Inside CERN Horizon

Five days ago, hundreds of the world's brainiest people

descended on a hotel in Chicago.

Good morning, ladies and gentlemen.

They have come to hear news from particle physicists

working at CERN.

Last year, researchers there had started running

the Large Hadron Collider at the highest energy ever...

..and a rumour quickly emerged.

They were on the brink of a huge discovery.

We started hearing these mysterious noises

about something going on at CERN.

This may be what I have been spending an entire lifetime

waiting for.

A strange bump on a graph suggested that they might have discovered

a brand-new particle...

..that could revolutionise physics...

Right here, right now at CERN, in 2016,

is THE most exciting time and place in the history of science.

If you want, really, to change the conditions of humanity,

then you need breakthroughs.

..and could change our understanding of how everything works.

The discovery of a new particle may mean a complete rethinking

of the conceptual basis of the physics world.

For the last eight months,

it looked like the universe was about to be turned upside down...

..and Horizon has been inside CERN following the story.

I doubt that it will be named after me,

but I can think of it like this, that it might be!

There was a short circuit on a circuit-breaker developed

which arced and damaged the nearby equipment.

Two teams of physicists...

..one massive machine...

and a dream.

Was the bump was just a glitch in the data,

or the biggest physics discovery in over a century?

A Nobel prize is possible.

Bonjour. Bienvenue a CERN.

This is the European Organization for Nuclear Research - CERN.

CERN is home to half of the world's particle physicists...

..and the biggest particle-hunting machine that has ever been built.

The Large Hadron Collider, or LHC.

Inside this pipe, two beams of protons

are sent hurtling around a 27km loop

before being smashed together

to create subatomic particles.

In November 2015, researchers here got

a tantalising glimpse of what they thought might be

a brand-new particle.

A particle that could transform our understanding

of how the universe works.

Now they're trying to find it.

The Large Hadron Collider has been hunting for particles since 2009...

..and it's the job of British physicist Mike Lamont

to keep it running.

Today, it's having one of its off days.

This is not a cock-up.

We stop because,

as you can see,

there's a huge amount of stuff down here -

big systems, cooling, ventilation,

cryogenics, etc,

and this stuff needs a bit of periodic tender loving care.

With over 4,000 miles of cabling and 100,000 processor cores,

the LHC is one of the most complicated machines in the world.

She is not a simple beast to operate,

and a lot of time we spend wrestling it under control.

We need very powerful magnets to bend the beam around in a circle,

so basically, these are superconducting magnets,

they're cooled with superfluid helium at 1.9K.

The fact that this actually works at all

is a real testament to an awful lot of hard work, modern technology,

planning, precision on a completely remarkable scale.

With the hunt on for a potential new particle,

Mike and his team are trying to run the LHC

at its highest ever energy,

and it's making their job more challenging than usual.

We had a very interesting month,

with a number of fairly major technical problems,

including the famous weasel,

which took us out for about six days,

but from now on, after this maintenance period,

it's pedal to the metal for two or three months.

To try and find new particles,

the LHC does something that was once completely out of our grasp.

It recreates the conditions that existed just after the Big Bang.

The Big Bang was an explosion that happened

at the beginning of the universe, when all matter was created.

So, this is the year zero, and if we draw a line...

From this point, the universe expanded,

getting cooler, its energy dispersing.

..to where we are in the universe now, where humans exist,

that's 14 billion years.

We know that when the universe was 9 billion years old,

the sun was formed,

and over 8 billion years before that,

the first stars were born,

but the LHC is able to look even further back in time

to when all that existed were the fundamental building blocks

of the universe - particles.

So, in a way, the Large Hadron Collider

is like a time machine,

trying to create the conditions that happened

just in the few millionths of a second after the Big Bang

to see what particles existed when the energy density

of the universe was really, really high.

To do this, the LHC makes use of

one the most famous scientific discoveries ever made.

What we're doing is using the very high energy of the protons

in the collision using Einstein's equation E = mc2...

..which tells us that mass and energy are equivalent,

so we have protons and they're going round and round the LHC,

and we have one set of protons going round this way

and we have another set of protons

which are going around in the opposite direction,

getting faster and faster, closer to the speed of light,

and more and more energetic.

