Good evening, everybody.
My name is Alex Halliday.
I'm the Physical Secretary and Vice President of
The Royal Society.
I'd like to ask you all to switch off your
mobile phones and in particular, I also need
to tell you about some emergency procedures.
There's not going to be any fire drills tonight
so if something does happen and we have an
alarm, you need to go out through this exit
here or the exit you came in through when
you arrived.
There will be plenty of people around to show
you as well.
The main thing that I want to do is to introduce
you to our speaker tonight for the Bakerian Lecture,
John Ellis, but before I do that, I’ll just say
a little bit about the Bakerian Medal and Lecture.
This is the premier lecture that the Royal Society
has in the physical sciences.
It was established as a lectureship through
a bequest by Henry Baker FRS, of £100 for a
narration or discourse on such part of natural
history or experimental philosophy at such time
and in such manner as the President and Council
of the Society for the time being shall please
to order and appoint.
The lecture series began in 1775, in the year
following Baker’s death.
Henry Baker is particularly famous for a piece
of work entitled The Universe: a Poem Intended
to Restrain the Pride of Man.
So it is particularly apt that tonight's Bakerian
Lecture is given by an expert on the fundamental
scientific beauty of the Universe,
Professor John Ellis.
He was awarded the 2015 Bakerian Lecture for
his groundbreaking contributions to the physics
of the Higgs boson and his attempt at unifying
the fundamental forces of nature through
his work at the LHC.
Let me just tell you a little bit about John.
He attended King's College, Cambridge,
earning his PhD in Theoretical High Energy
Particle Physics in 1971.
After a post doc position at Slack and then
at Caltech, he went to CERN and has held an
indefinite contract there since 1978.
He was awarded the Maxwell Medal and the
Paul Dirac Prize by the Institute of Physics
in 1982 and 2005 respectively and is an
elected Fellow of the Royal Society since 1985.
And at the Institute of Physics since 1991.
John was appointed Commander of the Order
of the British Empire (CBE, that is), in the 2012
birthday honours for services to science and
technology.
John’s research interests focus on phenomenological
aspects of particle physics through, though he
was one of the pioneers of research that was
actually at the interface between particle
physics and cosmology.
Which he has since turned into a subspecialty
of its own; particle astrophysics.
John is frequently invited to give public lectures
on particle physics and related topics.
I don't know how many of you know this,
but in the two year period of 2004 to 2005,
he gave public lectures in Geneva in French,
in Warsall in English, in Grenada and Barcelona
in Spanish and in Rome, in Italian.
While at CERN he often gives introductory
talks to visitors ranging from official delegations
from the United Kingdom to physics teachers at
the high school level.
Ladies and gentlemen, I’m very pleased to
present Professor John Ellis.
[Applause].
So thank you very much, Alex, for that introduction.
Thank you very much to all of you for taking the
time to come here this evening.
So it's a particular pleasure and an honour for me
to give this lecture which I regard as a sort of
recognition of the fact that particle physics
has been living through a particularly exciting
period in the last few years and what I would like
to do is to share with you some of that excitement.
I chose as my title the Long Road to the Higgs
Boson - and Beyond.
You can perhaps imagine that one of those
little peaks on the horizon there is the Higgs
boson or possibly what may lie beyond
the Higgs boson.
I'd like to award a little prize to anybody who
recognises where this picture was taken.
So I’ve already mentioned the 'H' word and here
is a picture of Peter Higgs in 1965, shortly after
he proposed his theory, proposed the existence
of the Higgs boson particle.
This picture was actually taken while he was
visiting the University of North Carolina in
Chapel Hill.
If the resolution was a little bit better, you might
be able to make out some of his secrets there
on his desk.
Anyway, questions that I’m going to be addressing
later on in this talk are first of all, what is
Higgs telling us?
In a sense, not just of what Peter Higgs
told us but also what is the particle that
bears his name now telling us?
What else might there be out there on
the horizon on the previous slide and how do
we set about finding it?
So it's already been mentioned that there is a
close connection between particle physics and
cosmology.
In this slide here, I’ve tried to bring that
all together.
Some of the older members of the audience,
not looking at anybody in particular,
may recognise this as being a slide rule with a
logarithmic scale going all the way from
10-32cm which is the smallest distance
scale that we can imagine thinking about,
early in the big bang, to 1028cm which is the
size of the visible Universe today.
And on this logarithmic scale, roughly half
way along, we have the human scale so here
is a picture of Albert Einstein and his kid sister,
of the order of one metre high, so almost half
way along that logarithmic scale.
So we understand a fair amount about what
Albert Einstein and his kid sister were made of.
We know that they're made of molecules, that
those molecules were combinations of atoms.
That those atoms contained nuclei concentred
in the centre with electrons whizzing around
the outside.
That was discovered in the first half of the
20th Century.
In the second half of the 20th Century, we
discovered that protons and neutrons are
in fact not elementary objects but are in fact
composite objects made up of quarks which
you can see here.
