Virginia Tech researchers are partners in long-standing international research projects that have brought the world closer to understanding the sun and the mysterious subatomic particles called neutrinos. Meanwhile, in an underground laboratory near the university’s campus, physics researchers in the College of Science are initiating new neutrino studies.
“Each of these experiments is at the crest of the advancing wave in neutrino science and will directly impact particle physics, stellar astrophysics, and cosmology for years to come,” says Raju Raghavan, a long-time international neutrino researcher who arrived at Virginia Tech in 2004 as professor of physics and director of Virginia Tech's Institute of Particle, Nuclear, and Astronomical Sciences.
“Discoveries in this area of science can potentially lead to a better understanding of the origins of the earth, sun, and stars,” says Bruce Vogelaar, professor of physics and also a veteran neutrino researcher on the world scene.
Neutrinos are among the fundamental particles of the universe. They are tiny, nearly massless, uncharged particles. Neutrinos originate from many sources: the center of the sun, the interior of the earth, and from terrestrial accelerators and nuclear reactors.
Neutrino experiments conducted by the Virginia Tech group look at all these sources with different objectives for particle physics, astrophysics, and cosmology.
“Neutrinos are kind of funny,” says Jonathan Link, assistant professor of physics who has recently joined Virginia Tech’s neutrino team. “I would compare them to a place kicker in football. You don’t see them very often but their role is critically important. Indeed, neutrinos played a central role in the big bang theory of how the world came into existence and, as the universe aged, helped to form the elements.”
Virginia Tech researchers were participants in important research announced in 2007 regarding the findings of a path-breaking neutrino experiment called Borexino, in which Raghavan and Vogelaar have been active for more than a decade. For the first time, Borexino attacked the problem of detecting low-energy neutrinos — for example, those emitted by the sun.
The Borexino collaboration consists of more than 100 scientists from Virginia Tech, Princeton University, and groups from Italy, France, Germany, Russia, and Poland. The 20-year project was funded in part by the National Science Foundation. In this collaboration, researchers observed tell-tale signals of neutrinos emitted by thermonuclear fusion reactions that power the sun. Deep within the sun’s interior, at approximately 15 million degrees, protons and light elements fuse in a series of reactions that convert hydrogen into helium and release about 25 million times more energy per gram than TNT, oil, or coal.
Now a new project to study particles from the sun has been created just minutes from Virginia Tech under a Southwest Virginia mountain. “The Kimballton Underground Research Facility provides shielding from cosmic rays, large cavern size, and easy access, features coveted by the physics community to develop next generation detectors to answer fundamental questions about our universe,” says Vogelaar.
The energy of the sun is predominantly due to the basic thermonuclear fusion of two protons, or hydrogen nuclei, by far the largest components of the sun. This solar reaction can be detected on Earth by the neutrinos that it emits, the so-called proton-proton neutrinos. Detecting them has been a holy grail of physics for 50 years, but it is extremely difficult because of their very low energy, even lower than the neutrinos observed by Borexino.
Raghavan invented the first method to attack the problem of detecting proton-proton neutrinos directly, and he developed a series of technical innovations crucial for its feasibility. This experiment is now called low-energy neutrino spectroscopy (LENS); but the experiment will not only observe the proton-proton neutrinos, it will also measure the entire low-energy solar neutrino spectrum with high accuracy.
Vogelaar, director of the Kimballton research facility, emphasizes Kimballton will be a unique and powerful resource, not only for low energy neutrino spectroscopy and other university experiments, but also for a national and international community of researchers. Kimballton adds a major new dimension to Virginia Tech’s research in experimental neutrino science — a box seat for observing our universe with “neutrino” eyes, helping fulfill part of the vision members of Virginia Tech’s neutrino research group have had for many years.
The Kimballton Underground Research Facility at Virginia Tech is drawing researchers from around the world for development of extremely low-background detectors to address some of the most important questions in physics today.
By being deep underground, the facility avoids background noise from cosmic rays and, through local shielding, avoids radiation from the limestone rock itself.
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