The map idea is something
that arose because I write
for The Guardian and I'm also--
Obviously, I'm a teacher at UCL.
And you get used to explaining
fairly abstruse details
of physics to people.
And if the audience
is paying attention
and if you're doing
your job properly,
then it can kind of work.
You can pretty much
explain anything.
But then you realise that people
acquire a bit of knowledge here
and a bit of knowledge there and
they've no real idea of the big
picture, have these all
things linked together.
So my idea of the map has sort
of come from how, in my head,
I kind of view these things.
The particle
physics, in general,
and what we're trying to
do in particle physics
in terms of the big picture of
how these things fit together.
So I'm going to try and
talk you through that.
You can think of it as--
I also get asked how do you
picture the strange things
that you study at CERN.
Well this is, if you'd like, a
view of what goes on in my head
sometimes.
What we're going to do here--
it could be quite disturbing
sometimes there.
So I'm going to take you on some
journeys into particle physics.
Now we don't have long enough
to go through the whole book.
And I'm not going
to try, don't worry.
So we'll skip over some bits.
But we are going
to try and give you
an idea of what our mission is.
And what it's all
about is understanding
the fundamental
constituents of matter.
What is the physical
universe made of when
you get right down to it?
If you break things into
smaller and smaller pieces,
do you end up with a common list
of the same pieces everything
is made of?
And what are the forces
between those things?
And the answer at the
moment is, yes you do.
You end up with a finite number
of infinitely small, what
we call, fundamental objects
that everything else is
made of.
And the first of those objects
was discovered by this guy.
This is JJ Thompson at Cambridge
with his experiment sitting
on his desktop.
And what he was doing was
studying a phenomenon,
then was called cathode rays.
This is his cathode ray tube.
There's a gas in there
that's fluorescing
as these mysterious
rays pass through it.
And you create them by
heating up an electrode here
and applying an
electromagnetic field.
Which was all very cutting
edge stuff at the time.
And he did various
experiments balancing
electric and magnetic
forces and showed
that these things were actually
corpuscules that always had
the same master charge ratio.
And then they devise
ways to measure the mass.
And in the end it
convinced everyone
that these were not waves,
they were particles,
they were electrons, in fact.
And that, the electron
than was established
as the first
subatomic particle and
the first fundamental particle.
And despite 100
years of trying, it's
still a fundamental particle.
We have not managed to
break one of them yet.
As far as we can see, there's
nothing inside an electron.
It is infinitely small.
And it is our sort of
gateway to this map.
So this is us on a little boat
here coming in from the west.
The west here is kind
of everyday life.
And as we go further east
we get smaller and smaller
and we go to higher
and higher energy.
And I'll show you how
those things are actually
the same thing shortly.
But the electron is our port of
access to this subatomic world.
And the first place you
kind of go from there
is atomic physics.
The electron is a
subatomic particle.
There are electrons
in every atom.
And you very quickly start--
you're able to work out
that an atom is not--
although an atom of say, sodium,
is the smallest piece of sodium
you can possibly get.
It's not the smallest
piece of matter.
You can break a sodium atom up.
You can break it into
electrons and a nucleus.
And it won't be sodium any more.
But there are still smaller
things inside the atom,
in sodium.
And the same for all atoms.
So you start looking around
on the periodic table.
And you find that life is a
little different in this map.
We've travelled to something
that isn't actually looking
quite like everyday life.
And the first
manifestation of that
is that when you have electrons
bound to these nuclei,
you find that
they're not allowed
to have just any old energy.
They're bound in fixed orbits.
Now orbits in the solar system,
which is the kind of model
that Bohr had for the atom.
Orbits in the solar
system, once you
fix the distance of a
planet from the sun,
than its velocity, is
period of orbit, is fixed.
So there is a certain
lack of flexibility
already there, for
a stable orbit.
But with the atoms
it's even worse.
There's only certain
orbits that are allowed.
In principle, the
earth could have--
it could be anywhere on
a continuum from the sun.
It could be very hot or
it could be very cold.
It can be anywhere in between.
But that's not true
for an electron
going around the nucleus.
There's only certain energies
of orbit that it can have.
And it turns out
that that's actually
because the orbit model is
not a good model in the end.
It's not a good picture
of what's going on.
The best feature that's
going on is actually
you have to take this
fundamental particle
and you have to introduce
wavelike properties to it.
Because the best analogy
that we think of here is you
can imagine where in nature are
the discontinuous things where
you can't have a contimum
of energies, for instance.
And that happens with waves, it
happens on the guitar strings.
So a guitar string will
support a fundamental note.
It will support a
harmonic one octave up.
It will support
the next harmonic.
But that's all it will support.
You can't have notes
in between unless you
start pressing threats
down and changing
the length of the strings.
And that's the analogy
that Bohr initially used.
And that's the
analogy that leads
to quantum mechanics, in fact,
for how the electrons are
bound around an atom.
So it turns out the
electrons can only
have these particular orbits
because that certain number
of wavelengths of the electron
fit into that particular orbit.
There are certain
barren states that
have particular
resonant frequencies.
And they're the only
ones that are allowed.
And if you want to
change them, you
have to change the
electric charge
of the nucleus which
is like changing
the length of the string.
So that means that when the
electrons jump between orbits,
and this is how we
knew this was the case,
that they will emit energy
at certain frequencies,
at certain energy levels.
