Just over ten years ago, NASA-affiliated researchers set out to observe cosmic rays showering down on Earth from above. During the experiments in Antarctica, physicists found something unexplainable, something that could change everything we think we know about physics.
The Antarctic Impulsive Transient Antenna (ANITA) balloon experiment began in 2006 when the balloon spent a month hovering over Antarctica’s ice. Using sensors, ANITA began detecting high energy neutrinos interacting with the ice sheet below.
Neutrinos are unique in that they don’t lose energy as they disseminate throughout the universe. Because of this, neutrinos are capable of providing humans with a peek into the vast expanse of the universe that would otherwise be unavailable.
According to Motherboard, the Soviet physicist Gurgen Askaryan once theorized that “when a high energy particle interacted with a dense dielectric medium - a type of insulating material that doesn’t conduct electricity - it would produce a shower of secondary charged particles whose radiation can be detected by standard radio antennas. This interaction, now known as the Askaryan effect, allows physicists to detect particles that hardly interact with normal matter (like neutrinos) by observing their secondary effects.”
During ANITA’s time in the Antarctic, it detected never before seen “upward-pointing cosmic-ray-like events.” The rays detected had horizontal planes of polarization, which may suggest they didn’t originate in space. The detection of these events means a new type of particle may have been evading detection by sophisticated particle accelerators since we began using sophisticated particle accelerators.
Thanks to the Standard Model, physicists have known that cosmic rays are capable of reaching and penetrating Earth. However, according to the model, those rays shouldn’t be able to pass all the way through our planet. So are the anomalous high energy particles measured by ANITA originating from Earth, or are they actually passing through it?
Some existing physics models that exist beyond the Standard Model involve theories that the interactions between cosmic rays and ice actually produce micro black holes that open into small dimensions. ANITA’s first mission didn’t detect the black holes, but it did detect the Askaryan effect.
Last week, a group of researchers posted a new theory about the rays measured by ANITA. The group, led by Pennsylvania State University physicist Derek Fox, suggests ANITA may have found evidence of a particle that lies completely outside of the Standard Model of physics.
The Standard Model has been successful as long as we’ve been using it, but it hasn’t been able to explain everything. For example, things like gravity and the accelerating expansion of the universe are not adequately explained by the model. That’s where the physics beyond the Standard Model (BSM). Some of those theories include string theory and extra dimensions.
Fox’s theory relies on a type of BSM called supersymmetry. “We argue that if the ANITA events are correctly interpreted then they require some beyond the Standard Model particle,” Fox told Motherboard. “The likely properties of the particle seem consistent in at least some ways with the predicted properties of the stau in some supersymmetric models.”
In order to delve further into the unknown when it comes to these upward-pointing cosmic rays, they must also be observed at other locations. Fox and his colleagues took the first step when analyzing data from the IceCube Neutrino Observatory in the Arctic. Despite the difference in detection systems, three events were identified in the data that were analogous to the cosmic rays observed by ANITA in Antarctica.
Fox’s theory is only one interpretation of the ANITA data. The fourth ANITA mission was launched in 2016 and researchers are hopeful that its data, once completely analyzed, will reveal additional examples of these unusual cosmic rays.