So these quarks were postulated actually
also in 1964, although their physical reality
was revealed somewhat earlier than the Higgs boson.
Okay, so that's what's going on inside
Albert Einstein and his kid sister, and way
back in the big bang, we were interested in
distance scales which were even much smaller
than the size of the quark and the electron.
Now, in the way large scale of course, we've got
galaxies, we've got telescopes which we use to
study the structures of those galaxies and try
to figure out how they were formed.
Now, there are puzzles about that and I’ll come
back to at least one of those puzzles later on.
It seems that galaxies are held together by
some sort of invisible stuff called dark matter,
which is not the same as the stuff that
Albert Einstein was made of.
Also, that dark matter seems to have played
a key role in enabling galaxies to form in
the first place.
So what we're going to try to do with our
experiments, for example, like the Large
Hadron Collider, is not only to push further this
understanding of the visible matter in the
Universe but also to answer some questions about
the large scale structured Universe and for
example, what the dark matter might be.
I'll come back to that later on.
So particle physics roughly speaking, covers
the 20th Century with a few years before when
the electron was discovered and of course,
a few years subsequent to when the Higgs
boson was being discovered.
Many of the most important discoveries in
particle physics in the first half of the 20th Century
were made with cosmic rays and this is a picture
of Victor Hess about to go up into the upper
atmosphere and observe ionisation associated
with incoming charged particles, some of them
of extremely high energy.
So when these particles strike the upper
atmosphere, their energy is converted into
other particles and it was studies of those particles
that revealed many new features of our
Universe, for example, antimatter was first
discovered in the cosmic rays.
But around the middle of the 20th Century, it
was realised that if you wanted to study these
particles systematically, you would need to do
it under controlled laboratory conditions using
beams of particles with known energies, known
compositions and that's how particle accelerators
such as the accelerators at CERN came to be
constructed.
So those experiments revealed what we have come
to call the Standard Model of Particle Physics.
So this is a theory that was proposed in the 1970s,
or the 1960s by Abdus Salam whom you see here,
originally from Pakistan though he did much of his
most important work whilst at Imperial College.
And two American physicists: Glashow and Weinberg.
Now, their theory made essential use of the ideas
of Peter Higgs and his colleagues, which I will come
back to in a moment.
So in the 1970s, experiments at CERN and elsewhere
started finding new physical phenomena of the
type that were predicted within the standard
model.
And this was followed in the 1980s and 1990s
by very detailed experiments that confirmed
many predictions of the Standard Model with
extremely high accuracy.
For example here, if you look very carefully you
can see a little red dot there and that's the
experimental measurement which you see agrees
perfectly with the green theoretical curve there,
calculated in the Standard Model of Salam, Glashow
and Weinberg.
So what does this model consist of?
So it describes the visible matter in the Universe
and as I’ve already mentioned, the nuclei
of the visible matter are made up out of quarks
and we know about six different types of quark.
I mentioned electrons.
There’s a couple of heavier electron-like particles:
the muon, one of those particles discovered in
cosmic rays and a heavier one called the tau that
was discovered using particle accelerators.
And associated with each of these, there is
a different type of neutrino.
We know that from those experiments in the
1990s, there are just three different types
of neutrino.
So these then are the basic building blocks of matter.
If you're going to build something, you have to
stick those building blocks together and that’s
the role of the fundamental forces.
So some of these you know very well:
gravitation, for example, we're just celebrating now
the centenary of Einstein's theory of
general relativity.
Electromagnetism, which actually were combined
together by James Clerk Maxwell while he was
Professor at Kings College, London, just very
slightly over 150 years ago.
He actually presented his paper here at the
Royal Society on the 8th December in 1864.
Then there were two other forces that act mainly
inside nuclei: there is a strong nuclear force
that holds nuclei together and then there is the
weak nuclear force that's responsible for
forms of radioactivity.
So what you see on this slide, I like to think of
as being in some sense, the cosmic DNA.
It encodes all the information that you need to
make all the visible stuff in the Universe.
Including Nigel Farage.
However, perhaps I should have put an 'almost'
in the previous sentence.
Not almost Nigel Farage, but almost all the
information you need to make Nigel Farage.
Because what you see on this slide misses out on
one thing which is an explanation of where
particle masses come from.
Clearly, some particles have to have masses,
for example, if the electron didn't have a mass
it would fly away from nuclei at the speed of light
and you'd never make any atoms.
If the quark didn't have masses, nuclear physics
would be completely topsy turvy and also very
important is the mass of this particle here,
the W particle that carries weak nuclear forces.
That particle as I’ll discuss in more detail in
a moment, is very heavy and if it were not heavy,
radioactivity would not be a very, very weak
force and life would be impossible.
So it's very important to understand where
particle masses come from.
So let me just discuss this issue in a little
bit more detail.
So there are particles that carry the fundamental
forces and the prototype of this is of course,
the photon.
The photon was in some sense, introduced by Planck.
