DOCSLIB.ORG

Detecting Neutrinos

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Detecting Neutrinos extremeexperiments Detecting MASSIVENeutrinos BY EDWARD KEARNS, TAKAAKI KAJITA AND YOJI TOTSUKA 68 Updated from the August 1999 issue COPYRIGHT 2003 SCIENTIFIC AMERICAN, INC. SUPER-KAMIOKANDE DETECTOR resides in an active zinc mine inside Mount Ikenoyama. Its stainless-steel tank contains 50,000 tons of ultrapure water so transparent that light can pass through 70 meters of it before losing half its intensity (for a swimming pool that figure is a few meters). The water is monitored by 11,000 photomultiplier tubes that cover the walls, floor and ceiling. Each tube is a handblown, evacuated glass bulb half a meter in diameter. The tubes register conical flashes of Cherenkov light, each of which signals a rare collision of a high- energy neutrino and an atomic nucleus in the water. Technicians in inflatable rafts clean the bulbs while the tank is filled (right). INSTITUTE FOR COSMIC RAY RESEARCH (ICRR), UNIVERSITY OF TOKYO ne man’s trash is another man’s treasure. For a physicist, the trash is “background”—some A giant detector Ounwanted reaction, probably from a mundane and well-understood process. The treasure is “signal”— in the heart of a reaction that we hope will reveal new knowledge about the way the universe works. Case in point: over the past two decades, several groups have been hunt- Mount Ikenoyama ing for the radioactive decay of the proton, an exceed- ingly rare signal (if it occurs at all) buried in a back- in Japan has ground of reactions caused by elusive particles called neutrinos. The proton, one of the main constituents of demonstrated that the atom, seems to be immortal. Its decay would be a strong indication of processes described by the Grand neutrinos Unified Theories that many believe lie beyond the ex- tremely successful Standard Model of particle physics. metamorphose Huge proton-decay detectors were placed deep under- ground, in mines or tunnels around the world, to es- cape the constant rain of particles called cosmic rays. in flight, strongly But no matter how deep they went, these devices were still exposed to penetrating neutrinos produced by the suggesting that these cosmic rays. The first generation of proton-decay detectors, op- ghostly particles erating from 1980 to 1995, saw no signal, no signs of proton decay—but along the way have mass the researchers found that the supposedly mundane COPYRIGHT 2003 SCIENTIFIC AMERICAN, INC. posited, physicists have assumed that they LIGHT are massless. But if they can change from KOV REN one flavor to another, quantum theory in- CHE dicates that they most likely have mass. Muon-neutrino And in that case, these ethereal particles could collectively outweigh all the stars in Muon the universe. A Bigger Neutrino Trap AS IS SO OFTEN the case in particle physics, the way to make progress is to build a bigger machine. Super-Kamio- kande, or Super-K for short, took the ba- sic design of Kamiokande and scaled it up by about a factor of 10 [see illustration on preceding pages]. An array of light-sensi- tive detectors looks in toward the center of 50,000 tons of water whose protons may decay or get struck by a neutrino. In either Electron-neutrino case, the reaction creates particles that are spotted by means of a flash of blue light Electron known as Cherenkov light, discovered by shower Pavel A. Cherenkov in 1934. Much as an aircraft flying faster than the speed of sound produces a shock wave of sound, an electrically charged particle (such as an electron or a muon) emits Cherenkov CONES OF CHERENKOV LIGHT are emitted when high-energy neutrinos hit a nucleus and produce light when it exceeds the speed of light in a charged particle. A muon-neutrino (top) creates a muon, which travels perhaps one meter and the medium in which it is moving. This projects a sharp ring of light onto the detectors. An electron, produced by an electron-neutrino motion does not violate Einstein’s theory (bottom), generates a small shower of electrons and positrons, each with its own Cherenkov cone, of relativity, for which the crucial veloci- resulting in a fuzzy ring of light. Green dots indicate light detected in the same narrow time interval. ty is c, the speed of light in a vacuum. In neutrino background was not so easy to Neutrinos are amazing, ghostly parti- water, light propagates 25 percent slow- understand. cles. Every second, 60 billion of them, er than c, but other highly energetic par- One such experiment, Kamiokande, mostly from the sun, pass through each ticles can still travel almost as fast as c it- was located in Kamioka, Japan, a mining square centimeter of your body (and of self. Cherenkov light is emitted in a cone town about 250 