[APPLAUSE]
Well, thanks, Martin, for that
very generous introduction.
That was very kind of you.
So it was actually 5 and
1/2 years ago almost now
that CERN announced to
the world they discovered
a new-- what they cautiously
described at the time--
as a new boson, which
we've now sort of fairly
confidently concluded is
at least a Higgs boson.
And around that time,
suddenly particle physics
was all over the news.
Brian Cox was wheeled into
every television studio
to explain to slightly
bemused-looking TV anchors
what spontaneous
symmetry breaking was.
And then everyone sort of
moved on with our lives,
and forgot about us.
And you might be forgiven for
thinking that actually, we
put our feet up at CERN and just
had a holiday for the last five
years.
Because there hasn't really
been another big breakthrough,
at least not one
that's got in the news.
So what I want to talk
to you about today
is what we actually
have been up to.
And particularly,
there's something quite--
it's true there hasn't been a
really big breakthrough yet.
But just in the
last year or two,
there have been some
really intriguing signs
that we might be-- and being
very cautious about this--
we might be about to discover
something really quite
profound.
So this is CERN,
which is the European
Organisation for Nuclear
Research just outside Geneva.
It's a sort of the
size of a small town.
The population of CERN at any
one time is about 2,500 people.
There are about 7,000
physicists from around the world
who are involved
in research there.
And it's got everything that
a small town should have.
It's got a restaurant.
It's got a post
office, travel agents.
It's got hotels.
It's a kind of town populated
exclusively, though,
by particle physicists.
So you can kind of imagine
what that must be like.
[CROWD LAUGHS]
This was the scene in the
main auditorium at CERN
on the 4th of July, 2012.
Now, this is as excited
as you will ever see
particle physicists getting.
They were sort of
clapping, cheering,
people punching the air.
One of the people in
the crowd described it
as being like at
a football match.
I'm not sure he'd ever
been to a football match.
But, I mean, it
was certainly very
lively by physics standards.
And this is what they
were all cheering.
There was a bump.
So physicists get very
excited about bumps.
If you want to know what
a Higgs boson looks like,
this is basically what a
Higgs boson looks like.
It looks like a bump in a graph.
So I'll explain
actually what this shows
a bit later in the lecture.
But really, the thing
you're looking for here
is, there is this
smoothly falling line.
And then there's this
little, tiny excess here.
And that was the
smoking gun telling us
that there was a
new particle that
had been found which,
over the last few years,
has been almost
certainly confirmed
to be the Higgs boson that Peter
Higgs predicted back in 1964.
So what is a Higgs
boson, you might ask.
And that's a very
reasonable question.
So I'm going to very
briefly take you
on a quick tour of
particle physics
to try and understand what
this thing actually is.
So let's start with maybe
something slightly more
familiar.
So this is the periodic table
of the chemical elements which
dates back to the 19th century.
So at the end of
the 19th century,
the understood theory of what
the universe is made from
is, there are more than a
hundred different chemical
elements.
And thanks to Dalton's
atomic theory,
what he said was that for every
element-- hydrogen, and helium,
lithium and so on--
there was a atom, which was
a fundamental, indivisible,
indestructible little thing.
And you had different atoms,
one for every element.
So that was the sort
of Victorian view
of the nature of matter.
So here's your atom.
Then at the turn of the 20th
century-- so 1897, actually,
the Cavendish Laboratory,
where I work--
a particle was discovered.
The first elementary
particle that we found,
called the electron.
And that led over
the next few years
to a revision of the
structure of the atoms.
So the atom, as I
said before, was
thought to be something hard,
indestructible, indivisible.
When the electron was
discovered, that was revised.
And we get the model
of the atom that we all
learn about in school, which
is a nucleus which contains
most of the mass of the atom.
And that's positively charged.
And around the atom
go these electrons.
Now, the periodic table if
you look at it in the way
that the elements
were arranged, there
are certain patterns
in the properties
of the different
chemical elements.
So, for example, if you look
at the group 1 elements,
they all tend to
react in similar ways.
And they get more
reactive as you go down.
But there are clear
patterns in the way
the elements are arranged.
And that was sort of indicative
of some deeper structure.
And this is the
deeper structure.
So essentially you can
explain the properties
of all these different
elements by different numbers
of electrons going around
the outside of atoms.
And those electrons
are what determine
the chemical properties of
that particular element.
Now, this isn't the
end of the story.
So if you zoom into
the nucleus, it
was discovered in sort
of the early 1930s
that the nucleus itself
is made of smaller things.
And these are called
protons and neutrons.
So these are smaller
parts, smaller particles,
which make up most of
the mass of the atom.
The proton is
positively charged.
The neutron is
electrically neutral.
They're much, much
heavier than electrons.
They're about 2,000 times
more massive than electrons.
Now, this may be where
your sort of school physics
ended, possibly.
But in the 1960s,
it was discovered
that actually protons and
neutrons themselves are not
fundamental.
They're made of
even smaller things.
And those smaller things
are what we call quarks.
Quarks, depending on your taste.
So the proton is made
of two up quarks--
which are these red
triangles-- and one down quark.
And the neutron is made of two
down quarks and one up quark.
And that's it.
So that basically says
that all of matter--
every atom in the universe,
everything that we know about--
is made up, actually,
of just three
different elementary particles.
So you have the
electron, first of all,
discovered by JJ Thomson
in Cambridge in 1897.
And the two quarks, the up
quark and the down quark.
So everything that exists
is made of just these three
things.
So you are just
quarks and electrons
arranged in a rather
peculiar way, essentially.
And these are the
first three particles
of what we call
the Standard Model.
Now, the Standard Model
of particle physics
is a rather boring name for
something quite extraordinary.
It's really the closest we
have to a complete description
of the universe at
the fundamental level.
Well, it misses quite
a few things, actually.
But the main thing
that you might
be familiar with that it
doesn't include is gravity.
But other than that, it's got
it pretty well pinned down.
So you've got these
three particles
that make up all the
matter that we're made of.
Then there's something else that
gets added to this table called
a neutrino.
Neutrinos are sort
of like ghosts.
They're these invisible,
almost undetectable particles.
There are trillions of them
going through you right now.
They're produced by the
sun in vast quantities.
They go straight through you,
straight through the earth.
And they very, very rarely
interact with the ordinary
matter that we're made out of.
So that's why we're not really
that aware of the existence
of neutrinos most of the time.
So this column of four
particles makes up
what we call the first
generation of matter.
Now for some reason which
we do not understand,
nature provided us with
two additional copies
of these particles.
There's something called
the second generation.
And in the second
generation, all the particles
are exactly the same as
in the first generation
except they're more massive,
and they're unstable.
So, for example, the
electron has a sort
of heavy cousin called the
muon, which is about 200 times
more massive than the electron.