Then we get one proton beam

and the other proton beam

going at the highest energies,

and then we smash them together.

At the moment of collision,

the energy is converted into mass

in the form of thousands of particles.

Although most will be ones we already know about,

the hope is that undiscovered particles might also be created

that could help explain some of the mysteries

of how the universe was formed.

SHE BLOWS

But creating particles is just the beginning.

Detecting them requires

some of the most sophisticated machines in the world.

I come into the cavern hundreds of times in a year

and every time I walk in,

my jaw still drops a little bit when I see ATLAS.

We built this thing. We REALLY built this thing.

Dave Charlton runs the snappily named

A Toroidal Large Hadron Collider Apparatus, known as ATLAS.

It's the largest particle detector on the LHC circuit.

The collisions take place right in the centre of the experiment,

about 30 metres away from where we're standing.

ATLAS has seven different detecting systems

arranged in layers around the collision point.

They're poised to capture evidence of the particles

that have been produced.

Dave hopes that ATLAS will lead the hunt for the potential new particle,

but he's not the only one

with a giant particle detector at his disposal.

There's another massive detector on the LHC circuit -

the Compact Muon Solenoid.

CMS.

It's run by Italian physicist Tiziano Camporesi.

The croissant has become something almost associated to me

because I've grown into the habit of bringing croissants every morning

to the crew which is working at the experiment.

So now, if I show up without croissants,

they are disappointed.

No, actually, I like this... I like this habit.

You know, when you have a ritual,

you don't want to change it because it will bring bad luck.

Tiziano's machine, CMS, is very similar to Dave's.

CMS is big. It's a 14,000-tonne object...

..which basically is five storeys high

and something like 26 metres long.

But ATLAS is slightly bigger.

Look at the size of it. As you can see,

it's really a huge experiment.

25 metres high, 45 metres long.

These detectors are purposefully designed

to do the same thing in two different ways.

You could see it as an oversized camera,

something like a 100-megapixel camera.

Nowadays, a digital camera might be 25 megapixels, 25 million channels,

but we're able to read out our 100 million channels

40 million times a second.

The idea is that new particles

will be seen by both detectors independently.

It can help ensure their findings are valid,

but that doesn't stop both teams

wanting to be first to make a discovery.

We understand that there is some healthy competition

between us and ATLAS, so we are convinced that CMS is better.

HE CHUCKLES

There IS a rivalry between the experiments.

We don't want to lose.

If CMS and ATLAS detect a new particle,

it could be the most important physics discovery in over 100 years.

Ah, you've made it! Come on in. We can talk about some physics.

It's going to be fun.

By the beginning of the 20th century,

particle physicists like Professor Jim Gates

had ascertained that milk, bowls, glasses -

in fact, everything we see around us -

is made from atoms...

..and that atoms themselves are made of even smaller subatomic particles.

From the 1950s, hundreds of particles were discovered...

There was this strange quark -

and this was not the order in which they were discovered -

and then the top quark...

and the most familiar particle of them all, the electron.

All of our electronics come from this.

And so we kept discovering particles -

neutrino, gluon...

But the influx of new particles did little to help explain

how the universe really behaved.

So, this is the state of knowledge about particles

in the 1950s, '60s and '70s.

It was a zoo of particles jumbled about -

confusion, no order.

It was only by studying their characteristics

that physicists could begin to understand

how these particles worked together.

It turned out that the electron, in fact, has another particle

very similar to it called the muon.

This family of particles was called the leptons

and they were soon joined by another - the quarks.

Quarks are really important,

because they are what you need to construct protons and neutrons.

And now, with protons, neutrons and the electron,

you can construct atoms.

From atoms, you can construct cells, molecules, compounds

and, ultimately, us -

so these guys are really, really important.

This group are the known as the fermions -

they're particles that make matter -

but you can't build a universe with fermions alone.

They're held in patterns

and interact through particles known as force carriers.

One of them is the photon, the particle of light.

It is the carrier of the electromagnetic force -

so, we're going to put that up here.

Then there are other forces in nature beside the electromagnetism -

there's a weak nuclear force.