kilometers (155 miles) everything else). But because they seldom along the flight path of such particles. from Tokyo (as the neutrino flies). Scien- interact with other particles, generally all In Super-K, the charged particle gen- ) tists there and at the IMB experiment, lo- 60 billion go through you without so erally travels just a few meters and the cated in a salt mine near Cleveland, Ohio, much as nudging a single atom. In fact, Cherenkov cone projects a ring of light this page used sensitive detectors to peer into ultra- you could send a beam of such neutrinos onto the wall of photon detectors [see il- pure water, waiting for the telltale flash of through a light-year-thick block of lead, a proton decaying. and most of them would emerge unscathed EDWARD KEARNS, TAKAAKI KAJITA and Such an event would have been hid- at the end. A detector as large as Kami- YOJI TOTSUKA are members of the Super- den, like a needle in a small haystack, okande catches only a tiny fraction of the Kamiokande Collaboration. Kearns, pro- among about 1,000 similar flashes caused neutrinos that pass through it every year. fessor of physics at Boston University, by neutrinos interacting with the water’s Neutrinos come in three flavors, cor- and Kajita, professor of physics at the ); ICRR, UNIVERSITY OF TOKYO ( atomic nuclei. Although no proton decay responding to their three charged partners University of Tokyo, lead the analysis THE AUTHORS was seen, the analysis of those 1,000 re- in the Standard Model: the electron and team that studies proton decay and actions uncovered a real treasure—tanta- its heavier relatives, the muon and the tau atmospheric neutrinos in the Super- lizing evidence that the neutrinos were un- particle. An electron-neutrino interacting Kamiokande data. Totsuka recently be- preceding pages expectedly fickle, changing from one spe- with an atomic nucleus can produce an came the director of KEK, Japan’s na- cies to another in midflight. If true, that electron; a muon-neutrino makes a muon; tional particle physics laboratory, after phenomenon was just as exciting and the- a tau-neutrino, a tau. For most of the sev- serving as spokesperson for Super-K ory-bending as proton decay. en decades since neutrinos were first since its inception. DAVID FIERSTEIN ( 70 SCIENTIFIC AMERICAN THE EDGE OF PHYSICS COPYRIGHT 2003 SCIENTIFIC AMERICAN, INC. ZENITH (PERPENDICULAR TO THE EARTH’S SURFACE) lustration on opposite page]. The size, shape and intensity of this ring reveal the properties of the charged particle, which θ in turn tell us about the neutrino that pro- INCOMING duced it. We can distinguish the Cheren- COSMIC RAYS θ kov patterns of electrons from those of O muons: the electrons generate a shower of IN SUPER-K R particles, leading to a fuzzy ring quite un- EUT N like the crisper circle from a muon. From G the Cherenkov light we also measure the TIN ATMOSPHERE energy and direction of the electron or mu- OSCILLA on, which are decent approximations of the energy and direction of the neutrino. θ Super-K cannot easily identify the third type of neutrino, the tau-neutrino. θ Such a neutrino can interact with a nu- ZENITH cleus and make a tau particle only if it has enough energy. A muon is about 200 times as heavy as an electron; the tau, about 3,500 times. The muon mass is well within the range of atmospheric neutri- nos, but only a tiny fraction are at tau en- ergies, so most tau-neutrinos in the mix will pass through Super-K undetected. One of the most basic questions ex- HIGH-ENERGY COSMIC RAY striking a nucleus in the perimenters ask is “How many?” We COSMIC atmosphere (below) generates a shower of particles, have built a beautiful detector to study RAY mostly pions. The pion’s sequence of decays produces neutrinos, and the first task is simply to two muon-neutrinos for every electron-neutrino. Equal count how many we see. The related neutrino rates should be seen from opposite directions (above) because both result from cosmic rays hitting question is “How many did we expect?” the atmosphere at the same zenith angle, θ. Both these To answer that, we must analyze how the ratios are spoiled when muon-neutrinos traveling long neutrinos are produced. distances have time to change flavor. Super-K monitors atmospheric neu- AIR NUCLEUS trinos, which are born in the spray of par- ticles when a cosmic ray strikes the top of our atmosphere. The incoming projectiles (called primary cosmic rays) are mostly PIONS protons, with a sprinkling of heavier nu- clei such as helium or iron. Each collision MUON generates a shower of secondary particles, mostly pions and muons, which decay ELECTRON during their short flight through the air, 2 MUON- creating neutrinos [see illustration at NEUTRINOS 1 ELECTRON-NEUTRINO right].
