Neutrinos are nearly massless elementary particles that interact extremely weakly with matter. As you read this sentence, trillions of neutrinos are streaming through your body at nearly the speed of light, yet you don't feel a thing. It has been said that a neutrino could easily pass through light years of lead before disturbing even one atom - quite the feat for a particle that may hold the key to understanding the dearth of antimatter in our Universe! Not only are these subatomic speed ninjas extremely difficult to detect, but they actually possess a kind of quantum mechanical ADD as well. Neutrinos are known to spontaneously change between three distinct types, or flavors, during the course of their travels. Two of these so-called flavor oscillations have already been observed, leaving just one unaccounted for... until now.
Just a few days ago, scientists from the T2K experiment in Japan released data that suggests they may have witnessed the third flavor oscillation. At the T2K experiment, a beam of muon neutrinos is isolated from a proton stream at J-PARC in Tokai, and sent to the Super-Kamiokande detector in Kamioka, 295 kilometers away. The goal of the experiment is to see how many muon neutrinos change into electrons neutrinos along the way by detecting the number of electron events at the far detector. In an experiment of this nature, approximately 1.5 electron events that have nothing to do with neutrino flavor oscillations are to be expected. But when the background noise and other rogue neutrino events were filtered out of the data, 6 solid events remained: 6 events that suggest the appearance of electron neutrinos with 99.3% confidence, a 2.5 sigma result.
Due to the earthquake that struck Japan back in March, the T2K experiment has only been able to gather 2% of the total data it was designed to. So with 98% of the data still forthcoming, a 2.5 sigma is a pretty promising result. Physicists are hoping that understanding this last flavor oscillation will allow them to probe the differences between neutrinos and their anti-particles, anti-neutrinos. If the mechanism of flavor oscillation differs between the two sets, it may lead scientists to a better understanding of CP violation, the phenomenon believed to be responsible for the abundance of matter over anti-matter in our universe.
Showing posts with label neutrino. Show all posts
Showing posts with label neutrino. Show all posts
Saturday, June 18, 2011
Tuesday, November 9, 2010
Talking weak sauce at the NASW luncheon.
It was almost like kindergarden. One by one, decked out with our nametags and matching knapsacks, each of us chose a boxed lunch and filed into the classroom. There we sat, in a circle, waiting for the woman whose job it was that day to teach us something new. But when Dr. Bonnie Fleming of Yale University arrived, it wasn't a group of five year olds that she stood before; instead, it was a small group of science journalists from around the country, all gathered there to eat, relax, and listen to the latest news in neutrino physics.
"Neutrino physics is a field with many great stories," Fleming began. She then went on to explain that one of the most well-known of these stories is that of flavor oscillation. As it turns out, neutrinos have a sort of quantum mechanical ADD. Rather than sticking with one identity, neutrinos tend to change states spontaneously over the course of their travels. An electron neutrino may suddenly become a tau neutrino, and then a muon neutrino, and then a tau neutrino once more long before you or I have had the chance to ask, "what the- ?"
Regardless of flavor, however, all neutrinos have been said to interact via the same fundamental force: the weak force. As we sat dutifully munching on our sandwiches, Dr. Fleming invited each of us to lay one of our palms on the table and count to three. During that short time, she explained, over a trillion neutrinos had passed through every one of our outstretched hands. Indeed, a neutrino could pass straight through 200 Earths before having any appreciative chance of hitting anything. Physicists call it the "weak" force for a reason.
However, new research at Fermilab has suggested that there may be a fourth, even lazier type of neutrino - one that, unlike its electron, muon and tau counterparts, interacts via the gravitational force rather than the weak force. Perhaps surprisingly, gravity is actually the weakest of the four fundamental forces. If you're not convinced, just rub a balloon against your hair, stick it to the wall, and rest easily in the knowledge that you have just overcome the gravitational influence of the entire planet. Gravity's unbelievable frailty would make directly detecting the alleged new flavor of neutrino, dubbed the sterile neutrino, one of the most daunting tasks yet undertaken by the particle physics community. As it is, neutrinos are notoriously difficult to pin down. "We can only detect their flavor by whatever charged lepton they turn into," said Fleming.
As if neutrinos weren't hard enough to wrap your head around. Rather than exhaust myself by asking any more questions, I just sat there, ate my cookie, and let Dr. Fleming do rest of the talking.
"Neutrino physics is a field with many great stories," Fleming began. She then went on to explain that one of the most well-known of these stories is that of flavor oscillation. As it turns out, neutrinos have a sort of quantum mechanical ADD. Rather than sticking with one identity, neutrinos tend to change states spontaneously over the course of their travels. An electron neutrino may suddenly become a tau neutrino, and then a muon neutrino, and then a tau neutrino once more long before you or I have had the chance to ask, "what the- ?"
Regardless of flavor, however, all neutrinos have been said to interact via the same fundamental force: the weak force. As we sat dutifully munching on our sandwiches, Dr. Fleming invited each of us to lay one of our palms on the table and count to three. During that short time, she explained, over a trillion neutrinos had passed through every one of our outstretched hands. Indeed, a neutrino could pass straight through 200 Earths before having any appreciative chance of hitting anything. Physicists call it the "weak" force for a reason.
