The Quark

Listen on iPlayer (to 25/9/08)

By 1930s it was accepted that everything was made of protons, neutrons and electrons. In the 1960s a plethera of particles were discovered. Some particles decayed quicker than others. Particles were named lambda, p11, k, sigma, x,y, strange - the particle zoo. Murray-Gelman came up with an organising structure - a periodic table of particles. He hypothesised that all particles were a combination of 3 quarks eg Up/Down/Strange quarks eg 2 up quarks + 1 down quark was a proton, 2 down quarks + 1 up quark was a neutron. Experimental evidence for quarks was derived in the 1960s - from Stanford in California - electrons were used to bounce of protons. Protons were shown to made of 3 different particles eg football with 3 ball bearings inside it. If fire a bullet at the football some of the bullets will bounce of some of the ball bearings occassioanly.

Up down strange discovered first then charm, top, bottom. Always held together by the strong force eg 2 and 3 quarks never one quark. Look inside a prison or proton can see the quarks. Marcos Chown (book: Afterglow of creation) cf Tomatoes all quark gluon plasma. Gluon (wikipedia) glue together the quarks in a proton!

Timeline of Particle discovery (wikipedia).

Search BBC iPlayer for 'big bang'

Search BBC iPlayer for 'big bang'

On the hunt for the Higgs boson - Stephen Hawking

On the hunt for the Higgs boson

Hawking’s books have made him a world-renowned theoretical physicist

The sum of human knowledge could be massively increased on Wednesday - but Professor Stephen Hawking could find himself $100 poorer.

As Cern prepares to switch on the Large Hadron Collider (LHC) below the French-Swiss border, the physicist has a bet that it will not find the Higgs boson - the most highly sought-after particle in physics.

Dubbed the "God particle" because it is so crucial to our understanding of the Universe, it is thought to give everything its mass.

The most powerful physics experiment ever built, the LHC will re-create the conditions present in the Universe just after the Big Bang.

When subatomic particles like protons are smashed together in the LHC, the energies released will create an array of new particles - some of which have not been seen since the big bang itself. It will give scientists a glimpse into how these building blocks of matter are made.

Both the LHC, and the space programme, are vital if the human race is not to stultify, and eventually die out Large Hadron Collider Radio 4's Big Bang day

"The LHC will increase the energy at which we can study particle interactions, by a factor of four. According to present thinking, this should be enough to discover the Higgs particle, the particle that gives mass to all the other particles," Professor Hawking told the Today programme.

Previous particle accelerators have failed to find it, but because the LHC is so much more powerful, there is hope that it will succeed. Even a failure, Professor Hawking says, would be exciting, because that would pose new questions about the laws of nature.

"I think it will be much more exciting if we don't find the Higgs. That will show something is wrong, and we need to think again. I have a bet of $100 that we won't find the Higgs."

He believes another important discovery that the experiment could make is superpartners, or particles that should theoretically exist. They are "supersymmetric partners" to those particles we already know of at present.

"Their existence would be a key confirmation of string theory, and they could make up the mysterious dark matter that holds galaxies together. Whatever the LHC finds, or fails to find, the results will tell us a lot about the structure of the Universe," he says.

The CMS detector will search for the Higgs boson

Some fear the experiment may create a black hole that will tear the Earth apart - there have even been two last-minute legal attempts to stop it - but Professor Hawking dismisses the idea that the LHC is in any way dangerous.

"If the collisions in the LHC produced a micro black hole, and this is unlikely, it would just evaporate away again, producing a characteristic pattern of particles. Collisions at these and greater energies occur millions of times a day in the Earth's atmosphere, and nothing terrible happens."

Parallel universe?

The human race is characterised by an insatiable quest to understand things, and the LHC is an example of our willingness to invest in that quest.

It is however difficult to predict whether it will bring any practical advances in the scale of our lifetime. But the LHC might reveal something completely unexpected about the workings of our Universe, and that, says Professor Hawking, is what makes physics so satisfying.

"Throughout history, people have studied pure science from a desire to understand the Universe, rather than for practical applications, or commercial gain. But their discoveries have later turned out to have great practical benefits.

"It is difficult to see an economic return from research at the LHC, but that doesn't mean there won't be any."

Asked if he would be able to choose whether the LHC or the space programme is more important in advancing our knowledge of the Universe, Professor Hawking says that would be like "asking which of my children I would choose to sacrifice".

