 |
Neutrinos: Ghostly particles with unstable egos
September 06, 2011They were always mysterious. 26 years had to pass before the prediction of theoretical physics was confirmed and the existence of neutrinos was finally proven experimentally in 1956. The reason for this ordeal: Neutrinos only interact by the weak interaction with other particles of matter. When a cosmic neutrino approaches the earth, it has the best chance of passing through the whole globe unhindered. It is correspondingly difficult to find direct evidence of neutrinos with the help of a detector. Further decades passed in the discussion about their masses: None or small but finite mass? In the meantime it is considered certain that the ghostly particles are carrying mass, if only a virtually infinitesimal amount: According to today's knowledge, no neutrino should exist that is heavier than 1 eV (an electron "weighs" about 500,000 eV!). There are three types of neutrinos. This is also believed to be true today, so that neutrinos can each easily be classified in one of the three particle families in the framework of the standard model.
The knowledge of the neutrino mass is based on numerous experiments, in which so-called neutrino oscillations were observed. Neutrinos freely flying through the space of a particular family (i.e. the electron neutrino) can transform themselves spontaneously into a neutrino of another family affiliation (the muon neutrino or tau neutrino). One refers to an oscillation because the neutrino may change its family affiliation periodically during an extended journey. Such oscillations are only possible if the particles are carrying mass. The experimental evidence of neutrino oscillations (and thus a neutrino mass other than zero) is among the greatest breakthroughs of modern particle physics in the past 20 years.
The conversion process among different neutrino flavors depends on three so-called mixing angles Theta 12, Theta 23 and Theta 13. In interplay with the neutrino mass-squared differences they regulate the transition probabilities among different flavors. Of the three mixing angles only two are well known and have large values, while the third one Theta 13 is at the focus of current searches. So far, it was known that its value had to be small compared to the other two neutrino mixing angles. That is, Theta 13 = 0 could not be excluded. In the past, several independent projects have tried to measure this elusive parameter without success. The most important piece of information came in 1998 from the Chooz experiment in France, which established that the oscillation evoked by Theta 13 cannot be larger than approximately one tenth of those induced by the each of the other two neutrino mixing angles.
Three years ago a group of theoretical physicists of whom one, Antonio Palazzo, is now at the Excellence Cluster Universe, the others at the University and INFN of Bari, evidenced for the first time a weak hint of non-zero Theta 13 thanks to an accurate work of global analysis of all the existing neutrino oscillation data. In the meantime, two accelerator experiments (MINOS and T2K) were at work to nailing down Theta 13 and they have recently released their results. Notably, both experiments point towards a non-zero Theta 13, in agreement with the hint evidenced by the group of theorists. By combining their previous findings with the new accelerator data, in June 2011 the same group came for the first time to a statistically clear conclusion according to which sin² Theta 13 ≈ 0.02 with a confidence level of at least 3 Sigma. This means that the odds against Theta 13 > zero are 1:400.
However, physicists are very prudent and, before claiming a discovery, need to have a higher confidence level of 5 Sigma, diminishing the odds against Theta 13 > zero to 1:1 million. In order to provide secure evidence, the researchers are performing other experiments. Among these, the reactor experiment Double-Chooz, in which physicists of the Universe Clusters are strongly involved, will have a crucial role. For this purpose, it has been developed a particularly effective, terrestrial neutrino source: The particles (more precisely: anti-neutrinos) are generated and emitted during the fission processes in a nuclear power plant in particularly high flux. About 1020 antineutrinos leave a typical reactor every second. For this reason, a new experiment, the inheritor of the forerunning Chooz experiment, has started in the vicinity of the nuclear power plant in the French municipality Chooz. Thanks to this setup the value of Theta 13 will be measured with a precision that hitherto has not been achieved.
The principle behind the Double-Chooz experiment is very simple: Immediately after their generation in the reactor, several anti-neutrinos collide with a detector located 400 meters away. The spatial proximity ensures that no oscillations (or only extremely few) occur between emission and initial detection. The first detector thus measures the electron anti-neutrinos, which haven't transformed to muon and or tau neutrinos yet. A second detector of identical construction is located approximately 1,050 meters away from the reactor. If the value of the neutrino mixing angle Theta 13 is large enough, a part of the electron anti-neutrinos will become muon or tau anti-neutrinos as a result of the oscillations. The electron-anti-neutrino rate observed at the second detector therefore is much smaller than expected without oscillations.
Both detectors are filled with about 10 tons of scintillation fluid. If an electron-anti-neutrino interacts with a proton within the fluid, this will lead to inverse-beta decay: The proton captures the electron-anti-neutrino thereby transforming into one neutron by emitting one positron. Both particles generate one quick flash each in the liquid in a set time sequence. 390 photo sensors mounted on the walls of the vessel record the events. The Double Chooz experiment started physics data taking in April 2011 and will search for corresponding signals for five years. The detector performance and the status of data taking will be reported at the TAUP conference in Munich from 5 to 9 September 2011. First results are expected by the end of this year.