It has carriers - we call them the W and the Z particle.

This family is completed by the gluons

that hold matter together inside an atom,

and the Higgs, responsible for giving the other particles mass.

And now we have the modern Standard Model,

born around 1973,

where the fermions are all sitting here divided into two families

of quarks and leptons,

and these guys are the force carriers.

It is the best-tested, most tested piece of science

that has ever been constructed.

It literally explains tens of thousands of observational facts.

It is just an amazing triumph

that almost nobody has ever heard of, outside of physics.

The Standard Model has served as a map to our understanding

of the particles in the world around us for over 40 years...

..but physicists have hoped, for almost as long,

that it's not the end of the story -

that other particles will also exist

that could help explain

some of the more troublesome mysteries of the universe.

The problem is finding them.

I'm not going to disturb these guys.

These guys are doing serious work!

Fixing the chair, yeah! Fixing the chair!

THEY LAUGH

At CERN, it takes hundreds of researchers

writing millions of lines of computer code

to scour collisions for signs of new particles.

This thing is a raw image,

as they come in, basically unfiltered,

from the collisions which are happening 100 metres below ground,

under our feet.

What makes the job even harder is that undiscovered particles

will only exist at very high energies

like those inside the LHC -

and almost as soon as they're created, they decay

into the stable particles that we're familiar with.

So, I'd like to change this 60...

Let's say... Make it 1, or...?

So the teams aren't looking for the particles themselves,

but for the trails they leave behind.

This is detective work,

because, basically, you are seeing fragments of the disintegration,

you are trying to understand from the behaviour of the fragments

how the particle was to start with.

It's a task for some of the brightest minds in physics

working around the clock.

What we really like is a young brain, I have to tell you!

Because, I mean, these guys are amazing.

I lived through that, I know what it means -

once you become in my position,

the level of stress becomes a different one.

Towards the end of last year,

it looked like all the hard work would pay off.

28-year-old Dr Livia Soffi is an analyst for CMS.

She was once a European artistic roller-skating champion.

I really like to relax, to stay a little bit under the sun

without staying in the office.

I really like the lake,

because when I was younger, I used to go to the sea -

now we cannot go to the sea,

but we have the lake, it is nice, as well.

Then we can take an ice cream -

there is an Italian ice cream place close to here,

so it's very nice.

Last November, Livia found something unexpected in the data

coming from the CMS detector.

What she saw was a mysterious bump on a graph.

So, basically, the idea is that if you do not have anything new,

you will see the dashed line,

and if the solid line, here, the observation,

is inside these two bands,

this means that everything is quiet,

then the fluctuation is not interesting.

When the fluctuation goes outside the bands,

this means that your expectation and what you observe

are not so compatible.

It might not look like much,

but the bump indicates that,

at the energy of 750 giga-electronvolts,

the LHC is producing unexpected bursts of photons.

We have two possibilities.

Either our detector is not working - but this is not the case,

because we know that it is well performing -

or we have observed something.

I have never seen something like this in my life.

This could be evidence of a brand-new particle.

A particle that disappears into a pair of photons

almost as soon as it's created.

And what made the bump even more exciting

was that it wasn't just seen in CMS.

James Beacham is an analyst at the other detector, ATLAS.

To my mind, right here, right now at CERN, in 2016,

is THE most important time and place in the history of science,

because we have just pushed forward, as a species,

into an energy regime where we have never been.

No-one's ever looked here.

APPLAUSE

On the 15th of December, both ATLAS and CMS

presented their findings.

We, of course, observed a little bump at 750 GeV...

It was in this seminar that the science community learnt

that the mysterious bump was being seen

by both the CMS and ATLAS detectors.

It was an extremely exciting seminar that we had here at CERN,

and, to me, watching, you know,

and then, suddenly, he shows this little thing,

and I'm like, "This is very intriguing."

The implications of such a little bump,

if it turns into, potentially, a new particle, are super-huge.

This is completely uncharted territory.

The excitement quickly spread out into the physics world.

Within weeks, 300 papers had been written by theorists

trying to determine what this potential particle might be.

When the result was announced,

the whole theory group was just crazy -

crazy with discussion,

crazy to understand what it was...

