[ Music and Background Conversation ]
>> Dr. William Phillips: Good
morning [background conversations].
It warms my heart so much to see such a good
crowd to come out for my friend, Jim Gates.
Last year -- late last year -- sometimes after
the historic announcement of the observation
of the Higgs boson by two teams at Cern, a NIST
colleague told me that we needed to get someone
to come to NIST to tell us
what the Higgs was all about.
After years of media hype about
the Higgs, it had finally arrived.
But what is it and why is it such a big deal?
Having experienced a few talks that purported
to tell me that, but that I didn't understand
at all [background chuckles], I thought
very carefully about who should be asked
to explain the Higgs to a pedestrian
experimentalist like myself.
And I thought carefully.
And it didn't take me too
long before I concluded
that Jim Gates was the right person for the job.
Jim did his undergraduate and graduate work
at MIT writing the first doctoral
thesis there on supersymmetry.
The University of Maryland captured him in 1984,
and he's now the John Toll Professor of Physics
as well as being the Director at the
Center for String and Particle Theory.
And a Regence Professor of the
University of Maryland's system,
which is the highest professorial honor that
the entire Maryland system awards its faculty.
He serves his country as a member
of the President's Counsel
Advisors on Science and Technology.
And Jim is the recipient of many awards and
honors for his work in scientific research.
And in bringing science to the public.
Last month the President awarded him
the nation's highest scientific honor,
the National Medal of Science.
I [pause] -- here is Jim with the President,
about to have the President
hang that medal around his neck.
I was really pleased with this award.
I was also thrilled to be at the
White House for that ceremony.
That's what I saw from my perspective
off in the wings [chuckles].
And it turns out that Jim told
the President a joke [chuckles].
Which the President found very funny.
But apparently Jim's not revealing
what that joke was [chuckles].
We had a wonderful time at the White House.
We had a wonderful time at
that gala celebration.
I convinced Jim and his family to pose
for this picture in front of the poster
for his National Medal of Science.
Now you can't read the citation,
but let me read it for you.
Because it illustrates why I knew that
Jim was the right guy for this job.
So the citation reads, "For contributions to the
mathematics of supersymmetry in particle field
and string theories" -- that's
not what I asked him for.
"And extraordinary efforts to engage the public
on the beauty and wonder of fundamental physics.
Jim Gates.
[ Applause ]
>> Jim Gates: Bill thank you
for that kind invitation.
This is not my first time coming
out to NIST to give a presentation.
And there's someone in the audience that
has actually been with me on a number
of occasions when I've presented.
And first -- it's also great --
let me acknowledge all the wonderful
friends that I have not seen in a while.
Catherine, for example, and Kurt, and just --
Marlin, and just so many other people
out here just that I've come --
had our paths cross over the years.
So it's great to be back.
But as I said, there's one
person in the audience
that told a story once that
I've never forgotten.
And so we were sitting at an event very
similar to this where I was to present.
And an introduction was going on.
Unfortunately it was not as brief as Bills.
In fact, the introduction went on and on
and on and I started getting very nervous.
I'm always nervous before
I speak; this didn't help.
And the person next to me leaned over
and said, you know we've all heard
of a man that needs no introduction.
[ Laughter ]
But that is an introduction that needs no man.
[ Laughter ]
The person who made that comment
is actually in the room today.
I won't reveal his identity, but I will ask
him later whether he remembers telling me that,
and I've never forgotten that.
[ Laughter ]
So we're going to do a little
review of the standard model.
This is the first time I've presented this talk.
And so this was specifically
designed for today's presentation.
I'm sure I'll be giving a talk again.
I've tried to throw in all the bells
and whistles and the kitchen sink,
so that we can A) Understand some physics.
But B) Also have some fun along the way.
So let's start with the standard model.
And the standard model is
a collection of particles.
And so you've probably seen this
kind of representation before.
We have the sets of quarks.
Up, down, charm, strange, top and bottom.
We have a set of leptons -- that
is particles that are very similar
to the electron -- the Muon and the tau.
And then there are things in nature
that are like neutral electrons.
We call them neutrinos.
So this is part of what our species has
been learning about for just over 100 years.
And in fact, the first elementary
particle was actually the electron.
It was first theorized by an electrochemist
by the name of J.G. Stoning [phonetic]
who was trying to figure out
how electroplating worked.
And he had the idea that if there
was something in nature smaller
than an atom he could understand
why electroplating worked.
And so he thought of this idea.
First people to see a chunk of
matter smaller than the atom.
And he also gave it a name.
He called it the electron.
So the electron was the first
elementary particle.
And it was known to us by -- at least one
of us in our species, by about 1870 or so.
In addition, there are sort
of objects that carry forces.
So these objects are all subject to forces.
But the forces are -- actually have carriers
which we call force particles
or gauge particles.
The photon is the carrier of
the electromagnetic force.
There are 8 gluons which carry
the color, chromodynamic force.
There are the W and Z bosons.
This is neutral.
There's a plus and minus version of that.
And they carry the weak nuclear force.
You will notice I'm not talking about gravity,
which is also one of the fundamental forces.
And the reason is because the standard
model does not incorporate gravity
into its description in a manner
that's consistent with the laws
of special relativity and quantum theory.
So it's sort of on the outs.
So all of these particles
behave like spinning tops.
We physicists have a number called
H Bar, and we can measure the rate
at which these particles spin in terms of H Bar.
For all of the matter particles,
which are called fermions,
this number J turns out to be 1/2.
For all the force carries, which we call boson,
this number J turns out to be the number 1.
So there's already a dichotomy
in the structure of the universe.
Quarks appear in triplets
in terms of nuclear matter.
You can either have triplets of quarks
or you can have quark/anti-quark pairs.
The triplets are called hadrons.
The quark/anti-quark pairs are called mesons.
And you can, by putting together different
combinations you get ordinary protons
or antiprotons.
Neutrons, lambdas, omegas.
And so you can sort of think of a hadron
as a bag into which you throw quarks.
And those collections are then nuclear matter.
So here's a picture of a proton, or at least
some sort of representation of a proton.
By the way, all the images
in my talk are allegories.
And they're all backed up by equations.
So rather than simply throw you
page after page of equations,
it's much simpler to show you the
concepts behind the equations.
