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You’re probably familiar with the Large Hadron Collider.
You know, the massive ring beneath the France-Switzerland border
that smashes teeny tiny particles together at near light speed,
and hasn’t made a black hole that sucked up the Earth,
like some people feared?
Yep. That Large Hadron Collider.
Better known as the LHC.
Over the past 15 years, the LHC has done a lot of awesome science,
and made some pretty significant discoveries.
So it deserves that name recognition.
But there are other particle smashers in the proverbial pipeline.
They’re not all bigger,
but they all hope to be better probes of the subatomic.
So let’s have a look at a few of these upcoming megastructures,
and what they’re going to help us learn about reality as we know it.
Our current best understanding of the subatomic world
is called the Standard Model,
and it can explain the physics of almost everything,
from why your coffee cools down after hours at your desk
to how radio waves carry your favorite tunes halfway around the world.
It all comes down to a collection of elementary particles…
the fundamental building blocks of our reality.
That includes particles that make up you and me,
like electrons and the quarks inside protons and neutrons.
And it includes more exotic bits of matter.
But it also includes even weirder particles called bosons.
We’ll get to the most infamous one of those in just a moment.
As tidy as the Standard Model appears to be,
there’s a lot that it can’t explain.
Which brings us to particle accelerators.
They help physicists fill in some of these gaps
by taking advantage of the fact that energy can create mass and visa versa.
You know, the good ol’ E equals M C squared.
Using super strong magnetic fields,
these massive machines ramp up beams of their subatomic specimens
to nearly the speed of light,
and smash them together to watch the energy
from those collisions turn into brand new particles.
The LHC’s most famous accomplishment
is probably the detection of the Higgs Boson,
which was spotted back in 2012.
Has it really been that long? Apparently so.
But maybe it feels like yesterday because after all this time,
there’s still a lot we don’t know about it.
We know the Higgs boson has the very special job
of giving other particles in the Standard Model mass,
but we still don’t know how it does that.
So to probe the mysteries of the Higgs Boson in more detail,
several countries are developing their own version of a Higgs Factory.
Some, like China’s Circular Electron Positron Collider,
or CERN’s Future Circular Collider,
will feature two 100 kilometer rings
that accelerate particles in opposite directions.
If that sounds huge, it is.
Here’s what the FCC will look like next to the LHC.
Both of these upcoming colliders build on and improve
the existing design of the LHC and use a lot of the same tech.
With every trip around the ring,
the particles get an energy boost from an electrical pulse.
And powerful magnets with the strength of five
and a half MRI machines help steer the beams
to keep them going around in a circle.
Once the particle beams are up to speed,
they’ll come together at either two or four collision points,
each equipped with its own detector.
They’ll need to go through a series of upgrades,
but eventually, these extra large colliders will smash particles
with over seven times the energy that the LHC currently achieves.
And that extra energy means physicists can study
these subatomic particles in even finer detail.
But Higgs Factories don’t have to be ring-shaped.
Two other designs, the Japan-hosted International Linear Collider
and CERN’s Compact Linear Collider, feature a straight line.
One upside to using a linear accelerator over a circular one
is that you only need the speeding-up bits,
not the magnetic steering bits.
So they can be cheaper to build.
The downside is, you only get one go at speeding up the particles,
so the boosting tech has to be really good
or the collider has to be really long.
But whether straight or bendy,
all these Higgs Factories have the same goals.
See, the LHC is kind of messy when it comes to making these elusive Higgs bosons.
Because it uses hadrons, which are clusters of quarks,
all those collisions end up making a bunch of different particles.
And that creates a lot of noise when you’re trying to work out
what’s going on in the specific collisions that create a Higgs Boson.
So instead of complicated hadrons,
Higgs Factories will smash electrons with positrons,
the electron's positively charged antimatter twin.
Unlike quarks, they can exist as solo particles.
And when you combine that with the fact
that matter and antimatter cancel each other out,
it means the collisions between an electron
and positron produce way fewer kinds of particles.
So There’s a lot less noise for researchers
to hunt through when trying to study the Higgs.
After finding a way to churn out all these Higgs bosons,
physicists will use them to fill in a bunch of gaps in the Standard Model.
For example, the fact that the Higgs Boson is a mass-giving particle
should mean that it’s quite heavy,
or at least as heavy as the particles it’s interacting with.
But it’s actually light, subatomically speaking.
So the Higgs Boson may not be the only particle out there that gives other particles mass.
It may have a partner in crime that our experiments
haven’t had enough power or sensitivity to detect yet.
And these Higgs Factories may be just the advancement we need.
So electrons and positrons are great because they’re less complicated than protons.
But protons do have one thing going for them.
They’re heavy. And that heaviness translates into energy.
To get the best of both worlds, physicists want to smash a particle called the muon.
Muons can basically be thought of as the electron’s heavier sibling.
In fact, if an electron had the mass of an adult human,
then a muon would be an elephant.
Not only can muons have a lot more energy in them when collision time comes,
their heftiness means they don’t lose a lot of energy
while they’re being swung around their ring.
That means an accelerator doesn't need to work as hard
to speed them up compared to their much lighter electron and positron friends.
Plus, there’s the added benefit that the collider doesn’t have to be massive.
A muon collider that’s 10 kilometers long can achieve similar energies to the LHC,
whose particles loop around a 27 kilometer-long track,.
And a more compact collider leaves less of an environmental footprint.
But muons do have their downsides.