And the reason we're
not made of muons
and there aren't
muons hanging around
is because if you
make a muon, it
will very quickly decay into
an electron and some neutrinos.
So these second
generation particles
don't hang around very long.
They're unstable,
but you can make them
in high-energy collisions
like at the LHC, for example.
Then there's the
third generation,
which is even heavier.
So these are-- what is this?
4x3.
12 particles are the
matter particles.
So they make up the kind of
solid stuff of the universe,
essentially.
Or, at least, they would if
they weren't all unstable apart
from this first column.
And we do not know-- it is
a big mystery-- we do not
know why there are two
extra columns in this table.
It's a bit like the periodic
table in a way where
you have this sort of structure
and you can see these patterns.
But you don't actually
understand yet-- back
in the 19th century--
what underlies this.
But there's something
suggestive here.
Something that sort of
hints that maybe there's
some deeper structure
that could explain
why we've got this rather
peculiar set of matter
particles.
And I'll come back to
that in a little bit.
And then the last ingredient
in the Standard Model
are the force particles.
So there are three fundamental
forces in the Standard Model.
Probably the most
familiar to you--
and one that a lot of important
work was done in this building
on-- is electromagnetism.
So by Faraday, and Maxwell,
and various others.
So that's the force that
causes electrons to stick
to the nuclei of atoms.
It binds atoms together.
It's responsible for chemistry.
It's responsible for basically
most of the stuff that
is important to us.
And the particle that transmits
the electromagnetic interaction
is the photon, the
particle of light.
So light itself is also an
electromagnetic phenomenon.
Then there are three
other particles which
you may not have heard of.
There's something
called the gluon which
is the force particle
of something called
the strong nuclear force, which
is a force that binds quarks
together inside
the atomic nucleus.
And binds protons and
neutrons together.
And it's called a gluon because
it glues things, essentially.
And then there's two rather
weird ones called the W and Z
particles.
And these are
particles that transmit
a third force, an
even weirder one
called the weak nuclear force.
Now, the weak nuclear
force doesn't really
bind things together
like electromagnetism
or the strong force.
This force is responsible for
causing particles to decay.
So when a muon turns
into an electron,
that happens through
the weak force.
And I'll talk a bit more
about the weak force.
It's very important, the weak
force, although we don't really
notice it in our daily lives.
If it wasn't there,
the sun wouldn't
be able to fuse
hydrogen into helium.
And there would be no
matter in the universe.
So it's very important, even
though it's not something
we're very familiar with.
So this is a Standard Model.
And this was the
Standard Model as had
been sort of
studied and observed
on the 3rd of July, 2012.
And on the 3rd of
July, 2012, there
was one piece missing
which was this, the Higgs.
So, what is this
Higgs boson thing,
and why is it so important?
Well, to understand
that, we actually
need to ask a slightly deeper
question which is, what do I
actually mean by a particle?
So you could be forgiven.
The way I've described this to
you in the last few minutes,
you could get the idea that
maybe these particles are
somehow like little
LEGO bricks, or they're
a bit like the Victorian atoms.
They're sort of
solid little points
that move around
and stick together.
But actually, that's not
what modern particle physics
tells us particles are.
In fact, particles aren't
really what matters at all.
Our field is kind of
badly named in sense.
What actually we think
of as being fundamental
are not particles but fields.
If you've ever
held a magnet next
to a piece of steel
or iron, you've
felt the effect of a field.
So a field is something that
can cause, for example, a force
to be exerted over a
distance where there's
no physical stuff actually
causing that force
to be exerted.
A field can be, so for
example, a magnetic field.
And that can be
strong near a magnet,
and get weaker as you
move further away.
Or it could be a
gravitational field,
like the one that the
earth creates around it,
or the sun creates around it.
In particle physics, every
one of these particles
has an associated field.
So there is a field for the
quarks, for the electrons,
for the neutrinos, and for
all the force particles.
And the way we think
of these particles
are actually as
little tiny ripples
moving through these fields.
So this is a rather nice
cartoon by one of my colleagues
at Cambridge.
David Tong is a
theoretical physicist.
So, here you've got your
fields, this kind of blue sheet.
And then here you've got some
particles having a punch up.
So they're kind of these little
localised disturbances in these
fields.
And that's how we
think of all matter.
So electrons, quarks,
everything are just
little ripples moving
through these cosmic energy
fields that fill all of
space and are everywhere.
Which is quite a
sort of strange idea,
but that's really how
we think things are.
So coming back to the
Higgs, what is the Higgs?
Well, the problem
existed in the 1960s.
When the Standard Model
was being put together,
it was discovered
that if you tried
to make the particles in
the Standard Model massive,
then the theory broke down.
It'd give you
nonsensical answers.
So, in particular, there was a
particular problem with these W
and Z particles, these
particles that transmit
the weak nuclear force.
It was known that
if they existed,
they had to be
extremely massive.
But if you gave them mass
in the theory, the theory
it gave you nonsensical answers.
So there had to be
some solution to this.
And the solution
was, essentially,
to invent another field.
So just like the other fields
that these particles are
ripples moving about in,
what Peter Higgs essentially
said-- and, actually, five
other colleagues he was working
with round about
the same time-- was,
imagine that there is
throughout the entire universe
an additional cosmic
quantum field.
And as these massive
particles-- these things
that we think are
massive-- move through it,
actually they are imbued
with mass by this field.
So, for example, the electron--
which has a certain mass--
what the Higgs mechanism
tells us is actually,
the electron is mass-less.
But by interacting with
this cosmic energy field,
it acquires the
property of mass.
So Higgs wrote his
paper in early 1964.
And he had this idea
which was written down
with very elegant mathematics,
which looks a bit like this.
And don't worry, I won't try
and explain what this means.
And he sent it off
to the journal,
and his paper was rejected.
They basically said, this
has nothing whatsoever
to do with physics.
So Peter Higgs here, nice maths
but nothing to do with reality.
So Peter Higgs went
back to his paper
and he said, well,
I need to connect
this with something that could
be experimentally measured.
And what he added to
his paper was, actually,
basically one line that said,
if this cosmic energy field that
gives mass to all the
particles exists, then
you should be able
to create a ripple
or a disturbance in
it which would show up
as a new particle.
And that thing-- that
ripple in the Higgs field--
is what we call the
Higgs, the Higgs boson.
So the thing that gives mass
to the particles we're made
of, at least, is this field.
And the Higgs
really is the proof
that this field is out there.
And that's why finding
it was so important,
because the Higgs mechanism--
this Higgs process by which
the particles get
mass-- is absolutely
fundamental to the
Standard Model.
It's kind of like the
keystone in an arch.
If you take it away, the whole
theory just falls in on itself.
People were almost kind
of convinced, actually,
that this thing
must be out there.
And that's why finding
it was so, so crucial.
And why everyone
got so excited back
on that day on the 4th of July.