At least he introduced the quantum hypothesis.
But it was actually Einstein who postulated the
physical reality of the photon as a way to
understand how light interacts with matter.
The photoelectric effect.
And it was actually for his postulation of the
photon, the explanation of the photoelectric
effect that Einstein got the Nobel Prize; not
either special or general relativity.
So the photon can be regarded as a sort of
prototype of a particle that carries a fundamental
force.
So historically, the next one to be discovered was
that associated with a strong nuclear force.
So there’s a theory of that, which is modelled
after Maxwell's theory of electromagnetism.
It predicted a whole bunch of particles
called gluons which were expected to be massless
like the photon.
These were discovered in 1979 using a method
that was suggested by Graham Ross who is
sitting in the second row, and Mary Gaillard
and myself a few years previously.
Now, the gluon, as I said, is massless like
the photon.
The next force particle to be discovered was
the one associated with the weak interactions.
So there's been an idea floating around,
going all the way back to the 1930s and Yukawa,
that the weak radioactive forces might also be
due to the exchange of some sort of a particle
called W for weak, I guess.
But there were no very clear predictions as to
how heavy that particle might be until the
Standard Model came along.
That Standard Model predicted that those particles
should weigh about 80 times the mass of the
proton: 80GeV.
To discover them required a very big experimental
effort and somewhere in the audience is John Dowell
who was a key member of the club...
Second row again.
A key member of the team that discovered
the W particles.
The leader of that team was Carlo Rubbia who
you see here smiling.
You don't always see him smiling, do you?
But this occasion, he was smiling.
There is a big puzzle.
This particle, I said it weighted about 80 times
the proton mass and so that means it weighs
as much as a medium sized nucleus.
So what on earth gives such a large mass to
(quote unquote) 'such a small particle'?
So I've been talking about mass and many of you
will have a dim memory of learning in school that
weight was proportional to mass, according to Newton.
And you all remember that Einstein told us that
energy is related to mass and E = mc^2.
So you might think, okay well we know about mass.
But unfortunately, these distinguished gentlemen
somehow forgot to explain where the mass comes
from in the first place.
They related it to other quantities but they
didn’t explain the origin of mass.
And that's where Peter Higgs and his colleagues
came in with a theory for where particle masses
might come from, which is written on the
blackboard there and I’m sorry if some of you are
disappointed that I’m not wearing it on my T-shirt
today but... Anyway.
So it was a key prediction of this theory that
was made by Peter Higgs in his 1964 paper,
that this mechanism would predict the existence
of a massive particle which has come to be known
as the Higgs boson.
And this is the particle which was discovered
48 years later in 2012 at CERN, as I will discuss in
more detail in a moment.
And just I can't help reminding you that
Peter Higgs was actually both an undergraduate
and a graduate student at Kings College, London.
So how does this Higgs et al idea work?
So their basic idea is to postulate what we
physicists call a field, some sort of universal
medium extending throughout all space.
And I’d like to propose to you an analogy for
thinking about how this idea works by taking you
to the middle of Siberia in the middle of winter.
Okay, so you've got snow everywhere as far as
the eye can see, homogeneous, isotropic snow field
extending in all directions.
Now, suppose you that try to go through this
Higgs snow medium.
So if you’re clever or fortunate, you may have
skis; then you skim across the top of the snow.
In some sense, you don't interact, at least not
deeply with that Higgs snow field.
That's rather like a particle that travels through
the Higgs field without interacting,
like the photon which has no mass.
It always travels at the speed of light and likewise,
the skier always moves very fast.
On the other hand, maybe you've got snow shoes.
You’ve got snow shoes and you sink into the snow.
You interact with that Higgs snow field and you move
slower than the skier, much like a particle
travelling at less than the speed of light,
like an electron possibly.
Then finally, maybe you're really crazy and you
try to walk across Siberia in your boots.
If you do that, you're going to sink very deeply
into that snow field.
You're going to interact very strongly with the
Higgs field; you're going to travel much slower than
the speed of light, like a particle with a very
large mass.
So that's the basic idea that was proposed
independently by Englert, Brout and Peter Higgs
back in 1964.
Now, what Peter Higgs did in his paper was go a
little bit further and say what is the quantum
of snow?
We know what it is: it's the snowflake.
He said there must be a quantum of this Higgs field
and that is what we call nowadays the Higgs boson.
So you may be forgiven for thinking that this is
a somewhat flaky theory.
You could also try to push the analogy a
little bit further, for example, snowflakes;
every snowflake is different because they are
composite objects made up out of smaller things,
water molecules inside.
You could ask yourself is it just one Higgs boson
or are there many, possibly an infinite number of
different Higgs bosons?
And having found one Higgs boson, that’s one of
the next questions that we're trying to ask
with our experiments at CERN.
You might also ask, what happens if you heat
the Universe up?
If you go back to the beginning of the Universe,
the Universe would have been very hot.
Would that Higgs snow field have melted?
