The Next Big Particle Accelerator

Guinnessy writes "This year more than a thousand physicists gathered for three weeks at Snowmass Village, in the Colorado Rockies near Aspen, to talk about the future of particle physics in the US. Physics Today has a report on the meeting which says that the community should build a 500-GeV electron-positron linear collider. That's powerful enough to make mini black holes."

Comments

No black holes here.

[Christopher Thomas]

Nowhere in the article does it mention creating mini-black-holes. The purpose is to try to create Higgs bosons and to precisely measure their characteristics to get a better handle on how electroweak symmetry breaking works.

To create mini-black-holes, you'd need a Planck-energy accelerator. This is beyond our current ability to build, and will remain so for quite a while. Scientific American had an article many years ago about what you'd have to do to build a conventional linac that powerful; it ended up having to be constructed in space and taking 2% of the sun's power output to run.

On a more mundane scale, we have experimental evidence (from cosmic rays of the same energy) that nothing catastrophically bad happens in collisions at energies of up to about 1.0e30 eV. We're not going to produce energies this high for a very long time either (current accellerators get in the 1.0e13 range at most; that's 100,000,000,000,000,000 times too low to be a concern).

Re:No black holes here.

[SL2C]

Actually, there is a fashionable idea in particle physics these days which goes by the name of "large extra dimensions" (large compared to the ordinary Planck length), which would bring the Planck scale, where you could expect to create mini black holes, down a lot (depending on the number of extra dimensions, geometry of spacetime in these additional dimensions, etc.) Lots of free parameters, by which you can get anything you like, much like in string theory ;-)
Anyway, in these scenarios you do expect black hole creation a the next linear collider, or in fact even at the LHC, currently under construction at CERN.

Also, very briefly the way experimental particle physics has worked over the last decades is to build proton and electron (possibly muon in the future) colliders alternatingly.

With hadron (proton) colliders such as the LHC you get high energies more easily because of less synchroton radiation (charges being accelerated, including going around a curve, radiate away a lot of their energy, increasing the power you need to operate the machine. This radiation is less if the particles are heavier, as is the case for hadrons). This way you create expected (and unexpected ;-) ) particles but identification and precision measurements are hard because hadron colliders are very messy (lots of unwanted particles created along the way, giving huge background to whatever you want to look at). This is because of the more complicated laws of physics of hadrons compared to leptons (electrons or muons).
People hope to find "the" (i.e. standard model) Higgs boson or something more unexpected (supersymmetry, mini black holes, ...) at the LHC in fact.

Then after some time when engineering has made enough progress to bring leptons up to comparable energies, you can do precision tests on whatever you have found already. Here it can be useful to have some data available from the hadron machine.
Anyway, you need both if you want to be sure about the laws of physics.

The question for the US IMO is if it wants to have world class particle physics in the future. Currently the strongest hadron collider in the world is at Fermilab in Chicago. This will be made obsolete (for direct fundamental particle searches) by the LHC, which is in Europe.

If the US fails again to build a world class machine, it will be built somewhere else in the world (Europe or Japan) and US experimental particle physics will be between in-trouble and non-existent for decades.

(I say this as a particle physicist in Europe.)

On the question why it fundamental physics should be done - as far as technology is concerned, there are sometimes spin-offs in the short run (such as the WWW, developed at CERN), and revolutions in the long or very long run (e.g. all semiconductor technology would be unthinkable without basic research in quantum mechanics in the first decades of the 20th century). Maybe it will happen again. Nobody can tell. Also, it's culture and it's fun. Taxpayer decides if this is interesting enough.

Science

[virg_mattes]

> As long as there are people living below the poverty line, blue
> skies projects like this should not get funding from the federal government.

Although I understand your point, there are a few issues to consider. The first is that, since the poverty line is more or less a percentage measure, there will always be people below it (it's like saying, "until everyone earns in the top 60 percent wage bracket"). The second is that there will always be social issues that require funding, but it's very short-sighted to say there should be no funding for science until all of the relevant social issues are solved, since all of the relevant social issues will never get solved, and pure science research often leads to practical applications that solve some of the social issues. You must always remember that funding is never an all-or-nothing proposition, and it shouldn't be. The developers of radio science could never have imagined that someday their ideas would be used (in MRI) to diagnose diseases without surgery, and saying that such studies shouldn't have been funded until we cured all diseases would have been very short-sighted.

In short, most funding poured into scientific studies is wasted. The problem is, you never know beforehand which projects will be duds and which will transform the world. So, we must strike a balance, and this particular machine has showed much promise in revealing new secrets, so its price tag may very well be paid back with a cure for cancer or cheap, renewable energy that will make coal- and oil-fired power plants obsolete.

Virg