So with the discovery
of the Higgs,
this completes the Standard
Model of particle physics
that I've been
telling you about.
And this theory is really a
kind of incredible achievement,
actually, because it can be
used to pretty much explain
all the physics that
we can see around us.
So you can use this
animal in principle
to describe everything from how
a light bulb produces photons
to how atoms are fused
together inside stars.
It's the closest
we have, as I said,
to a theory of everything.
To give you a sense of
the predictive power
of this theory, this is--
actually, what I'm going
to tell you about now
is the best scientific
prediction anywhere in science,
as far as I'm aware.
So, here's the electron.
Now the electron as well
as having electric charge
also behaves a bit like
it's a tiny bar magnet.
So it has a north
and a south pole,
and it gives off
a magnetic field.
And you can use a Standard
Model to calculate
how strong the electron's
little bar magnet should be.
And you can do this to
absolutely fantastic precision.
So essentially what you do
is, you use a supercomputer.
You put the theory
into the computer,
and you calculate, and
you get a number that
looks like this, 11596521807.3
plus or minus 2.8 times 10
to the minus 13.
So it's a very small number,
but very precisely calculated
with a very small uncertainty.
This is your
theoretical prediction.
Now if you do a very,
very clever experiment,
you can measure
this quantity-- it's
a very, very tiny quantity--
to a very high accuracy.
And this is what you get.
11596521817.8 plus or minus 7.6.
So you can see, these
numbers agree right down
to the last sort of three
significant figures.
And the difference between
this number and this number
is within the
experimental uncertainty
on this measurement.
So this is a prediction
and a measurement
accurate to one
part in a billion.
That is really kind
of extraordinary.
So that tells you that this
Standard Model is definitely
on to something.
I mean, you don't get this
kind of result by accident.
So its a really stunningly
successful theory, but it
is not without some problems.
And these problems are
actually what motivated,
in part, the building
of the Large Hadron
Collider in the
first place, as well
as the discovery
of the Higgs which
is really kind of closing
the chapter of 20th century
physics.
What everyone was
actually really after--
well, a lot of
people were after--
were answers to some big,
unsolved questions that
the Standard Model
cannot address.
Now, I'll go back
to this picture.
So this is actually an image
taken by the Hubble Space
Telescope.
It's called the Hubble
Ultra-Deep Field.
And what essentially it
is is where the telescope
is pointed at a very
dark patch of sky, where
there are almost no stars.
And you wait for
a very long time
and wait for
extremely faint light
to build up on the
sensor of the telescope.
And eventually, this is
the image that you get.
So what you can
see in this image,
there are actually a few stars.
They're the things with the
kind of cross twinkie patterns.
But everything else,
pretty much, is a galaxy.
These are extremely
distant galaxies, sort of
almost out to the edge of as far
as we can see with telescopes.
So, for example, in the
centre of the image,
you can see there's a kind
of cluster of galaxies,
these kind of blobs.
Now, hopefully you should
be able to also see
that on this image, there
is this smearing pattern.
So there's kind of these
circular structures arranged
around this central
cluster of galaxies.
And what this smearing
is, is something
called gravitational lensing.
So this is essentially where
light from a distant galaxy
travels towards the earth.
Now thanks to Einstein, we
know that gravity doesn't just
make matter move in
orbits or curves.
It also curves
space time, and it
will cause light to
travel in curved paths.
So what's actually happening
is imagine you have your--
if my galaxy is here and
the Earth's over there,
and there's something heavy
in between me, the galaxy,
and the earth over there.
As the light leaves
the galaxy and travels
past this heavy object,
it's bent by its gravity
and pulled back towards
the earth again.
And what you end up getting,
it basically acts like a lens.
And you end up getting this
kind of smeared multiple image
of the same galaxy
across the whole sky.
And this lensing effect
can actually, therefore,
be used to work out how much
matter there is in the centre
of this image.
Because the more gravity,
the more mass there is here,
the more strongly lensed
the light will be.
And the more pronounced
this effect will be.
So what you can do is,
if you use this lensing,
you can work out how
much mass, effectively,
there is in the
centre of this image.
And then you compare that
with the visible light
that you can see.
So we can see there are
lots of galaxies here.
This is obviously a very
large amount of mass.
And what you actually
find, though,
is that there is a very large
discrepancy between the amount
of stuff you can see with
your optical telescopes
and the amount of stuff
we know needs to be there
to explain this lensing effect.
And if you overlay a map
of where the matter appears
to be in this image from
lensing, this is what you get.
You get this kind of
bluish purple cloud.
This is evidence of
something called dark matter,
which is essentially some
kind of invisible substance--
and which we don't
know what it is--
which apparently makes up a very
large fraction of the universe.
In fact, it's far,
far more abundant
than the atomic matter,
the stuff the Standard
Model describes basically.
So you have evidence of
dark matter from lensing.
You also have evidence
of dark matter
from simulations
like this, which
show how the universe
formed in the early stages.
And essentially,
you find that if you
want to show how structure
in the universe formed,
you need dark matter.
If you don't put dark matter
into your simulations,
then you don't get a universe
that looks like the one
we live in.
So this is from the
Illustris Simulation Group.
Rather lovely thing.
Anyway, you can sort of see
galaxies bursting to life
and stars turning on things.
Really pretty.
But you need the dark
matter to make this work,
and to agree with what we
see out there in the sky.
And through these kinds of
techniques-- through lensing--
and also by looking at
the rotations of stars
around galaxies--
you can calculate
to a fairly high
degree of confidence
how much dark
matter is out there,
even though we can't see it.
And this is what you get.
This is our cosmic pie.
And essentially what you see
rather extraordinarily is this
slice here-- which
I've labelled atoms--
which is basically
us and everything
that we can see when
we look up at the sky.
So all the galaxies, and stars,
and planets, the universe.
And everything the Standard
Model describes is just 5%
of the total content
of the universe.
27% of it-- so more than five
times more of the universe--
is made of this invisible
dark matter stuff.
And we don't know what that is.
And then 68% is something
called dark energy,
and we really don't
know what that is.
So dark energy is some kind
of mysterious, repulsive force
that appears to be causing
the universe to expand
at an ever-increasing rate.
So the lesson from
this is essentially,
when you hear the
word dark in physics,
you should get very suspicious
because it basically
means we don't know what
we're talking about.
And this is really an
extraordinary position
to find yourself in.
You've constructed what seems
to be this stunningly successful
theory over a century with
all these clever experiments
and clever theories.
And then you realise that
what you've been describing is
actually only a tiny
fraction of the total content
of the universe.
So we're in this
extraordinary position
of having a theory
that works really,
really, really well in the very
narrow domain in which we've
applied it, but tells us
basically nothing about 95%
of what's out there.
So that is definitely
a bit of an omission,
I suppose you could say,
in the Standard Model.
