LHC Prepares Marathon Higgs Hunt

gbrumfiel writes "Physicists at the Large Hadron Collider are preparing to run the collider until the end of 2012 in the hopes of finding the Higgs particle, part of the mechanism that endows other particles with mass. The machine was originally supposed to stop in 2011 for a year long upgrade, but scientists now think they can find the Higgs if they run for longer. 'If we stop the machine with 3,000 people apiece in the experiments waiting for data, there is no way we could get home at night without having slashed tyres on our cars,' says Sergio Bertolucci, CERN's director for research and computing."

Re:I Got A Bad Feeling About This...

[Anonymous Coward]

Yes, that's right, because looking for the Higgs is not like looking for your keys in the drawer, but like looking for a "shooting star". You can say "Oh, my keys are not in the drawer, I looked twice", but you can't say "Oh there are not shooting stars (well, meteorites to be precise), I looked at the sky twice". In particle colliders you get bazillions of events, you register a tiny fraction of them and by analyzing a fraction of the ones you registered you try to build the big picture, so the more experiments the better your chance of "seeing" exotic events.

Re:What if it doesn't exist?

[grimJester]

A few years, maybe 3-5, should be enough to rule out the Higgs over the entire range of masses it could have. From what I gather, since the percentages of some processes no longer add up to 100 at LHC energies, something has to be there. It's theoretically possible this something could be heavy enough and hard enough to see that the LHC wouldn't find it, but no actual models predict anything that would be invisible at the LHC.

Re:What if it doesn't exist?

[Maritz]

I'm sure some physicists will be actually quite disappointed by finding the Higgs. Although it seems to be required in order for the standard model to be a success, it would actually be quite exciting if it isn't found as it means a whole different paradigm for mass is at work in the real universe. I believe for example I've seen Brian Cox say that he would be more excited by a lack of a Higgs than by finding it, although the politicians who fund these things might not be too happy I suppose.

The main reason that there is a broad consensus that the Higgs exists is simply that nobody seems able to think of a simpler mechanism through which mass might work.

Re:What if it doesn't exist?

[Steve Max]

Actually, we'd love to see the Higgs, and something else. Other Higgs-like particles, supersymmetric particles, Kaluza-Klein modes, anything else. This would confirm that the standard model is a good approximation for the energy ranges where we're using it, and that there is something beyond that. Not finding the Higgs would be interesting too, because we'd have to rethink almost everything we know.

The worst-case scenario is finding the Higgs and nothing else. Then we'd be out of jobs.

Re:Gee, why cooperate when you can be redundant?

[grimJester]

As I see it, the Higgs could fit into one of two energy ranges:

1. A range that the limited LHC and Fermilab can both probe now, with the LHC having some advantage.
2. A range that only the full LHC can reach.

If it falls into the latter, then nobody is discovering the Higgs for a few years until they get the LHC in gear. If it falls into #1, does it REALLY matter that much who finds it first?

Currently excluded [wikimedia.org]

Tevatron sensitivity, slide 18 [indico.cern.ch]

Only the 180 - maybe 190 GeV range is allowed but outside the Tevatron's reach energy-wise. The LHC and Tevatron aren't redundant, though. Any signal seen by both can be combined for more certainty.

Upgrading the LHC from 7 to 14 TeV doesn't really help find the Higgs.

Also, who knows what other interesting physics we'll find at the higher LHC design energies, that we're just pushing off for years sticking where we are at now?

I don't know what the odds of not seeing SUSY at 7 TeV but seeing it at 14 are, but I don't think they're that great. If SUSY exists at the electroweak scale, at least some of the particles should be seen at 7 TeV. OTOH, colliding at 14 TeV should make it easier (faster) to see new particles, even if they are around 1 TeV. Dunno what the arguments for and against running a year more before the upgrade have really been.

Re:What if it doesn't exist?

[Steve Max]

Actually, I work with neutrinos. The latest MiniBooNE/MINOS results are really, really weird; I'd hold any conclusions for now, because they have very little statistics for the antineutrino runs (and some lack of knowledge of the primary proton beans). Some say the next MINOS analysis is already on its way and will be very surprising, but we'll see.

The main problem is that those experiments suggest that CPT symmetry is broken (or, in non-technical terms, that a reaction with antimatter isn't the same as the same reaction with matter with the opposite charge, time reversed and seen in the mirror). CPT symmetry can be shown to be equivalent to Poincaré invariance [wikipedia.org], which means that these results challenge not only the standard model, but special relativity itself [cdsweb.cern.ch]. Such an extraordinary claim needs really extraordinary evidence, so let's wait for more statistics for now.