When muons are made in a lab,
they don’t tend to bunch together into a nice,
tidy beam that you can fire down a pipe.
And you need a tight beam so the muons have a high chance
of hitting each other when the beams collide.
So even though we’ve known about these particles since the 1930s,
and scientists have wanted to build a muon collider since the 1960s,
we still don’t have one up and running.
Progress has been made, though.
For example, an experiment called MICE,
or the Muon Ionization Cooling Experiment,
has managed to reliably fire protons
onto a target and then supercool the resulting beam of muons.
Like condensing steam back into liquid water,
this supercooling corrals the particles into a much narrower beam.
But the cooling also slows the muons down,
so a bunch of electromagnets need to speed them back up, while keeping them bunched up.
Repeat this cooling and speeding a couple of times,
and you’ve got yourself a muon beam ready for study!
Oh, and this all happens before the muons enter the main particle accelerator ring.
At the moment, we don’t have an operational supercollider dedicated to muon studies.
But there is a joint mission between CERN and Fermilab
in the U.S. to build one by 2045.
When it gets up and running,
researchers can use it a bit like a Higgs Factory
to create and study Higgs Boson particles.
But the energy they get out of muons could be 20 times greater
than the Higgs Factories we mentioned before,
which could allow them to witness new subatomic particles and interactions.
They could even use a muon collider to uncover evidence of dark matter,
this mysterious invisible stuff we’re pretty sure is out there,
and is more abundant than all of the matter we can see,
but we don’t know what it actually is.
Now there’s one more particle from the Standard Model
that physicists are particularly keen to study, and that’s the neutrino.
Neutrinos are the neutrally charged cousins to electrons and muons,
but are so light we don’t even know what their masses are.
In fact, neutrinos are often described as ghosts.
They can stream through the entire Earth as if it’s not there.
And that’s not their only superpower.
Neutrinos are shape shifters, as well.
Imagine buying milk chocolate at the store
and coming home to find it’s white chocolate,
then opening the packaging to find out it’s dark.
I know, I know, I’d be disappointed, too.
Neutrinos and their antimatter twins each come in three flavors,
and at any given moment can switch, or oscillate,
between those flavors.
All this means that neutrinos are incredibly difficult to detect,
let alone study.
But incredibly difficult does not mean impossible.
There are multiple neutrino detectors around the world that are hard at work,
picking up the handful of unlucky neutrinos
whose ghostly powers failed them at just the wrong moment.
But so far, scientists have mostly relied on the Sun as their neutrino source.
Which is a bit annoying.
You’d think they’d want more control over exactly how many neutrinos are made,
and what flavors they are.
Well, enter DUNE, the Deep Underground Neutrino Experiment.
This massive, 1300 kilometer-long experiment
will run all the way from Fermilab in Illinois
to the Sanford Underground Research Facility in South Dakota.
And DUNE is a bit unusual as far as particle accelerators go.
There’s no tunnel or ring for the neutrinos to traverse that distance.
Neutrinos don’t need any of that fancy infrastructure.
They’ll just fly straight through the earth!
To make its neutrino batches,
DUNE’s Fermilab accelerator will smack protons
into a block of graphite to create new particles.
But the most important of those new particles are positively charged pions,
which are a type of hadron.
These pions are unstable, and quickly decay into muons and neutrinos.
While the muons get trapped,
the neutrinos can just zoom through Fermilab’s detector,
and then off toward the Sanford detector.
Which is pretty darn massive.
When construction finishes,
the Sanford detector will have four tanks
that are each six stories tall and a football field long.
And they’ll be filled with 17,000 tons of liquid argon.
When a neutrino gets close enough to one of those argon nuclei,
it can emit yet another kind of particle in our Standard Model…
either a W or Z Boson.
Whichever boson pops into existence will quickly crash into a nearby argon,
creating a particle shower not entirely unlike what we see
in more traditional particle accelerator collisions.
And some of those particles will be electrons,
which are captured by ultrasensitive instruments on the tanks’ walls.
That’s how DUNE will indirectly detect neutrinos,
but the neutrino’s ghostly nature means these events will be pretty rare.
Scientists are expecting to pick up around 10 per day when they get started.
The detector back at Fermilab will work in a similar way.
It’s just a lot smaller.
So scientists will be able to compare the results coming from both
to investigate the neutrino’s shapeshifting powers.
They might even figure out why there’s so much matter in the universe.
According to the Standard Model,
the energy of our universe’s birth should have created an equal number
of matter and antimatter particles.
A perfect balance that would make some supervillains weep with joy.
But reality seems to be out of balance, favoring matter…
unless there’s some section of the universe
we can’t find that has entire antimatter galaxies,
filled with antimatter stars and planets,
and maybe an antimatter you.
So scientists hope to see whether or not matter neutrinos
and antimatter neutrinos oscillate according to the same rules.
If they don’t, well, maybe one consequence
is our universe’s preference for matter.
As for how long we might have to wait to get those answers,
a prototype DUNE has already been tested out.
The whole experiment plans to be online by the mid-2030s.
Which, given the scale of a megaproject such as this, is right around the corner.
So it’s a very exciting time ahead for the field of physics!
By building these spectacular machines to study
Higgs Bosons, muons, and neutrinos
, there’s the possibility we’ll have a totally new understanding
of our universe within our lifetimes.
It takes a ton of investment to build these accelerators
that probe the parts of our world that are too small to see.
But if it reveals the fundamental nature of reality?
Well, I say it’s worth it.
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