There are other
problems as well.
So we don't know what
95% of the universe is.
That's pretty big.
Another one is to do with
something called antimatter.
So that table I showed
you at the beginning
with all the matter particles--
the quarks, the electrons,
and their cousins,
and the neutrinos--
for every one of
these particles,
there is a sort of a
mirror image particle.
This has been known about
for a very long time.
It was discovered
back in the 1930s,
predicted by someone
called Paul Dirac.
And then discovered in
experiments very shortly
afterwards.
Every particle in this
table, as I've said,
has a mirror image where
all the properties are
exactly the same, but
the electric charge
is the other way around.
So, for example, the electron--
which is negatively charged--
has a positively charged
version called the positron,
or the antielectron
depending on what you prefer.
And there's your
muons, antimuon.
There's the up quark and the
anti-up quark, the down quark,
the anti-down quark, and so on.
And these are also part
of the Standard Model.
We know these things exist.
They can be created very
reliably in experiments.
Their properties are studied.
And we know they're out there.
And we also know that
they are actually
indistinguishable from
the matter particles,
except for their charges
being the other way around.
Now this is a bit of
a problem, actually,
because if you naively apply
this sort of understanding
of matter-antimatter to the
formation of the universe, then
this is what happens.
So at the Big Bang, you have
a huge amount of energy.
And that energy is converted
into matter and antimatter.
And in the Standard
Model, whenever
you make a matter
particle, you also
have to make the corresponding
antimatter particle.
So if you make an electron, you
also make with it the positron.
And there's this cosmic kind of
maelstrom, all these particles,
antiparticles being created.
And at the same time as
they're being created,
they're also bumping
back into each other,
and annihilating, and
turning back into lights.
You have this interchange
between energy,
and matter, and antimatter.
And it's boiling
and boiling away.
And then eventually what happens
is the universe expands enough
that it cools down low enough
that all the matter-antimatter
meet up, annihilates,
and what you're left with
is a cold, dark, and
lifeless universe
with a few photons whizzing
through the infinite blackness.
This is what the
Standard Model says
the universe should look like.
This is what the universe
looks like, though.
[AUDIENCE LAUGHS]
Copyright Lucasfilm.
So the existence of stuff,
and us, and galaxies
is a bit of an inconvenience
if you're a theorist.
We don't understand
that, either.
So there must be
some kind of process
by which you can allow a little
bit more matter to survive
this cosmic annihilation at
the beginning of the universe.
And actually, you
can work out how big
that imbalance has to be.
It only has to be
very, very tiny.
If you look at the sky and
count, essentially, the number
of photons whizzing
through space,
there's a rough correspondence
between how many photons
there are out there and how
many particles and antiparticles
annihilated at the beginning.
Because every annihilation more
or less creates two photons.
And there are about
a billion photons
for every atom in the universe.
And what that tells
us is that, really, we
are one billionth leftover of
a much larger amount of stuff
that was there at the beginning.
But we don't know how
this billionth survived.
It shouldn't be there by rights.
It should have all been wiped
out, and we shouldn't be here.
So that's two big problems.
There's the fact we don't know
where 95% of the universe is.
And, also, the theory tells us
the universe shouldn't exist.
So, two big problems.
I'll come up to a third one.
And this is one that's
probably motivated
a lot of theoretical physicists,
since Einstein, really,
in the '20s and '30s.
So this is a problem
to do with gravity.
Now gravity, as it
turns out, although it
feels quite strong--
it sticks us to the
floor, if you fall out
a window it hurts quite a lot--
it's actually terribly weak.
It's a fantastically weak force.
And this cartoon
illustrates that point.
So we have the earth, which is
pretty large by any standard.
And it's got a
gravitational attraction,
and it's pulling
on this paperclip.
I can use a very weak fridge
magnet, which is only this big,
to pick up that paperclip.
So that magnet is overcoming
the gravitational attraction
of this huge ball of rock
many, many, many times larger
in terms of mass.
So that tells us, essentially,
that the electromagnetic force
is way, way, way
stronger than gravity.
If you had a magnet
the size of the Earth,
it would be
fantastically powerful.
You can compare these two.
So if we say that
electromagnetism
has a strength of one, then
gravity strength is this.
[SPEAKER LAUGHS]
Ten to the minus
36, more or less.
I won't read that one out.
And this, it's a
real puzzle, this.
Why is there such
a huge hierarchy
between gravity and
the other forces?
So the strong, the weak,
and the electromagnetism
are all way, way, way
stronger than gravity.
And we don't understand
why that is, either.
So there are lots of
problems, potentially.
It's also very big problems.
And that's what's a
large part the LHC was
built to try and solve.
Fortunately, though, there
are some possible theories
out there that could
explain some of these.
And one of the most popular is
an idea called supersymmetry.
Now supersymmetry,
the essential idea
is to invoke a new kind
of symmetry in nature.
And it's a symmetry,
a rather odd symmetry.
So it's not really like this
mirror image of antimatter,
but it's kind of comparable
to it, I suppose.
So in supersymmetry,
there is a symmetry
between the matter particles.
So that's things
like the quarks,
and the electrons,
and the neutrinos.
And the force
particles which are
the gluons, the photons,
and the weak particles,
and the Higgs, as well.
And in supersymmetry,
every matter particle
gets a force particle partner.
And every force particle gets
a matter particle partner.
So you end up with an
extra table of particles
that look like this.
And they all have
really stupid names.
So basically, if
you want to know
what particle's name
is in supersymmetry,
you add an S to the front of it.
So the electron
becomes the selectron.
The muon becomes the smuon.
I think worst of all, possibly,
is the strange s quark.
[AUDIENCE LAUGHS]
Anyway, there should be
some kind of commission
to name things.
I don't know how this happens.
They're called sparticles.
It sounds very silly the
way I've described it.
It's very clever, supersymmetry.
I don't want to do it down.
The interest in supersymmetry
really began in the '80s,
and it's been the most popular
extension of the Standard Model
for a very, very long time.
And that's because
it's incredibly
good at solving some
of these problems
that I've described to you.
So, in particular, dark matter.
So one of the reasons
that supersymmetry
is very popular with
particle physicists
is that often, the lightest
sparticle is stable.
And often, it's also
electrically neutral.
And that's exactly what
you want for dark matter.
So I said dark
matter is invisible.
And that's because it doesn't
reflect, absorb, or emit light.
And things that don't emit,
absorb, or reflect light
are electrically neutral.
So you have an electrically
neutral particle that
doesn't interact with photons.
It could well make up the
dark matter in the universe.
So that's one reason for
liking supersymmetry.
Another one.
There's a sort of
obsession in physics,
which is to try to unify
things, to simplify
complicated phenomena into
one sort of single underlying
phenomena.
And that's true with the
forces, particularly.