And that is, in
fact, how we know
what anything that we
can't touch or smell
is actually made of.
So this is a spectrum,
electromagnetic spectrum,
of a fluorescent bulb.
You can see as you excite
the electrons in there,
they're jumping between
particular levels
and they give off
particular wavelengths
of light corresponding
to those energy levels.
And likewise, this is a
spectrum, this is from the sun.
This is the emission
spectrum of the sun.
And you see there
are dark lines in it.
And each one of
these dark lines is
where elements in
the sun's atmosphere
are absorbing
particular energies
because those energies,
the electrons,
can jump between levels.
And these characterise the
elements there in the sun.
So the only reason
that we know what
the stars and the planets
that are not our own planet
are made of, is by observing
these kind of emission spectra.
In fact, the element helium
was just called helium
from Heliox, the sun god.
It was discovered on the
sun before we discovered it
on the earth by looking
at emission lines.
So that introduces, although
the electron started off
as a fundamental
particle, it's now
suddenly got wavelike
properties because it's
like a note on a guitar string.
And that's the kind of, the
insight in quantum mechanics,
actually these fundamental
particles are not particles.
Neither are the ruby waves.
They're a new kind of object
called a quantum excitation,
if you like.
But because of those
wavelike properties,
there's then the very clear
connection between the energy
and the size.
So on this map, as we
go east, we're going--
looking at smaller
and smaller things,
deeper into the heart of matter.
But we're also
going up in energy.
And the best way of illustrating
that connection here
is in this little
video that I've got,
which I hope I can make work.
This is super high tech.
You're going to
see a ripple tank.
But I think it really
shows you what's going on.
And this is this connection
between the very small
and the very large.
So if you imagine this as a
beam of particles, and this
is my detector here.
OK, and I'm looking
for some new particle.
So someone is going to put
a blob in there in a moment.
Come on with the blob.
They always take longer than
I think they're going to.
So they put a blob in there.
You guys see how a particle
detector will have spotted it
because this is a shadow.
So you could register
this presence.
If you did some
calculations, you
could probably tell what
size it was, maybe even what
shape it was if you were very
careful with your measurements.
So that works as an experiment.
Now they put another blob in.
This blob now is
completely invisible.
If you look, the
detecter can't see it
because the waves
reform around it.
And that's because the blob
is smaller than the wavelength
of the waves.
So we don't have the
resolution to see it.
So what do we do, we
turn up the energy,
which turns up the frequency,
shortens the wavelength.
And now you see the
shadow forming again,
you can see it again.
So that's really
this connection.
That's what particle
physics is about.
That's why we have
high energy machines.
Because we want to
see small stuff.
If we want to see small stuff,
we need short wavelengths.
If we want short
wavelengths we need to see--
We need to-- sorry,
I've just spotted
an old friend in the audience.
It put me off.
Hi, Nigel!
If you want to see small things,
you need short wavelengths.
So that means high frequency,
which means high energy.
So that's why particle physics
is also high energy physics.
That's why we need huge
colliders and things to try
and see the very small stuff,
because of this connection
between wavelength,
frequency and resolution.
If you think about it, if our
eyes are sensitive to radar,
then I wouldn't be
able to see you now
because radar has
wavelengths of metres
and you'd be smaller than that.
So I wouldn't see you.
But our eyes are actually
sensitive to hundreds
of nanometers, which is pretty
good for seeing small stuff.
But if you wanted
to see smaller,
you'd go up in energy, which
means x-rays, or electron
microscopes, and in it.
So you can think
of the big particle
colliders like the
Large Hadron Collider,
is just the biggest,
most powerful,
highest resolution
microscopes we can build.
So I've already mentioned the
Large Hadron Collider, that's
one of the stars of the show.
At least you get to
the east of the map.
So I'm kind of
skipping over a whole
of the rest of this
stuff, which is
there is kind of our exploration
of the subatomic world.
And bringing you right
up to date to what's
going on the east coast.
So this, this is
if you like, this
is the standard model on
the threshold of ruining
the Large Hadron Collider.
Now that's my, the weird
stuff that goes on in my head,
if you like.
This is a more conventional way
of viewing the standard model.
It tells us that we
have the electron here,
our old friend that we saw.
It's been around
for a long time.
It has a neutrino that
comes with it, which
is actually very hard to see.
There are lots of
them in this room,
they don't interact very much.
But they're emitted,
for instance, copiously
from the sun.
And then we have here
the quarks-- the up
quark and the down quark.
And if you take an
up and a down quark,
you take two ups and a
down, you can make a proton.
If you take two downs and an
up, you can make a neutron.
If you take protons
and neutrons,
you can make every atomic
nucleus in the periodic table.
If you add the electrons,
you can make every element
in the periodic table.
And every molecule, and
then so on from there.
So in principle, this is
enough to build everything,
so long as you
include the forces
like the photon and the gluon,
the strong nuclear force
is what holds quarks together.
The photon, which is what's
coming out of this laser,
and this is the
electromagnetic force carrier.
And then the W and the zad,
which carried a weak force.
Which is always hard to say
what the weak force does
because it's so short
range, it doesn't
get outside the atomic nucleus.
But it is, for instance,
integral to the fusion
reactions and the sun.
So it's kind of important.
The sun wouldn't
work without it.
And it's the only force the
neutrinos actually experience.