Establishing that Theta 13 is effectively different from zero would entail that all the three mixing angles are non-vanishing. This would provide the three neutrino flavors with maximal freedom of flipping one to each other. In turn, such a high degree of freedom is the necessary condition to generate CP-violation in the leptonic sector, i.e. to give rise to a different behavior of neutrinos and anti-neutrinos. The observation of CP-violation is now the next target of neutrino physicists as it would have significant consequences for several unanswered questions of modern physics. It could soon be clarified, in particular, whether neutrinos were responsible for the minimal surplus of matter compared to anti-matter in the early Universe. Without this asymmetry, all matter would have been transformed to radiation shortly after the birth of the Universe. There would be no galaxies, no stars or planets and no one who could measure Theta 13.
Technische Universitaet Muenchen
Related Neutrino Current Events and Neutrino News Articles
Dynamic, dark energy in an accelerating universe
It was cosmology that drew Irene Sendra from Valencia to the Basque Country. Cosmology alsogave her the chance to collaborate with one of the winners of the 2011 Nobel Prize for Physics on one of the darkest areas of the universe.
12 Matter Particles Suffice in Nature
How many matter particles exist in nature? Particle physicists have been dealing with this question for a long time. The 12 matter particles contained in the standard model of particle physics?
Huddersfield physicist join global partners for an investigation of the Big Bang particle
SCIENTISTS at the University of Huddersfield are collaborating with experts at some of the world's leading research institutes in an attempt to unravel the mysteries of a particle that played a role in the creation of the universe.
Crews complete first block of North America's most advanced neutrino experiment
Today, technicians in Minnesota will begin to position the first block of a detector that will be part of the largest, most advanced neutrino experiment in North America.
In neutrino-less double-beta decay search, UMass Amherst physicists excel
Physicists Andrea Pocar and Krishna Kumar of the University of Massachusetts Amherst, part of an international research team, recently reported results of an experiment conducted at the Enriched Xenon Observatory (EXO), located in a salt mine one-half mile under Carlsbad, New Mexico, part of a decades-long search for evidence of the elusive neutrino-less double-beta decay of Xenon-136.
Peering into the heart of a supernova
Each century, about two massive stars in our own galaxy explode, producing magnificent supernovae. These stellar explosions send fundamental, uncharged particles called neutrinos streaming our way and generate ripples called gravitational waves in the fabric of space-time.
Tevatron scientists announce their final results on the Higgs particle
After more than 10 years of gathering and analyzing data produced by the U.S. Department of Energy's Tevatron collider, scientists from the CDF and DZero collaborations have found their strongest indication to date for the long-sought Higgs particle.
Tin-100, a doubly magic nucleus
Stable tin, as we know it, comprises 112 nuclear particles - 50 protons and 632 neutrons.
Underground search for neutrino properties unveils first results
Scientists studying neutrinos have found with the highest degree of sensitivity yet that these mysterious particles behave like other elementary particles at the quantum level.
Physicists close in on a rare particle-decay process
In the biggest result of its kind in more than ten years, physicists have made the most sensitive measurements yet in a decades-long hunt for a hypothetical and rare process involving the radioactive decay of atomic nuclei.
More Neutrino Current Events and Neutrino News Articles
 |
Neutrino by Frank Close (Author) Neutrinos are perhaps the most enigmatic particles in the universe. These tiny, ghostly particles are formed by the billions in stars and pass through us constantly, unseen, at almost the speed of light. Yet half a century after their discovery, we still know less about them than all the other varieties of matter that have ever been seen. In this engaging, concise volume, renowned scientist and writer Frank Close gives a vivid account of the discovery of neutrinos and our growing understanding of their significance, touching on speculative ideas concerning the possible uses of neutrinos and their role in the early universe along the way. Close begins with the discovery of radioactivity by Henri Becquerel and Marie and Pierre Curie, the early model of the atom by Ernest... |
 |
Neutrino Physics, Second Edition (Series in High Energy Physics, Cosmology and Gravitation) by Kai Zuber (Author) When Kai Zuber’s pioneering text on neutrinos was published in 2003, the author correctly predicted that the field would see tremendous growth in the immediate future. In that book, Professor Zuber provided a comprehensive self-contained examination of neutrinos, covering their research history and theory, as well as their application to particle physics, astrophysics, nuclear physics, and the broad reach of cosmology; but now to be truly comprehensive and accurate, the field’s seminal reference needs to be revised and expanded to include the latest research, conclusions, and implications. Revised as needed to be equal to the research of today, Neutrino Physics, Second Edition delves into neutrino cross sections, mass measurements, double beta decay, solar neutrinos, neutrinos from... |
 |