And unifying the different
forces in physics
has been a sort of ongoing
quest since Maxwell
unified electricity and
magnetism in his equations
back in the 19th century.
So this is a rather confusing
graph, unfortunately.
I don't know why it's produced
this way, but it's upside down.
But basically what
you've got here,
this axis is the strength of
the three different forces
in the Standard
Model except they
get stronger as you go
down rather than going up.
But don't worry
about that too much.
Now if you do
experiments and measure
the strength of these
forces, what you find,
rather curiously, is that
the strength of the forces
change as you go higher
and higher in energies.
So that basically means
if you have some collider
and you bash particles
into each other,
the harder you hit them into
each other, the forces--
the strength of these
forces-- alter, essentially.
And what you see in the Standard
Model if you do experiments
at higher and higher energies--
and these are energies that are
way higher than we can actually
produce in an experiment,
but this is done with
theoretical calculations--
you find that at some very,
very high energy scale,
there is a point where
these three lines--
the electromagnetic
force, the weak force,
and the strong force--
sort of come together
a bit, but not quite.
If you introduce supersymmetry,
these lines meet rather exactly
at a particular place,
labelled unification.
And this suggests that with
supersymmetry, these three
forces are unified into
some single overlying
force which possibly
should be called the force.
And so that's another reason
for liking supersymmetry.
It unifies these three
apparently disparate forces
into one.
Actually, we've already
unified these two.
That's partly what
the Higgs is involved
in, but never mind about that.
It's just a strong force.
The other reason to
like supersymmetry
is that we've now doubled the
number of fundamental particles
to discover.
So people like me are kept
employed for a very long time.
So that's good.
So we like supersymmetry.
Another possible theory.
So this one tries to explain
the weakness of gravity.
So there are a number of
different versions of this
out there.
Essentially, these
theories posit
an extra dimension of space--
or sometimes more than one
extra dimension of space--
as a way of explaining
the weakness of gravity.
Now, this is apparently
an image of what
extra dimensions look like.
OK.
I'm not so sure.
Yeah, apparently it is, anyway.
The idea is there is some
extra directions in which you
can move than the up and down,
left and right, and forwards
and backwards.
And the reason that we
don't observe them is either
because the particles
that we're made of
are stuck on our
three-dimensional sort of space
time, and only certain
things can travel
through these high dimensions.
Or it's because these
extra dimensions are
squished up very tiny,
and therefore they're
impossible to observe.
And the way you explain
the weakness of gravity
is usually by
gravity leaking away
into these extra dimensions.
So gravity can move through
all of the dimensions of space
and therefore it's diluted,
whereas electromagnetism
is restricted to just live
inside these three dimensions
that we're familiar with.
And if you want to know
the results of having
extra dimensional
theories like this,
this is what an extra
dimensional theory looks like,
according to the Daily Express.
So you make a
black hole at CERN,
and it swallows
the entire world.
We haven't seen that yet.
Actually, this is what
they really look like.
Basically in extra
dimensional theories,
often you can make
tiny black holes.
So this is where you
collide your particles
with enough energy
they actually collapse
a little region of
spacetime for a tiny moment
into a black hole.
And the reason we're not really
worried about these black holes
eating the earth like in
that rather silly animation
is that according
to Hawking's theory,
these black holes should
almost immediately evaporate.
So as soon as they're
created, they just go poof.
And this is a simulation
of one of these black holes
disintegrating.
So the black hole
was here, and it's
turned into a whole
load of other particles.
And they give a very
characteristic signature
in your detector if you manage
to make one of these things.
And it's not the whole
world falling into a hole.
Finding the Higgs
was one objective,
but finding all these
things was a really big part
of the reason the LHC
was built. And I'm now
going to take you on a
brief tour of this really
extraordinary machine.
So this is a map of Europe.
We're going to zoom
in on Switzerland.
This is Lake Geneva.
Geneva is just down here,
and CERN's about there.
If we go in a bit closer,
this is an aerial shot
from a plane of the Geneva area.
So again, you can
see Lake Geneva.
The city of Geneva is
this kind of grey smudge.
This long thing here
is the airport runway.
CERN's over there.
And then marked in
yellow on the countryside
is the route of the
Large Hadron Collider.
So this is the largest
scientific instrument
ever built by the human race.
By some measures, it's the
largest machine ever built.
It's 27 kilometres
in circumference.
It crosses the
Swiss-French border twice.
This yellow line is
not there in real life.
It's about a hundred
metres under the ground.
The main reason it's
underground is actually
not because it's dangerous and
somehow emits lots of radiation
that you'd need to
be shielded from.
It's because it would be very
expensive to buy 27 kilometres
of land to build it on.
So it's just below the surface.
And the way it works is really
quite simple and rather brutal.
Over here at CERN,
there is a bottle
of hydrogen gas about
this large, which
is plugged into a 30 metre
long particle accelerator.
And that hydrogen is
taken out of its canister.
It's zapped with
an electric field.
The hydrogen atoms
are ripped apart.
The electrons are ripped
off the hydrogen atoms.
And you're left with
protons, which are just
the nuclei of hydrogen atoms.
And those are sent
down at an accelerator.
And then they're sent through a
series of accelerators at CERN.
So imagine kind
of whizzing around
a number of different loops.
Eventually, it goes into this
ring called the Super Proton
Synchrotron, which
back in the '80s
was the largest particle
accelerator in the world.
But now it's just a
feeder for the much bigger
Large Hadron Collider.
So you have a beam of protons,
one going this way, one
going the other way.
And then at four
points around the ring,
these protons are
brought into collision
inside gigantic,
three-dimensional digital
cameras that take
photographs, essentially,
of these collisions,
and try to see
if we've created new particles.
So if you go underground,
this is what you see.
Very, very, very long blue tube,
curving away into the distance.
They're about eight
access shafts that
take you down to the tunnel.
People actually use
bicycles to get around,
because the distances
are so large.
So this blue tube is essentially
the world's largest thermos
flask.
Inside it, there is a bath
of liquid helium at minus 271
degrees Celsius.
Bit less than two degrees
at absolute zero, the lowest
possible temperature.
And the reason it's very
cold is because of the way
that these particles are
steered around the ring
are using incredibly
powerful magnets.
And these magnets
are superconducting,
which means they have no
electrical resistance.
And that means you can
create extremely strong
magnetic fields,
but they only work
at very, very low temperatures.
So the whole machine
is cooled down
with liquid helium
pumped intravenously
through this entire ring to
make the magnets operate.
The engineering challenges
in building this
are absolutely extraordinary.
To give you one fact
that I found amazing
when I learned it, is that--
maybe you remember
it from school--
if you get a piece of
metal and you cool it down,
it gets a little bit smaller.
It contracts slightly.
So you're cooling down a 27
kilometre long basically piece
of metal by 271 degrees.
And what happens when you do
that is the entire machine
shrinks by 30 metres in length.