One of the strange things
about being a physicist is
that we work a little bit
like authors of novels.
You know, novelists create characters and
then tell stories with their characters.
And in fact, if you speak to people who are
novelists, sometimes they tell you things like,
at a certain point the character
had a story to tell me.
And it was my role to be
the conduit of that story.
That's exactly what we physicists do.
We create mathematical novels
with mathematical characters.
And sometimes those characters tell us stories
that we didn't know were
there when we began the novel.
The story of anti-matter, for example,
was a very interesting example of that.
Where Dirac wanted to write an equation
consistent with relativity and quantum theory.
Wrote the equation, and then
because of that equation found
that the electron had an evil
twin called the positron.
So it's an example of a character
telling a story
that you didn't know was there
when you started writing it.
So protons are dynamical things.
So in this little cartoon we're going
to try to grab one of the protons --
one of the quarks and pull it out.
We can't quite manage it.
And in fact, what we wind up afterwards
is in fact two bits of nuclear matter
where a quark/anti-quark pair was created
in the process of trying to pull them apart.
We don't believe you can ever
pull quarks out of nuclear matter.
And we have a set of mathematics that
underlies quantum chromodynamics.
And that we believe that there's a phenomenon
known as infrared slavery, which is responsible
for this permanent capture of quarks
in the interior of nuclear matter.
If we're going to do some more physics however,
we take these objects and
arrange them in patterns.
So each of these symbols you
can think of as a wave function.
If you're thinking of usual quantum mechanics.
So let me take the quark wave
functions for the up and down quarks.
And also observe that quarks come in triplets.
So let me arrange the up and down
wave functions in this matter.
This L & R stands for left and right,
and we'll come back to that later.
I can do the same for the charm and strange
quarks and for the top and bottom quarks.
Now the next thing we're going to do is not
something that's obvious because after all,
we're just taking all these particles that
we saw and we're putting them in patterns
in anticipation of doing some physics.
Let me arrange the leptons so
that we only have the neutrino
and an associated electron in a doublet.
Not in a 2 x 3 matrix, but in a 1 x 2 matrix.
Same thing for the Muon particle.
Same thing for the top particle.
Oka and then finally all the right-handed
leptons we'll just write separate
wave functions.
And that's a very strange
way to start taking things.
It looks willy-nilly like we
simply took the wave functions
and threw them together in
just an arbitrary fashion.
But in fact, that's not the case.
As we will see shortly, the arrangement of
those patterns in fact is dictated by the forces
that we see acting on these objects in nature.
So how do forces act on these things?
Well we have something called
the interaction paradigm.
And the basic idea is, that we can imagine
that these dots of lights here are electrons.
And if one electron is to
impact the presence of a second,
it has to actually send a message carrier
that tells the second object I'm here.
You're an electron.
You need to move away from my location.
So there's a message being conveyed.
The message carried here is in fact the photon.
And so this is, in fact, a cartoon.
But it's also a technical device that we
physicists use called a thymine diagram.
From this diagram I know how to write
integral expressions to measure this force.
Now in the world of the very
small, quantum theory rules.
Quantum theory tells us that in fact, the
story we just told was just the beginning
of a much more complicated story.
In this story -- in this version
we have the two electrons.
Again, one electron's trying to communicate
to the second that you ought to be repelled.
But in the process it emits a
photon which it then reabsorbs.
And then it admits the second photon which
is the message carrier about the repulsion.
It turns out that this is a different
mathematical expression than the first.
Or we could do this, where the
first electron sends out a photon,
which at this point disintegrates
into a particle/anti-particle pair,
which we can imagine be a core
compositor -- electron and positron.
Since they have opposite charges
they attract to each other.
And you get to this point they're
anti-matter; they destroy each other,
just like in Star Trek [chuckles].
Creating a second photon which is
then absorbed by the second electron
with a message you ought to be repelled.
So in the world of quantum,
the only thing you can say
about an experiment is the initial points.
Here we have two electrons that are
the initial part of the experiment.
We observe two electrons at
the end of the experiment.
And in between something happened.
And there are many, many
versions of what the something is.
And as you include more and more complicated
versions of the pictures, you get greater
and greater accuracy with respect to
the quantum behavior of the system.
This is simply pertubation theory.
How successful is this?
Because you might think, gee that
seems like a rather ad-hoc means.
And if any of you have ever studied
relativistic quantum field theory,
and had to face for the first time the burden
of seeing what covariant
relativistic quantum field theory looks
like as formulated by Feynman, it's shocking.
It's brilliant, but it's totally shocking.
I remember to this day, being a graduate
student, understanding what it was
that Feynman had put together for us.
How good is it?
Well, you know, physics is not a
faith-based discipline [chuckles].
Now many people don't quite understand that.
The thing that keeps us from being a faith-based
belief system is that at the end of the day,
observation is what rules our paradigms.
And this is a lesson that Einstein
claims Galileo drummed into us.
And therefore it makes Galileo
the father, not only of physics,
but of all of science that
observation rules today.
Pure thought alone cannot be the arbiter
by which we come to understand nature.
So there's this one property -- there's this
thing called the electron dipole moment.
There's this thing called
the electron dipole moment.
And we've been measuring for about 60 years.
And we keep measuring it to
greater and greater accuracy.
When I was looking this up,
this was the measurement.
Since it's an experimental result,
there's always some uncertainty
of how well the equipment's working.
And this number down here turns out to be
hundreds and hundreds of thymine diagrams.
Those complicated pictures that I showed
you, to calculate the same property.
And as you can see, to the accuracy that is in
the experimental setup, these two numbers agree.
And so quantum mechanics -- I like to call
this the best known number in all of science.
Because we have a theoretical prediction
of this number to unprecedented accuracy.
We have an experimental measurement
of this number to incredible accuracy.
And these two things agree
to 8 or 10 decimal places.
There's no other number in science
that I know that I can say this about.
And so this gives us confidence that
quantum theory is an accurate description
of our reality.
However, there are dangers in the quantum world.
And one of these dangers are
things we call anomalies.
How does it work?
Well in the classical physics we
learn about conservation laws.
So electrical current is
conserved at the classical level.
But if the laws of quantum mechanics
are enforced, is that a true statement?