Er... That's it!

This was the moment, it seemed.

We started hearing these mysterious noises

about something going on at CERN,

and it had a very prosaic name - the 750 GeV bump.

It sounds like a dance, to me.

I thought it was a joke - but then I began to look more carefully,

thinking that, "Oh, my goodness, this may be

"what I have been spending an entire lifetime waiting for."

By the beginning of this year,

the race was on for ATLAS and CMS to gather more collision data

to see if the mysterious bump would reappear,

or if it was simply a statistical fluctuation.

The fact that the two experiments

seem to see a hint of something in the same place is fascinating,

but the statistics are too low with the current data sample

to get too excited.

It's more potential excitement, at this stage,

for the experimentalists

rather than cast-iron established excitement.

For the bump to be confirmed as a new particle,

the two teams work independently,

both trying to collect enough data

to reach a level of statistical certainty known as 5-sigma.

I mean, to give you a feel for the scale of the statistics

for the Higgs discovery,

we had a few tens of events

that were identified as being signal-like Higgs events,

but we had looked in a million billion events.

So, that's the complexity of the science that we do.

It's really...

I mean, people talk about a needle in a haystack,

but it's a needle in a haystack of haystacks of haystacks!

A grain of sand in an ocean.

It's a huge task,

but with the physics world desperate for news,

the teams have just three months

to announce if they really have found a brand-new particle.

The big thing is our conference in Chicago.

The first week of August. By that time, we should have...

..I think at least doubled the data which we took last year.

As you know...

MUSIC: A Kind of Magic by Queen plays in background

This is specific to our experiment.

You have to realise that the guy who designed our architecture here

for taking data, he is a Queen fan,

so all of the change of states of the machines,

or of the experiments, are basically announced

by a snippet of a Queen song.

Everybody has become aware of the meaning and of the Queen songs!

"It's a kind of magic" means that you have managed to start the run.

The last time particle physicists were this excited, prizes were won.

This is the Nobel medal which I received in 2013.

I think it had something to do with some work I did in...

When was it? 1964.

Make way, please.

On the 4th of July, 2012,

Peter Higgs arrived at CERN for an announcement.

On the day itself, I found myself

being besieged by crowds of physicists

who had more or less camped out overnight

in the hope of getting into the lecture theatre,

which was really already fully booked.

So good morning...

Fabiola Gianotti, who is now Director-General of CERN,

was part of a team from ATLAS.

The atmosphere was absolutely amazing,

it was a big, big emotion.

So you can see here some beautiful events,

selected by our pic search.

We were working days and nights,

nourished and pushed only by adrenaline,

because we didn't have the time to sleep, to eat - it was fantastic.

So this channel has a tiny rate...

At this conference, CMS and ATLAS confirmed that they had found

a particle predicted by Peter nearly half a century earlier.

..extremely clean, except one big spike here, in this hadron here.

An excess, with a local significance of 5.0 sigma,

at a mass of 126.5 GeV - thank you.

It was 48 years from the time that the theory was formulated

as something which might be useful in particle physics,

to the discovery of the particle.

So it was a long wait.

I think we have it. Do you agree?

LAUGHTER AND APPLAUSE

Everybody cheered and got up, it was rather like the end of

a football match, rather than a scientific seminar.

Then I went into hiding again and had some lunch and escaped.

Fly home before anybody else tried to capture me.

The Higgs boson was the final piece needed

to complete the maths of the Standard Model.

But an unpredicted new particle, like the 750 GeV bump,

could be even more significant.

If the bump which has been seen recently is genuine,

that is opening up a new era.

So it's very exciting.

The hope was that if it really is a new particle,

the bump could help physicists answer some of life's big questions.

Like, "How stable is our universe?

"Does it have hidden extra dimensions?"

And an old bugbear - "What is the universe actually made of?"

In the 1930s, evidence emerged that the luminous matter,

the matter which forms the stars, it cannot be sufficient

to justify the dynamics of what we observe in the sky.

There should be something else that gives a gravitational pull.

Physicists faced the rather disturbing realisation that

they don't really know what makes up most of the universe.