And so that looks like
we got everything really.
But then for the reasons
that are not clear,
these are copied again.
So here we have the charm
quark and the strange quark,
which are like the up and
the down only heavier.
The muon, which is like
the electron, only heavier
and its neutrino.
And then the top and the bottom
quarks are heavier again.
And the tau lepton and so on.
And then it stops.
There's no more
copies like that.
There might be other particles
that will come to the end,
but there's certainly
nothing like this anymore.
We know that.
And that looks like
everything in the universe
is made of this.
And this stuff is not
made of anything else.
This is fundamental.
And that's where we were when
we turned on the last chapter
on Collider, and you
could express that.
We know so much
about this theory.
You could actually
express it mathematically
and do very precise
calculations with it
and, actually, correlate
the parameters in it.
So what you see here is a
plot from March 2012, which
is a significant date, as you
will see in a moment, where
we've got two of the things
that are not very well known
in the Standard Model.
So this is the mass
of the top quark.
This is the mass of
the W boson, which
is one of the carriers
of the weak force.
Of all the parameters
in the Standard Model,
these are the kind of
two least constrained.
So we're looking at where--
what all the
calculations tell us,
how they have to be correlated.
And you see these
grey bands on here.
They're telling us where
the missing element
from the Standard Model is.
And there is a missing element,
which I kind of skipped over,
which is the fact that in the
Standard Model, as I described
it here, we have a real problem
in that we can't actually
accommodate the mass
of these particles.
So we know that the
W and the Z boson,
in particular,
have a lot of mass.
As the model was written
down on that slide,
you can't actually
accommodate that.
What was postulated to
explain that mass is the Higgs
boson, which you've
probably heard of,
and which is shown here.
And at this stage,
we could kind of
say, well, for this whole
theory tying together, A, there
has to be a Higgs boson, or more
than that, its mass has to lie
within one of these bands.
Because it has to intersect
these limits here.
Everything else was excluded.
If it was here,
we'd have a problem,
because it's looking
like it's not
within the allowed region
from the other parameters.
So it really sort of
had to be in this band.
And that, in terms
of the map, that's
this fuzzy coastline here.
We don't actually
know what's going on.
We've got the W and
the Z boson here.
They have to have mass.
In order to have mass, we
have to have A Higgs boson,
but we've actually not been
able to survey this land at all.
And that's, of course, where
my experiment comes in.
A little bigger
than JJ Simpson's.
It's not just mine.
There's a few other
people involved.
This is the view you get as you
approach Geneva Airport, which
is here.
This is Mont Blanc
on the horizon.
This is Lake Geneva.
And this, of course, is
the Large Hadron Collider.
And what we're doing in there
is colliding the two highest
energy beams of
particles that we've ever
managed to control, and
steer, and accelerate.
We're bringing them into
a head-on collision.
Four points on the ring--
CMS over here, ALICE here,
ATLAS here, LHCb here.
We're surrounding those
points with detectors
that will allow us to
detect the debris when
the particles collide, and
we're making measurements.
And you know now that
because this is high energy,
these measurements
will be giving us
clues about the very, very
smallest detail that you can
see inside of the proton, which
we know, inside the proton,
there are quarks and gluons.
But maybe this
could even-- shows
this stuff inside the quark.
Maybe for the first time,
we'll get over the edge
and see something there.
And in particular, maybe we
will get over to the east coast
here.
Well, we certainly will.
It was built in order to have
enough energy to get over
to the east coast of what we
call-- where the bosons live--
Bosonia-- and see
what's going on
and whether the Higgs
is really there or not.
So you probably know
the answer to that.
And we did discover
the Higgs boson.
If we didn't, the
Nobel Prize Committee
is going to be very embarrassed.
But I want to show you
the data, and I want you
to kind of understand the data.
Because, also, how
we discovered that
is important to what we're
doing now and why what
we're doing now is
important and interesting.
So this is the most
technical of the talk.
Don't panic.
It doesn't get any
worse than this.
This is a diagram representing
a particle collision.
This is how we look at
these particle collisions.
This is a Feynman diagram.
I'm sure lots of you have seen
them before, but some of you
certainly will not have done.
They're really intuitive
little cartoons
of how a particle
collision happens.
So this is supposed to be
an electron coming in here--
or positron, which
is the anti-particle
of an electron coming in here.
Annihilation to a photon--
it's the wiggly line here.
And then decay, back again
to electron and a positron.
Now, that's the kind
of intuitive cartoon
of what might happen
if you collided
an electron and a
positron together.
But it's more than that,
because every line and vertex
in this diagram has
a corresponding term
in the equations you would write
down in quantum field theory
to actually calculate the
probability of this really
happening, OK?
And there's a problem
in this if you
take what we know about physics
and you try and look at this.
If you treat it
classically, there's
a problem in that we know
that energy is conserved.
So if there's a
lot of energy here,
there has to be a
lot of energy here.
There will be a
lot of energy here.
This is what you put in.
This is what you measure.
So we know there's
lots of energy.
So there must be lots
of energy in the middle,
because energy is conserved.
We also know that energy
is equal to mc squared.
It equals mc squared.
The energy is equal to
the mass of the particle
times the speed of light
squared of the particle
if the particle is at rest.
And this guy in the
middle would be at rest,
because you do it in
the central mass frame.