"Both the LHC, and the space programme, are vital if the human race is not to stultify, and eventually die out. Together they cost less than one tenth of a percent of world GDP. If the human race cannot afford that, it doesn't deserve the epithet, human," he added.

Scientists have spoken, if cautiously, of the experiments at Cern venturing into realms long regarded as those of speculative science fiction - multiple universes, parallel worlds, black holes in space linking different levels of existence.

If a black hole is produced, it might look like this in LHC data

Professor Hawking says that a parallel universe may be a universe very different to the one we recognise.

"According to the sum over histories idea of Richard Feynman, the Universe doesn't just have a single history, as one might think, but it has every possible history, each with its own weight. A few of the histories will contain creatures like me, doing different things, but the vast majority of histories will be very different."

In 1974 Professor Hawking argued that due to quantum effects, primordial black holes created during the Big Bang could "evaporate" by a theoretical process now referred to as Hawking Radiation in which particles of matter would be emitted.

Under this theory, the smaller the size of the micro black hole, the faster the evaporation rate, resulting in a sudden burst of particles as the micro black hole suddenly explodes.

In the past Professor Hawking has joked that if the LHC does creates micro black holes - even if they are rather short-lived ones - it could win him the Nobel prize. However, he now says he does not believe this is something that is imminent.

"If the LHC were to produce little black holes, I don't think there's any doubt I would get a Nobel prize, if they showed the properties I predict. However, I think the probability that the LHC has enough energy to create black holes, is less than 1%, so I'm not holding my breath."

Science of LHC

The Large Hadron Collider (LHC) will smash two beams of particles head-on at super-fast speeds, recreating the conditions in the Universe moments after the Big Bang, writes BBC science reporter Paul Rincon.

Scientists hope to see new particles in the debris of these collisions, revealing fundamental new insights into the nature of the cosmos.

They will be looking for new physics beyond the Standard Model – the framework devised in the 1970s to explain how sub-atomic particles interact.

The Standard Model comprises 16 particles – 12 matter particles and four force-carrier particles. The Standard Model has worked remarkably well so far.

But it cannot explain the best known of the so-called four fundamental forces: gravity; and it describes only ordinary matter, which makes up but a small part of the total Universe.

Also, one of the most important particles in the Standard Model – the Higgs boson – has yet to be found in an experiment.

Today, the Standard Model is regarded as incomplete, a mere stepping stone to something else. So the LHC should help reinvigorate physics' biggest endeavour: a grand theory to explain all physical phenomena in Nature.

However, some physicists point out that Nature has a habit of throwing curve balls. And some of the most exciting discoveries at the LHC could be those that no-one expects.

THE HUNT FOR THE HIGGS

There is an essential ingredient missing from the Standard Model. Without it, none of the 16 particles in the scheme would have any mass.

An extra particle is required to provide all the others with mass – the Higgs boson. This idea was proposed in 1964 by physicists Peter Higgs, Francois Englert and Robert Brout.

According to their theory, particles acquire mass through their interactions with an all-pervading field, called the Higgs field, which is carried by the Higgs boson. It is the only Standard Model particle that has yet to be observed experimentally.

The CMS is one of two LHC experiments looking for the Higgs

As such, the search for the Higgs has become something of a cause celebre in particle physics. Finding the Higgs is one of the main science objectives for the LHC.

The Atlas and CMS experiments are both designed to see it, if it is there. This means that scientists working on these respective experiments will be competing to see it first, once the LHC begins its "science run" sometime in 2009.

The US Tevatron particle accelerator, though less powerful than the LHC, is also engaged in the hunt for the Higgs.

IN THE DARK

All the matter that we can see in the Universe – planets, stars and galaxies – makes up a minuscule 4% of what is actually out there. The rest is dark energy (which accounts for 73% of the cosmos) and dark matter (23%).

Dark energy cannot be observed directly, but it is responsible for speeding up the expansion of the Universe – a phenomenon that can be detected in astronomical observations.

Astronomers have mapped dark matter's distribution, but have no idea what it is

Like dark energy, dark matter can only be detected indirectly, as it does not emit or reflect enough light to be seen. But its presence can be inferred through its effects on galaxies and galaxy clusters.

Physicists know virtually nothing about the nature of either dark energy or dark matter. But they can speculate.

According to one idea, dark matter could be made up of "supersymmetric particles" - massive particles that are partners to those already known in the Standard Model.