Load more

Recommended publications
  • Neutrinos and Beyond — Opening a New Era of Cosmic-Ray Research
    ADVERTISEMENT FEATURE THE UNIVERSITY OF TOKYO Neutrinos and beyond — Opening a new era of cosmic-ray research Takaaki Kajita, a recipient of the 2015 that neutrinos are massless. These discov- Nobel Prize in Physics, and other re- eries, which resulted in Kajita’s 2015 Nobel searchers at the University of Tokyo’s Prize in Physics, were made a team led by Institute for Cosmic Ray Research (ICRR) him in 1998. have been exploring new realms in par- Kajita acknowledged his success owed ticle physics research. Kajita’s work on a lot to the strong support he received neutrinos and related research at ICRR from two mentors and former supervisors is leading the world in this field. — Masatoshi Koshiba and Yoji Totsuka. Koshiba was awarded the 2002 Nobel Prize The path to a Nobel prize in Physics for detecting neutrinos pro- Particle physics and astrophysics are duced in supernovae using Kamiokande, among the most active research fields at the predecessor of Super-Kamiokande. the University of Tokyo, and its Institute for Totsuka led the Super-Kamiokande proj- Cosmic Ray Research (ICRR) is leading the ect as Koshiba’s successor. Totsuka’s con- world with explorations in these areas. ICRR tribution was so great that many believe is best known for its research on neutrinos he would have shared the Nobel Prize with using the world’s largest underground neu- Kajita if he were alive. trino detector, Super-Kamiokande. The de- Kajita’s award-winning work dates tector is located in a mine in central Japan back to 1986 when he earned his PhD for and is filled with 50,000 tons of pure water.
    [Show full text]
  • Research in Kamioka and Kakenhi Takaaki Kajita Director of Institute for Cosmic Ray Research (ICRR) the University of Tokyo Rese
    Research in Kamioka and Kakenhi Takaaki Kajita Director of Institute for Cosmic Ray Research (ICRR) The University of Tokyo Research Theme Implemented in FY2017: First Detection of Gravitational Waves Using Cryogenic Laser Interferometer (Grant-in-Aid for Specially Promoted Research) I have conducted research underground Kamioka, Gifu Prefecture, since I was a graduate student. The first experiment I participated in was the Kamioka Nucleon Decay Experiment (Kamiokande). The experiment was initially proposed by Professor Masatoshi Koshiba, who was my thesis advisor, to search for proton decay. Professor Koshiba collaborated with a company to develop an unprecedentedly large 50-centimeter diameter photomultiplier tube (PMT) for the Kamiokande experiment. The PMT served a very important role in supernova neutrino observations that verified the supernova explosion mechanism and solar neutrino observations that confirmed the so-called solar neutrino problem. It is well known that, due to these achievements, Professor Koshiba received the Nobel Prize in physics in 2002. It is common for a large apparatus such as this to be realized by submitting a budget request from a host institute after long, vigorous discussions in relevant researcher communities. In this case, however, the enthusiasm of the relevant researchers in view of the importance of Kamiokande experiments made it possible to realize the experiment quickly with funds from various sources. Kamiokande initially materialized through collaboration with the University of Tokyo’s School of Science, to which Professor Koshiba belonged, the former National Laboratory for High Energy Physics (KEK), and the Institute for Cosmic Ray Research (ICRR) of the University of Tokyo. Although I was only a graduate student at that time and knew nothing about budgets, all of us participating in the effort recognized that people thought that this experiment was very important and endeavored to realize it as soon as possible.
