The Top 5 Problems of the Standard Model

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The Standard Model of Particles Physics is  

the best theory we have for how the  universe works on subatomic scales.

It’s not even a close competition.

Like Lebron versus a  snail in a dunking contest.

No other theory is as good at describing the  

particles that make up reality and  how they interact with one another.

But despite how impressive the  Standard Model is, it is also wrong.

And it’s wrong in ways that leave some absolute  whopper mysteries for scientists to solve.

So here are five of the biggest  problems with the Standard Model,  

as well as some ways physicists  are trying to patch the cracks.

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In 2013, two physicists won  the Nobel Prize in Physics for  

predicting the existence of a single  subatomic particle: the Higgs Boson.

They made their predictions back in the 1960s,  

but the Higgs Boson wasn’t officially discovered  through experimental observations until 2012.

The Higgs Boson helps give all the  other subatomic particles their mass,  

so the Standard Model just  doesn’t make sense without it.

Hence why physicists spent  so long trying to find it.

In the annals of particle physics  history, this was just one of  

many times the Standard Model described a  thing before we knew it actually existed.

And by “we” I mean humanity as a collective.

Because, you know, some of us were too busy not  being born, or being teenagers, to contribute.

But for the Higgs Boson, there was one major  problem: The particle that CERN discovered  

had a mass of 125 gigaelectron volts, or  roughly 130 times the mass of a proton.

That might sound kinda big for  a single subatomic particle.

But it’s too light.

Much too light.

It might be as many as 34  orders of magnitude too light.

That’s ten million billion billion  billion times what it “should” be.

Now, I had to pull out the scare quotes because  the Standard Model can’t really predict the mass  

of the Higgs Boson at all, because the equation  for its mass depends on a number that’s unknown.

It’s called the UV cutoff, and it’s  the point at which the energy levels  

of the thing we’re observing are  too high for our math to work.

But like I said, we don’t actually  know the exact value of the UV cutoff.

It’s just vaguely…over there, somewhere.

Since we don’t actually know  that number, our theories have  

to work for all possible values of the  cutoff, including really enormous ones.

Which means the equation would need  equally enormous negative values  

somewhere else to balance that out and give us  the mass we’ve observed for the Higgs Boson.

What could cause this uber  convenient cancellation?

We have no clue.

And unfortunately, that means we’ve  run into a case of finetuning.

And finetuning gives physicists the willies.

It’s not impossible that nature could  

so carefully and so precisely balance  the energy checkbook of the Universe.

But when a theory requires such  a precarious balancing act,  

physicists get jumpy and try searching  for something entirely different.

One of the leading ideas to explain  

the mysteriously-normal-sized  Higgs boson is supersymmetry.

We don’t have time to get into the physics of  exactly how it helps, but it poses there’s a  

whole set of particles lurking at energies higher  than we’ve been able to create in experiments.

These new particles would be paired  with Standard Model counterparts.

Like traditional quarks would  be partnered with supersymmetric  

squarks, and leptons would be  partnered with, yes, sleptons.

These new guys have some properties that are  opposite from their Standard Model partners,  

and this opposite-ness shows up  in our equations as a minus sign.

So if supersymmetry particles really do exist,  

the calculation for the Higgs mass would better  agree with what we actually observe…without  

scientists having to just add a number  without knowing why it should be there.

There’s still no solid evidence of supersymmetry,