Neutrino Cosmology by Dr Julien Lesgourgues (Author), Dr Gianpiero Mangano (Author), Gennaro Miele (Author), Dr Sergio Pastor (Author) The role that neutrinos have played in the evolution of the Universe is the focus of one of the most fascinating research areas that has stemmed from the interplay between cosmology, astrophysics and particle physics. In this self-contained book, the authors bring together all aspects of the role of neutrinos in cosmology, spanning from leptogenesis to primordial nucleosynthesis, their role in CMB and structure formation, to the problem of their direct detection. The book starts by guiding the reader through aspects of fundamental neutrino physics, such as the standard cosmological model and the statistical mechanics in the expanding Universe, before discussing the history of neutrinos in chronological order from the very early stages until today. This timely book will interest graduate... |
 |
The Physics of Neutrinos by Vernon Barger (Author), Danny Marfatia (Author), Kerry Whisnant (Author) The physics of neutrinos--uncharged elementary particles that are key to helping us better understand the nature of our universe--is one of the most exciting frontiers of modern science. This book provides a comprehensive overview of neutrino physics today and explores promising new avenues of inquiry that could lead to future breakthroughs. The Physics of Neutrinos begins with a concise history of the field and a tutorial on the fundamental properties of neutrinos, and goes on to discuss how the three neutrino types interchange identities as they propagate from their sources to detectors. The book shows how studies of neutrinos produced by such phenomena as cosmic rays in the atmosphere and nuclear reactions in the solar interior provide striking evidence that neutrinos have mass, and it... |
 |
Neutrino Hunters: The Thrilling Chase for a Ghostly Particle to Unlock the Secrets of the Universe by Ray Jayawardhana (Author) Detective thriller meets astrophysics in this adventure into neutrinos and the scientists who pursue them For more than eighty years, brilliant and eccentric scientists around the world have been searching for the incredibly small bits of matter we call neutrinos. Trillions of these ghostly particles pass through our bodies every second, but they are so pathologically shy that neutrino hunters have to use Olympic-size pools deep underground and a gigantic cube of Antarctic ice to catch just a handful. Neutrinos may hold the secrets to the nature of antimatter and what the universe was like just seconds after the big bang, but they are extremely elusive and difficult to pin down—much like the adventurous scientists who doggedly pursue them. In Neutrino Hunters, the... |
 |
Fundamentals of Neutrino Physics and Astrophysics by Carlo Giunti (Author), Chung W. Kim (Author) This book deals with neutrino physics and astrophysics- a field in which some of the most exciting recent developments in particle physics, astrophysics and cosmology took place. The book is the most up-to-date, comprehensive and self-contained treatment of key issues in neutrino physics. It discusses all the topics vital to the understanding of the nature of neutrinos such as what they are, how to describe them, how they behave in nature, and the roles of neutrinos play in shaping our Universe. The book provides comprehensive discussions, both experimental and theoretical, with relevant mathematical details, on neutrino oscillations, extra-terrestrial as well as terrestrial neutrinos and relic neutrinos. It also discusses many implications of current experimental data on rector,... |
 |
Neutrino C.A.T. by TTA Press Neutrino C.A.T is a short story first published in the online magazine A Writer's Choice Literary Journal in 1998. It was my second published story and soon after its appearance the solar neutrino ‘problem’ was resolved and hence the background became both obsolete and unnecessary. However I still like it despite those, and other, flaws. When I posted this I assumed I could set the price to zero. Unfortunately that proved to be impossible. Sorry about that. I 'll have to post a test file such as a TTA Press publication (rather than myself) that will be worth your money. This story is a test file uploaded to check formatting and appearance before we try any TTA Press publications on Amazon. Please have a look at it on your e reader, or any other mobile device... |
 |
Neutrino Physics (Series in High Energy Physics, Cosmology and Gravitation) by Kai Zuber (Author) Neutrino physics remains one of the most exciting fields of fundamental physics today. The neutrino's position at the intersection of particle physics, astrophysics, and nuclear physics ensures continuing interest in the subject. Major activities at accelerators like Fermilab, KEK and CERN, in addition to underground facilities like Gran Sasso, Kamioka and Sudbury, continue to enhance our understanding of the origins and properties of neutrinos, and their implications for the Standard Model and cosmology. Neutrino Physics provides an up to date and comprehensive introduction to the subject as well as an invaluable resource for researchers in physics and astrophysics. Starting with a brief historical overview the author proceeds to review fundamental neutrino properties, the... |
 |
The Neutrino: Ghost Particle of the Atom by Isaac Asimov (Author) PB |
 |
The Happiest Man in the World: An Account of the Life of Poppa Neutrino by Alec Wilkinson (Author) The Happiest Man in the World buoyantly describes seventy-four-year-old David Pearlman, a restless and migratory soul, a mariner, a musician, a member of the Explorers Club and a friend of the San Francisco Beats, a former preacher and sign painter, a polymath, a pauper, and a football strategist for the Red Mesa Redskins of the Navajo Nation. When Pearlman was fifty, he was bitten on the hand by a dog in Mexico and for two years got so sick that he thought he would die. When he recovered, he felt so different that he decided he needed a new name. He began calling himself Poppa Neutrino, after the itinerant particle that is so small it can hardly be detected. To Neutrino, the particle represents the elements of the hidden life that assert themselves discreetly. Inspired by Thor... |
| © 2013 BrightSurf.com |