A leading dark matter candidate is the neutralino, the lightest of these "super-partners". And some theoretical physicists have proposed a link between the Higgs mechanism and dark energy.

MIRROR, MIRROR

Each basic particle of "ordinary" matter has its own anti-particle. Matter and antimatter have the same mass, but opposite electric charge.

For example, a proton has an anti-particle called an anti-proton (a proton with a negative charge). An electron has an anti-particle called a positron (an electron with a positive charge).

In the same way that an ordinary proton and electron can come together to form a hydrogen atom, an anti-proton and a positron can form an atom of anti-hydrogen.

When a particle of ordinary matter meets its anti-particle, the two disappear in a flash, as their mass is transformed into energy.

They are said to "annihilate" one another. But equal amounts of matter and anti-matter must have been produced in the Big Bang.

So why did matter and anti-matter not completely annihilate each another after the birth of the Universe?

Today, we live in a Universe almost entirely composed of ordinary matter. Scientists will use the LHC to investigate why this is, and what happened to all the anti-matter.

DOUBLE TROUBLE

Attempts to unify gravity with the other fundamental forces have come to a startling prediction: that every known particle has a massive "shadow" partner particle.

Atlas is one of the experiments that could find evidence for supersymmetry

All particles are classified as either fermions or bosons. A particle in one class has superpartner in the other class, "balancing the books" and doubling the number of particles in the Standard Model.

For example, the superpartner of an electron (a fermion) is called a selectron (a boson). Evidence for supersymmetry would enable the "unification" of three fundamental forces - the strong, weak, and electromagnetic – helping to explain why particles have the masses they have.

It would also give a boost to string theory – one stab at a grand "theory of everything". But string theory is not dependent on discovering evidence for supersymmetry.

OTHER DIMENSIONS

In addition to the four dimensions we already know about, string theory predicts the existence of six more.

Some physicists even think the existence of these extra dimensions could explain why gravity is so much weaker than the other fundamental forces. Perhaps, they argue, we are not feeling its full effects.

This might be explained if its force was being shared with other dimensions. If these extra dimensions do exist, the LHC could be the first accelerator to detect them experimentally.

At high energies, physicists could see evidence of particles moving between our world and these unseen realms. For example, they could see particles suddenly disappear into one of these dimensions.

Alternatively, particles originating from an extra dimension could suddenly appear in our world.

THE HOLE TRUTH

According to some physicists, the LHC can operate at high enough energies to generate mini-black holes.

However, the vast majority of particle physicists say there is no need for alarm. If any should be created, they should evaporate quickly.

How a black hole might look if it is generated in the collider

A recent report dealing with the collider's safety acknowledged the possibility that the LHC could create these primordial black holes.

The report says: "If microscopic black holes were to be singly produced by colliding the quarks and gluons inside protons, they would also be able to decay into the same types of particles that produced them.”

The suggestion that black holes could be made in the LHC has stoked fears that one of these micro-black holes could swell in size, swallowing up the Earth.

In March, plaintiffs requested an injunction in a US court stopping the LHC from switching on.

However, physicists stress that any such phenomena would be short-lived and thus would pose no threat to our planet.

'Big Bang' experiment starts well

My daughter and I sat in the car today spellbound listening to Andrew Marr on the Today programme on Radio 4. At 8.30am today the LHC experiments started in earnest with the first protons being fired around the LHC.

More from Today programme

By Paul Rincon
Science reporter, BBC News

The LHC has been in construction for some 13 years

Scientists have hailed a successful switch-on for an enormous experiment which will recreate the conditions a few moments after the Big Bang.

They have now fired two beams of particles called protons around the 27km-long tunnel which houses the Large Hadron Collider (LHC).

The £5bn machine on the Swiss-French border is designed to smash protons together with cataclysmic force.

Scientists hope it will shed light on fundamental questions in physics.

The first - clockwise - beam completed its first circuit of the underground tunnel at just before 0930 BST. The second - anti-clockwise - beam successfully circled the ring after 1400 BST.

We will be looking at what the Universe was made of billionths of a second after the Big Bang Dr Tara Shears, University of Liverpool What is the Large Hadron Collider?

The beams have not yet been run continuously. So far, they have been stopped, or "dumped", after just a few circuits.

By Wednesday evening, engineers hope to inject clockwise and anti-clockwise protons again, but this time they will "close the orbit", letting the beams run continuously for a few seconds each.