We think yes, but it's kind of difficult to figure
out how you actually probe that experimentally.
So as I said, these ideas were proposed in 1964.
But for a decade or so, I think that the number
of scientific papers on the Higgs boson could
perhaps be counted on the fingers of one hand.
But in 1975 together with Mary Gaillard and
Demetri Nanopolous, we said this is the key thing
that you need to find if you really want to prove
that the Standard Model is correct.
This is the keystone of the scientific arch.
And so we set out to figure out what we call the
phenomenological profile of the Higgs boson.
Of course, back in those days, these ideas were
regarded as being very speculative and so we
were somewhat diffident and cautious in the way
we wrote our paper and we wrote an infamous
sentence at the end saying,
'We do not want to encourage big experimental
searches for the Higgs boson.'
Fortunately, our experimental colleagues treated
this theoretical advice with the respect
that it deserved.
So this is just one example of what a Higgs boson
produced at the LHC might look like.
This is actually an old computer simulation
where you’ve got a couple of protons colliding:
one this way, one this way.
Their energy is converted into dozens of other
particles; some of them are charged.
Those yellow tracks that you can see there.
Some of them are neutral particles and they
just leave blobs of energy that you see over here.
In this particular simulation, also a Higgs boson
was produced.
The Higgs boson is unstable and it's a neutral
particle that you don't see directly but you can
see what it decays into, if you're lucky.
In this particular simulation, it decayed into
these energetic particles over here, an
electron - positron pair and to those energetic
particles over there, a muon pair.
So that's one example of the sort of thing that
the LHC experiments set out to look for
and one example of what they actually did find
in 2012.
So the long road to the discovery of the LHC,
of the Higgs boson passed through many other
accelerators before it finally reached the LHC.
So here is a picture of the Large Hadron Collider
in its underground tunnel.
It's got a circumference of about 27km.
It's on average about 100m underground.
Thousands of billions of protons circulating,
each with the energy of a fly, making perhaps
something like a billion collisions per second.
And the job of the experiments is to go through
those collisions and try to not just find the origin
of mass but also possibly the nature of
dark matter, the primordial plasma that filled
the early Universe and so on.
So talking of the connection between
particle physics and cosmology, I can't resist
pointing out that those tubes where the particles
go round in the accelerator are circulating in
a vacuum which is similar to interplanetary space.
The pressure in the beam pipes is ten times lower
than on the moon.
You need that lower pressure because you want
to make sure the particles go all the way around
and hit each other rather than get stuck
hitting a molecule of gas as they go around.
Also I would argue that particle physics is cooler
than cosmology because our refrigeration system
cools the magnets guiding the particles down to
1.9 degrees above absolute zero whereas outer
space, the temperature as measured in the
cosmic microwave background radiation is 2.7 degrees
above absolute zero, so my cosmological friends,
we are 0.8 degrees cooler than you are.
Except of course, when we make a collision and
when we make a collision, the energies of the
colliding particles is converted into lots of other
particles and this is actually a simulation of a
collision between two nuclei in the LHC.
When that happens in extremely small volume,
you’ve got an effective temperature which is
perhaps a billion times higher than in the heart
of the sun.
Okay, so you produce your collisions, you
produce your particles; now you want to see what
particles they were and there are four major
particle detectors located around the ring
of the Large Hadron Collider.
Two of them in particular, ATLAS and CMS were
designed with the discovery of the Higgs boson
and possibly dark matter in mind.
This other one, the LHCb, this is working for the
matter: antimatter difference and ALICE over there,
that's one that's trying to understand the
primordial plasma that filled the Universe when
it was a fraction of a second old.
So what have those experiments found?
I think it's fair to say that the discovery of a new
particle, that now we have identified as the Higgs
boson triggered what can only be described
as Mass Higgsteria, perhaps not just amongst
particle physicists.
So what was the discovery of a new particle 
based on?
So it was based on the observation of interesting
events by both ATLAS and CMS.
To be fair, I’m going to show one of each.
So here is an event from the ATLAS experiment
which is actually very similar to the computer
simulation that I showed a few minutes ago.
So here you see the place where the collision
took place; you see some charged tracks coming out.
You see some deposits of neutral energy.
And what you also see is one, two, three, four
almost straight red lines.
Those are the tracks of energetic particles that
might have come from the decays of a Higgs boson.
Now, if you just see one such event you can't
be sure because there are other processes in
the Standard Model, boring processes that could
produce similar events but this certainly has the
right look and feel about it.
Event from CMS.
So in this particular case, I’ve chosen an event
which might be the decay of a Higgs boson
into two photons.
So this decay of the Higgs boson is two photons
with something that Mary Gaillard, Demetri Nanopolous
and I calculated in 1975 and so for us, it was
particularly exciting and gratifying when the
experiments started observing events that might
have that explanation.
So here again, you see the charged particles
coming out, the yellow tracks.
Here you see some dashed lines.
Those are not tracks, but here you see deposits
of energy and those could be photons,
as I said, coming from the decay of the Higgs boson.
