Will the LHC Smash Supersymmetry? 196
gbrumfiel writes "The Large Hadron Collider is just getting ready for its next big science run. One thing researchers hope it will find is evidence for supersymmetry, a theory that could help to unify fundamental forces and explain mysterious dark matter. But as Nature reports this week, the LHC has shown no signs of supersymmetry in data from last year's run. If super particles don't appear by 2012, then physicists might give up on the theory for good."
Re:high enough energy? (Score:5, Informative)
No. We can never smash hard enough to disprove supersymmetry unless we find something that directly contradicts it. To put it another way, if all the LHC finds is a Higg's and expected results from the standard model, it doesn't actually disprove supersymmetry since any model of supersymmetry has so many parameters that you can tweak a few of them and lift the superpartners back up above the LHC's maximum energies. That is *always* going to be possible -- theoretically a limit would be if we had particle accelerators that reached the Planck energy and people would finally be saying "hang on, something's up here; we should be seeing quantum gravity by now and we're still not seeing the quarkinos", but in reality we're never getting to anything like an energy that would rule it out.
What's a lot more likely in my mind is that more physicists will begin to drop supersymmetry and look at something else that may actually have observable effects at "low" energies while otherwise the supersymmetry bandwagon will roll happily on with slightly more tightly-constrained parameters.
The hope is that the LHC not only doesn't see supersymmetry but *does* see something utterly unexpected. That's what I want from it. (Actually I want specifically no Higg's boson, and no supersymmetry.) Something unpredicted would rule out supersymmetry not least because any supersymmetric model that could account for it would be a posteriori -- constructed purely to do that and most likely grossly ugly as a result. By definition something unexpected is not a straight prediction of supersymmetric theories, and any model constructed purely to explain it will be under suspicion.
Before getting onto the next bit, the Higg's is not associated with supersymmetry, it's part of the standard model and doesn't require supersymmetry to exist. The Higg's is the last part of the standard model that is yet to be observed. They're different topics, and the LHC is hoped to shed light on both of them. As far as supersymmetry goes, the LHC was built basically to give us a pointer for where to go beyond the standard model and forms of supersymmetry are currently the most widely-favoured options.
The fear (at least my fear) is that the LHC will find nothing. Squat. No supersymmetry, nothing outwith the standard model -- but from my point of view, that it does find a Higg's. That would appear to add support to the standard model, which is a bit of a pain because the standard model's already broken since we *know* neutrinos have to have mass and fudging the standard model to put them in is pretty contrived.
However, not finding a Higg's at all would be brilliant -- so strictly speaking, the LHC finding *nothing at all* would be good. Because the Higg's should be within its capabilities and if it's not there there'll be a lot of head-scratching going on, and I always prefer things being rethought and reanalysed over mindlessly employing techniques chiefly developed in the 40s with QED and brought to fruition in the 70s with QCD and the electroweak theory.
But, in all fairness, I'm not a particle physicist, I'm a cosmologist.