Pushing back the frontiers of knowledge is
what my colleagues and I do, but there are
a couple of different approaches.
Actually, to keep the topic manageable, I’d
like to talk only about particle accelerators
and, specifically, a couple of different ways
they can be designed to teach us some of the
universe’s secrets.
So how does a particle accelerator work?
Well, generally we take a charged particle
from an atom and accelerate it with electric
fields.
So let’s show how it works using animation,
so you can get a basic idea.
It’s expensive, and it will blow this year’s
video budget, but, well, you guys are worth
it.
So I’m going to need some help from my CGI
wizard.
Maestro, can you materialize an atom in my
hand right here?
Thanks, great.
So you guys know that atoms are made of protons,
neutrons and electrons.
I’m just going to reach in and grab a proton,
which is found at the center of atoms and
has a positive electric charge.
So don’t try this at home- they’re slippery
little suckers.
Okay.
Got it.
Actually, two.
The second one will turn out to be handy.
Alright-so I don’t need this anymore.
And I’ll take the second one and put it
in my pocket.
Now I have my proton.
Maestro, it would be helpful if you could
now materialize an electric field for me.
This is actually pretty easy to do.
The easiest way is to just have two metal
plates and connect them to a battery.
The result is that an electric field is set
up between the plates.
Electric fields push charged particles.
So I’m going to put my proton in the electric
field and it’s going to be shot off to my
left.
So here goes.
Watch.
Oops.
Sorry Maestro.
I probably should have told you to get out
of the way.
The electric field I just used was a relatively
low one, but I could have used a bigger one.
Maestro, can you crank up the electric field
a little bit?
And this time, watch out.
Alright, so I’m going to use the second
proton.
I’m to release it right now.
When I put it in the stronger electric field,
the proton moves faster and it gains more
energy.
So that’s the first point – by increasing
the electric field or using a few other tricks,
we can get a particle to move with more and
more energy.
So far, I just shot one proton at a time using
the electric field, but I could have shot
more.
I have a bucket here full of preselected protons
and I could reach in and get two protons and
the electric field will accelerate both.
Grab three and three will be shot by the field.
Or I could just dump out the whole bucket
out and accelerate a whole ton of protons.
See- like this.
That was pretty dramatic, but maybe it wasn’t
the smartest of ideas.
Maestro, can you make this all go away?
And sorry about the welt.
This illustration shows that when we scientists
make a beam of particles, there are two different
important parameters.
One is the energy of the particles and the
second is the number of particles that are
accelerated.
To simplify things, we’ll call the first
important parameter energy and the second
one luminosity.
Luminosity depends, among other things, on
the number of particles in a beam.
So those our terms- energy and luminosity.
So now we get to the point.
The best particle accelerators have both high
energy and high luminosity.
But sometimes you have to make a compromise
and pick one or the other.
So what are the benefits of the two?
Well, the easiest to understand is energy.
You’ve no doubt heard about Einstein’s
equation E = mc2.
Basically, that equation says that energy
and mass are equivalent and that you can convert
energy into mass.
So if you want to make a heavier kind of subatomic
particle than has ever been made before, you
need to use a very high energy beam.
This is the basic idea behind the Large Hadron
Collider, or LHC, the world’s most energetic
particle accelerator, located just outside
Geneva, Switzerland.
In it, beams of protons are accelerated to
travel at almost the speed of light to the
mind-boggling and unprecedented energy of
13 trillion electron volts of energy.
That’s about ten million times higher than
the energy involved when an atom splits in
a nuclear reactor.
Mind you, I’m not talking about the entire
energy output of the reactor.
I’m just talking about a single atom.
A reactor has millions of trillions of trillions
of atoms.
But it’s still incredibly impressive to
accelerate a single particle with the energy
ten million times higher than the energy released
when an atom is split.
So this method for studying the frontier of
knowledge is very direct.
Want to make a heavier particle, make a higher
energy accelerator.
This is very straightforward.
How luminosity comes into play is a bit trickier.
To understand this, you need to invoke the
rules of quantum mechanics.
In quantum mechanics, things are weird.
Events that are supposed to be impossible
actually can occur, but very rarely.
If you put an object in a room with a closed
door, there is a small chance that the object
will suddenly appear outside of the room.
In the familiar world of objects and rooms
this is insanely rare, but in the world of
particles, it’s still rare- but at least
more likely.
To give a more concrete way of thinking of
this, in the particle physics world, there
are phenomena that super, incredibly, unlikely
– that can essentially never happen.
Kind of like you winning the lottery.
If you’re playing the lottery, you have
essentially zero chances of winning if you
buy a single ticket.
But if you buy hundreds of tickets, your odds
are improved.
Buy a million tickets and your chances of
winning are improved even more.
So that’s why luminosity is important in
particle physics.
If you’re looking for something rare and
you collide a single particle, chances are
that you won’t find the rare thing.
But if you collide trillions and quadrillions
and quintillions of particles, you increase
the chances that one of those particles will
do that rare thing and you’ll make a discovery.
So that’s the difference between the energy
approach and the luminosity approach to discovery.
If energy is kind of like using a sledgehammer,
luminosity is a more subtle and gambling approach,
and both have their merits.
So which is better?
Well what better way to find that out than
to have the two of them duke it out?
How about we do that using these two guys
as a metaphor.
What should we make them do?
I’ve got it!
Arm wrestling!
This match will determine the particle physics
research champion of the world.
Our two contestants are looking pretty buff.
Let’s meet them.
Weighing in at 13 trillion electron volts,
we have Eric “The Hammer” Energy.
He’s looking fit and dangerous.
His opponent, weighing in at 30 trillion protons
per pulse, is Lenny “The Lottery” Luminosity.
You can tell he’s been working out.
Are you guys ready?
Then let’s get ready to rumble.
As our champions battle, let’s talk about
how these approaches are being used in today’s
research.
The CERN laboratory has banked on using the
high energy beams of the Large Hadron Collider
to do their research.
In contrast, Fermilab, which is my own laboratory,
has elected to build the highest luminosity
beams of protons ever made to study exceedingly
rare phenomena involving particles called
muons and neutrinos.
In fact, these high luminosity beams have
a chance of making discoveries that even the
Large Hadron Collider might not make.
Yeah, I’d better stop this before someone
gets hurt.
Okay, guys- chill.
You’re both winners.
Really, it’s okay.
Both are great ways of doing research.
Cool?
Alright, so shake hands- it’s alright.
Alright Maestro, can you get me out of here?
Thanks Maestro.
That was pretty intense.
The bottom line is that there are very different
approaches to making particle beams and either
of them could end up leading to a paradigm
overturning discovery.
There’s no way to know which will make a
discovery first.
Energy and luminosity are both champions.