So 95% of what is around in our universe

is not the ordinary matter that we are used with,

and that the Standard Model explains.

This is very frustrating for particle physicists,

but particle physicists always look on the bright side,

and they see that there is an opportunity.

This unidentified stuff has been called "dark matter"

and "dark energy".

And the bump could bring us a step closer

to finding out what it actually is.

The 750 GeV particle cannot be the dark matter,

because we know that it decays very quickly into two photons,

meaning that if it were around in the cosmos, it would have

disappeared very quickly, so we know that it cannot be.

However, there has been speculations that the 750

must be part of a bigger family.

Inside this family,

there could be one particle

that plays the role of the dark matter.

So, even if the 750 is not dark matter,

it could be related to the particle giving rise to the dark matter.

This may have a lot of implications

in understanding the structure of the universe,

understanding how this dark matter was formed

and understanding its role in the universe.

A new particle could well have a profound effect.

But first, they had to find it.

It's the middle of May at CERN.

And with just over two months until the important summer conference,

the mission to gather data continues.

So we are just getting ready to go to work.

My boyfriend is hiding.

SHE LAUGHS

You can come out.

If he wants to.

The LHC has been providing an unprecedented amount of collisions

for the teams on the detectors.

We had the longest fill in the history of the LHC.

And this happened over the weekend, so basically,

starting from Friday and then continuing through Saturday.

Dr Magda Chelstowska is part of the ATLAS team,

and it's her job to clean up and format the data as it's collected.

I think of myself as a person who gives birth to the data.

So I feel that it is my child, it is my kid.

Because I prepare the data and I polish it and massage it

and make it into something which then can go out and be on its own.

The race is on to see which team will be first to gather

enough data to find out if the bump is back.

When we know that we are very close to making

a major breakthrough in physics,

we of course want to do it as soon as possible,

because we don't want the experiment on the other side to beat us to it.

ATLAS and CMS are working blind, accumulating and processing the data

without actually being able to see what it's showing.

It means the two teams can't influence either their own

or the other's results.

THEY CHUCKLE

And with a discovery of this potential significance, for ATLAS,

it is up to Dr Marco Delmastro to make sure nothing is left to chance.

It's always difficult to see whether this excess is a new particle

or not, because nature is behaving in a sort of stochastical way.

We will be spending days and nights, basically,

going through all the stuff,

from the current that we measure inside the detector

to the piece of software that transforms current to energy,

and then tell us where the things are in the detector

and how they are constructed, to the very end.

In the back of my head, there is always a small devil

sitting on my shoulder, saying,

"Are you sure you checked everything?

"Are you sure that there is nothing wrong in what you're doing?"

That is my worry, and still is my worry, so yeah,

I think it is going to stay there for a while.

As the teams crunch the data,

speculation about what the new particle might be is rife.

Jim Gates hopes it could prove a theory known as supersymmetry.

He has been studying this idea for nearly 40 years.

For a long time, the idea of supersymmetry was pooh-poohed.

In fact, I remember all throughout graduate school,

I had colleagues working on other things that were considered

"good physics", and there I was in the corner,

the only student in my team working on this supersymmetrical stuff.

The idea of supersymmetry was born when physicists started

questioning why the Standard Model wasn't mathematically more balanced.

So here is the triumph of the study of the standard models.

And many of us who were studying physics then looked at this,

and we noticed that there is a lack of balance here, a lack of symmetry.

To make this obvious, let me put some lines on the table.

And you can see that there are

two quadrants here that are empty.

Physicists are very sensitive to the lack of symmetry or balance.

And we can ask the question,

"What would the world look like if it were balanced?"

And we ask the question with mathematics.

Supersymmetrists found that the Standard Model

could be given balance if a mirror image

of each of the particles also existed.

They were called "superpartners" or "sparticles".

So if the universe is supersymmetric,

there must be another particle

on this side that we call the selectron.

And also, that has to occur for its neutrino,

which we would call a sneutrino.

For the muon, there's another particle called the smuon.

We physicists, when we make great triumphs, are so happy

that we get giddy, so we name things in a silly manner.

The idea is deceptively simple.

Each ordinary matter particle

has an undiscovered supersymmetric force partner.