So I already mentioned John Dowell sitting in the
second row who co discovered the W boson.
Perhaps I’ll also make a mention of Oliver Buchmuller
also sitting in the second row, who played a
very important role in the discovery of the Higgs boson,
in particular the search for these famous Higgs
gamma-gamma events.
So it was the observation by both ATLAS and CMS
with a high statistical significance of events like
those that convinced the collaborations first of all,
and then the rest of the particle physicist community
that a new particle had indeed been discovered
on July 4th 2012.
Which we've come to call Higgsdependence Day.
So here you see a whole bunch of happy physicists
and I would like to pay particular tribute in this
picture to on the left, Chris Llewellyn Smith.
He was the Director General of CERN who got
the construction of the Large Hadron Collider
approved back in 1994.
And here, Lyn Evans who was the guy who
more than anybody else, was responsible for the
construction and the success of the LHC.
He was the person who led the construction
through all those years.
The other guys, those are just other director
generals of CERN. [Laughter].
So this is a very exciting picture for two reasons.
But not what you might think.
So it's an exciting picture because here we have
Francois Englert, one of the people who
independently proposed this idea for generating
particle masses and here is Peter Higgs.
And this occasion in the main CERN auditorium in
2012 was the first time they'd ever met.
They had proposed their theory independently 48
years before but they had never met.
So here they are, still smiling.
So that's one reason for liking this picture.
The other reason is Fabiola Gianotti here, who
was actually the spokesperson of the ATLAS
collaboration at the time who presented the
ATLAS discovery of a new particle and who has
subsequently been elected the next CERN
Director General.
So what was seen?
So this is just one slide which combines unofficially
the results from ATLAS and CMS.
So what has been done here is to plot the data,
subtracting off all the other crap that you expect
to find coming from the Standard Model.
So this fluctuates up and down but it's always
pretty close to zero, indicating there is nothing
beyond what was previously known in the 
Standard Model.
So no Higgs boson on the left; 
no Higgs boson on the right.
What's going on here?
Here, if you're combining all the data you get
an enormous peak, and enormous signal,
indisputable significance; this is certainly a
new particle and the question is, is this actually
the Higgs boson emerging from the background?
So since 2012, what the particle physics community
has been doing is trying to figure out whether
this really is the missing piece in the particle
Higgsaw puzzle: does this particle have the
right properties?
If you like, is it the missing piece of the puzzle?
Does it have the right shape?
Does it have the right size?
So I just wanted to talk a little bit about that
and how we convinced ourselves that this
really is, if not the, at least a Higgs boson?
So this is one of the things I’ve been working
on in the last couple of years with my PhD
student, Tevong You, who is sitting back in the
third row.
So one of the things that we interrogated the data
to discover was whether this particle couples
to other particles proportional to their masses.
And so we set up a very simple parameterisation
and we found that indeed, the couplings to other
particles are consistent with the Standard Model
prediction.
The Standard Model predicted this correlation
with mass, shown as a red line.
Our best fit has the dash line plus and minus 1 sigma
the dotted lines.
This certainly looks like a bog Standard Model
Higgs boson.
And it was on the basis of plots like this that
we wrote in one of our papers that this
particle walks and quacks like a Higgs boson.
Somewhat to our surprise, I think that phrase
actually did appear in the journal.
So another way of analysing the data which
many other people have done besides us,
but since I’m more familiar with our analysis,
let me just show you what we did.
It's to put together all the information about the
couplings to bosons, so if you like, force particles
and all the couplings to fermions, if you prefer
matter particles.
And we scale them all by factors of a and c,
relative to the Standard Model prediction.
So here is a, the boson coupling along here is c,
the fermion coupling up there.
There is the Standard Model, one for both of those
parameters, the little green star.
Then we put together the information that was
available on the Higgs couple to bottom particles,
to tau leptons, to photons, to W particles,
Z particles and then finally you combine all
the information in this Global fit.
And it's impressive the way that when you
finally overlay all these various different
final states, you finish up very close to the
Standard Model prediction.
There is absolutely no evidence here of any
deviation from the Standard Model.
So many people have been analysing the data since
2012 and they convinced the Nobel Prize
committee in 2013 to declare that
'Today we believe that beyond any reasonable doubt,
it is a Higgs boson.'
Now, Tevong and I are actually very proud
because that quotation was lifted directly from
our paper, but there is a little bit of an irony here.
It was in the pre-publication version of our paper.
Then when we sent it to the journal, the referee
said, "No. 'Beyond any reasonable doubt' is not
a scientific judgement."
So we had to remove that phrase from the paper,
so that particular phrase was good enough for
the Nobel Prize Committee but not good enough
for the journal.
So the discovery of the Higgs boson has
been a big deal.
Without it, there would be no atoms because
massless electrons would fly away from nuclei
at the speed of light; there would be no heavy nuclei.
Weak interactions would not be weak; radioactivity
would be a strong force and life would be impossible.