So this thing which has to be
aligned to kind of micron level
has to be able to contract by
30 metres without breaking,
and without misaligning,
and without going wrong.
And the fact that it
works is really amazing.
These are the other
parts of the machines.
You have the very,
very long blue tube.
And then at four
places around the ring,
this tunnel opens out into these
huge subterranean caverns that
are sort of cathedral-sized.
And inside these caverns are
extraordinary looking machines
like this.
This is the Compact
Muon Solenoid,
which is a strange use
of the word compact.
So this thing is 15 metres high.
So there's a guy in a hard
hat for scale, just there.
It's 25 metres long.
It weighs 12,000 tonnes.
It contains enough iron
to make two Eiffel Towers.
Essentially what this thing is,
is an incredibly sophisticated,
gigantic, 3D digital camera.
So what happens is, the protons
come in through this beam pipe,
and in one from the
other direction.
This thing is
barrel-shaped, so you
imagine it goes off
the edge of the image.
They collide in the centre.
You get a whole load of
stuff going everywhere.
And this detector
records those collisions
in real time, actually 40
million times every second.
This is another one of these.
There's four of these things.
This is the biggest of all.
This is ATLAS, which
is kind of a rather
good, cool-sounding name.
It's a bit of a
tortured acronym,
so I won't try and tell you
what it actually stands for.
But essentially, ATLAS
is even bigger than CMS.
This thing is 25 metres
high, 40 metres long.
It's absolutely huge.
If you ever get a chance
to go to CERN and get down
underground to
see these things--
which I think is quite
difficult, sadly,
these days because
it's quite busy there--
I mean, when I saw
them a few years ago,
they really are the most
amazing things you'll ever see.
They're absolutely unbelievable.
So ATLAS does, essentially,
a very similar job to CMS.
They're two different
experiments.
They work on similar
principles, but have
completely independent teams,
and independent technologies.
And they're really
there to cross-check
each other's results.
So this is a
representative image
of what happens when
two particles collide.
Really, it's actually
a real image.
This has got the
date on it, I think.
So it says 2011, June 25th,
at 6:30 in the morning.
This is two protons meeting.
The reason we're doing
these collision experiments
is, what we're actually
doing is making matter.
You quite often hear particle
accelerators or colliders
described as atom smashers.
And that sort of suggests
that what we're doing
is breaking atoms apart in
order to see what's inside them.
But that's not really
what we're interested in.
People have known
what's inside atoms
for quite a long time now.
What particle
colliders actually are
are ways of making matter
that doesn't normally
exist in the universe.
So you load a huge amount
of energy onto each protons.
They're given huge speeds.
They're going at 99.9999991
percent of the speed of light
when they collide.
At this point, they're
carrying 7,000 times their rest
mass energy as kinetic energy.
So that means you can make
something, essentially,
that is 14,000 times heavier
than a proton in the collision.
They come together.
Their kinetic energy is
converted into matter,
and that's what you're seeing.
So you're seeing hundreds
of particles being created.
And these are not
things that are
coming from inside the proton.
Well, in some cases they are.
But a lot of it is stuff
that's being made, essentially,
out of this kinetic energy.
This process of collisions
happens 40 million times
every second inside all
four of these experiments.
And they run for
most of the year.
So usually from about April,
March, through to just
before Christmas.
So 24 hours a day with
occasional technical stops.
So you can get a sense of
how many of these collisions
it produces.
It's absolutely vast,
and the data challenges
of coping with this
rate of collisions
is really extraordinary as well.
So I'm going to try and
briefly now explain to you
what that bump was in that graph
I showed you at the beginning.
So how do you find
a Higgs boson?
Well, two protons collide.
And if you're
extremely lucky, they
will create a Higgs particle.
Now, the Higgs particle only
lives for a tiny fraction
of a second.
I think it's something like
10 to the minus 24 seconds.
So way, way, way too
short to be detected.
The Higgs doesn't ever
reach the detector.
It's created and it
disintegrates instantly.
Now, one of the
ways it can decay
is into two particles of light.
So you get two
high-energy photons--
two gamma rays-- that fly
out from the collision
point that came from
this Higgs decay.
And this is what
this event shows.
This is from ATLAS,
again from 2011.
So you can see these two big
bars here are two photons.
So what an analyst does--
a physicist-- will say,
OK, I'm looking for the Higgs.
So go through all these
trillions and trillions
of collisions, and find
me all the collisions
where there were two
high-energy photons produced.
Because they might have
come from a Higgs boson.
And then you take the
energy of those two photons.
You add them together, and
you work out what was the mass
of the object which
they came from,
which was created right at
the centre of this collision.
So you're kind of reconstructing
what the Higgs sort of decayed
into from the bits
that you end up
flying through your detector.
It's a bit like kind
of blowing up a car,
and trying to work
out what kind of car
it was from the bits of
shrapnel that go flying past,
essentially.
And what you then do is you
take all these pairs of photons.
You calculate the energy--
the total energy-- and
you plot it on a graph.
And that's all this is.
On the vertical axis, you've got
the number of pairs of photons.
And on the horizontal
axis, you've
got the total mass of the object
they would have come from.
Now, most of the time
when you see two photons,
they didn't come from a Higgs.
They came from something else.
So there's lots of
ways of making photons.
If you bang protons together
very hard, you get lights.
That's what happens.
So most of the time, it's just
background noise, essentially.
And the reason the
bump is important
is at a certain mass--
which is 125 times, more or
less, the mass of the proton--
you can see this little excess.
And that's because every
time you make a Higgs,
the Higgs is always the same.
A Higgs always
has the same mass.
So the photons from
the Higgs will always
add up to the same mass.
So you get a little excess
at that particular value.
So this bump is the sign that
this thing is really there.
And the thing that really
convinced everyone on that day
back in July 2012 was
that both experiments--
ATLAS and CMS-- both saw
a bump in the same place.
And that was where
everyone stood up,
and everyone really got
excited and started cheering.
So that's great.
So the LHC switched
on for the first time
successfully without
blowing itself up in 2009.
It ran for about 2 and 1/2 years
until the Higgs was-- the Higgs
announcement came in July 2012.
And everyone was very,
very happy that day.
But then since
then, there's been
a kind of a string of bad news.
This is a story from
2011-- actually,
even before the
Higgs was found--
saying certain results were sort
of really causing some problems
for some of the other theories
that we were looking for,
particularly supersymmetry.
So there were some ideas
when the LHC was first
switched on that there'd be so
many supersymmetric particles--
so many sparticles-- we wouldn't
be able to handle them at all.
We wouldn't be able to read
out the data quickly enough.
Actually what
happened is, there's
not been a sign of
these things at all.
So there's one from 2011.
This is another one from 2015.
"LHC Keeps Bruising 'Difficult
to Kill' Supersymmetry."
