After an exhausting year of investigation, a team of scientists has come up empty on trying to find a mysterious and ghostly particle called the sterile neutrino. The research is one of the latest attempts on the search for the strange particle.

Researchers from 40 different institutions including MIT and the University of Wisconsin, had been working for over a year at the IceCube Neutrino Observatory located in the South Pole. The primary goal of the investigation was to find or notice the presence of a sterile neutrino among the 20,000 neutrinos within the study, yet the research came out empty-handed.

The IceCube laboratory at the Scott Amundsen South Pole station is dedicated to find the evasive neutrino particle. Image Credit: Huffington Post
The IceCube Laboratory at the Scott-Amundsen South Pole Station is dedicated to finding the evasive neutrino particle. Image Credit: Huffington Post

The search for this ‘hidden’ particle has kept scientists busy for the last decade. However, investigations at the Scott-Amundsen Station in the South Pole continue to lead researchers to a dead end. Although time has helped science by providing different theories and perspectives of the sterile neutrino mystery, not major breakthroughs have come in the area.

Understanding neutrinos and the ghostly particle that could explain dark matter

Neutrinos are part of the fundamental particles in the universe, yet science has had a hard time understanding them, for which they are currently the particles with less information.

These particles are, in a way, similar to electrons but with the small difference that they do not carry an electric charge and electromagnetic forces don’t affect them. Making them able to travel without being noticed and to pass through matter without having any effect on it. Unlike many other particles, neutrinos are only impacted by weaker forces that do not include electromagnetism. There are four ‘flavors’ of neutrinos known in the science world, the electron, muon, and tau which all stand for Greek letters.

Thanks to the small interaction neutrinos have with matter, they can travel without being detected. According to scientists, billions of these particles pass through every human body on Earth every minute without being noticed, yet science was able to understand them because they have a weak nuclear interaction.

The three known particles are all related to a form of electrons in lighter and heavier versions. For a long time, scientists have debated the possibility of a fourth type of neutrino that doesn’t fit the technical chart of the currently known particles.

Detailed information about the search for neutrino particles inside (or below) the IceCube Lab. Image Credit: WISC.
Detailed information about the search for neutrino particles inside (or below) the IceCube Lab. Image Credit: WISC.

This hypothetical particle doesn’t interact with matter, nor scientists or physicists can detect them, but it is believed the sterile neutrino might interact with gravity. For a long time, the sterile neutrino has been labeled as the mystery-solving particle. That could help science understand the world behind the dark matter of the universe and the asymmetry between matter and antimatter in the Universe.

Since neutrinos have the possibility to change from one flavor to another, scientists have theorized about the chance of catching a tau neutrino, for example, transforming into a sterile neutrino.

That’s why researchers at the IceCube Neutrino Observatory decided to perform a year-long experiment to find the missing particle. Scientists used the Antartic laboratory and its kilometer-long particle detector, which is buried deep in the soil of the South Pole.

Around 5,000 light sensors are embedded into the ground and are suspended by 86 strings that go 2,450 meters deep inside of the floor. According to MIT, the size of the particle detector is equivalent to the vertical distance of five Empire State Buildings.

Researchers can detect neutrinos when they pass through ice since they produce an electrical charge and the 5,000 light sensors turn on. This way, scientists can determine the amount of neutrinos passing through. The team of scientists has to separate the neutrino particle from all of the other particles, to determine then the energy and the number of neutrinos passing through, which is not an easy process.

During the investigation, researchers developed a model that could predict the number of neutrinos they would see inside the observatory if there was an absence of sterile neutrinos.

The predicted numbers matched the final results, which means no sterile neutrino was caught in the process of converting to another form of neutrinos or vice-versa. The news is a bitter consequence of the science world and to the hopes of resolving the dark matter mystery.

“We had a very good chance of seeing these particles, but they just weren’t there. This has made the case for sterile neutrinos weaker,”  says MIT graduate student Gabriel Collin, in a statement to MIT news.

Previous research had already denied the possibility of sterile neutrinos existing or at least being detected, in 2007 an experiment denied seeing any activity or proof of the particles.

Most recently, as reported by the New Scientist, in 2010 another experiment was able to find evidence of the evasive particle which inspired more experiments to look for the mysterious sterile neutrino.

Even though the investigation held by the IceCube Neutrino Observatory failed to see the particle, there’s still more data to analyze that could provide information and even prove the existence of the sterile neutrino, in the future.

Source: MIT