And we also know that
the mass of the photon
is zero, which is
a bit of a problem.
Because c squared may be
big, but it's not big.
If n is 0, then mc
squared will be 0,
and energy in the
middle, then, would be 0.
So that's an apparent
contradiction.
And the way around
that contradiction
in quantum mechanics is--
as you say, well, actually,
this particle is never observed.
In some sense, it's
not a real particle.
It's required, because if you
don't put it in the equations,
you don't get the right
answer for the probabilities.
But you never observe it.
It's like in a
two-slit experiment,
trying to ask which slit
the particle went through.
You're kind of not
really observing it.
Although, the
presence of both slits
clearly determines
the result you see.
And so we call them
virtual particles.
We say they're not real.
And virtual
particles are allowed
to have a mass that isn't
exactly what the mass
of the real version would be.
So our real focus on
those types of zero mass--
the virtual one doesn't have to.
Now, as a residual--
as a kind of memory of
what the real mass would
be in the virtual
particle, there's much more
chance of this happening if
the particle in the middle
can have the right mass.
But if it has to have
the wrong mass in order
to conserve energy,
then the probability
doesn't drop to zero.
It will drop, but it will
not drop completely to zero.
OK, so that might tell you--
it might make you
think-- actually,
this is a pretty silly
experiment to do.
Because if the photon was
zero mass, the more energy you
put in these beams, the less
likely this is to happen,
the less events you're
going to collect.
Why are you doing that?
The reason we did it at
CERN, before we had the LHC,
is because there's
another particle--
can be in this diagram--
the Z boson, which is the--
if you remember, it was
one of the force carriers
of the weak force,
along with the W.
And the Z does have mass.
The Z has a mass about 90
times the mass of the proton.
So if you chain
things up, you can
make the energies here match.
Then you can make
these guys have
total energy that's 90 times
the mass of the proton.
And then the Z can have
exactly the right energy
in the middle of that diagram,
and everything will work.
And that's what you see.
So that's the technical
bit, over really,
because everything
I've just told you
is now shown again in this plot.
What this plot is showing
you is the probability
of that process happening, OK?
Or, actually, with a different
decay, but it's the same.
The probability of the
electron and the positron
annihilating to a
photon or a Z. And this
is as a function of
essentially mass energy, which
is essentially just the
energy of the wiggly line
in the middle, or the mass--
the factor of c squared
in between them.
So what you see
is all the things
I just described to you,
in that as you push a zero,
the probability is very
high, because the photon is
very near its correct mass.
As you push to higher
and higher energies,
the probability drops and drops.
Then as you get to
the mass of the Z--
when the Z cannot
be a correct mass,
you get a peak in
the probability.
And that's because
at that point,
those three things line up.
Energy conservation
equals mc squared,
and the Z has the right
mass, till you get its peak.
And then as you go
higher again, it
drops again, because
the Z has got to have
too much mass as well in there.
The reason I'm
showing you this is
because this is basically how
you discover a new particle.
When you collide two
particles together,
you've got a mass
of stuff produced.
But if there's a new
particle in there
and you measure the
products of that collision,
then you'll see a peak when
the products of that collision
lead to it--
can come from a particle
of the right mass.
So if you make a
Higgs boson, one
of the things it can
decay to is a pair
of photons, which is
what's shown here.
This is a picture from the ATLAS
detector on the Large Hadron
Collider.
So if you imagine, this is a
slice through the detector.
It's called the
detector cylinder.
You imagine one of
the beams coming
from behind-- from the
back of the room and one
coming from behind the screen.
And they collide
in the middle here
and then get these debris
produced when they collide.
Most of this is
not so interesting,
but these two yellow blobs
are really high energy.
You see the histogram here.
So those are two
photons produced.
One of the things that might
have produced those photons
is actually that somewhere
in your collision,
you had a diagram
like the one I showed,
but it produced the Higgs
boson in the middle.
So you can count those photons.
You can detect the
pairs of photons.
And you can do a
bit of calculation
and say, well, if those photons
came from a new particle,
what would its mass have been?
What would the mass
of the wiggly line
in the middle of that
diagram, basically, have been?
And you could just plot them.
I'm going to show you
a plot, which is apart
from the animation-- the same
as the plot you just saw before,
pretty much.
You've got the number of times,
the number of pairs of photons
up here.
You've got the mass
of the particle that
might have produced
those photons there,
and you're looking for a bump.
And then you see there's
a lot of statistics,
a lot of fake bumps, which all
kind of recede into the noise,
but one bump, which
grows and stays--
which is this one here.
And that's the evidence.
The first evidence for the fact
that the Higgs boson exists.
And at that point at
125, roughly times
the mass of the proton,
you have a coincidence,
where now you have a diagram
where two gluons, in fact,
interlay.
There's a Higgs boson produced
in the case of two photons.
And at that point,
energy conservation
and the mass of the
Higgs equals mc squared--
all line up.
And you get a peak in the
probability, which is there.
And if you see it today--
I showed you a plot from just
before this was announced.
We announced this
on the 4th of July,
actually 2012, and then
collected a bit more data
afterwards.
But you see the dates of
which this data was collected.
That was the discovery
of the Higgs boson.
That was the point
at which we went
from this map with fuzziness
in the east to this map,
where we filled in--
we find there's a kind of
ridge of mountains here,
which is what we call the
physics changes at that point.