Cern has not yet announced when it plans to carry out the first collisions, but the BBC understands that low-energy collisions could happen in the next few days. This will allow engineers to calibrate instruments, but will not produce data of scientific interest.

"There it is," project leader Lyn Evans said when the beam completed its lap. There were cheers in the control room when engineers heard of the successful test.

Montage of key moments from switch-on

He added later: "We had a very good start-up."

The LHC is arguably the most complicated and ambitious experiment ever built; the project has been hit by cost overruns, equipment trouble and construction problems. The switch-on itself is two years late.

The collider is operated by the European Organization for Nuclear Research - better known by its French acronym Cern.

The vast circular tunnel - the "ring" - which runs under the French-Swiss border contains more than 1,000 cylindrical magnets arranged end-to-end.

The magnets are there to steer the beam - made up of particles called protons - around this 27km-long ring.

Big Bang Day

Eventually, two proton beams will be steered in opposite directions around the LHC at close to the speed of light, completing about 11,000 laps each second.

At allotted points around the tunnel, the beams will cross paths, smashing together near four massive "detectors" that monitor the collisions for interesting events.

Scientists are hoping that new sub-atomic particles will emerge, revealing fundamental insights into the nature of the cosmos.

Major effort

"We will be able to see deeper into matter than ever before," said Dr Tara Shears, a particle physicist at the University of Liverpool.

"We will be looking at what the Universe was made of billionths of a second after the Big Bang. That is amazing, that really is fantastic."

The LHC should answer one very simple question: What is mass?

LHC DETECTORS ATLAS - one of two so-called general purpose detectors. Atlas will be used to look for signs of new physics, including the origins of mass and extra dimensions CMS - the second general purpose detector will, like ATLAS, hunt for the Higgs boson and look for clues to the nature of dark matter ALICE - will study a "liquid" form of matter called quark-gluon plasma that existed shortly after the Big Bang LHCb - Equal amounts of matter and anti-matter were created in the Big Bang. LHCb will try to investigate what happened to the "missing" anti-matter

"We know the answer will be found at the LHC," said Jim Virdee, a particle physicist at Imperial College London.

The currently favoured model involves a particle called the Higgs boson - dubbed the "God Particle". According to the theory, particles acquire their mass through interactions with an all-pervading field carried by the Higgs.

The latest astronomical observations suggest ordinary matter - such as the galaxies, gas, stars and planets - makes up just 4% of the Universe.

The rest is dark matter (23%) and dark energy (73%). Physicists think the LHC could provide clues about the nature of this mysterious "stuff".

But Professor Virdee told BBC News: "Nature can surprise us... we have to be ready to detect anything it throws at us."

Full beam ahead

Engineers injected the first low-intensity proton beams into the LHC in August. But they did not go all the way around the ring.

Technicians had to be on the lookout for potential problems.

Steve Myers, head of the accelerator and beam department, said: "There are on the order of 2,000 magnetic circuits in the machine. This means there are 2,000 power supplies which generate the current which flows in the coils of the magnets."

If there was a fault with any of these, he said, it would have stopped the beams. They were also wary of obstacles in the beam pipe which could prevent the protons from completing their first circuit.

Superconducting magnets are cooled down using liquid helium

Mr Myers has experience of the latter problem. While working on the LHC's predecessor, a machine called the Large-Electron Positron Collider, engineers found two beer bottles wedged into the beam pipe - a deliberate, one-off act of sabotage.

The culprits - who were drinking a particular brand that advertising once claimed would "refresh the parts other beers cannot reach" - were never found.

In order to get both beams to circulate continuously around the LHC, engineers have to "close the orbit". The beams themselves are made up of several "packets" - each about a metre long - containing billions of protons.

HAVE YOUR SAY

I think it is disgraceful that huge sums of cash have been spent on this project

Robert, Spain

Send us your comments

The protons would disperse if left to their own devices, so engineers use electrical forces to "grab" them, keeping the particles tightly huddled in packets.

Once the beams are captured, the same system of electrical forces is used to give the particles an energetic kick, accelerating them to greater and greater speeds.

Long haul

The idea of the Large Hadron Collider emerged in the early 1980s. The project was eventually approved in 1996 at a cost of 2.6bn Swiss Francs, which amounts to about £1.3bn at present exchange rates.

However, Cern underestimated equipment and engineering costs when it set out its original budget, plunging the lab into a cash crisis.

FROM THE TODAY PROGRAMME More from Today programme

Cern had to borrow hundreds of millions of euros in bank loans to get the LHC completed. The current price is nearly four times that originally envisaged.