So as I said, the existence of the Higgs boson
is a very big deal.
So then comes the next question:
What else is there beyond the Higgs boson?
This is what I’d like to discuss in the remaining
few minutes of my talk.
What else might there be out there on the horizon?
Is there anything out there on the horizon?
So here I take as my basic text,
that well known scientist, James Bond... [Laughter]
Actually, there is a scientific connection on this
picture because this lady here is a nuclear physicist.
So anyway, I would argue following James Bond
that the Standard Model is not enough and
in deference to James, I give 007 reasons for
claiming that the Standard Model is not enough.
Empty space is unstable.
What is the dark matter?
What is the origin of the matter in the Universe?
I've talked to you about the masses of electrons
and quarks; What about the neutrinos?
They seem to have a completely different origin
for their masses.
I've talked about the weak force being weak
because it's carried by a massive particle but
why is that massive particle not much, much heavier?
What makes the weak force so strong?
How do we understand the enormous size of
the Universe which many people think is due to
some sort of cosmological inflation early in the
history of the Universe?
Can we make a quantum theory of gravity?
I could go on but after all, James Bond was 007.
So let me talk a little bit about some of these issues.
Dark matter.
So astronomers tell us that most of the matter
in the Universe is invisible dark matter.
It could be that it's made up out of what are called
supersymmetric particles.
So according to supersymmetry, all the known
particles are accompanied by others, as yet
unseen, generally much heavier and maybe dark
matter is composed of these invisible (so far)
supersymmetric particles.
This is actually something which I’ve worked on,
proposed to some extent back in 1983.
Is that something that you could look for at the LHC?
Well, you couldn’t see the dark matter particles
directly because they don't leave tracks.
They carry away energy and momentum invisibly.
But what you can do is to look for events where
there is obviously energy missing.
So this is an example of a simulation where you're
looking along the beam axis and you see a whole
bunch of particles, energy, momentum coming out
on one side of the event but not on the other.
There’s imbalance.
That imbalance, of course, is not real;
at least in this simulation, the missing energy and
momentum is carried away by invisible dark 
matter particles.
So the experiments at the LHC are looking for
such events and in fact, Oliver and I and the group at,
well, Kazuki sitting there in the third row,
are busy analysing LHC data to see how heavy
those supersymmetric particles have to be.
So when CERN issues a press release about
antimatter physics, it can be guaranteed that
it's going to appear immediately on the BBC website.
This may be in part because of Star Trek.
It may be also in part because of Tom Hanks.
Just in case anybody was nervous, we don't
make enough antimatter to blow up the Vatican
or even power up the Enterprise.
What we're interested in is to understand the
difference between matter and antimatter.
So antimatter was actually postulated by Dirac
back in the 1920s, combining relativity and quantum
mechanics, he predicted there should be particles
which had the same mass as regular particles
but opposite electrical properties.
And indeed, they were discovered, as I mentioned
earlier, in cosmic rays and are now used in 
medical diagnosis.
Thousands of people every year who have diagnoses
using positron emission tomography.
Just so you know, even the most abstruse
discovery in fundamental physics might turn out to
have some sort of unexpected application.
Now, it came as a big surprise when it was
discovered experimentally that actually,
matter and antimatter particles are not quite
equal and opposite.
And it's been suggested that might be linked
to the fact that the Universe as a whole contains
matter but not antimatter and experiments at the
LHC in particular have dedicated experiments
trying to make that possible connection.
Another issue beyond the Standard Model that
I mentioned earlier on was to try to make a
quantum theory of gravity.
This is the framework which you would need if
you wanted to unify the fundamental interactions,
which was Einstein's dream.
This is what he was working on the last decades
of his life.
Unfortunately, or fortunately, I should say for us
theoretical physicists, he didn't succeed in making
a theory of everything, but that doesn't stop
us from trying.
One of the ideas that he worked with was the
idea that there might be additional dimensions
of space and this is actually an idea that's come
back into favour in the last decade or so,
in particular in the context of String Theory.
So how would you know if there were additional
dimensions of space?
One possibility is that gravity would become strong
because of the effects of those extra dimensions,
already at the energy scale of the LHC.
And if that were the case, conceivably, when you
collided particles at the LHC, you might be able to
make microscopic black holes and here is a lovely
simulation of a black hole with lots of energy
coming out and... Okay.
Now, this got some people a little bit nervous.
Whenever you hear the word 'black hole' then some
people start thinking, 'Well, maybe these black
holes are going to eat up the entire Earth.'
Well, of course that's not what happens.
The same theory that predicts that you can make
these things also predicts that they decay.
And if you don't believe that argument,
remember that those cosmic rays have been
bombarding the Earth for billions of years and
we're still here.
All that we're doing with the LHC is we're just
repeating what cosmic rays have been doing for
billions of years under controlled conditions.
So please do not lose any sleep over microscopic
black holes.
However, just in the last few months, a new scare
story has come out.
