The hypothetical quantum black holes, which are miniscule objects that could form for a fleeting instant and provide insights into one of the most pressing challenges in today’s physics, are still being sought at the Large Hadron Collider (LHC). The result itself, which was just published, confirms that there are no quantum black holes, but the findings also allow scientists to exclude some theoretical possibilities and enhance future attempts to find new physics, the researchers said.
What is a Quantum Black Hole?
The kind of black holes that most people are familiar with are very large objects, created by the collapse of the gravity of a large star. Quantum black holes, however, would be very different. They are imagined tiny objects that, according to some theories, vanish within a fraction of a second after they are born and are smaller than an atomic-sized particle.
The significance of this is because they might touch both gravity and quantum physics. General relativity is the best theory for gravity and large objects, and quantum physics is the best theory for matter and forces at the smallest scales. These two combined into a full theory is one of the big problems in physics.
If there are any extra dimensions of space, scientists have suggested quantum black holes might also come into existence in high-energy particle collisions. These ideas are not in the standard model, which is the theory that describes the known elementary particles and their interactions.
How the LHC Looks for Them
At CERN, the LHC is a machine designed to produce very high energy particle collisions that destroy protons. There is no room for a small black hole to just sit in the detector because if one was created under some of the theories being tested, it would vanish almost immediately.
Rather, researchers look for the particles and energy that might be emitted when it breaks down.
Analysis of the latest data was performed with the Compact Muon Solenoid (CMS) detector which collected data in proton-proton collisions. The researchers searched for unusual events with a lot of energy and unusual patterns of energy that might resemble what’s expected of microscopic black holes.
An important property is called sphericity. In this scenario, the microscopic black hole that is rapidly disappearing would be able to emit particles in a multitude of directions, leaving a more spherical signature in the detector.
A new phase-space distance method was also employed with a machine-learning method known as a Support Vector Machine, which was supervised. It is an approach that allows the identification of possible signal events among the vast number of “background” collisions of particles. In the analysis the researchers said the phase-space method was superior to the traditional sphericity measure.
No Evidence of Quantum Black Holes Was Found
No evidence of quantum black holes resulting from the analysed collisions was found.
This does not imply that the experiment was a failure. A null result in particle physics can be a significant constraint on which types of particles or phenomena might occur in a specific circumstance.
The CMS analysis put more stringent limits on some of the microscopic black hole models and the extra dimensions models. The published CMS data did not include semiclassical black holes that are sub 8.4 to 11.4 tera-electron-volts, depending on the model and number of extra dimensions.
Scientists participating in the project call this the “funny way to slim down the choices.” Rather than find the particle, the experiment can rule out regions in which it might be found.
But Why Are They So Important?So, Why Are Extra Dimensions Important?
Some models feature additional dimensions which are also central to their predictions of quantum black holes at collider energies. There are several ideas that have been proposed to explain the difference in the strength of gravity, relative to the other fundamental forces, and how gravity may act differently at very small distances that may be due to the existence of a lot more dimensions than we already know.
The LHC can examine gorgeous, really small distance scales, as improved high-energy collisions will allow scientists to study shorter wavelengths. Microscopic black holes are a theoretical possibility that, if they were to exist, would disintegrate very quickly into more common particles, according to CMS.
The new results, therefore, do not rule out all models, but rather rule out some of them.
New Physics is being searched for Continued.
But without quantum black holes, there are a number of big questions left unanswered. A complete theory that combines the theories of quantum mechanics and general relativity has yet to be developed by physicists.
The new study is still helpful, though, on the grounds that it brings an approach to search that might be applicable to some other phenomena as well as black holes. Using the phase-space approach, researchers can find unusual particle events and look at theoretical phenomena.
The CMS collaboration is also still working on the data from the LHC. Theories that are not yet confirmed or discarded will be tested again in the future in more depth, such as with future measurements from the High-Luminosity LHC.
At the present time, quantum black holes are only a theoretical entity. However, each search will reduce the number of options available. Experiments at the LHC are still probing physics in a new realm, whether it is the discovery of a new particle, the discovery of an unexpected interaction, or a whole new field of thinking about the nature of space-time.