However, new research at Fermilab has suggested that there may be a fourth, even lazier type of neutrino - one that, unlike its electron, muon and tau counterparts, interacts via the gravitational force rather than the weak force. Perhaps surprisingly, gravity is actually the weakest of the four fundamental forces. If you're not convinced, just rub a balloon against your hair, stick it to the wall, and rest easily in the knowledge that you have just overcome the gravitational influence of the entire planet. Gravity's unbelievable frailty would make directly detecting the alleged new flavor of neutrino, dubbed the sterile neutrino, one of the most daunting tasks yet undertaken by the particle physics community. As it is, neutrinos are notoriously difficult to pin down. "We can only detect their flavor by whatever charged lepton they turn into," said Fleming.
As if neutrinos weren't hard enough to wrap your head around. Rather than exhaust myself by asking any more questions, I just sat there, ate my cookie, and let Dr. Fleming do rest of the talking.
Tuesday, August 31, 2010
Peer pressure: radioactive decay succumbs to sun's infuence.
The sun is getting full of itself. Apparently, transitioning into the active phase of its 11-year cycle, throwing off solar flares, and giving rise to sensational aurorae are not enough. Now, new research suggests that our star might also be messing around with radioactivity here on Earth. According to a team composed of scientists from Stanford and Purdue Universities, radioactive isotopes like silicon-32 and chlorine-36 decay at slightly different rates, depending on where the sun's core is in its rotation.
Image courtesy of NASA/Goddard.
The researchers found that decay rates changed by about 0.1% over the course of a recurring 33-day cycle. These measurements fit current theoretical models of the sun's inner rotation quite well. Interestingly enough, they also coincide with the occurrence of solar flares and correlate with the earth's yearly orbit around the sun. "Finding that the decay rates fluctuate in a pattern that matches known and theoretical solar frequencies is compelling evidence for a solar influence on decay rates," said Jere Jenkins of Purdue University, a lead engineer on the team.
The main suspect in this emerging investigation is the solar neutrino. Neutrinos are (nearly) massless, electrically neutral elementary particles that are only subject to the weak force; they can therefore travel extremely long distances without interacting with anything at all. Every second, the earth is pummeled with an innumerable amount of solar neutrinos. In fact, 65 billion neutrinos will pass though every square centimeter of your body in the time it takes you to read the word "radioactivity."
The first recorded evidence of a neutrino. A proton, muon, and pi-meson (right) leave diverging tracks that result from a single neutrino striking the chamber.
Image courtesy of Argonne National Laboratory.
So, if neutrinos don't interact with anything, how could they cause such changes in the decay of radioactive isotopes? Researchers don't really have an answer to that question. Jenkins' words say it best: "What we're suggesting is that something that can't interact with anything is changing something that can't be changed." However, if the team's data does turn out to be accurate, it could have broad implications. Scientists could use changing decay rates to predict and prevent the power outages and technological malfunctions that often accompany solar flares. Variable decay rates could also affect both archeological carbon dating and medical radiation treatments. Thanks to allegedly inert neutrinos, the sun's 11-year cycle might do more than just put on pretty light shows.
Image courtesy of NASA/Goddard.
The researchers found that decay rates changed by about 0.1% over the course of a recurring 33-day cycle. These measurements fit current theoretical models of the sun's inner rotation quite well. Interestingly enough, they also coincide with the occurrence of solar flares and correlate with the earth's yearly orbit around the sun. "Finding that the decay rates fluctuate in a pattern that matches known and theoretical solar frequencies is compelling evidence for a solar influence on decay rates," said Jere Jenkins of Purdue University, a lead engineer on the team.
The main suspect in this emerging investigation is the solar neutrino. Neutrinos are (nearly) massless, electrically neutral elementary particles that are only subject to the weak force; they can therefore travel extremely long distances without interacting with anything at all. Every second, the earth is pummeled with an innumerable amount of solar neutrinos. In fact, 65 billion neutrinos will pass though every square centimeter of your body in the time it takes you to read the word "radioactivity."
The first recorded evidence of a neutrino. A proton, muon, and pi-meson (right) leave diverging tracks that result from a single neutrino striking the chamber.
Image courtesy of Argonne National Laboratory.
So, if neutrinos don't interact with anything, how could they cause such changes in the decay of radioactive isotopes? Researchers don't really have an answer to that question. Jenkins' words say it best: "What we're suggesting is that something that can't interact with anything is changing something that can't be changed." However, if the team's data does turn out to be accurate, it could have broad implications. Scientists could use changing decay rates to predict and prevent the power outages and technological malfunctions that often accompany solar flares. Variable decay rates could also affect both archeological carbon dating and medical radiation treatments. Thanks to allegedly inert neutrinos, the sun's 11-year cycle might do more than just put on pretty light shows.
Subscribe to:
Posts (Atom)