What next?

What next?

The LHC is still new, but its successor - the International Linear Collider (ILC) – is already being discussed. So why build two high energy colliders that operate on the same principles?

The LHC is a ‘discovery’ machine, a general purpose tool that will open up new areas of physics and demonstrate the existence, or not, of predicted new laws and particles. The ILC is a precision instrument that will allow scientists to explore in detail the discoveries made by the LHC.

The ILC is still at the planning stage, no location for the machine has been agreed and much feasibility testing has to be conducted before the construction phase.

Where is the LHC?

Where is the LHC?

The LHC is physically located in a circular 27km (16.5m) long tunnel under the Swiss/French border outside Geneva, but as an international project the LHC crosses continents and many international borders.

In the UK, engineers and scientists at 20 research sites are involved in designing and building equipment and analysing data. UK researchers are involved with all four of the main detectors and the GRID. British staff based at CERN have leading roles in managing and running the collider and detectors.

Most, if not all, research teams are contributing to GridPP. 

UK LHC centres:

·                                 Brunel University, (CMS)

·                                 Imperial College - University of London, (CMS, LHCb)

·                                 Lancaster University, (ATLAS)

·                                 Oxford University, (ATLAS, LHCb)

·                                 Queen Mary - University of London, (ATLAS)

·                                 Royal Holloway – University of London, (ATLAS)

·                                 STFC Rutherford Appleton Laboratory, (ATLAS, CMS, LHCb)

·                                 University College London, (ATLAS)

·                                 University of Birmingham, (ATLAS, ALICE)

·                                 University of Bristol,  (CMS, LHCb)

·                                 University of Cambridge, (ATLAS, LHCb)

·                                 University of Durham, (theory)

·                                 University of Edinburgh, (LHCb, GridPP)

·                                 University of Glasgow, (ATLAS, LHCb theory)

·                                 University of Liverpool, (ATLAS, LHCb)

·                                 University of Manchester, (ATLAS)

·                                 University of Sheffield, (ATLAS)

·                                 University of Sussex, (theory)

·                                 University of Swansea,

·                                 University of Warwick,

·                                 University of the West of England

Who benefits?

Who benefits?

There are two types of benefit that the LHC project produces for the UK. The less easily measured benefits are:

• ·                                 new understanding of the physical world,
  
• ·                                 training of world class scientists and engineers,
  
• ·                                 maintenance of a vibrant, world class UK research base and,
  
• ·                                 a leading role in a major international project.
  

More easily appreciated are the knowledge, expertise and technology that is spun off from the LHC and can be directly applied to development of new medical, industrial and consumer technologies.

The science of the LHC is far removed from everyday life, but the fact that the science is so extreme constantly pushes the boundaries of existing technical and engineering solutions. Simply building the LHC has generated new technology.

The LHC is not primarily about building a better world. Rather, it allows us to test theories and ideas about how the Universe works, its origins and evolution. The questions asked, and answers found, are so fundamental that the information from LHC experiments will only be applied many years in the future, if at all. However, this is an experiment and one of the surprises from the experiment may be new science that can be applied almost immediately.

What will the LHC do?

The LHC will allow scientists to probe deeper into the heart of matter and further back in time than has been possible using previous colliders.

Researchers think that the Universe originated in the Big Bang (an unimaginably violent explosion) and since then the Universe has been cooling down and becoming less energetic. Very early in the cooling process the matter and forces that make up our world ‘condensed’ out of this ball of energy.

The LHC will produce tiny patches of very high energy by colliding together atomic particles that are travelling at very high speed. The more energy produced in the collisions the further back we can look towards the very high energies that existed early in the evolution of the Universe. Collisions in the LHC will have up to 7x the energy of those produced in previous machines; recreating energies and conditions that existed billionths of a second after the start of the Big Bang.

The results from the LHC are not completely predictable as the experiments are testing ideas that are at the frontiers of our knowledge and understanding. Researchers expect to confirm predictions made on the basis of what we know from previous experiments and theories. However, part of the excitement of the LHC project is that it may uncover new facts about matter and the origins of the Universe.

One of the most interesting theories the LHC will test was put forward by the UK physicist Professor Peter Higgs and others. The different types of fundamental particle that make up matter have very different masses, while the particles that make up light (photons) have no mass at all. Peter’s theory is one explanation of why this is so and the LHC will allow us to test the theory. More of the Big Questions about the universe that the LHC may help us answer can be found.

What is the LHC?

The LHC is exactly what its name suggests - a large collider of hadrons. Strictly, LHC refers to the collider; a machine that deserves to be labelled ‘large’, it not only weighs more than 38,000 tonnes, but runs for 27km (16.5m) in a circular tunnel 100 metres beneath the Swiss/French border at Geneva.

