On 4 July, when physicists at Cern, the European Organisation for Nuclear Research, announced that they had discovered a Higgs boson-like particle, one estimate suggested that the word "Higgs" was being mentioned in a news bulletin every 72 seconds around the world.

Despite few people outside theoretical physics understanding what the "God particle" really was, it was easy enough to grasp researchers' excitement at the indication that the linchpin of the Standard Model of physics, predicted half a century ago, had been found.

But contrary to popular perception, rather than being an end goal, finding the Higgs boson - which essentially explains why some particles have mass - is just the beginning for physicists.

And this may sit uncomfortably alongside the big question of whether "Higgsteria" will translate into public or political support for further investment in particle physics, or, crucially, in an international machine to succeed the Large Hadron Collider.

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Cern's member states, including the UK, have already agreed to fund upgrades to increase the energy and intensity of the LHC by 2020.

But according to Barry Barish, Linde professor of physics at the California Institute of Technology, there are important details of the Higgs boson that the LHC will struggle to detect and plans to build another machine are already under way.

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Lyn Evans, the Welshman who was former project leader of the LHC, is at the helm of the team coordinating international efforts to build a successor, with Professor Barish leading the bid for the most developed project, the International Linear Collider (ILC).

Professor Barish said that another machine is needed to make the most of investment in the LHC.

"Essentially we've made half the investment; it's a question of whether building the other half is worthwhile," Professor Barish told Times ÖйúAƬ.

"The LHC cost something in the order of $5 billion to $10 billion (?3.2 billion to ?6.5 billion) and this would be similar, but we have a history of needing these complementary instruments when the science is rich."

Things could really start to Clic

Two options are on the table: the ILC, which in theory could be built as soon as its design report is published next year; and the Compact Linear Collider or Clic, a higher-energy particle collider being designed at Cern for which the necessary technology remains years away.

Since the 1960s, three generations of machines have followed a pattern in which "general purpose" proton experiments, such as those conducted at the LHC, are followed by precision machines that collide electrons with their antiparticles, positrons.

Only such a machine could explain exactly how the Higgs boson gives different particles different mass and probe any strange phenomena that emerge from the LHC, such as candidates for the elusive concept of dark matter, said Professor Barish. For physicists, these questions are at least as interesting as confirming the existence of the Higgs boson, if not more so.

But with each generation of new machine, the energy usage and costs have increased. As a result, future accelerators and colliders almost certainly will have to be worldwide collaborations and convincing governments to fork out will be no easy task.

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UK expenditure on the LHC may amount to less than the cost of a pint of beer per taxpayer per year, but in the face of the worst financial crisis in a generation, any government will struggle to justify signing off on a contribution of some ?1 billion towards building a new collider.

Chris Llewellyn Smith, former director general of Cern, agreed that success at the LHC was essential but not sufficient for building the case for constructing a new machine.

"The (LHC) detectors are working beautifully so I would be surprised if it couldn't get a huge amount of information from them already. I'm prepared to be convinced we need something new, but I've yet to see the case," he said.

When he fought to get funding for the LHC in the mid-1990s, Professor Llewellyn Smith faced an uphill struggle in securing funding from Germany, which was facing the financial challenge of reunification, and the UK, which was keen to cut back wherever possible and was arguably rather "anti-particle physics", he said.

Getting approval for a new machine will rely on creating a really good technical case, building unanimity across the physics community, being able to ensure a reasonable budget across the board and gaining public support.

"I think the main thing that's changed [since getting approval for the LHC] is that there wasn't that much public interest or widespread support for what we were doing in those days," said Professor Llewellyn Smith.

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"I think that in gaining approval for any new project, public opinion is going to play a greater role."

It was hype about how the LHC might destroy the Universe and court cases against it that first drew the media's eye, he said.

"That was pretty scary, but in retrospect nothing better could have happened to Cern - [it made] headlines all over the world."

Eastern acceleration

Professor Barish said that the discovery of the Higgs boson and surrounding public interest will only help the case for another machine.

"Clearly the discovery of something like the Higgs particle...means a big boost for particle physics in general and [for] both support for future work on the LHC and any case one wants to make for a complementary machine."

But Brian Foster, professor of experimental physics at the University of Oxford and Europe's senior representative on the committee designing the ILC, acknowledged that public opinion, although helpful, was not enough.

France and Switzerland's willingness to host Cern was crucial, "but Europe, with the LHC, is not in a position to build another, as it quite rightly wants to exploit the LHC", said Professor Foster.

Nor is the US, the home of so many successful accelerators in the past, likely to step up.

"There's no history of the US hosting anything international apart from the UN. The US hasn't learned how to do something it doesn't control yet, and that would take a while," said Professor Barish.

Funding may yet come from the East. Following a failed bid to host the international nuclear fusion facility, Iter, that is now being built at Cadarache in France, Japan has both the infrastructure and government support necessary for a project such as the ILC.

And the country is "making extremely positive noises" about hosting the facility, Professor Foster said.

If Japan came forward, both China and India would be likely to make sizeable contributions, he added, making the collider the first worldwide physics collaboration to be built in Asia.

With these countries taking the lion's share of costs, other nations would be more likely to contribute.

"Within two years Japan might come forward. If I were a betting man, I'd be willing to risk a little bet on that," Professor Foster said.

Even if a successor to the LHC gets built, the future of "big physics" beyond that is more hazy, said Professor Barish.

"The reason machines have gotten bigger and more expensive is that the ultimate limitation...is materials," he said.

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"In my mind, [the LHC's successor] will be the last of that generation. Anything beyond that will only happen if new technology, at least promising or plausible, (is) developed. And that's past our lifetimes."

elizabeth.gibney@tsleducation.com.