But the answer turns out to
be it doesn't have to be.
In fact, in quantum theory we can draw a graph
like this where these lines here represent,
for example, the motion of an electron.
This is a photon coming in.
And then in the interior of this --
I'm sorry, these are gauge particles.
In the interior of this we have
an electron running around a loop
in the same kind of way of my animations.
And if you calculate this diagram, it turns
out you can get two different answers.
Now there's a very famous
story about this calculation,
and I don't know whether it's true or not.
But it goes that the first person to
figure this out was a graduate student.
He was calculating this diagram
and it was an assignment
that his thesis advisor had given him.
He did the calculation one
way, he got one answer.
And then he, to check it, he decided
the calculation a different way;
he got a different answer.
Well, you know, that sounds like there's
a bug in your calculation somewhere.
So you go back and you try to debug it.
So he checked the calculations
one way, got the same fist answer.
Checked it the second way he
got the same second answer.
Then he took it to his advisors, said,
I can't figure out what I'm doing wrong.
So then the advisors start
looking at the calculation.
And he checked all the calculations
one way, they were just fine.
Checked all the calculations
the other way it was just fine.
And so the advisor was sort of scratching his
head; he said I don't know what's going on here.
The graduate student made the correct choice.
Because he was thinking about being a
theorist; the chose to be an experimentalist.
[ Laughter ]
But this shows the dangers of anomalies.
They cannot be that by simply performing a
calculation two different ways you get two
different answers.
That's not consistent with how
the mathematics of physics works.
And so it turns out that these
things called anomalies can, in fact,
destroy current conservation
in the quantum realm.
And you have to work very hard
to make sure they don't occur.
And in fact, we can see -- I have this
cartoon illustration, and classically it's
like rolling a little ball down
the side of a -- the lip of a bowl.
Classically it's always -- if you put
it in the same place at the same time,
it's always going to roll
in exactly the same way.
If you do this quantum mechanically, well
first of all you can get particle production.
So maybe more particles come out
than you initially put there.
And then instead of following the nice,
classical paths, some of them decide to wander
around because quantum mechanically
they are allowed to do that.
And then finally some of them decide
not to go down to the bottom at all.
That's the analog of breaking
a current conservation law.
And so anomalies, in principal, allow
for this kind of behavior to go on.
But if you do, then you have a
theory with no predictive power.
So what has to happen is you have
to find ways to avoid anomalies.
It turns out that in the standard model,
this is done by the electrical charge
assignments to the quarks and the electrons.
It turns out if you look at the charge of the up
quark, it's 1 plus the charge on the down quark.
If -- and now if you actually plug
in the charge on the electrons.
So this is 2/3, 1/3 -- yeah 2/3 and
1/3 -- well yeah that part works.
This is -1 because a charge on
the election is minus the charge
on the -- minus the charge on the proton.
So you put a -1 here, you find out
that this is, indeed, the number 4/3.
And so what happens is you avoid
these funny triangle anomalies
that would destroy the predictability theory.
Because the charges of the quarks and the
charges of the leptons are exactly what you need
to make sure that those triangle
diagrams all cancel among themselves.
So how'd the hunt for the Higgs get started?
And now we're going to do a
little bit of heavy lifting.
And I promise you that we won't be doing
this the entire talk, but I want to take you
through some of the rationale about
why people think that the Higgs ought
to exist, and now how did we get there?
We're going to start with an
equation called the "Wave" equation.
And I apologize for anyone in the
audience who is feeling uncomfortable.
Please don't bring out the
Holy Water [chuckles].
The wave equation is a standard device that we
physicists use to talk about extended media.
And we can solve it by writing
essentially what looks like a 4A transform.
You plug this into the wave equation, it tells
you that this constant E here must be related
to P -- and through this equation.
But then you recognize this, perhaps as what
Einstein teaches us, is the relationship
between energy and momentum for a photon.
That's the equation that they obey.
The Klein-Gordon equation is like the
wave equation but you put a mass term in.
You can again try to substitute the 4A
series type solution -- or 4A transform.
Plug it into the differential equation.
You find out the relationship
between E and P and M is this,
and of course this is Einstein's
famous E=MC squared.
This is its origin terms of the
equations that we physicists use.
And for a plane wave, moving along the
Z axis and cylindrical coordinates,
let me just simply note that once the
solution can be written in the bottom form.
Well the wave equation, in fact,
and the Klein-Gordon equation are
in fact the same equation except that in
one case you have a potential equals 0.
In the other case you have
a potential that's not 0.
But they're -- otherwise
they're the same equations.
Well, we're -- folks out here do a lot
of stuff in the electromagnetic spectrum.
And as you probably recall, everything we know
about electricity and magnetism comes to us
from Maxwell, who actually first figured this
out in the 1860s although his famous treatise
wasn't written for about a decade afterwards.
But Maxwell's equation --
and I'm teaching a course
on electromagnetism right now at Maryland.
And I'd like to point out that Maxwell's
equations are the results of 40 or 50 years
of work by lots and lots of physicists.
The thing that Maxwell did which was really cool
was that he added one term to the equations --
namely this term called the displacement term.
And then he gets credit for Kulon's
[phonetic] work and [Inaudible]
and all of those [background chuckles].
That's really cool I think, but
to me, the -- my -- to me the --
my favorite term is this sign right here --
I'm sorry, it's actually this sign
here which is called Lenz's Law.
It just shows that if you had done physics
early enough, you could put a correct sign
in the equation and get a law of physics
named after you [background chuckles].
So you take these equations
that Maxwell gives us.
Now the thing about Maxwell's equations is that
the electric and magnetic fields denoted by E
and B are really like velocities
in classical physics.
And so just like [inaudible],
velocities have a --
depend on position, the electromagnetic
potentials
of fields actually depends on potentials.
These things V & A. And now if you
take these things and substitute them
into the Maxwell's equation you
get another mathematical mess.
And so, you know, you look at that
and say, hmm, that doesn't look at all
like how I got to Einstein's equation.
But it would if I could get
rid of this term right here.
Than this would begin to look like
the equation for Klein-Gordon.
Turns out I can get rid of it.
There's a property called gauge invariance
that lets me set this combination to 0.
And when I do that, then Maxwell
equations look -- reduce to this form.