However, the collider is only one of three essential parts of the LHC project. The other two are:

the detectors, which sit in 4 huge chambers at points around the LHC tunnel and

the GRID, which is a global network of computers and software essential to processing the data recorded by LHC’s detectors.

The LHC’s 27km loop in a sense encircles the globe, because the LHC project is supported by an enormous international community of scientists and engineers. Working in multinational teams, at CERN and around the world, they are building and testing LHC equipment and software, participating in experiments and analysing data. The UK has a major role in leading the project and has scientists and engineers working on all the main experiments.

Tests of Big Bang: The CMB

Tests of Big Bang: The CMB

The Big Bang theory predicts that the early universe was a very hot place and that as it expands, the gas within it cools. Thus the universe should be filled with radiation that is literally the remnant heat left over from the Big Bang, called the “cosmic microwave background radiation”, or CMB.

DISCOVERY OF THE COSMIC MICROWAVE BACKGROUND

The existence of the CMB radiation was first predicted by George Gamow in 1948, and by Ralph Alpher and Robert Herman in 1950. It was first observed inadvertently in 1965 by Arno Penzias and Robert Wilson at the Bell Telephone Laboratories in Murray Hill, New Jersey. The radiation was acting as a source of excess noise in a radio receiver they were building. Coincidentally, researchers at nearby Princeton University, led by Robert Dicke and including Dave Wilkinson of the WMAP science team, were devising an experiment to find the CMB. When they heard about the Bell Labs result they immediately realized that the CMB had been found. The result was a pair of papers in the Physical Review: one by Penzias and Wilson detailing the observations, and one by Dicke, Peebles, Roll, and Wilkinson giving the cosmological interpretation. Penzias and Wilson shared the 1978 Nobel prize in physics for their discovery.

WHY STUDY THE COSMIC MICROWAVE BACKGROUND?

Since light travels at a finite speed, astronomers observing distant objects are looking into the past. Most of the stars that are visible to the naked eye in the night sky are 10 to 100 light years away. Thus, we see them as they were 10 to 100 years ago. We observe Andromeda, the nearest big galaxy, as it was about 2.5 million years ago. Astronomers observing distant galaxies with the Hubble Space Telescope can see them as they were only a few billion years after the Big Bang. (Most cosmologists believe that the universe is between 12 and 14 billion years old.)

THE ORIGIN OF THE COSMIC MICROWAVE BACKGROUND

One of the profound observations of the 20th century is that the universe is expanding. This expansion implies the universe was smaller, denser and hotter in the distant past. When the visible universe was half its present size, the density of matter was eight times higher and the cosmic microwave background was twice as hot. When the visible universe was one hundredth of its present size, the cosmic microwave background was a hundred times hotter (273 degrees above absolute zero or 32 degrees Fahrenheit, the temperature at which water freezes to form ice on the Earth's surface). In addition to this cosmic microwave background radiation, the early universe was filled with hot hydrogen gas with a density of about 1000 atoms per cubic centimeter. When the visible universe was only one hundred millionth its present size, its temperature was 273 million degrees above absolute zero and the density of matter was comparable to the density of air at the Earth's surface. At these high temperatures, the hydrogen was completely ionized into free protons and electrons.

Since the universe was so very hot through most of its early history, there were no atoms in the early universe, only free electrons and nuclei. (Nuclei are made of neutrons and protons). The cosmic microwave background photons easily scatter off of electrons. Thus, photons wandered through the early universe, just as optical light wanders through a dense fog. This process of multiple scattering produces what is called a “thermal” or “blackbody” spectrum of photons. According to the Big Bang theory, the frequency spectrum of the CMB should have this blackbody form. This was indeed measured with tremendous accuracy by the FIRAS experiment on NASA's COBE satellite.

Tests of Big Bang: The Light Elements

Tests of Big Bang: The Light Elements

NUCLEOSYNTHESIS IN THE EARLY UNIVERSE

The term nucleosynthesis refers to the formation of heavier elements, atomic nuclei with many protons and neutrons, from the fusion of lighter elements. The Big Bang theory predicts that the early universe was a very hot place. One second after the Big Bang, the temperature of the universe was roughly 10 billion degrees and was filled with a sea of neutrons, protons, electrons, anti-electrons (positrons), photons and neutrinos. As the universe cooled, the neutrons either decayed into protons and electrons or combined with protons to make deuterium (an isotope of hydrogen). During the first three minutes of the universe, most of the deuterium combined to make helium. Trace amounts of lithium were also produced at this time. This process of light element formation in the early universe is called “Big Bang nucleosynthesis” (BBN).

NUCLEOSYNTHESIS IN STARS

Elements heavier than lithium are all synthesized in stars. During the late stages ofstellar evolution, massive stars burn helium to carbon, oxygen, silicon, sulfur, and iron. Elements heavier than iron are produced in two ways: in the outer envelopes of super-giant stars and in the explosion of a supernovae. All carbon-based life on Earth is literally composed of stardust.