Scientists discuss Next Big Thing in physics

Two LHC magnets are seen before they are connected together Cern

Top scientists have been meeting in Geneva to discuss the future of particle physics and the possible replacement for the world’s largest particle smasher.

Some 150 international experts, government officials and directors of major research centres gathered at the European Organization for Nuclear Research (Cern), the particle-physics laboratory which houses the smasher, for a four-day seminar that ended on Thursday.

According to the International Committee for Future Accelerators (ICFA), which organised the event, the science of particle physics “has reached a decisive moment”.

Experiments at particle accelerators, together with observations of the cosmos, bring unprecedented opportunities for discovery, it said in a statement.

 

 “We have been working over the past ten years on what will follow Cern’s Large Hadron Collider (LHC),” ICFA Chairman Pier Oddone told swissinfo.ch.

Oddone is also director of the US Fermi National Accelerator Laboratory (Fermilab) in Illinois which last week shut down its Tevatron collider – the world’s first major accelerator – after 26 years in operation. This leaves the LHC to carry the baton.                 

But what comes after the LHC? Two possible long-term successors to the particle smasher, which is in the second year of a 20-year lifespan, are being examined.

The hope is that a new, more-precise machine would be able to pick up small hints from the huge LHC and help unlock puzzles like dark matter and dark energy.

Straight smasher

One proposal is the International Linear Collider (ILC), an international electron-positron collider project launched in 2005.

The ILC would be a 30-50-kilometre-long straight-path machine, unlike the LHC which swings particles around an oval-shaped 26-km underground tunnel to get them almost to the speed of light before smashing them together.

                                   

The other is the Compact Linear Collider (CLIC), under design at Cern, which potentially has significantly higher energies but is shorter than the ILC.

Cern Director-General Rolf Heuer said a technical design report for the ILC and a concept design report for the CLIC were due at the end of 2012.

“We are moving ahead on the research and development in order to be ready when we find something at the LHC,” Heuer told journalists. “The ILC has a more limited energy range than the CLIC but is more mature.”

Oddone said the ILC looked the likely successor but remained cautious.

“Until the LHC tells us the shape of the landscape and what the physics is, we can’t say responsibly what the next machine is going to be,” he said.

Funding

The ILC’s outline plan says construction could start within the following 5-8 years, but there are doubts over how it will be financed.

Costs, originally thought to be around $6 billion (SFr5.5 billion) in 2007, are understood to have shot up since then.

                                  

But Heuer said he was optimistic that countries would help fund the next-generation particle smasher.

“There is willingness as long as we make a good scientific case and have convincing technology,” he said. “I see lots of countries knocking on Cern’s door and they wouldn’t do so if they didn’t want to participate in such an endeavour.”

There is much speculation over the possible location of the new collider. The US and Europe are said to be doubtful, while Japan has expressed an interest. China and Russia are also thought to be in the running.

Higgs soon?

In the LHC, which began operating at the end of March 2010, Cern engineers and physicists have created billions of miniature versions of the Big Bang by smashing particles together at just a fraction under the speed of light.

                  

The power at the LHC was ramped up this spring, creating reams of new data for analysis and scientists are starting to pinpoint the precise level of high energy where the Higgs boson may be found.

This is the so-called “God particle”, the linchpin of the Standard Model of particle physics on the Big Bang. It is believed to give mass to other objects and creatures in the universe.

Heuer said the LHC had so far delivered 30-40 per cent of the total volume of data originally due by the end of 2012.

“This is why we are so confident that the Standard Model-Higgs boson can be solved by next year,” he said.

Meanwhile the jury is still out on Cern scientists’ announcement in late September that they had recorded the neutrino, a subatomic particle, going faster than the speed of light – against a key Einstein tenet. Top scientists at the meeting said they were still sceptical over the research, which is currently undergoing confirmation.

Large Hadron Collider

In the LHC, high-energy protons in two counter-rotating beams are smashed together to search for exotic particles.

The beams contain billions of protons. Travelling just under the speed of light, they are guided by thousands of superconducting magnets.

The beams usually move through two vacuum pipes, but at four points they collide in the hearts of the main experiments, known by their acronyms: ALICE, ATLAS, CMS, and LHCb.

When operational, the detectors see up to 600 million collision events per second, with the experiments scouring the data for signs of extremely rare events such as the creation of the so-called God particle, the yet-to-be-discovered Higgs boson.

The $7.5 billion (SFr6.9 billion) machine was launched with great fanfare on September 10, 2008, but broke down nine days later when a badly soldered electrical splice overheated, causing extensive damage to the massive magnets and other parts of the collider deep underground. It cost $40 million to repair and improve the machine.

Since the restart in March 2010 it has performed almost flawlessly, giving scientists valuable data and allowing it to quickly eclipse the next largest accelerator, the Tevatron at Fermilab near Chicago.

Simple protons have been replaced with heavier lead nuclei for collisions. The LHC, which currently operates at 3.5 trillion electron volts, will be upgraded in 2013 so that it can run at seven trillion, starting in 2014. A short technical stop is planned at the end of 2011.