If I set J and row to 0, than this is exactly
the form of the Klein-Gordon equations
that I showed you two transparencies ago,
that lead to the famous equation E=MC squared.
Except with M=0.
The photon is a solution to these equations,
and if you write out a plane way solution moving
along the Z axis, it actually has this form,
which looks a lot like the Klein-Gordon
equation except for this factor.
And if we -- let me point this out.
So let me go back.
I'm writing the standard -- for those
of you who know some electromagnetism,
this is the standard plane-wave
solution for motion on the Z axis.
But I've written it in cylindrical
coordinates, not XY coordinates.
And since it's written in cylindrical
coordinates, the unit vectors are stars --
unit vectors in the radial directions and rings.
Unit directions and angle directions.
And so a photon, in some sense looks like that.
It's a bunch of stars and rings
moving along an axis [pause].
But in fact, that funny dependence
we saw there is
in fact how you can tell the spin of a particle.
For the Klein-Gordon equation S was equal to 0.
For the photon, this S is equal to 1.
But in fact, we know of other
examples for this thing.
In fact, the Dirac equation has S = 1/2.
The Einstein equation has S = 2.
And so in fact, if you write out a field
equation, and look for a plane wave solution
and rewrite it in cylindrical coordinates
[chuckles], if you just get to this form,
you can actually read the spinoff by looking
at the [inaudible] angular
dependence of the wave form.
Something that I've never actually
seen in a book, but you can all work it
out for yourselves and prove it's true.
So suppose you want to have a massive photon.
Well one place might be to go back to
Maxwell's equations and add a couple of terms.
Proca did that.
And so you follow the logic, and what you
find is, once again you get this horrible set
of equations that doesn't
look at all relativistic.
But if you could apply this
condition, it would be relativistic.
Well it turns out you can't.
Because Proca's equations don't --
are not invariant under this property.
If they were invariant, you could write this.
This is nice and relativistic.
It would describe a photon that has a mass end.
So there's some problems there.
Now these problems bedeviled
particle physics back in the 1950s.
That's when people first realized these things
around that if you try to write an equation
for a massive photon, you would get
into mathematical inconsistencies.
And so for a long time no one knew what to do.
But then through the work of Anderson, Brout,
Englert, Guralnik, Hagen, Higgs, Kibble,
and tHooft -- in other words,
ABEGHHK'tH [background chuckles] --
these gentlemen found a solution for us.
And Peter Higgs, who's one of the
H's, is in fact the person who --
is the first person I knew who's actually
said, "If you're going to give credit to this,
give it to all of these folks because
they all played important roles."
Anderson, by the way, he
didn't do it relativistically,
he did a non-relativistic context.
But the rest of these folks who were the
6 winners of the Sakurai Prize in 2010,
actually did all contribute to what
we now call the Higgs Mechanism.
What's the idea?
Well first of all the idea is, just like
you talk about electric and magnetic fields,
in this context you have to
now think of something else
in nature that's like an electromagnetic field.
It's in a totally new object,
but it has many similarities.
We can introduce this thing I'd like to
call the ABEGHHK'tH field [chuckles].
And so we introduce this object.
This is kind of like a potential that
you would introduce for electromagnetism.
And you break it up into three parts.
One called the vacuum expectation value.
Another part called a Higgs Boson.
And a third part which is
called a Goldstone Boson.
And now you just take this thing
and you shove it into an equation.
And you ask, does this thing -- is it
consistent with the laws of special relativity?
And the answer is yeah, it
will be most of the time.
In fact you can give yourself some
latitude of putting plus and minus signs in.
And when you do that, life
gets really interesting.
Because those plus and minus signs
basically control the shapes of potentials.
In other words, think about
this as a rollercoaster.
If you had a rollercoaster, and you
were sitting at this point in this ride,
and someone came along and says,
okay, give me $10 to get in the car.
And they wait 5 minutes and they
say, okay, your ride's over with.
You probably wouldn't be
very happy with that ride.
Because if you're at the bottom of the
potential you're just going to sit there.
On the other hand, if you happen to get someone
to put you at the top of this potential,
and someone just gives you a slight push, then
the car goes rolling down the rollercoaster
and up the other side, and
gee, you get some fun.
So you might be willing to
pay $10 for that ride.
Now it turns out that these two functions,
which are the difference between these plus
and minus signs, if you put them in
the equations have dramatic effects.
So first of all, again, we're going to
get out of this mass stuff in a moment,
but I did want to go through
the entire discussion.
If you pick -- if you work out the potential,
you'll find out that it has one term
which is independent of H, and then
a term which is linearly dependent
on H, and then H squared and H4 terms.
The term that is independent
of H is actually a problem.
And the reason it's a problem because it would
imply that electrical current is not conserved.
So you have to make this term vanish.
There are two ways of doing this.
You can pick 50 = 0.
That's for the plus choice of the sign.
Or you could pick 5 0 square
= to this combination,
in which the energy does have an
H dependant piece and energy is --
and electrical current is conserved.
So a lot of math.
What's the takeaway?
Well the takeaway can be
taught in terms of pictures.
The idea is that there's an energy surface
that controls the behavior of something
in our universe called the Goldstone boson.
When you put the Goldstone boson
on the top of this energy surface,
the fluctuations will mean
that it won't stay there.
So we'll roll down the side of this energy
surface, and as it does, because it's coupled
to the W and Z particles, they become massive.
That's the Goldstone mechanism.
It's a very simple story to
tell I terms of pictures.
A lot of mathematical backup,
but that's the story.
That's the thing that drives
the discussions about the Higgs.
Now let me go back a stage, and remember that
in order to get to that nice, simple story,
we had to introduce something new in nature.
The Higgs Boson.
In the same way that the electric and
magnetic fields have been introduced.
[ Pause ]
Well, so far -- let me go back to
this picture just one more time.
So far I've explained to you that the
Goldstone Boson, which was that thing that was
after the Higgs in my mathematical expression,
is the object that gives
mass to the force carriers.
And in fact, in our world we're going
to actually need a more complicated
kind of Goldstone Boson.
We need 3 of them actually
because there's a W+ a W- and a Z0.
Each one of them has to have a Goldstone
Boson in order to be massive [pause].
So that explains mass for force carriers.