During winter, the LHC will be shut down, allowing equipment to be fine-tuned for collisions at full energy.

"What's so exciting is that we haven't had a large new facility starting up for years," explained Dr Shears.

"Our experiments are so huge, so complex and so expensive that they don't come along very often. When they do, we get all the physics out of them that we can."

Engineers celebrated the success with champagne, but a certain brand of beer was not on the menu.

Paul.Rincon-INTERNET@bbc.co.uk

The LHC's dress rehearsal goes with a hitch.

• Tom Feilden
• Tue 9 Sep 08, 03:09 PM
• Source: BBC
  

The LHC's dress rehearsal goes with a hitch.

Things are hotting up in the main control room here at Cern. We've just been through a full dress rehearsal for the big "switch on" of the Large Hadron Collider - due to take place at 8.30 tomorrow morning.
I watched on a giant computer screen alongside dozens of scientists and technicians as a beam of protons was fired down a linear accelerator, slung round two synchotrons to pick up energy, and finally dumped at the gates of the LHC.
Tomorrow those gates will be open, and - if all goes well - the first proton beam will shoot clockwise round all 27 kilometres of the LHC at very nearly the speed of light.
But it could have been very different. Last night a component on one of the cryogenics units - which cool the core of the machine to minus 271 degrees - snapped, and two sections of the LHC began to warm up again.
"It's just a little piece of wire about six inches long," operations group leader Paul Collier told me.
"But it just goes to show what can go wrong with a machine of this size and complexity."

The problem has now been fixed, and the temperature in both sections is falling back towards absolute zero. "Fingers crossed," Paul Collier says. "We're still on course for tomorrow. But if it happens again now we'll be in a lot of trouble".

But after all, something should go wrong in a dress rehearsal if it's going to be all right on the night...

The Big Bang Machine

Professor Brian Cox visits Geneva to take a look around Cern's Large Hadron Collider before this vast, 27km long machine is sealed-off and the experiment to create the simulation of a black hole begins. 

When it's up and running, it will be capable of creating the conditions that existed just a billionth of a second after the Big Bang. Brian joins the scientists who hope that the LHC will change our understanding of the early universe and solve some of its mysteries.

Broadcast on:

BBC Four, 9:00pm Thursday 4th September

Duration:

60 minutes

Available until:

9:59pm Thursday 11th September

Big Bang Day: Five Particles: The Electron

Simon Singh examines the significance of subatomic particles.

British physicist JJ Thompson's experiments with electric currents showed that atoms are divisible into elementary particles. But how has the power of electrons been harnessed for everyday use?

Broadcast on:

BBC Radio 4, 3:45pm Monday 8th September

Duration:

15 minutes

Available until:

4:02pm Monday 15th September

LHC Rap

Mysteries of the Universe will be solved, starting next Wednesday

Source: The Times.

Beneath the foothills of the Jura mountains, in a network of tunnels that bring to mind the lair of a crazed Bond villain, scientists will fire a first beam of particles around a ring as long as the Circle Line on the London Underground. This colossal circuit, 17 miles (27km) in circumference,

In the years ahead it will recreate the high-energy conditions that existed one trillionth of a second after the big bang. In doing so, it should solve many of the most enduring mysteries of the Universe.

This extraordinary feat of engineering will accelerate two streams of protons to within 99.9999991 per cent of the speed of light, so that they complete 11,245 17-mile laps in a single second. The two streams will collide, at four points, with the energy of two aircraft carriers sailing into each other at 11 knots, inside detectors so vast that one is housed in a cavern that could enclose the nave of Westminster Abbey.

The mountains of data produced will shed light on some of the toughest questions in physics. The origin of mass, the workings of gravity, the existence of extra dimensions and the nature of the 95 per cent of the Universe that cannot be seen will all be examined. Perhaps the biggest prize of all is the “God particle” – the Higgs boson.

“What we find honestly depends on what’s there,” said Brian Cox, of the University of Manchester, an investigator on one of the four detectors, named Atlas. “I don’t believe there’s ever been a machine like this, that’s guaranteed to deliver. We know it will discover exciting things. We just don’t know what they are yet.”

“The beam is 2mm in diameter and has to be threaded into a vacuum pipe the size of a 50p piece around a 27km loop,” said Lyn Evans, the LHC’s project manager, who will oversee the insertion. “It is not going to be trivial.”