And each force particle,

an undiscovered supersymmetric matter partner.

Once we've made this change we are looking at

not the Standard Model but a supersymmetric extension

of the Standard Model, where we get a balance on both sides -

there's a balance of the superpartners

to the ordinary matter...

There's a balance for the super force carriers

to the ordinary force carriers.

And this is what we've been wondering about for

over 30 years -

is it just mass or is it the universe we look at?

Devotees of supersymmetry believe that their theory solves

one of the most worrying mysteries of our universe.

At the smallest scales, the universe is in a constant state of flux...

seething with particles popping in and out of existence.

The best way to understand it is to try to understand

something about what's going on inside of a teapot.

We can see the water is boiling, there's bubbles coming out,

some are big, they explode, they disappear.

So if you imagine that this surface is the universe,

the bubbles popping in and out are actually virtual particles,

they're virtual electrons and photons -

all the particles that make up our universe,

they pop into existence and then they disappear.

This state of chaos is known as the quantum vacuum.

And Jim thinks that without supersymmetry,

it might make the universe unstable.

I'm going to use a set of quarters to represent our universe.

And...with a little bit of work I can get it to balance.

With the particles of the Standard Model, there's actually

a preponderance of one type of particle over the other.

And now let's follow what happens

if you let this preponderance work for a while.

It's as if you are pressing on the stack of coins,

but because of the preponderance

you are always pressing in one direction.

And what you find is that we are very close to being

in a situation where the universe might collapse.

Now, supersymmetry can help solve this problem.

So, if you have particles - all the ones we know about,

as well as the sparticles - they press, but they press

in opposite directions.

And our universe is a much more stable place.

And I know I would sleep much more quietly at night

knowing I live in a stable universe.

The problem is that in 30 years of research...

no sparticle has ever been found.

But is that finally about to change?

The 750 GeV bump might actually be one of these particles

that we've predicted by the mathematics of supersymmetry.

And if that's the case, it becomes the herald for supersymmetry.

For me it will mean several things. Emotionally it will be a great high.

I have been a supporter of the idea of supersymmetry

since I was 25 years old, first learning theoretical physics.

The dream was to find a magical piece of mathematics.

Simultaneously, an accurate description of something in nature.

It will be a source of intense joy.

With the hopes of theoretical physicists around the world

at stake, the pressure is on the LHC to keep providing collisions.

But running this machine at such high energy...

..is putting a huge strain on all its systems.

When it's running well, it runs well,

but there are a lot of things that can go wrong and do go wrong.

So it can get quite stressful.

Today, one of the accelerators that provides the LHC with protons,

the Proton Synchrotron - or PS -

has broken down.

This is one of the veritable workhorses of CERN,

and really is like the beating heart of the complex,

and at the moment the line is flat.

So we are in some of the oldest parts of CERN here.

The PS has been with us since 1959,

so there's some really old kit around here.

And...this beast here is what we call the rotating machine,

if you like, it's a kind of temporary energy storage system

which we use to power and de-power the PS machine,

the main bending magnets of the PS.

It was retired a few years ago, it was pressed back into service

because we've had a problem with the new version.

Unfortunately, last week a problem developed on this -

there was a short-circuit on a circuit breaker

developed downstairs, which arced and damaged the circuit breaker

and some nearby equipment.

Thanks to the failure of this near-50-year-old power supply,

the world's most expensive science experiment is just an empty pipe.

There's a huge experimental community on the LHC out there

really looking forward to getting as much data as they can this year.

And of course, there's a lot of pressure to get the complex

back up and running properly.

I still can't believe it says 1967 on there, actually.

If the LHC isn't running again soon, the worry for the experimentalists

is that they won't be ready for the August conference.

Another day that it's not coming in,

it's a bit frustrating. I like to wake up in the morning

to see how much data we took...

..overnight. But lately I haven't had any good mornings!

In the very beginning, there was a loss of 1.7 inverse picobarns

because of a problem. And then at the end of the run...

But the teams are determined to find a way around the problem.

So, we are considering suppressing our technical stops.

Which basically will put us on track for our goals of achieving

basically something like three times the statistics

which we have accumulated last year...

in time for the summer conference in Chicago.