But it doesn't explain mass
for things like the electrons.
So how do you get mass for electrons?
Well the analogy is, if you are
someone who works with magnets,
you know that if I have a magnetic field
pointed like this and I take a compass needle,
the compass needled would want
to align with the magnetic field
through what we call a dipole interaction.
And so the idea is, this thing, the Higgs field,
is like an electric field
or like a magnetic field.
And so ordinary matter has an interaction
energy in the presence of this thing.
And it acts -- in other words, is this
Higgs object causes ordinary matter to go
from wanting to be massless to being massive.
And all we do is we add an energy
term to our equations which depends
on the Higgs field and the fermions.
And then when the Higgs field rolls
to the bottom of the potential,
it leaves behind its vacuum value.
So this becomes a number.
And then this term here is exactly the
mass term that you need for fermions.
So what's the moral of the story?
Well it has 3 parts.
So let's go back and review them [pause].
The mathematics says, introduce
in nature this tripartite object.
The vacuum value.
The Higgs Boson and the Goldstone Bosons.
The Goldstone Bosons are responsible for
making force carriers become massive.
The vacuum value of the Higgs is responsible
for making fermions become massive.
But they're altogether in this nice, compact
form, and that is the Higgs mechanism.
Okay. So that's how the -- so we have
this sort of fairy tale which we can tell.
We say that ordinary matter gets its mass by
basically moving through a form of molasses
that allegorically is this vacuum
value that fills up all of space,
and through which all the other fermions move.
So how do you find a needle in a haystack?
Well, one way is to use computer simulations.
One of the things about particle
physics, which is often not understood,
is how close is the interplay between
the mathematics describing the processes
and the experimental measurements
of what's going on?
Because it turns out that unless you know --
a lot of people have the idea that
doing science is like going on a safari.
You know, you pay a lot of money.
You get on a -- some kind of a vehicle
in the middle of the plains of Serengeti.
You go looking and you say, ahh there's
a strange animal I've never seen before.
A lot of people think that's how physics works.
And for a lot of physics that's actually right.
Because the building of the safari carrier
is actually very sophisticated machinery.
The type of devices that
are developed here at NIST.
They allow you to probe nature
at smaller and smaller scales.
Thereby seeing things you couldn't see before.
So it really is like going on a safari.
But in particle physics that's
not the way it works.
In particle physics you have to
know what it is that you're looking
for in order to actually find it.
And so that's why in my part of physics, theory
is in fact input to doing the experiments.
You actually have to figure out what
kinds of signals do you need to be looking
for in order to verify or not a theory.
Very different view of how to do physics.
And so once you have the mathematics, you
could set up computer simulations saying,
if we did this, what kinds
of signals would we get?
And that's what drives particle physics.
There's an enormous -- particle physics
is broken up into three communities.
The theorists -- people like me who basically
play around with all the bizarre mathematics.
There are the experimentalists
-- those are the folks
who build the devices and do the measurements.
And in between these communities
are the phenomenologists.
They're the people who take the mathematics
and turn out wave forms and signal forms
and strengths of signals that will
be measured by the experimentalists.
And all three of these communities
have to work in concert.
So it's a very different way of doing
physics than most people appreciate.
Computer simulations are part of how we
generate the signals that we expect to find.
So such -- here's a simulation
for the Compact Muon Solenoid --
an event in the Compact Muon Solenoid
-- we'll come later to describe that.
This is a computer simulation
that one often sees online.
Here's a different one.
But again, these are all computer simulations.
So you set up the computer so that they tell
you what kinds of signals to be looking for.
We tag particles.
By that we mean when these collisions occur,
the ways that the particles
spray out can be complicated.
And we can measure things like the
energy deposition that they make.
Or the curvature of the path,
depending on magnetic fields.
And we use those to tag the
particles of what's being created.
So here's a closer view where you can
actually see some of the curvature.
So if an object curves one way
we know it's positively charged.
If it curves the other way, we
know it's negatively charged.
That's how we actually measure
the charge on these things.
By the curvature of their paths in
the presence of magnetic fields.
So we tag them this way.
And then we can look for
an energy deposition inside
of what are called calorimeters
[phonetic] which we'll come to in a moment.
So now we go to the -- a Large Hadron Collider.
I like to call it the World's
only Higgs knowledge factory.
It's the only place on the planet Earth that
you can go to learn about the Higgs particle.
At this point I probably want to hang
my head in a little bit of distress.
Because about just over a decade ago, my
community went to the rest of you folks and said
that we'd like to have a few dollars --
you know, it's like your teenage
son saying dad can I have the car?
We said we'd like to have a few dollars
to build this thing called the
Superconducting Supercollider.
It was an accelerator that would
have been built in Waxahachie, Texas.
It would have been 3 times as powerful
as the LHC, which is now functioning.
And it was not built.
It became, what I call the
perfect government project.
A couple of billion dollars
were spent to dig a hole
and then the hole was covered
up [background chuckles].
Now that's not quite what happened.
Because a lot of the technology
that would have gone
into the SSC is actually at
the LHC working right now.
So for example, the superconducting
magnets that make the LHC go,
those were actually developed for the SSC.
A lot of the detector equipment,
both in the CMS as well as the Atlas,
those were actually developed for the SSC.
So it's not quite right to say that we spent
a billion dollars and got nothing for it.
Because we did get the technology which, in
fact, is allowing us to pursue this physics now.
So if you flew over Geneva about 30,000
feet, you see something like this --
there are the Alps in the
background; here's Lake Geneva.
But you wouldn't see this red circle.
We put that there to guide your eye for
the location of the Large Hadron Collider.
The Large Hadron Collider is in fact
in a tunnel, under the city of Geneva.
Crossing the borders between
Switzerland and France.
And in this tunnel there
are a number of devices.
The Atlas device and the CMS
device we'll be concentrating on.
Because those are the devices that over 6,000
of your -- over 6,000 physicists work on;
large numbers of them being Americans.
That's the American contribution
to the LHC physics.
In fact, without this contribution,
it is unlikely that we would
have been able to see the Higgs.
So even though the accelerator's not on our
shores, our technology and our expertise
in manpower are in fact driving
this project to a large degree.
There are other experiments in
there such as Alice NLACB [phonetic]
where people are measuring
different things like the --
what's called the Cabibbo angles
for certain of the hadrons.