Will the Higgs Boson destroy the Universe in a
cosmic death bubble?
So in the... [Laughter].
I didn't say it, did I?
You laughed without me having to say it.
So the Daily Mail quoted Stephen Hawking as
saying 'Finding the God particle could destroy
the Universe.'
This of course, is bullshit. [Laughter].
It is true that the fate of the Universe depends
on the masses of the Higgs boson on the top quark,
but that's independent of whether we find and
measure them or not.
That's just a fact of nature.
So what is the issue here?
So it turns out that within the Standard Model,
if you don't put any new physics in and you try
to extrapolate the theory to high energies,
you find that while there is a region of parameter
space where it's perfectly okay, and there's a
region where it is not okay.
Our vacuum is unstable, and if you take seriously
what our distinguished colleagues from ATLAS
and CMS tell us, which of course we always do,
then the world average value of the Higgs boson
and the top mass sits there in the unstable region.
So presumably we need new physics to prevent the
Universe from collapsing.
So let me describe a little bit what the problem is,
using as my experimental equipment this glass of tea.
So we are here, sitting in a nice, stable vacuum.
But over there, there is another vacuum which is
completely different.
And there are quantum fluctuations a little bit
like jiggling the glass of water.
Now, in the Universe today those jiggles are
pretty unimportant but it's still conceivable that
you might see some sort of quantum tunnelling
process that goes through to that other vacuum
over there.
Whoops.
Now, this problem would have been much worse
in the early Universe when it was much hotter.
Those fluctuations would have been much larger
and they could have driven us over into the
unstable vacuum.
So what is the solution?
Well, the solution is to postulate new physics
and one example that Douglas Ross, sitting in
the second row, and I discussed some time ago
is supersymmetry which is a theory that does
lots of wonderful things, like we commented
that it could produce the dark matter but it
could also stabilise the Universe.
So if you were to ask me what is my top rated
hope for the next run of the LHC, it would be to
discover supersymmetry which, while there's many
reasons for liking it...
It's what you need in String Theory, it could
provide the dark matter and so on, and so forth.
So on that note, I will finish.
I hope I have convinced you that the Large
Hadron Collider is not only a very powerful
microscope for telling us about what's going on
inside elementary particles but it's also in some
sense, a sort of telescope looking back to the
beginning of the Universe but also perhaps
telling us something about its future fate.
Thank you.
[Applause].
So many thanks, John.
That was a fantastic lecture.
I not only learnt a huge amount about the
Higgs boson and the origin of the Universe but I
also learnt how to deliver a really great lecture.
Thank you very much.
We're going to...
This is being live streamed, televised and there are
going to be live questions coming in via Stefan,
or possibly coming in during the evening.
We've got about ten minutes, 15 minutes for 
questions.
If you could make your questions fairly succinct
and to the point, that would help and then we've
got more time for questions.
And over to you.
Yes, at the back.
I'll wait for a microphone to come over.
There's one here.
Simply to ask, when might we expect those results
from the LHC?
So just this month they're doing the first tests
of the accelerator.
It's been down for a couple of years for
revamping so that it can operate at higher energies,
so the first tests with me will be taking place
in a few weeks time but I think the first usable
collisions will be occurring some time in the Summer.
So sometime towards the end of this year,
I think the first results from this high energy run
will start trickling or cascading out.
So watch this space.
Stefan?
So we have a question here from Golan Prahar,
who is watching online.
Is there a fundamental limit at which our probing
of the nature of reality is beyond the reach of
even the biggest big science?
So I think there’s a number of issues here.
Okay, there’s technological issues, there's
financial issues and also probably conceptual issues.
So many people think that actually, there is a
minimum possible size and in fact, I mentioned it
right at the beginning of my talk; I talked about
Ten-32cm.
Many people think that actually there is no
smaller distance that one can define in any way.
But of course, particle accelerators I think will
never get anywhere near that distance.
I think that accelerator builders have been very
clever in terms of getting more and more bang 
per buck.
The number of bucks has also been increasing
a little bit but certainly, the amount of bang
per buck has been increasing very substantially.
And I think that to a large extent, we're in the
hands of the accelerator engineers to see whether
they can come up with some way of using those
bucks even more efficiently at some higher energy.
We've got some ideas about how to build a higher
energy accelerator.
One of the things that I’m working on at the
moment, I think it's conceivable to build another
generation of higher energy accelerators
but we'll see.
There's a question over here.
Yeah, at the end when you were talking about the
quantum fluctuations and how it would suggest that
you'd need new physics to suggest how in the
early Universe the extremely high energy levels;
it wouldn’t have been pushed over into sort of the
ultra dense Higgs field sort of region you were
talking about and with our current observations
we're seeing it suggested.
Is it... What I’m wondering...
Is it that basically one would expect almost
certainly that the quantum fluctuations would have
reached a level where based off of current
observations, what we would see it to suggest,
it would be pushed into that area or is it that
it might actually be just possible that that,
for whatever coincidental reason, didn't happen?
