After a short spell on the rocks, a mathematically elegant view of the universe is back in vogue. Recent hints of the Higgs boson at the Large Hadron Collider help explain why we have not seen evidence for the beautiful theory of supersymmetry yet – and point to fresh ways to focus the search.
Supersymmetry, or SUSY, is an extension to the standard model of how particles and forces interact. Via elegant equations, it posits that every fundamental particle – including quarks, electrons, photons and neutrinos – has a heavier, as yet unseen “superpartner” with slightly different properties (see diagram). This smooths some embarrassing wrinkles in the standard model. However, not one superpartner has yet shown up at the LHC, the particle smasher at CERN near Geneva, Switzerland, prompting fears that, despite its beauty, SUSY could be wrong.
That changed on 13 December, when LHC physicists reported that they might have found traces of the Higgs boson, the standard-model particle that is thought to give all others mass. The data suggested a mass for the Higgs close to 125 gigaelectronvolts, 133 times that of the proton and too light for a Higgs to survive without a heavier companion particle, which could be a superpartner.
“This is very good news for people who believe in supersymmetry,” says Howard Baer of the University of Oklahoma in Norman. He’s one of several researchers who have calculated what the suspected Higgs mass could mean for SUSY particle, or sparticle, detections at the LHC.
Baer reckons it can explain why sparticles have not yet been seen. Particles get their masses by interacting with the Higgs field; the stronger the interaction, the heavier the particle. So if the Higgs is confirmed at 125 GeV, which is heavy for SUSY models, many superpartners must be on the heavy side too. Baer and colleagues calculated that in several different versions of SUSY, a 125-GeV Higgs means squarks (the SUSY version of quarks) and sleptons (SUSY versions of electrons and neutrinos) must weigh 10,000 GeV or more, far too heavy for the LHC’s detectors to find