You have the electroweak
symmetry breaking scale.
But, indeed, the Higgs
boson was there as expected,
sitting on the edge
of the coastline,
there in the extremities
of our knowledge
in the frontier of energy.
But going back to the
more conventional view,
this is what we had, before
the Large Hadron Collider,
and then after the
Large Hadron Collider.
We had the Higgs boson kind
of making the whole thing hang
together and allowing the
other particles to have mass.
So that was 2012-- what
we've been doing since.
It was the Higgs boson-- is
the last fundamental particle.
I started with the electron.
Maybe that's the beginning
of particle physics.
Is particle physics over now?
Well, no.
There are a few things
missing from this map.
One of them is someone who can
draw Isaac Newton properly.
But this is supposed to be--
represent gravity, of course.
There is no mention
in our Standard
Model of particle physics.
There's no feature on that
map which represents gravity.
So we do have a good
theory of gravity.
We have Einstein's
general relativity,
which gives us a very good
theoretical model, absolutely
beautiful, and a very
precise theoretical model
of how matter occurs--
space-time and how
that leads to gravity.
So you could take the view
that I don't care, OK?
I've got a Standard Model of
particle physics over here.
Quantum mechanics.
I've got general relativity over
here, which describes gravity.
OK, so they don't work very
well together near a black hole,
or in the Big Bang,
or whatever, but I'm
going to ignore that and
just get on with life.
Now, that's not
very satisfactory.
It would allow you
to do most things.
For all practical
purposes, it's not the way
we like to think about physics.
And also, it's not
good enough anyway,
even if you want to
just get on and explain
everyday observations.
So the conflicts between
gravity and quantum mechanics
at the moment are basically
down to thought experiments,
but there are real observations
that don't work as well.
So even if you buy general
relativity and quantum
mechanics and don't worry
about the thought experiments,
you still cannot explain
how fast stars rotate around
galaxies.
If you do the
calculations, you say
this is how much matter
I see in the galaxy.
It comes from the
Standard Model.
And this is the gravitational
force it should produce.
It comes from
general relativity,
and this is how
fast they're going.
Then the answer is no.
Then that's not right, because
they're going too fast.
The galaxy should fly apart.
There isn't enough
gravity to keep
them spinning at that speed
without them flying off.
So something is awry.
Something has gone wrong.
And obviously,
this is a conflict
between the Standard
Model, which tells you
how much mass is in the galaxy
and the general relativity,
which tells you how
much gravitational
force that would produce.
And you can say, well--
also, either gravity is wrong
and there are people
trying to change--
modify general relativity to
account for that, or you say,
well, actually, there's
more matter in the galaxy
than we think, and we
call it dark matter.
And it's not part of
the Standard Model.
And we fill the
galaxy with that,
and that provides the
extra gravitational force.
It means things
can sit together.
It means the whole
thing hangs together.
Now, so you broke--
you've got to break--
at minimum, either one of the
theories has to be modified.
Most likely in such a situation,
both of them will change.
And there are other
ancillary-- there's
a lot more evidence than
just galaxy rotation curves,
now that there's
something going wrong,
and that it's
probably dark matter.
I would say that most physicists
think dark matter is out there,
but there are still people
working on modifying gravity,
so you don't need it.
So that's one massive--
actually, if you do the
sums in the calculations,
it tells you that something
like 80% of the universe
is dark matter, so it's
not a small correction.
It's kind of
embarrassing if you're
trying to explain what the
whole of the universe is.
And so that claim I made
about the Standard Model,
that everything is
made of this, is
clearly wrong by a factor of
five or something, at least.
So that's pretty bad.
There are other things
missing from our map.
One of them I should--
Jenny has probably
noticed this already.
But down in the corner, there is
another fuzzy bit of an island,
actually.
Down here where the
neutrinos live--
we don't really know
what's going on.
We only rather recently got into
this region with any confidence
and discovered that the
neutrinos have mass,
and that they are mixed
up amongst each other.
We still don't know, actually,
whether the neutrinos have
their own anti-particles, which
is why it sort of fades out,
before it gets into the
southern hemisphere, which
represents anti-matter in my
twisted view of the Standard
Model.
So this is an area, also,
where there's unsurveyed land--
where there are experiments
planned and in operation
that we'll be shedding light
on-- what's going on there.
That may give us some clue.
There's another--
actually, not as
gravity missing from
the Standard Model.
Another kind of
major embarrassment,
really, is the fact that most
of the theories in this--
most of the forces
in the Standard Model
treat matter and
anti-matter identically.
So if you start off
with a Big Bang,
you should end up naively
with equal amounts
of matter and anti-matter
around in the universe.
That's not true.
It's certainly not
true on the Earth,
otherwise it wouldn't
be here, I guess.
But as far as we can tell,
it's also-- all the galaxies
are made of matter
as far as we can see,
otherwise we'd see
annihilation, kind of boundaries
between them, and things where
matter and anti-matter come
together.
So as far as we can see,
the visible universe
is made entirely of matter.
Anti-matter is easy to produce.
And it should presumably
been produced copiously
in the Big Bang, but
it's not around anymore.
So we know there are some
clues in the Standard
Model as to where that
might have come from.
In fact, it's
connected to the fact
that there are three
copies of matter.
Once you've got three
copies of matter,
you can introduce slight
differences between the way
matter and anti-matter
are treated.