But these two detectors are the
main detectors that work at the LAC.
So how does the Higgs Production Factory work?
Well it's a proton/proton/synchrotron.
And we have some cartoons to illustrate that.
Generates beams -- it was designed at least for
-- to generate beams of up to 7 TeV per beam.
And it's a 27 Kilometers in circumference, at
a depth between 50 and 150 meters underground.
And it's not that the device is tilted, it's
that the ground tilts going towards the Alps.
The device is actually level, but the
ground tilts as you go towards the Alps.
So it's taller at one end than the other.
Here's a cartoon.
In the LAC, we have several
pre-acceleration places where we take protons
and we accelerate them using electric fields,
until they're moving .9999999
the speed of light.
Faster than anything we've
ever made move on this planet.
And then we use magnets to
bend them in circular paths.
We release the protons in this larger ring.
And around the larger ring -- as we will
just see in a moment -- there are --
there's the tunnel with a pipeline -- there
are actually two pipes that carry the protons.
And now we're inside one of those pipes.
In a moment we're going to see 4 or 5 protons
run past us -- those little pink balls.
In reality, the number of protons that
would be passing you is like 10 to the 11.
So this is just an illustration so
you get an idea of what's going on.
And so we allow these two
beams to meet at places,
and this is the cartoon of the CMS detector.
And in the interaction regions, we let these
protons run right head into each other.
And we get collisions.
And we watch what happens after that.
Now it's not this dramatic
[background chuckles].
But I've take a little bit of poetic license.
And the point is there's violent events
occurring in the interior of these devices.
These devices are basically large cameras.
They're the fastest, most
sensitive cameras we've ever made.
And they take pictures of what's going on.
So here's the actual -- inside
the tunnel at the LHC and a number
of you have probably seen this photograph.
Here's another view.
And this is my favorite view because
it actually shows what's going on.
These two bright lights here are in
fact the beams of photons circulating
in a counter circular fashion around the beam.
There's an outer layer which --
there are several outer layers.
One of them is a thermal layer.
We also have a shrink layer because
the magnets are superconducting.
So there it'd have to be kept very cool
in order to be able to bend the beams.
The actual beams you see here,
there's a vacuum chamber.
We pump the air out because you don't want
straight air molecules where the beams is
because you'll degrade your beam pretty rapidly.
And so it's a really high-tech
operation to get the machine to work.
And so it collides the protons.
Why are we colliding protons?
Because we want this to happen.
If you collide protons -- remember
protons are held in the interior
of matter by these things called gluons.
These force carriers for
those chromodynamic force.
When you collide protons together,
you can cause gluons to fuse.
And out of gluon fusion, because it's
a highly energetic state it will decay.
And typically it will decay into one
of these triangle type of diagrams
that we talked earlier being
the source of anomalies.
Now it turns out that QCD by
itself doesn't have anomalies.
And so these triangle graphs are perfectly fine
in the context of strong interaction physics.
A Higgs particle can't be
produced at this vertex.
And the Higgs particle is a highly excited
state, and therefore it rapidly decays.
One of its decay mode is into what
we call a top quark W boson loop.
Again, something that looks like a --
here -- I mean W quark or a W Boson loop.
Something that either has a top quark flowing
around it or a W Boson flowing around it.
But this thing, being a triangle
diagram can output two photons.
And we can measure photons.
We're good at that kind of stuff.
And so you run the computer simulations
to tell you what kind of patterns
of photons are generated by this process.
And then you go look to see if you
could find those kinds of patterns.
Here's another process comes
out of Gluon Fusion.
Again, you create the Hicks Boson by first
colliding the protons, getting Gluon Fusion,
which then goes into triangle graph.
And this times the Higgs Boson decays
into the Z particle, not the W. And then
from the Z you can get decay
as the four leptons.
And so you now go to look at
highly correlated four lepton beams
that are coming out of the spray.
This machine is an amazing machine.
Its performance has actually
astounded many of us.
Because normally when you build a device
this complicated, there's always --
I mean I don't have to tell
you folks here because many
of you work in the laboratories [chuckles].
You know how hard it is to actually get
devices to do what you want them to do.
This machine has the typical
sort of same difficulties.
And yet it has been functioning amazingly well.
These are some performance figures
that I was able to get from friends
who are part of the CMS collaboration.
At the end I'm going to acknowledge that.
But this is data of the performance on the
machines from the period of 2010 through 2011.
Where we're showing intensity of beams
-- I'm sorry, luminosity of beams,
which basically means the bunching of protons.
How bright is the beam?
Brightness here means how many
protons do you have in the beam.
As well as the efficiency of
the devices that capture them.
As you can see, the capture
region's shown here in orange.
The blue region's actually
the output from the beam.
As you can see, it's functioning greater
than 90% efficiency of the capture
of these beams in the two devices.
So as I said, the detectors were made here.
Well, that's not quite right.
The technology was developed here.
We assembled it all there in Geneva.
There are large groups of
American physicists that do this.
One of our detectors is called
the Compact Muon Solenoid.
This is a cartoon.
This is to scale.
That's a person.
So you can get some sense of the size
of the operation from this cartoon.
In a similar manner, here's
a real picture under --
when the device was under construction
there's a technician with a lab coat
and brown pants standing there
so you can see what it was like.
I don't know how many of
you saw the movie "Angels
and Demons" that came out a few years ago?
But if you remember that movie there
was this scientific establishment
where these evil forces were
trying to get antimatter.
That scientific establishment
was actually modeled on Cern.
And in fact, the producers, when they were
trying to figure out what kind of visuals
to make for the movie were
actually taken to Cern.
And they were totally blown away.
Because they had thought that there was some
magnificent machinery, but they had no idea
that it already existed in
our reality [chuckles].
And so they had to catch up.
So they had to catch up in their movie for
what was already going on in the laboratory.
This is the ATLAS Collider.
ATLAS -- I love the acronym ATLAS.
A Toroidal LHC Apparatus [background chuckles].
God what somebody had gone for a
stretch on that name [chuckles]!
But that's actually what it stands for.
Again to scale, you can see
two individuals to scale here.
Here's the device.
Here -- this time we talk about some of
the machinery, so we have calorimeters.
