This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Physicists at UC Santa Barbara have extended the search for evidence of microscopic black holes produced at the Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN). The formation of these tiny, fleeting objects at the LHC represents one way theorists have sought to resolve anomalies in our understanding of the basic structure of spacetime, while the method used to look for them demonstrates a new way of searching for new particles.
"Had we found evidence, we could have begun to directly study quantum gravity," said Tamas Vami, a researcher in the Compact Muon Solenoid (CMS) experiment who is conducting his postdoctoral work under the guidance of UCSB physics professor Joe Incandela. "It's a step toward unifying all of the known fundamental forces, which has been a goal of physicists for more than a century." But a null result does not make for a fruitless search, said Incandela Lab graduate student researcher Danyi Zhang. "It's not a dead end," she said.
"The result is an exclusion limit, which is a real, publishable statement: 'If this thing existed with these properties, we'd have seen it. We didn't, so we can rule it out here.' That's genuine knowledge about how the universe works." One of the mysteries of our universe is that we exist at a scale much lower than the one fundamental energy scale we know of, the Planck scale. This could be explained by new physics or a symmetry we have yet to detect, and theorists have determined that this new physics could appear at the energy scales accessible to the LHC.
Many new theoretical possibilities and experimental searches have excluded a large space of possibilities; the fact that no new physics has been seen at the LHC has created a real conundrum for fundamental physics. However, analogous situations have occurred before and have led to completely new paradigms, such as Einstein's relativity. In this context, the researchers said, null results are an important part of the record and serve to guide future ideas and experimental searches.
Vami's and Zhang's results are published in the journal Progress in High Energy Physics. The notion of black holes at the LHC began a couple of decades ago, when it was suggested that at high enough energies, and with the possibility of extra spatial dimensions (which are already required in string theory), quantum black holes could potentially form among the trillions of proton-proton collisions generated by the LHC particle accelerator. "They wouldn't stick around very long—if you made one, it would disintegrate immediately," said UCSB physics theorist Steven Giddings, an expert in the paradoxical implications of combining quantum mechanics with gravity and one of a few scientists at the time who proposed that under certain conditions these tiny voids in spacetime could exist.
The fact that these microscopic quantum black holes would evaporate instantly was then misunderstood in the popular imagination, which latched onto news of potential stable black holes at the LHC and ran with it. "People were more focused on the classical behavior of black holes," said Giddings, referring to those massive voids in spacetime, areas of extreme gravity that can eat whole stars, grow and merge. These LHC black holes would be the result of proton-proton collisions and as-yet-undiscovered extra dimensions.
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