And, indeed, there are those
differences in the weak force.
And, interestingly, if
you have only two copies,
you can't have
those differences.
Three is the minimum
number of copies you
need in order to have those.
And three seems to be
what there is in nature,
so maybe there's a clue
there as to what's going on,
but it's only a clue.
We don't have a
theory behind it yet.
And the little bits of violation
of the symmetry between matter
and anti-matter that we
see in the Standard Model
are not enough to explain
the gross discrepancy that we
see in the world around us.
The neutrinos may provide
another source of difference
between matter and anti-matter.
They may even be their own
anti-particles, as I say.
So there's a lot to find out
in that little bit of the world
as well.
But, really, what we're doing
is looking off the map now.
So I think what we've been
doing in the last five years
at the Large Hadron Collider--
I think we've been sort of
sitting on the coastline
here in the port, sometimes
just sitting around in bars,
listening to wild
stories from theorists
who've claimed that they've
seen stuff out here.
But we have a ship.
We have a vessel that's sailing.
We're actually
sailing these seas
with the Large Hadron Collider.
And what you see here is--
I don't know.
We've got quantum
gravity here, which
presumably is there somewhere.
We have dark matter.
Something may or
may not be there.
Maybe these are just dreams.
Maybe something else
entirely going on.
But this is what we're doing.
We have the large hadron.
As you saw in the animation
with the Higgs bump,
you saw the points, and
there were error bars.
And as you take
more data, the error
bars shrink and
shrink and shrink.
And it's only when they
shrink some point smaller
than the bump that you
actually see the bump.
You can actually resolve it.
That's really what we're doing.
We're repeating the same
experiment over and over again.
As I said, it's
not rocket science.
I don't know.
We're just sitting there.
We got the beams colliding.
Let's just keep them
colliding as often as possible
and record what happens.
You might think that,
how are we going
to learn new stuff from that?
Well, you already saw
in that Higgs plot
with just a few things there.
The error bars are too big.
There were fake
bumps everywhere.
You can't work out
anything from the noise.
As you shrink the statistical
uncertainties down,
you learn more.
It's like if I have a dice.
If I have a dice and I want
to know, is this a fair dice?
You could say,
asking the question,
is the Standard Model working?
Is the Higgs really there?
It's like saying,
is this dice fair?
So I rolled it six times.
And I say, well, the prediction
is if it's a fair dice,
I should get one 1, one 2, one
3, one 4, one 5, and one 6.
And I don't when I
rolled it six times.
So, do I conclude?
Well, I conclude nothing, of
course, because that's never
going to happen.
Very unlikely that you
would just get one of each.
But if I roll the dice,
I've got the patience,
and I roll the dice
six million times,
then I should really get about a
million 1s, about a million 2s,
about a million 3s,
and about-- and so on.
And if I don't, then
the dice is biassed, OK?
So that's really where we are.
It's like, how fair is the dice?
And you can carry on asking
that question forever.
But you're certainly
at the level--
at the moment now, we only
know at the level of 10--
20%, whether the
Higgs is really doing
what it's supposed to
be doing, for instance,
or whether any of these
monsters are actually there.
And as we collect
more data, then we'll
be either pressing down on
them and ruling them out,
or we'll be finding them.
Just to show you the
kind of game we play,
you know what these
diagrams do now.
This is a diagram just like the
one I had before with, I said,
a quark and an anti-quark
correlating and then
with a made-up particle
in the middle, OK?
Call it Z prime, because we
don't have much imagination.
But this is a new particle
with some unknown mass.
And you can say,
well, OK, I know
how to calculate that diagram
with my made-up particle.
I can go look for it and see.
And if it was there, it would
show up in one of these bumps.
And the data are here.
And today I don't have
any bumps in them.
This is not a bump.
This is just a turnover.
This is the way we
selected the data.
So there are no bumps--
so there's no-- that
theory is wrong.
And this kind of process
is going on over and over
and over again
with people trying
to find ways of explaining
some of the missing
things on the map.
They're looking for what the
consequence of those missing
things would be and
seeing with the data--
show any bumps in there,
that would possibly
betray that evidence, and
give evidence for that.
There is another way.
The data on the
Higgs in this slide
are shown from the ATLAS
and CMS experiments.
I'm on the ATLAS
experiment, actually.
They're the kind of
rivals that what we call
the general-purpose detectors.
One of the other experiments on
there is doing something else.
It's actually collecting
a lot of particles,
a lot of hadrons, which
have got quarks inside them.
It's collecting a lot of those
with b quarks inside them.
And it's measuring their
decays very precisely,
because the Standard Model
doesn't just tell you
how particles stick together.
It tells you, also,
how they decay.
And there are some interesting
hints coming from there.
In such talks, it's good to show
some of the-- we're watching
a lot of weird plots and
worrying about whether
the noise--
whether the data is going to
be different from the Standard
Model or not.
What you're looking
at here is a thought
from this other experiment--
LHCb here.
It has data from the
other experiments on it,
but LHCb is much better
at this measurement,
because that's what
it was designed to do.
And what you see here is--
the decay of a particular
particle-- this B0 particle
decaying to another hadron
and a pair of new ones.
It's not really
important, actually,
what the particulate decay is.
It's said that the
decay can be calculated
very precisely in
the Standard Model,
and then measured by LHCb
in the LHCb data, the most
precise in this
scatter of things,
which are the black ones here.