    [Show full text]
  • 1 FY 2015 Follow-Up of WPI Program by Program Committee February
    FY 2015 Follow-up of WPI Program By Program Committee February 2016 (This document reports on progress made under the WPI Program in FY 2014.) In FY2015, there were three important achievements: 1. Nobel Prize in physics awarded to Dr. T. Ka j i t a, P I of Kavli IPMU. (see section A, p2) 2. International Research Excellence Initiative (REI) workshop held jointly with Program committee meeting. (see section E, p5) 3. Future plan devised by the WPI program committee (see section E, p5) A. Dr. Takaaki Kajita, PI of Kavli IPMU, was awarded The 2015 Nobel Prize .................................... 2 B. Outline of WPI program .......................................................................................................... 2 C. WPI Centers ........................................................................................................................... 3 D. Follow up ............................................................................................................................... 4 E. REI International Workshop and 2015 Program committee meeting ........................................... 4 E-1. REI International Workshop ................................................................................... 5 E-2. Program committee meeting .................................................................................. 5 E-3. Future plan of WPI program ................................................................................... 5 F. Site visits ..............................................................................................................................
    [Show full text]
  • The Solar Neutrino Problem Has Not Been Solved
    I S S N 2 3 4 7 - 3487 Volume 13 Number 4 Journal of Advances in Physics The Solar Neutrino Problem Has Not Been Solved Jamal S. Shrair Helical Universe www.helical-universe.info [email protected] ABSTRACT A closer look at the data collected from different detectors, reveal that the so-called solar neutrino problem is far from being solved. And contrary to the assessment of the Nobel Committee, the experimental results from the Sudbury Neutrino Observatory cannot be regarded as a confirmation of the Standard Solar Model. In fact, the obsoleteness of the current model has been recently exposed by the crisis of solar abundance. Furthermore, using images obtained by the Solar Dynamics Observatory, researchers found the convective motions (the plasma motions within the Sun's interior) to be nearly 100 times smaller than current theoretical expectations. This is a clear verdict on the notion of thermonuclear reactions that are supposed to be the processes that generate solar neutrinos. KEYWORDS Solar neutrino problem, neutrino oscillations, neutrino detectors, solar physics, standard solar model, astrophysics, ACADEMIC DISCIPLINE AND SUB-DISCIPLINES Solar physics and Astrophysics SUBJECT CLASSIFICATION Fundamental Solar Physics and Astrophysics TYPE (METHOD/APPROACH) Quantitative and Qualitative INTRODUCTION Based on the hypothesis of the standard solar model, the number of neutrinos produced by the Sun per second is approximately 1.8 x , which means 400 trillion neutrinos pass through our bodies every second. The model, also assumes that the absolute majority of neutrinos is, generated from the P-P reaction, and 99.99% of solar neutrinos have energy which is far too low for detection.
    [Show full text]
  • Super-Kamiokande: the Road to Neutrino Oscillations
    Super-Kamiokande: The Road to Neutrino Oscillations James Stone Boston University A Symposium on the Occasion of the Benjamin Franklin Medal for the Experimental Discovery of Neutrino Oscillations April 25, 2007 Philadelphia April 1, 1996 Atmospheric Neutrinos Yoji Totsuka James Stone McDonald/Totsuka Symposium 2 Fluxes (106 cm-2s-1) •e : 1.76(11) •, : 3.41(66) •TOTAL:5.09(64) •SSM :5.05 Art McDonald (ee ) ( ) (SSM) Solar Neutrinos James Stone James Stone McDonald/Totsuka Symposium 3 Plan for Today’s Talk Focus on the role of atmospheric neutrinos in revealing neutrino oscillations. Tell the story of large water Cherenkov detectors and why we built them. Give details of the initial discovery of neutrino oscillations and the current data. Present additional checks and confirmations. Preview the future for precision measurements in neutrino physics. I’ll start with some historical milestones ... James Stone McDonald/Totsuka Symposium 4 Discovery of the Free Neutrino, 1956 “Project Poltergeist” Hanford and Savannah River Reactors p n e Fred Reines Clyde Cowan Liquid Scintillator with Cadmium Phys. Rev. Lett. 92:330 (1953) Science 124(3201):103 (1956) “... A Confirmation” Phys. Rev. 117(1) :159 (1960) James Stone McDonald/Totsuka Symposium 5 Oscillations and Neutrino Flavor Bruno Pontecorvo first suggested the possibility of neutrino oscillations if they had a small mass. Since only one neutrino was known, he was thinking that analogous to KK 00 mixing: J.Exp.Theor.Phys. 33 549 (1957) J.Exp.Theor.Phys. 34 247 (1957) In 1962, Lederman, Schwartz, Steinberger, et al. published evidence for the muon neutrino the their BNL/AGS experiment.