Those are the things that look at
the energy deposit of the beams
as they come out of the interaction region.
Muon detectors -- Muons are particles
that often get produced in such things.
And then we have various other trackers.
And then magnets of course
that help us bend the beam.
So that's how the technology works.
And that's a real picture of ATLAS.
Again you see our obligatory
technician during assembly,
this time with a brown vest
and brown pants -- hardhat on.
And then last, 4th of July.
Up until the 4th of July,
people like me would run around
and say, this is our table of elements.
You know the table of elements.
H on one side.
HE on the other and then you go
through the list invented by Mendeleev.
Every high school student
mostly encounters this thing.
Not too many high school students
encounter this version of it.
This is the newest table of elements.
We've been spending a couple of
trillion dollars for about over a couple
of decades to get this information.
This tells us how you put atoms together.
So to put an atom together you need electrons.
And then to get protons you
need to have up and down quarks
in those little bags that I talked about.
So this is the parts list
for the table of elements.
But on the 4th of July last, a new
bit was added to this parts list.
The announcement of the Higgs Boson.
The LAC collaboration loudly
announced to the world.
They flew Peter Higgs from
England to be there in Geneva.
And there was a festive spirit.
It was online.
You could share.
And the story came out that the
evidence for this thing that started off
as this H symbol and this piece of mathematics.
And that rule Goldberg that I
told you about to put mass in.
That this thing had progressed
from the mathematical storytelling
to being something seen in the laboratory.
That's the ark of the story.
The Higgs Boson is the first fundamental
particle that doesn't spin at all.
So if you had quarks or electrons,
they act like little spinning balls.
The Higgs particle doesn't spin.
It has spin 0.
The first fundamental object
with no spin whatsoever.
We can tell that because of the decay patterns.
If you look at the Higgs Boson when
it decays into a W+ and a W- --
the Higgs Boson being neutral -- you can
look at the predominance of the direction
of the spin of the W versus its momentum.
And for the Higgs particle, you'll find
out that the momentum vector for one
of the outgoing W's lines up with its
spin vector at the momentum vector
for the other W lines up with its spin vector.
So that's what tells you
that this thing was spin 0.
On the other hand, if you watch the W's
decay -- because the W themselves decay --
they will output an electron and a neutrino.
And what you find is that the spins for the
electron is counter to the direction of motion,
whereas the spin for the neutrino
is lined up or vice versa.
So that's how we know about the spin for the
Higgs particle by looking at the alignments
of the spins of the decay products
versus their directions of motion.
So I -- after I saw this
announcement last summer,
I sort of wiped my forehead and said, whew!
I've now seen item 1 on my bucket
list [background chuckles].
You see, there was this movie called "The Bucket
List" staring [pause] Morgan Freeman and Gene --
[background comments] Jack Nicholson, thank
you -- about these two guys that were dying.
And they had this list of things they want
to see before -- or do before they died.
And -- although I'm sometimes mistaken for
Morgan Freeman, I'm not [background chuckles].
I'll have to tell you folks some of
those Morgan Freeman stories, because --
in fact the last one happened two weeks
ago when I was on my way to South Africa.
It's very bizarre [background chuckles].
But I, as a theorist -- there are things I would
like to see before I leave this mortal coil.
This is my list.
And now I got to put in red one of the items.
I'd like to see gravity waves.
I mean, you know, our country's
spending several hundred million dollars
to have developed the Laser Interferometry
Gravitational Wave Observatory.
It's located in two places.
In Johnston Parish in Louisiana.
As well as the Old Hanford
Reservation in the state of Washington.
And the purposes of those devices
are to set waves of gravity.
Something we've never seen.
Again, something that up until this
point we only know these things
because the mathematic says that
gravity can behave like a wave.
So again, it's the mathematics
leading you to go look for something.
I'd like to see super-partners.
And we'll come to this.
And then finally, superstring M-theory.
Like boy I'd love to see
that before I quit this coil.
Probably aint going to happen.
How sure are we of this discovery?
Well, the way we -- particle physicists do it,
and the way most physicists do it,
is to talk about uncertainties.
And we have this figure of
measurement called Sigma.
And a particle physics discovery
is typically at the 5 Sigma level.
You can see the various levels.
3 Sigma represents about the same
likelihood of tossing 8 heads in a row.
A 5 Sigma's like a 1 in a million opportunity.
So we -- that's the Gold Standard
of discovery in the field.
You want to get to a 5 Sigma deviation.
Let me speed up here.
So what are the data telling us?
So if you look at the -- and again I had
a friend in CMS help me with this talk.
So if we look at the data, what we can find is
actually that we can produce Higgs particles
at the LAC and watch numbers of decay channels.
So some of the decays are actually
drawn here in terms of thymine diagrams.
We can watch Higgs go to 2 Gamma.
We can watch Higgs go into 2 bottom quarks.
We can watch Higgs go into tau particles.
We can watch Higgs go into W then watch Higgs
go into Z. And so these are different channels.
For each of these we have figured out what
the signals look like for a Higgs decay.
We build the devices and then
go look for those patterns.
And you do that.
And what you find out is that we -- if we, for
example, look at the Higgs to 2 Gamma channel,
you find out that we find very
definite signals at about 125.
That's why we're saying that there's a
Higgs particle at 125 G EV/C squared.
This thing here is rather interesting
and I'll come back to that in a moment.
Let me just move ahead.
You can also ask questions about decay channels
because we think we're good enough to be able
to figure out -- as you look at
all the possibilities of decays,
how do they line up on terms of mass?
And what we find in CMS data is
actually something rather interesting.
If you look at Higgs to bottom;
you look at Higgs to tau.
You looks at Higgs to W and
Higgs to Z and you get --
and this green, by the way, is the uncertainty.
You can see that the mass is pretty much
lining up on all of those different channels.
On the other hand, if you look at Higgs to 2
Gamma, the uncertainty here is actually in red.
And as you can see it's lying outside.
So there may actually be
something very strange going on.
In fact, when you -- if you're someone like me
and you heard that announcement last July 30 --
the 4th of July, you got very suspicious.
Because the language -- there were a
lot of weasel words in the language.
They were saying "Higgs-like".
I mean you can go back and
look in the [inaudible].