And the Standard
Model prediction
is these yellow boxes
with their uncertainties.
And you can see
there's a deviation.
Now, if that deviation
is true-- is correct,
then the Standard
Model is wrong.
And we have a clue,
then, maybe, of some
of the questions the Standard
Model doesn't answer.
At the moment,
significance of this is--
it's not enough for us
to be absolutely sure
that it's correct.
It could in the end.
As you collect more data
and the errors shrink,
it could regress to the
Standard Model again.
For those who care about sigmas,
it's about-- it's over 3 sigma,
but it's under 5.
It's at 3.4 sigma, which means
that if you did this experiment
something like 10 million
times, this might happen once
in five million times.
This might happen once, which
sounds like pretty long odds,
but we're doing a lot of
experiments a lot of the time,
so you have to factor that in.
So this is an example of one
of the kinds of distributions.
As well as looking
for bumps, we're
also doing things like this.
And we're watching
it really carefully.
And we're hoping all the time
that one of these monsters
is going to emerge from
the mist on the ocean
that we're exploring
to the east.
And we're hoping that we
can cope with that monster
when it emerges as well.
But we're hoping it
will give us a clue
as to some of the questions
that our current map does not
answer.
So this experiment is ongoing.
What you're seeing
here is the data.
Luminosity is
essentially the number
of proton-proton collisions
that we've had delivered to us.
You can see here this is each
year, so 2011, 2012, which
is the green and the blue.
So here and here.
They were running at 7
and 8 tera-electronvolts,
so about half the design energy
of the Large Hadron Collider.
But they were
enough, particularly
the 2012 data, where we
collected a lot of data.
They were enough to
discover the Higgs boson.
And then we have a gap.
We didn't take any
data in 2013, 2014,
because we were
refurbishing the machine.
So we could go more closer
to its full design energy,
so nearly doubled
the energy there.
And then we started
up again in 2015
and had a bit of a
frustrating year,
because we didn't manage
to get the machine working
as quickly as we'd hoped,
maybe in its new configuration.
Although, the high
energy-- we did
get the first high-energy data.
There wasn't very much of it.
But then 2016 was
absolutely a bumpier year--
here the pink one.
And last year was even better.
And every time-- you
know now what this means.
As we collect more
and more data,
we've beaten down
the error bars,
and we've got more
and more chance
of seeing new features emerging
from the statistical noise.
So where we see of them--
where we see a Z prime,
where we see some
dark matter, will
one of these branching
ratios give us
a clue as to where the
anti-matter has gone?
We don't know.
It might be.
Our ship just isn't
powerful enough.
It might be that the
Standard Model is isolated,
that this ocean
is actually empty.
Now, that would be, in
a way, disappointing,
because it's always fun to
discover a new particle.
And it would also
be disappointing,
because it would leave
us still without much
of a clue as to
what that matter is,
or how gravity-- if it's
in the picture or any
of the other things.
On the other hand, it would
be really new information.
We would not be anymore
sitting in the bar listening
to tales from theorists.
We would have a proper
survey of this ocean,
and we wouldn't hold that
there is really nothing there.
And it would be unusual, because
every other bit of energy
and every other leap
in energy that we've
had in physics-- we've
actually found new phenomena.
We found new stuff
and new understanding.
So we would-- if the Higgs is
really the last thing, not just
the last thing in
the Standard Model,
but the last thing within
an order of magnitude
of an energy of the Standard
Model, and within reach,
then that's interesting.
And it will shake up-- it
will kill a lot of theories,
and it will shake up
a lot of thinking.
And at some level, the
fact that we, so far,
haven't found anything
here is already
having that kind of effect.
But it's very early days.
We're going to get something
like a factor of a hundred more
data than we have now.
So it's too early to
say this is the case.
On the other hand, people
are taking the idea much more
seriously now than they were.
And, of course,
we're also thinking
about what we might do next.
This is a map, a kind of fancy
map, really, at the moment.
But it's a map of--
this is the Large Hadron
Collider, looking quite dinky--
or at Geneva.
This is a possible linear
collider you could build.
And this is a possible circular
collider you could build,
which would go to another
order of magnitude,
up in energy from the
Large Hadron Collider.
It's 100 kilometres round.
When I say you could build this,
what that means at the moment
is that the geology would allow
you to dig the tunnel, which
is not insignificant, actually.
I mean, you may think that
digging tunnels is boring,
but it's important.
Sorry.
But what we don't
know yet, of course,
is whether this is
scientifically the right thing
to do.
We don't know whether there
is really a science case
to do this.
These things absorb people's
careers for a long time
and a lot of effort.
So you need to be
absolutely sure you're
doing something interesting
before you embark on that.
That's the first stage.
Then, of course, we
have to persuade--
we have to work on it
to build the technology.
So we have to get the
magnets and the accelerators,
so that they will actually work.
And there's a lot of work going
on, on that at the moment.
And at some level, some
of it will work already,
and there's more to be done.
And then, of course, we have to
persuade the rest of the world
that it's worth paying for it,
and that they should do it.
This is a more kind of
artistic and artist impression
of this from the
ski resort in Jura
where we were over Christmas.
Looking down, this is
the LHC here again.
Mont Blanc in the
background again.
If you know the region,
it's incredible.
