Broaden the search for dark matter
Mario Livio& Joe Silk
Dark matter is living up to its name. In spite of decades of compelling evidence from astronomical observations showing the existence of matter that neither emits nor absorbs electromagnetic radiation, all attempts to detect dark matter's constituents have failed.
The presence of dark matter is inferred from its gravitational effects. Stars and gas clouds in galaxies and galaxies in clusters move faster than can be explained by the pull of visible matter alone. Light from distant objects may be distorted by the gravity of intervening dark material. The pattern of large-scale structures across the Universe is largely dictated by dark matter. In fact, about 85% of the Universe's mass is dark, accounting for about one-quarter of the total cosmic energy budget.
Despite its ubiquity, the nature of dark matter eludes us. Negative results have flowed from searches for candidate particles to explain it. In 2013, the Large Underground Xenon (LUX) experiment — the most sensitive detector of its kind — in the Homestake Mine in Lead, South Dakota, reported no signs of dark matter in its first three months of operation1. The Large Hadron Collider (LHC) at CERN, Europe's particle-physics laboratory near Geneva, Switzerland, has found no evidence for the existence of what some think are the most likely culprits: supersymmetric particles, theoretically predicted partners to the known elementary particles.
Is there light at the end of this dark tunnel? Possibly — but only if searches become bolder and broader. More varied particle types should be sought. Definitive tests need to be devised to rule out some classes of dark matter and some theories. If dark matter remains undiscovered in the next decade, then physicists will have to seriously reconsider alternative theories of gravity.
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http://www.nature.com/news/physics-broaden-the-search-for-dark-matter-1.14795
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