You can find the expression Higgs-like.
Which, you know, that's not
the way we talk [chuckles].
We don't say "Electron-like".
It's either electron or it's not, right?
You don't say Higgs-like, what is that?
And so at the time, there was data to suggest
that we had found something at a certain mass.
We didn't know whether it
was spin 0 then by the way.
We do now, with the latest
announcements of the data.
We've firmly established that it is spin 0.
But are we there yet?
The answer turns out no we're not.
This is an announcement that
was sent out by Rolf Heuer,
the Director of Cern on the 14th of March.
And I emphasize in red this
part of his statement,
"Or possibly the lightest of several bosons."
You see, it's not completely clear what is
going on at the LHC with the Higgs announcement.
I eluded to this a little
bit by showing you this data.
You'll notice that there's a dip there.
Now this is only at the 2 Sigma level.
And if you look at the history
of particle physics.
We're notorious.
I mean bumps come and go in our field.
And until you get them to -- you take
more and more data to assure yourself
that you're actually seeing a real
signal, you don't really know.
But this particular bump here has
lived through two data releases
of both collaborations and
both of them seem to see it.
So we're not there yet.
But does that mean that there's
more than one Higgs?
And why would there be more than one Higgs?
The answer turns out to be symmetry.
In 1977 I wrote the -- as was kind of -- as Bill
was kind enough to mention in the introduction,
I wrote the first thesis at MIT
on the subject of supersymmetry.
But that's actually only half the thesis.
The first half of the thesis is actually looking
at weak interaction physics and
in particular Higgs physics.
And so I was one of the first people at
MIT at least to look at the possibility
that in nature there might
be more than one Higgs.
So how does that actually occur?
Well it occurs because remember when I took
the wave functions, I just put them together
in what looked like a willy-nilly pattern.
And in particular, I have the --
I had the electron and it's
neutrino in one little doublet.
And then I had the Muon in this
neutrino in an entirely separate doublet.
But suppose they were part of a bigger object.
If they were part of a bigger object,
this begins to look more like quarks.
You move this way and you change the
electrical charge of the particles.
But if you move this way you will
change what's called family member.
If these were quarks, this is
the color direction of motion --
you change the color of quarks
as you move along this axis.
No one could tell you not to
try that idea for leptons.
And so in fact in my thesis, based on a model by
Teplis, Dikus, and Young [assumed spelling] --
I wound up in 1977 studying this model and
looking at this spectrum of the Higgs particles.
And what the model shows is that
you can have more Higgs particles
than the one that is the well accepted one.
But it means that the patterns in which
you assemble the particles are bigger
than the assumptions that we
made in the standard model.
So yeah, you can actually get more Higgs.
And it's relatively simple.
There's another way to do it.
If the extra bumps remain after the analysis,
then the post standard model
era will have begun.
A rich spectrum of Higgs-like fields
will be avatars of the existence
of symmetries beyond those
in the standard model.
So if you've seen the letters,
SU3 cross SU2 cross U1,
we may have to start adding
more letters and numbers.
That's what the -- the first thing I told you.
But it might even to me be more exciting.
Because it might be that we're beginning
to see the evidence of supersymmetry.
Now why is that?
Well, first of all I'm going to
assemble the universe for you.
So here we are, we've got
-- here's our universe.
I've even included the graviton here.
Or rather here.
And now these are the super partners.
These forms of matter and energy that,
in fact excited me as a graduate student.
The reason I wound up writing the
first thesis at MIT in 1977 at MIT
on this subject is that I
read the research papers.
And I realized that I was alive at a
time when people were saying new forms
of matter and energy could exist.
And I got so excited.
I ran around the Center for Theoretical Physics
like someone with their head on fire trying
to get someone to help me learn this stuff.
And there was no one in the center at all
that knew anything about supersymmetry.
So I wound up teaching myself the subject,
and in the process writing a PhD thesis.
I -- there was an added benefit
for writing that thesis.
Because when I defended that thesis I knew
more about what was in it than anybody
in the room [background chuckles].
And a friend of mine, who I worked with at
[inaudible], a guy by the name of Ernie Moniz,
who just became Secretary of Energy,
was on my Thesis Defense Committee.
And a few years ago, I asked him
a question to check my memory
of how wonderful my thesis defense had been.
I said, "Ernie do you remember what
you told me after the defense?"
And he said, "Yeah, that was the
best thesis defense I had ever seen."
But I always thought gee, they don't
know about the Kobayashi Maru [chuckles].
For those of you who are Star Trek fans,
you'll know that James Tiberius
Kirk passed the computer test
by changing the code the night
before the exam was taken.
That's what I had done in my PhD thesis defense.
Because I wrote that code.
So these super-partners, well are they there?
We don't know.
But why would they say more Higgs?
Well, first of all the super-partners --
well quarks have super-partners quarks.
Neutrino will have a super-partner neutrino.
The electron will have a super-partner electron.
The Muon has a super-partner that's Muon.
The tile particle has a super-partner
that's tile.
The Z partner has a super-particle that's Zeno.
The photon has a super-partner
called the photino.
The Gluons have super-partners, for
every one of these there are Gluinos.
My favorite super-partner is actually
this one right here [background chuckles].
I can't wait.
I would love to see a headline
splashed acrossed a newspaper.
W-I-N-O seen in Geneva [background chuckles].
Most people would think that
you're talking about some kind
of alcoholic specialist [background chuckles].
But we would know that it's a
super-partner that had been seen.
But the thing that is really weird
about this supersymmetric extension
of the standard model is that it
actually has 5 Higgs particles; not one.
So if we are seeing more Higgs particles
-- if we're beginning to see them --
then that could, in fact be the first sign.
Not that we're seeing the super-partners,
but we're seeing the extra Higgs
that the mathematics of supersymmetry
actually demands.
And so supersymmetry, why does
it need more than one Higgs?
Well remember I can tell you about
the triangle anomalies that can occur?
And that the quark charges and the up-and-down
quarks and associated family of leptons had
to have their charges in
exactly the right pattern
to not lead to mathematical inconsistencies?
It turns out in the super-symmetrical
models you need more Higgs
to avoid the mathematical
inconsistencies of the model.
Which is much more different than
finding an accidental symmetry [pause].
[ Applause ]