    [Show full text]
  • 21.8 N&V PJ BG.Indd
    NEWS & VIEWS NATURE|Vol 454|21 August 2008 OBITUARY Yoji Totsuka (1942–2008) Leader in the discovery of neutrino oscillations. Yoji Totsuka, a major figure in the world of of the supernova and of the neutrinos particle physics, died on 10 July after a long themselves. battle with cancer. He was a leading light Shortly after the supernova, Koshiba in the thrilling advances in the physics of retired and Totsuka became leader of neutrinos over the past 30 years, and was the Kamiokande project. Two seminal a notably resolute figure in seeing through results from the group were subsequently the rebuilding of the Super-Kamiokande published. The first observed a deficit in neutrino detector after a disastrous accident atmospheric neutrinos that could not be in 2001. explained by systematic experimental errors Born on 6 March 1942, in Fuji, Japan, or uncertainties in the background neutrino Totsuka received his bachelor’s, master’s and flux. Instead, some “as-yet-unaccounted-for PhD degrees from the University of Tokyo. physics”, as the paper put it, might explain His thesis project studied ultra-high-energy the data. The second crucially confirmed the particle interactions, so kick-starting his solar neutrino deficit recorded by Davis. lifelong passion for particle physics. As a In 1991, Totsuka obtained funding for a Totsuka also supervised the successful research associate with the University of successor to Kamiokande. This was Super- Belle B-factory, where particles known as Tokyo, he then travelled to the Deutsches Kamiokande, an underground detector B-mesons were generated to study differences Electron Synchrotron Laboratory in that contained 50,000 tons of water.
    [Show full text]
  • Discovery of Atmospheric Neutrino Oscillations
    Nobel Lecture Dec 8, 2015 Takaaki Kajita Institute for Cosmic Ray Research, The Univ. of Tokyo Atmospheric Neutrino Oscillations 1 Outline • Introduction: Kamiokande - the starting point - • Atmospheric neutrino deficit • Discovery of neutrino oscillations • Recent results and the future • Summary • Acknowledgements Atmospheric Neutrino Oscillations 2 Introduction: Kamiokande - the starting point - Atmospheric Neutrino Oscillations 3 Kamioka Nucleon Decay Experiment (Kamiokande) In the late 1970’s, new theories that unify Strong, Weak and Electromagnetic forces were proposed. These theories predicted that protons and neutrons (i.e., nucleons) should decay with the lifetime of about 1028 to 1032 years. Several proton decay experiments began in the early 1980’s. One of them was the Kamiokande experiment. Kamiokande (1000 ton Detector fiducial wall volume) Cherenkov light Photo detectors Charged particle Atmospheric Neutrino Oscillations 4 Kamiokande construction team (Spring 1983) M. Takita TK A. Suzuki T.Suda M. Nakahata K. Arisaka M. Koshiba Y. Totsuka T. Kifune Atmospheric Neutrino Oscillations 5 What are neutrinos? • Neutrinos; • are fundamental particles like electrons and quarks, • have no electric charge, • have 3 types (flavors), namely electron-neutrinos (νe), muon-neutrinos (νµ) and tau-neutrinos (ντ), • are produced in various places, such as the Earth’s atmosphere, the center of the Sun, …. • can easily penetrate through the Earth, the Sun… • can, however, interact with matter very rarely. A νµ produces a muon. A νe produces
    [Show full text]
  • Internationalizing KEK: the Early Days Cultural Differences You
    Vol.6 No.1 Internationalizing KEK: The Early Days Cultural differences you would encounter in Japan Child Education in Japan Living in Japan Congratulations to Prof. Koshiba for his being awarded a Nobel prize KEK News The Early Days Internationalizing KEK: The Early Days In recent times, the number of foreign researchers and the level of international activity at KEK is rather high. This has not always been the case. In 1982, when I first came to KEK started in 1982 for a year-long sabbatical leave, there were three foreign researchers at KEK, and not many more in all of Tsukuba. (In 1982, seeing a foreigner in Tsukuba was a rare event; when we came across each other we either already knew each other or, if not, introduced ourselves.) During this visit, I shared an office with Steve Schnetzer, who, at the time, was a KEK post-doc working on a PS experiment. Steve's PS experiment finished and my attempts to work with one of the emerging TRISTAN experiments was not very successful. We, therefore, decided to pursue some ideas for a TRISTAN experiment that resulted in the Letter of Intent for the AMY experiment. Our ideas must have been pretty good, because the KEK program committee gave us some kind of a tentative approval---with a condition that we find some collaborators. Our LOI had only six names on it, all from the US. When our efforts to find collaborators in Japan failed, we looked elsewhere. Our first success happened in 1983, when Steve Schnetzer, while touring in China, presented himself at the guardhouse of IHEP in Beijing and asked to see the laboratory.