At the University of Maryland near Washington, DC,

Professor Raman Sundrum has great expectations

about what the bump might be.

His hope is that it could be

a hypothetical particle that has near mythical status.

A force carrier particle of gravity -

known as an extra-dimensional graviton.

The discovery of a graviton could help solve a puzzle

that has baffled physicists for a long, long time.

Gravity seems strong, it seems like it's the first force that,

you know, cavemen would have known about, right?

It's the thing that dominates most of our lives,

just being pulled down to the Earth.

But we can sort of see why physicists

think that gravity is in fact the weakest force.

And a quick way to demonstrate that is to just take a simple object,

like a paperclip.

Watch gravity act on it.

But we can act on this paperclip with this magnet,

which seems much smaller, and perhaps much weaker than the Earth.

The entire gravitational pull of the planet can be easily overcome...

..with just a small magnet.

If you work this out you actually find that electromagnetism is

by far and away stronger than the force of gravity.

It's basically one followed by about 30 zeros times stronger than

the force of gravity.

That's how weak gravity is to a physicist.

Raman believes there is one mind-blowing way

to explain this puzzle -

the existence of a tiny, invisible extra dimension in our universe.

We're used to living in three dimensions of space -

we can travel forwards and backwards, left and right,

and up and down.

If you just look at the vast expanse of the grass,

it looks fairly flat,

and so you'd say, effectively, for my purposes, it's two-dimensional.

But if you're small, you can go places humans can't.

And the grass looks rather different.

From the bug's point of view, the grass

does not look that two-dimensional. Doesn't look that flat.

If it really gets in there, it can go up and down these clovers,

or up and down a blade of grass,

so it's really in there with the third dimension,

the vertical dimension.

The grass looks 2D to humans because we're so big,

and perhaps the same applies to our apparently 3D universe.

It might be that for human-size creatures like us,

we live in something that looks effectively three-dimensional.

And yet, there's another dimension -

a very small dimension that's sort of hidden to the naked eye.

But if you are a microscopic, subatomic particle,

you might be a little bit like that bug.

If an invisible extra dimension exists, it could mean

that gravity appears weak because we're only seeing

part of its strength. The rest is hidden - in the extra dimension.

And the discovery of a graviton in the LHC

could help prove this extraordinary theory.

That's part of what the LHC is doing when it collides protons.

The collision is incredibly energetic and that energy provides

the kind of quantum mechanical magnifying glass for these particles

to look inside the extra dimension and report back in an indirect way.

If it is a graviton, then that has very great significance.

It's the middle of June at CERN.

For the last four weeks, the LHC has been running so well

that the team from ATLAS have finally gathered enough data

to see if the bump is back.

The machine has been working over the clock and produced

a lot of collisions and now we have almost as much data as we got

in 2015, so it's kind of exciting times because the day has arrived

to look at this data and to see if there's something there or not.

I am VERY optimistic!

Well, last time, I was actually quite pessimistic

cos I didn't think that we would get enough data at this point,

so now my optimism is going up and up with each day!

My gut feeling - I...

Oh, I'm really oscillating, I would say, and, erm...

Yeah, I still hope there is something there.

The results will be revealed in an ATLAS team meeting.

You have to stay outside.

The secrecy is because ATLAS have beaten CMS to it

and they don't want them to know their conclusions.

An hour later, Marco and the team are out. The results are clear.

750 is here, so you will expect to see a bump somewhere here.

The data is the data, so unless we made

a very bad mistake in processing the data,

you can see by eye that there is no evident excess there.

It's very flat. There is no bump there.

Data that we have looked at from this year,

we haven't seen anything yet, which is a bit disappointing,

to be honest, but that's actually how most of our searches turn out.

We don't allow ourselves to hope, but, of course,

we are humans and we were probably

unconsciously hoping for something more and we're not seeing it.

It might simply mean there was a fluctuation

of the background noise in 2015 that has gone away,

so it's a bit disappointing, honestly,

and, of course, we are not in the position

to draw a definitive conclusion,

but, yeah, it could have been a more exciting day.

The only hope for the bump

is that it's been found by the other team, CMS.

