s laws of motion, if you hit a ball with a bat, the ball will have a force applied to it, and the bat will have an opposite force applied to it as well, as if they were in a closed system. In reality, there’s the muscles in your arms, the ground, the air molecules, etc, but those don’t really contribute much to the subject.
– Stars create matter so they are the opposite of black holes
Stars are matter clumped together due to gravity. They are not magical godlike beings that create matter out of nothing. A black hole is actually created from a very massive star after it’s death.
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