    [Show full text]
  • CP Violation and Flavor Mixing Makoto Kobayashi KEK and JSPS Plan
    CP Violation and Flavor Mixing Makoto Kobayashi KEK and JSPS Plan 1. Introduction to the Standard Model 2. Sakata and His Group 3. The CP Paper with Maskawa 4. Experimental Verification at B-factories 5. Lepton Flavor Mixing Introduction to the Standard Model u d u Electron p Proton（p） n Nucleus d d u Atom Neutron（n） Introduction to the Standard Model Fundamental Particles u c t Quark d s b e μτ Lepton νe νμ ντ Fundamental Interactions • Strong Interaction QCD • Electro‐Magnetic Interaction • Weak Interaction Weinberg‐Salam‐Glashow Theory Introduction to the Standard Model Established in 1970’s ・ Development of gauge theory 1971 ‘t Hooft Electro‐Magnetic Interaction Strong Interaction Weak Interaction ・ Discoveries of new flavors u c t 1964 Gell‐Mann quark model d s b u, d, s e μτ 1973 Kobayashi Maskawa νe νμ ντ Six‐Quark Model After 1970 Sakata and His Group 1947∼ Discovery of Strange Particles Hadron : strongly interacting particle p n π±0 Λ ΛΣΞ±0 KK± 0 Λ lairmoeM kata Saf osyteruoC Archival Library Strange Particles Shoichi Sakata 1911-1970 1956 Sakata Sakata Model All the hadrons are composite states of p,, n Λ : Fundamental Triplet Sakata and His Group Weak Interaction in the Sakata Model - decayβ n→ p + − e ν + strange paticle→Λ p + e− ν + p ν n Λ e μ 1959 Gamba, Marshak, Okubo B‐L Symmetry 1960 Maki, Nakagawa, Ohnuki, Sakata Nagoya Modelp : = B+ν ,, n = B+ e Λ+ =μ B Sakata and His Group 1962 Discovery of Two Neutrinos ν e ν μ Lepton Flavor Mixing e μ MNS Matrix 1962 Maki, Nakagawa, Sakata + + + + p = B ν1 , n = B e , Λ = B μ , p'= B ν 2 ν1 = cosθ ν e + sinθ ν μ ν 2 = −sinθ ν e + cosθ ν μ Neutrino Oscillation 4th Fundametal Particle (GIM scheme) 1962 Katayama, Matumoto, Tanaka, Yamada Sakata and His Group Cosmic Ray Events 1971 Niu et al.