It goes under the lake
and behind the Jura.
It's absolutely bonkers to
think that we would ever
build anything like
that, just to find out
how the universe works.
On the other hand, this
is 27 kilometres around,
and it's pretty bonkers already.
So I don't know.
We did that.
And maybe this will be
the right thing to do.
Maybe we'll do it.
And it's not--
just to finish up,
I like to say, also,
that it's not just
a matter of bigger tunnels
and more expensive,
bigger machines in that way.
A lot of technological
innovation
goes on to build these things.
CERN as an organisation has
had a pretty much flat budget
for the last two decades or
more and has done more and more
within that budget.
And the reason for
that is because we're
developing new technologies all
the time, not just that CERN,
but in collaboration
with industry,
in collaboration with other
labs around the world.
And that allows us to do more.
And a lot of the kind of
accelerated technology
that was cutting edge
when it was at CERN
is now routine use in
hospitals around the world.
And so I'm just going
to finish by showing you
one of the kind
of long shot ideas
that's going on in
CERN at the moment,
which we're also
working on at UCL.
This is the accelerator
complex at CERN.
So this is a lot.
This is actually-- they use
this diagram in the control room
at CERN to see how--
it lights up when they've
got the different bits
of the complex on.
And you see high CERN
has managed to do--
it's doing a lot more than
just the Large Hadron Collider.
So the SPS here, for
instance, because the collider
where the W and the Z
bosons were discovered--
it was the highest energy
machine at the time.
It's now a booster for
the Large Hadron Collider.
And you see that this is where
there's a linear collider where
the-- where are we here?
LINAC 2 and the end software.
So this is an output.
But this is where the protons
start at LINAC 1 and LINAC 2
and eventually, go
around various loops
and end up in the
Large Hadron Collider.
And here off this SPS, which
is the previous high-energy
machine before the LHC--
you see there's a test
beam here and this thing
called AWAKE on the end of it.
AWAKE is a plus--
is one of the accelerated
development technologies that's
going on at CERN.
And it's using an innovative
way of accelerating particles,
which I'm going to try
and illustrate in that.
So you have a plasma, which
is nuclei and electrons freed
from each other in a gas of
electrons and charged ions.
And you fire a laser through it.
So you've got to imagine
these particles here
are particles-- are
electrons in the plasma.
And as you fire a
laser through it--
the electrons or a beam
of particles through it--
then the electrons get--
move around.
And you see that they oscillate.
And you think, OK, well that's
not such a huge surprise.
But because they're
oscillating, the electric field
is being developed in that
in the way that we'll see--
I'm going to turn
off their field when
the next one comes through.
So I turned off the field.
You see there?
You see there's this kind
of after-bunching coming
after them as the particle-- the
charged particles of the laser
go through first?
You see these guys are
getting pulled along
quite fast behind it.
That's because there's a very
strong electromagnetic field
following it.
If we pause-- I'm going to turn
off the field once more when
the next wave comes in.
All right, look at this.
Watch how they loop around, and
you get this huge boost here.
That kind of technique
will actually
allow you to sustain an
electromagnetic gradient that
is higher than any
material can sustain.
One of the limiting factors
on the energies we can get to
in a particle accelerator
is whether you
can maintain an accelerating
gradient, actually,
on any piece of material.
In this case, you
don't need to do that.
If you can fire an electron and
that it could ride this wave,
you can turn from--
you can turn a 400 GV proton
into a 400 GV electron, which
is-- and a 400 GV electron
is impossible to get
in the current Collider setup.
So this is just--
there are other--
this is one of the--
if you could build a bunch
of plasma cells like this
and get them focused
and make it work,
then you could,
in principle, get
to the energies of the
Large Hadron Collider
or the 100 kilometre Collider
in order of magnitude
higher than the LHC.
You could, in
principle, get access
to those energies
in a few metres,
rather than a few-- or
maybe a few hundred metres
rather than a few
kilometres and consequently,
save a lot of money and time,
as well if you can make it work.
Now, there's a huge if there.
This technology is
under development.
It doesn't work at the moment.
For very high energies, it's
being tested and developed.
It does, however, already
work, and it's already
being used in hospitals
to get lower energy
beams quickly with a laser
and much more cheaply.
So that's the kind
of zone we're in now.
We're sailing eastward
from the Higgs boson
and with the Large Hadron
Collider at the moment.
We're looking there.
If we find something
there, it may give us
very clear pointers
for exactly what
machine we need to build next.
And then we'll come
and start arguing
with the politicians
and the public
to persuade them
that it's worthwhile.
If we don't get any
clues, then we'll
be looking at things
like the neutrinos.
We'll be looking at more
rare decays and things
as well, looking there
for clues as well.
And either way, we'll
be continually pushing
technologies to allow us to do
more for less, so that we can
actually study the universe more
closely within the resources
that we have available.
So what I've given
you there is a kind
of lightning tour of this
Map of the Invisible,
starting with the electron.
I skipped the middle
a bit, more or less,
and ended up in the far east.
But it gives you some idea,
I hope, of what we're doing,
and why, and where we are.
And the rest of
it is in the book.
These journeys are
going to continue.
It's been an amazing time the
last few years to be a particle
physicist, but it's continuing.
And I decided to finish
by thanking Chris, who
drew the figments of my
imagination, in the maps.
And that's all.
Thank you very much.