"Popular physics theory
running out of hiding places."
So you get the idea.
And this has really,
honestly, been
the story, actually, of the last
4 and 1/2 years, 5 years now.
Since the Higgs was
discovered, there's
been lots of very important
physics being done,
don't get me wrong.
So, for example,
one of the things
ATLAS and CMS have
been doing is studying
the Higgs to truly
try and pin down,
is this thing really
the Standard Model Higgs
boson that Peter Higgs
said should be there?
Or is it some other, more
exotic type of a thing?
Maybe it's a supersymmetric
Higgs boson, for example.
But all those
measurements seem to say
it actually looks very, very
like the Standard Model Higgs
boson.
And all these other
theories-- extra dimensions,
supersymmetry-- so far, there
hasn't been any sign of them.
And people, I
think, have honestly
been getting a little
bit anxious about this.
There was a big moment of
excitement back in 2016.
This was the summer of 2016.
A new bump turned up.
I told you physicists
like bumps.
So this is a very similar plot
to the one I just showed you.
It's, again, adding up pairs
of photons from inside--
in this case, inside
the ATLAS experiment.
And what they saw,
again, was something that
maybe looked a bit like a bump.
And it was at much
higher mass this time.
So the Higgs mass was about
125 protons, more or less.
This thing was
about 750 protons.
So it was much, much heavier.
And this created a huge
amount of excitement
at the time, possibly a
little bit prematurely.
So the thing you have to
be very careful about--
and experimentalists and,
generally, physicists
as a whole are
very cautious when
they see something like
this, because there
is a certain chance
that this kind of bump
could just be a fluctuation.
It's just sometimes
just by random chance,
you might happen to get a
few more pairs of photons
produced at that mass.
And it's a bit like
rolling a dice,
and occasionally you might
roll 10 6's in a row.
Even if that's very improbable,
if you do enough experiments,
you'll get that kind of
result once in a while.
So maybe this was just a
statistical fluctuation,
but people did get very excited.
This is a graph that shows
the excitement of physicists.
So this result was
announced around the 15th
of December, 2015.
And this is the
number of papers put
on the archive over
the next 10 days.
So you can see just
by Christmas Eve,
there were almost 100 papers--
theoretical papers--
trying to explain
what this little
wobble in a graph was.
So there was a huge
amount of excitement.
And, you know,
maybe not justified.
As it turned out, it wasn't
justified, unfortunately.
So when ATLAS produced
the results again
with more data, what they
found was this little wiggle
had disappeared.
And, essentially, it
was that it seems--
no one made a mistake.
It wasn't that the
experiment had got it wrong
Just sometimes by
luck or bad luck,
sometimes you get a little
fluctuation in your graph.
And it makes you think,
briefly, that you've
discovered something new.
But actually, you
haven't, sadly.
But I said there was
sort of something
interesting happening.
And there's actually
a series of results
that have come out of the
experiment that I work on.
Now I can't claim to
have been instrumental
in these measurements
myself, but it's
been very exciting being kind
of an observer in all of this.
So my experiment is called the
Large Hadron Collider beauty
experiment, LHCb.
Well, beauty stands
for a particular type
of particle, the b quark, which
is actually usually referred
to as the bottom quark.
But we would rather be
known as beauty physicists
than bottom physicists.
So it's the LHC
beauty experiment.
It's not as pretty
as ATLAS and CMS.
It does look a bit like
a multicoloured toast
rack or something.
But it's a very, very
clever experiment.
What LHCb does is really rather
different to the other two
big guys, ATLAS and CMS.
So broadly speaking,
what ATLAS and CMS do
are what we call direct
searches for new physics.
By which I mean, they want
to bang protons together.
So here's your one
proton, another proton.
They're given lots of energy.
They're smashed into each other.
And then you make some
new, much heavier particle,
and you observe it, like
the Higgs, for example.
And this kind of direct process,
the mass of the thing that you
can make is limited
by how much energy
you can put into the collision.
So if you know Einstein's
equation, E equals mc squared.
So that tells us that
energy and matter are
essentially interchangeable.
So if you have E energy
here and E energy here,
then the amount of
mass you can make
is 2E divided by the
speed of light, squared.
So that tells you how
heavy the thing is
that you can possibly create.
And that's one way
of doing physics.
And that's how the
Higgs was discovered.
And that's how a lot
of the dark matter
searches or supersymmetry
searches work as well.
What LHCb does is
a bit different.
It does measurements which are,
broadly speaking, indirect.
Now, as a sort of
a silly analogy,
have you all heard the
joke, how would you
know an elephant's
been in your fridge?
Footprints in the butter.
Yeah, exactly.
So if you'd like, ATLAS and
CMS are hunting elephants.
They're going out into
the jungle with a shotgun,
and trying to find an elephant.
Don't do that.
And what LHCb are
doing, actually,
is trying to find footprints
left by elephants.
So in a way, they're kind
of complementary in a sense.
If there aren't very many
elephants in the jungle,
running across one
might be quite rare.
But if it leaves footprints
all over the place,
you might be able to infer
there's an elephant out there,
although you may not know
exactly what type of elephant
it is from just looking
at its footprints.
So that's the sort of an
analogy for what we're doing.
In terms of the actual
physics, the b, as I said,
stands for b quark, or bottom
quark, or beauty quark.
So what we tend to
study are the ways
that the b quark can decay.
So, for example, you
have this green blob
represents a b quark.
And let's say it can decay into
some other set of particles,
some three other particles
that it will disintegrate into.
Now in the Standard
Model, any decay process
where one particle turns
into a bunch of particles
usually happens
via the weak force.
So this is the
force that mediates
these kind of decay processes.
So essentially, this particle
goes via the weak force
into these three particles.
And just like you
could use the Standard
Model to predict very accurately
the property of the electron--
I showed you that
very long number
at the beginning-- you can
also use it to work out
how often should a b quark
turn into these particular sets
of particles.
And you can calculate
that number often
to quite a high
level of accuracy.
Now if there exists
some other force field--
let's say there's a fifth force.
Let's just make it there.
Could be supersymmetry, it
could be something else.
If that force exists,
it can very subtly
influence the way
these particles decay.
It effectively provides another
route from the initial state
into the final state.
So the Standard Model
might be the strongest way
of getting from your b quark
into your set of particles
that you're decaying into.
But your new physics
can also provide a root.
And that essentially
will slightly
enhance the decay rate.
The kind of game
we generally play
is, we measure these
sorts of decay rates--
how often does a b quark turn
into some set of particles--
and we compare that number with
what the Standard Model tells
us it ought to be.
And if that number
disagrees, that
can be an indirect hint
that some other matter,
some other particle,
some other force field
is coming in, and
helping that decay along.
It's precision physics.
Rather than going out, and
banging things into each other,
and looking for some big
particle that you're creating,
you're studying
much more abundant--
these are still
created in collisions.