It's possible that we are incredibly lucky and that
the overwhelming majority, majority, majority,
majority of the nth of bits of the Universe are
over there down the hole, right, and that we just
happened to be the one tiny little bit that
didn't go down the hole.
If you believe that, I mean it's possible but I
don't think it's very plausible.
I think it's much better to try to find a theory
that avoids going down the hole at all.
There's a question there in the middle.
I think the one further back was the first one.
Yeah, that gentleman.
You mentioned that the energy to be used in the
LHC will be increasing this year, which will
hopefully garner more results.
I just wondered, exactly in terms of a percentage,
what that kind of jump in energy would be and
how certain you are that it would actually work,
and if it didn't, what would be the future steps
from then on?
Well, of course we're absolutely sure that it's
going to work. [Laughter].
So the plan is this year to increase to 13TeV
in the centre of mass whereas previously it was
operating at 8TeV, so that's roughly speaking,
a 60% increase and there will also be a
higher collision rate.
The hope is eventually to push it on up to
maybe 14TeV but that’s not immediate.
And I would say that all the augers are favourable
at this point and they’ve been doing many, many
tests to train the magnets to make sure they can
get up to 13TeV and so far, things look good.
Yes, another question there at the back.
I'm trying to understand the relation between the
Higgs field, which you said is always there,
permeating the whole Universe and the Higgs
particle which may not exist at all if you don't
bother to make any more.
So are there any other Higgs particles in the
Universe; can the Higgs field just carry on
regardless of their being in the absence of 
Higgs particles?
Higgs field carry on in the absence of Higgs particles?
Right.
So in quantum physics whenever you have a field,
you also have fluctuations in that field which
mean that in principle, you will always have a
physical particle if you produce enough energy
which can produce that excitation.
So in fact, cosmic rays have been producing Higgs
bosons for billions of years.
Actually, it would be interesting to do a
calculation how often cosmic rays hitting the Earth
produce Higgs bosons?
But they’ve been doing it all the time.
But of course, in a cosmic ray you're never going
to find it because first of all, they’re produced
only in an infinitesimal fraction of the total
number of collisions and when they are produced,
in general they decay into stuff that's very
difficult to pick out.
But in principle, ever since the beginning of the
Universe, Higgs bosons have been made,
physical Higgs bosons.
At the front here.
Stefan has got another online question.
There's a guy about halfway back on the right
hand side with dark hair who has a question.
So we have another question online from
Brian Tea.
This is CERN is famous for being the home of the web.
How crucial will current advances in distributed
computing be to furthering our understanding of the
Universe in the future?
Yeah, well of course in order to analyse those
data, I mean they're produced centrally at CERN
but then they're distributed around the world.
So there is a distributed computing system called
the Grid, that has been used to analyse those data.
Nowadays, new models for distributed computing
are coming online.
There is the Cloud, for example, which a lot of people
are perhaps familiar with.
Something which I find a very fascinating idea
is the possibility of outsourcing the analysis
of LHC data to ordinary people, like you.
Okay, or like him.
And this is something which is now being tried
for theoretical simulations and I think it has
great potential for the future.
I think we’ve got time for one last question.
I think there was one, whereabouts?
On the left hand side here, was it?
I see a guy half way down the right hand side.
Down there, half way down on the right.
A bit further forward.
There we go.
Great.
Thank you for the amazing lecture, Professor.
My question is about supersymmetry.
It definitely has some mathematical beauty but
the LHC hasn't yet found any evidence for it so
if that is the case for the coming years when the
LHC would be working at full potential, do you think
it might be time to give up hope on supersymmetry
and search for other beyond the Standard Model
theories?
So obviously, we would be disappointed if the LHC
didn't find direct evidence for supersymmetry.
But I think there’s many other places where one
could look for supersymmetry.
For example, one could look for manifestations of
supersymmetric dark matter scattering off matter
in underground laboratories or annihilating in
outer space.
Another thing which I personally find very
fascinating and I’m working on at the moment
is early Universe supersymmetric cosmology.
So I mentioned the theory of cosmological inflation.
If you believe in supersymmetry, you have to
make a supersymmetric model of inflation.
But does that have some sort of specific
characteristic signature that we could pick out?
So like I said, I’d be very, very disappointed if
the LHC found no evidence of supersymmetry but
that wouldn’t necessarily mean that I would 
drop supersymmetry.
So John, we need to wrap this up now but before
you go, we need to present you with a little
something, so there are three somethings.
The first is a scroll which lists you as this year's
winner of the Bakerian Prize and Lecture.
And you can give him a round of applause for that.
[Applause].
Just checking.
Yes, the second thing is the medal for the
Bakerian Prize and Lecture.
Another round of applause.
[Applause].
And then there’s some envelope here,
which is for you as well.
Thank you very much indeed.
[Applause].
Okay, thanks very much.
Thank you. That was fantastic.
Really, really good.
Thank you very much, everybody.