    [Show full text]
  • Dr. Takaaki Kajita: Tackling the Mysteries of the Universe By
    Japan’s 2015 Nobel Prize Winners Tackling the Mysteries of the Universe by Studying Neutrinos Dr. Takaaki Kajita, Nobel Prize in Physics Dr. Takaaki Kajita, director of the Institute for Cosmic Ray Research (ICRR) at the University of Tokyo, was one of the two winners of the 2015 Nobel Prize in Physics. The award was for the discovery of a type of neutrino oscillation; this showed that neutrinos have mass, contrary to what was previously assumed. In announcing the award, the Royal Swedish Academy of Sciences noted, “The discovery has changed our understanding of the innermost workings of matter and can prove crucial to our view of the universe.” Neutrinos are among the most common particles in the universe. They are constantly flying through the space around us in large numbers. But since they very rarely react to other matter, they are extremely difficult to detect. They have been studied at an observatory in Kamioka, Gifu Prefecture, using detectors—Kamiokande and its successor, Super-Kamiokande—installed in a mine site 1,000 meters (about 0.6 miles) underground to avoid interference from unrelated cosmic rays. Now plans are being made for an even more powerful detector, Hyper-Kamiokande. Dr. Kajita began his study of neutrinos as a research associate at the University of Tokyo in 1986. Neutrinos are observed using a huge tank full of purified water and highly sensitive photomultiplier tubes to detect the light given off on the rare occasions when a neutrino strikes a water molecule. Based on analysis of a tremendous volume of observational data, in 1998 he discovered the phenomenon of neutrino oscillation, meaning that the particles sometimes change type.
    [Show full text]
  • CP Violation and Flavor Mixing
    REVIEWS OF MODERN PHYSICS, VOLUME 81, JULY–SEPTEMBER 2009 Nobel Lecture: CP violation and flavor mixing* Makoto Kobayashi KEK, Oho, Tsukuba-shi 305-0801, Japan and JSPS, Ichibancho, Chiyoda-ku, Tokyo 102-8471, Japan ͑Published 15 July 2009͒ DOI: 10.1103/RevModPhys.81.1019 I. INTRODUCTION of the fourth quark was there, but no one thought of the six quarks. We know that ordinary matter is made of atoms. An In the following, I will describe the development of atom consists of the atomic nucleus and electrons. The the studies on CP violation and the quark and lepton atomic nucleus is made of a number of protons and neu- flavors, putting some emphasis on contributions from Ja- trons. The proton and the neutron are further made of pan. The next section will be devoted to the pioneering two kinds of quarks, u and d. Therefore, the fundamen- works of the Sakata School, from which I learned many tal building blocks of ordinary matter are the electron things. The work on CP violation will be discussed in and two kinds of quarks, u and d ͑see Fig. 1͒. Sec. III. I will explain what we thought and what we The standard model, which gives a comprehensive de- found at that time. Section IV will describe subsequent scription of the current understanding of the elementary development related to our work. Experimental verifi- particle phenomena, however, tells us that the number cation of the proposed model has been done by using of species of quarks is six. The additional quarks are accelerators called B factories.
    [Show full text]
  • DESY Inform August 2008
    DESY 08/2008 Newsletter of the informFORM ª Research Centre DESY Hidden Van Gogh Picture Uncovered HASYLAB helps art historians to reveal a hidden Van Gogh Van Gogh’s pictures are fascinating – even more so when one masterpiece conceals another one under its surface. At HASYLAB, an expert team from Belgium and the Netherlands has revealed a hidden Van Gogh painting. Materials scientist Joris Dik from Delft University, conservator Luuk Rutgers van der Loeff from Kröller-Müller Museum in Otterlo and chemist Koen Jansens from Ant- werpen University were thrilled to be able to reconstruct not only a sketch but a real painting – the portrait of a peasant woman. Previous research had already shown the vague outline of a head under- neath the painting entitled “Grasgrond” (grassy landscape). For a clear identifi - cation, however, the picture had to travel Karen Rickers-Appel at the experiment: With intense synchrotron radiation the team of experts was able to measure to Hamburg. very small amounts of mercury and anti mony in the lower layers of paint. Preparations for the revealing measure- ments at DORIS were quite sophisticated: traceable in low concentration, the in- From the exchange of letters it is known an insurance, special transport and air- tense antimony fl uorescence line reveals that he had sent some of these portraits conditioning of 55 percent humidity at the bright areas of nose and chin. Pig- to his brother Theo, who was an arts 24 degrees were absolutely essential. ments containing mercury were used for dealer in Paris. When Van Gogh came to DORIS coordinator Wolfgang Drube and the reddish lips and cheeks.
    [Show full text]