I mean, we're still banging
things into each other.
But the thing with
the b quark is,
you make billions, and
billions, and billions of them.
So you can make very,
very precise measurements.
And you can detect, potentially,
these very subtle effects
caused by new forces that
lie beyond the energy
that the collider
can reach, actually.
So that's the advantage
of indirect measurements.
And it's complementary
to what ATLAS and CMS do.
Now, the thing that's
been really interesting
in the last couple of years
are tests of something
that sounds a bit arcane
called lepton universality.
And this is
essentially a property
of the Standard Model,
which is the leptons which
are the electron, the muon,
and the tau, these three
negatively charged particles.
So they're each
heavier than the other.
The electron's the one we found
more than a hundred years ago.
It has a heavier
version, the muon,
and an even heavier
version called the tau.
And in the Standard Model,
all three of these particles
are treated identically.
So that means that all
the forces interacts
with these three
particles pretty much
in exactly the same way.
And that means if you
compare two processes that,
say, involve
electrons and muons,
they should have exactly
the same rate, more or less.
And what we've been looking
at at LHCb is this process.
So you have your b
quark, your beauty quark,
and it decays via the weak force
into a strange quark and two
electrons.
So that's the decay.
It's from one
particle into three.
And the two electrons
are the crucial bit.
They are things to
pay attention to.
Now a test of this idea, a
test of lepton universality--
the fact the Standard Model
treats all of these different
versions of the
electron the same--
that tells us that if we
look at a corresponding decay
where the b quark turns into a
strange quark and two muons--
which are the heavier versions
of the electron-- then
the rate of this should
be exactly the same
as the rates of this.
And when people started to
think about this measurement,
there wasn't any
really very good reason
to think that it was going to
produce anything interesting.
It was good to test it.
The lepton
universality is a sort
of principle of
the Standard Model.
So it's good to test these
things, just to make sure.
And what they found was--
this is what the
Standard Model says.
If you take the
number of muon decays
and divide it by the
number of electron decays,
they should be equal.
So what the Standard Model says
is, this number, more or less,
should be 1 to quite a
high level of precision.
In 2014, LHCb produced a paper,
and this is what they measured.
So that's even balance
between muons and electrons.
They measured 0.75
plus or minus 0.1.
So it seems that
there were fewer muon
decays than electron decays.
Now, this isn't yet anything
to get terribly excited about.
So if you look at the
uncertainty-- it's 0.1--
this number is only
0.25 away from 1.
So that means you only
need to kind of-- you know,
I talk about these
fluctuations that
can fool you into thinking
you found something new.
It wouldn't take a very
big fluctuation just
to send your number
down a bit, and make
it look like you've seen
something new and interesting.
So there was definite
interest in this.
It's what we call a sort
of 2 sigma effect, which
means it's about two errors away
from what you expect it to be.
And there were lots
of papers produced
in 2014 as a result of this.
Then just this
year, the experiment
produced a equivalent
measurement.
So it's with a
slightly different set
of particles, but basically
the same basic thing.
So comparing muons
and electrons.
And this is what they measured.
So they measured 0.68
plus or minus 0.08.
So this is a little bit
further away from one.
It's very close, as well, to
what was measured in 2014.
These are two independent
measurements, though,
so they're not
using the same data.
They're using
different sets of data.
The fact that they line up
like this is quite intriguing.
And it's caused some really
quite serious interest.
So these measurements are,
at the moment, the biggest
deviations from
the Standard Model
anywhere in any experiment
that we're aware of.
And it's not just these.
There are a few other
measurements as well,
of similar sorts of
processes that all
show slight discrepancies
with the Standard Model.
Nothing independently
yet to really be sure
that it's something new.
But they all seem to be
lining up in a consistent way.
And people are still
rightly being very cautious.
Because it could be when
these measurements are
updated in a year or two,
that it goes back to 1.
That it was just some
statistical fluke.
Or maybe we made a mistake.
Maybe we've missed
some systematic effect
in the experiment.
Hopefully that's not the case,
but that's always possible.
So it could be that these
things will disappear.
But the other
possibility is, it's not
a statistical fluctuation.
We haven't messed up.
This is actually the
sign of something
really fundamentally new.
And what's interesting is, it's
something that no one really
expected, either.
It's not supersymmetry, and
it's not large extra dimensions.
It's something else.
And that, in a way, would
be even more exciting,
because finding something
that you really didn't expect
is quite often when the
biggest breakthroughs happen.
So what could this be?
There are lots, as I said--
I showed you that
graph with a hundred
papers for that previous bump.
There are something
like 450 papers
now out there citing these
two results from LHCb,
and a number of other
results as well.
I'll mention just
one, and that's
partly because it's
a theory that some
of my colleagues at the
Cavendish Laboratory
have been talking about.
Again, very cautiously.
So what their line is,
it's extremely unlikely
that this is a real effect.
Because the Standard
Model works so well,
if we're going to say that
it's broken in some way,
that requires really
extraordinary evidence.
But if this is real, then it
could be telling us something
really, really fundamental.
And it's a question
that, in a way,
that's been slightly ignored.
And it's back to
this picture again,
this picture of
the Standard Model
that we had at the beginning.
So I said that there are these
three generations, the quark,
and the up quark and down
quark, and the electron.
And then this charm, and the
strange quark, and the muon.
The top and the bottom
quark, and the tau.
And I said, we don't know why
there are three generations.
We don't know why there
are these particles.
Well, one of the
possible explanations
of this discrepancy could
explain this structure.
So what we might be
on the edge of finding
is some extension of
the Standard Model
that will a bit like the
discovery of the electron
in the 19th century explain
this peculiar periodic table
of particles that we currently
have at a deeper level.
It essentially involves
invoking an additional force,
a new, very strong
force at high energy.
And it would also imply some
other very interesting things.
Apart from possibly being a
clue to explain this problem,
it would also tell us
that the Higgs is not
an elementary particle at all.
It's not fundamental.
It's actually made of other
things, other strongly
interacting exotic particles.
So it would really
change, fundamentally,
our understanding of
the Standard Model.
And it would be very exciting if
this does turn out to be real.
Now, people in my experiment
are working very hard.
Everyone's trying to get into
this area, as you can imagine,
including me.
So I'm starting to sort of
do measurements like this,
or trying to do
measurements like this.
There will be updates
to these papers
quite soon, so probably
within the next year.
Certainly within
the next year or so.
So the answer to
this question should
be coming in very short order.
So either we're going
to confirm this effect
or it's going to
disappear, and we're all
going to get very depressed.
But hopefully it's the
first and not the second.
But it is a very exciting time
to be in particle physics.
So definitely keep
your eyes peeled
over the next year or
two, because we should
get an answer either way.
Thanks very much.
[AUDIENCE CLAPS]