They don't know about the ATLAS results and, three days later,

they're ready to look at their data.

I am very excited.

At least in my life, working life,

it's the most exciting moment.

So now we're going to open the reports.

And there's nothing.

So, no bump.

Nothing is there.

We just see something that is compatible with the expectations.

There was just... There have been many times in the past.

It will happen in the future.

Too bad. Of course, you are hopeful that somebody finds something

cos that's basically why we do the job,

but it basically tells everybody now that we don't need to be excited

because the fluctuation we saw for the moment is gone

and now we have to wait for the rest of the data.

So, I'm looking at it and, er...

And...

there is nothing.

The results are shared with the rest of the team at the weekly meeting.

Can you hear me?

The 750 bump now doesn't look very healthy, put it like this.

So, I'm going to report on the status of the analysis.

I would give it 95% probability that it was fluctuation

and in fact we always said that and we tried to keep very cool about it.

Obviously, I would have preferred that nature had surprised us

because it was a real surprise, this 750 thing.

On the other hand, if this thing had been real, it would have really

meant a complete change of the way we interpret nature,

so it has always been in the back of my mind

that this thing could be a fluctuation.

We got permission to look at data over the weekend

and now if we look at data,

what we can see is the observed 750 is not confirmed.

But in the next months, we'll get four times more statistics

so by that time, one will be able to tell for sure.

It's the 5th of August.

Tiziano and Dave are in Chicago for the conference.

The time has come for them to share the results of their hunt

for the 750 GEV bump with the rest of the physics world.

It's a great pleasure to be here today to talk about the first half

of the highlights from the LHC and the way we've organised this...

Further data has confirmed what the teams feared.

But then, as you will have heard,

we were looking at the 2016 data

and I'm afraid to say in the 2016 data,

there is no clustering around the 730-750 GEV region

and so there's about four times more data and so, from this,

we have to conclude that the 2015 excess

was most likely a statistical fluctuation.

The dream of the 750 GEV bump is over.

It would have been a revolution.

Yep, we would have broken the Standard Model of particle physics.

It would have sent a lot of theories back to the drawing board.

The bump was just a fluctuation in the data.

That it was seen by both detectors was a highly unlikely coincidence.

The bump was a cruel statistical fluke.

It's simply the kind of thing which can happen because basically

when we're dealing with statistics, it's like,

you know, flipping a coin five to ten times,

you can always get heads.

And the disappointing news

quickly reaches the rest of the physics world.

We'd have vastly preferred that it WAS there because it would have

definitely heralded a much richer particle physics

that would play out, guaranteed, in the next few years.

Scientists are human and so we have feelings just like everyone else.

I guess, in my case, I would say disappointment

but not discouragement, and so we have to look a little bit harder.

The 750 GEV bump didn't live up to anyone's hopes.

But the quest to understand the mysteries

of the particle world are far from over.

Back at CERN, the hunt for particles goes on

and they're certainly not giving up.

We are clever beings.

Human beings are clever beings, so our intrinsic wish

and our intrinsic duty and right

is really to be intelligent, clever beings.

Today, the LHC is operating at the highest capacity it's ever achieved.

The machine is performing exceptionally well at the moment.

We really are somewhere where we didn't expect to be.

Things aren't breaking down very often and we're sitting there

for 24 hours at a time with stable beams continually producing

these high rates of collisions to the experiments

and nothing's going wrong.

These bottles have come from ATLAS and CMS. We had a small celebration.

We actually reached design luminosity a couple of weeks ago.

This was actually a quite profound achievement for the LHC.

The Large Hadron Collider is the most ambitious

scientific experiment ever undertaken.

For now, it's holding on to its secrets,

but the teams working there

still hope that they will be the ones to unlock them.

One day. Oh, there's a huge amount more in the LHC.

We've barely started the journey at this point, clearly.

We have another 20 years of data-taking

and we will have huge, huge data samples

and lots of sensitivity to new particles if they're there.

I'm excited about the future.

The one thing where I would not be ready to bet

is whether the discovery's going to happen in the next six months,

the next three years or the next ten years.

It all depends on how kind nature is going to be with us.