Window to the Dark Side of the Universe
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Old Soldiers by Michael Riordan
Old soldiers by Michael Riordan Twenty years ago this month, an this deep inelastic region in excru experiment began at the Stanford ciating detail, the new quark-parton Linear Accelerator Center in Cali picture of a nucleon's innards fornia that would eventually redraw gradually took a firmer and firmer the map of high energy physics. hold upon the particle physics com In October 1967, MIT and SLAC munity. These two massive spec physicists started shaking down trometers were our principal 'eyes' their new 20 GeV spectrometer; into the new realm, by far the best by mid-December they were log ones we had until more powerful ging electron-proton scattering in muon and neutrino beams became the so-called deep inelastic region available at Fermilab and CERN. where the electrons probed deep They were our Geiger and Marsd- inside the protons. The huge ex en, reporting back to Rutherford cess of scattered electrons they the detailed patterns of ricocheting encountered there-about ten times projectiles. Through their magnetic the expected rate-was later inter lenses we 'observed' quarks for preted as evidence for pointlike, the very first time, hard 'pits' inside fractionally charged objects inside hadrons. the proton. These two goliaths stood reso Michael Riordan (above) did The quarks we take for granted lutely at the front as a scientific research using the 8 GeV today were at best 'mathematical' revolution erupted all about them spectrometer at SLAC as an entities in 1967 - if one allowed during the late 1960s and early MIT graduate student during them any true existence at all. -
Quantum Mechanics Quantum Chromodynamics (QCD)
Quantum Mechanics_quantum chromodynamics (QCD) In theoretical physics, quantum chromodynamics (QCD) is a theory ofstrong interactions, a fundamental forcedescribing the interactions between quarksand gluons which make up hadrons such as the proton, neutron and pion. QCD is a type of Quantum field theory called a non- abelian gauge theory with symmetry group SU(3). The QCD analog of electric charge is a property called 'color'. Gluons are the force carrier of the theory, like photons are for the electromagnetic force in quantum electrodynamics. The theory is an important part of the Standard Model of Particle physics. A huge body of experimental evidence for QCD has been gathered over the years. QCD enjoys two peculiar properties: Confinement, which means that the force between quarks does not diminish as they are separated. Because of this, when you do split the quark the energy is enough to create another quark thus creating another quark pair; they are forever bound into hadrons such as theproton and the neutron or the pion and kaon. Although analytically unproven, confinement is widely believed to be true because it explains the consistent failure of free quark searches, and it is easy to demonstrate in lattice QCD. Asymptotic freedom, which means that in very high-energy reactions, quarks and gluons interact very weakly creating a quark–gluon plasma. This prediction of QCD was first discovered in the early 1970s by David Politzer and by Frank Wilczek and David Gross. For this work they were awarded the 2004 Nobel Prize in Physics. There is no known phase-transition line separating these two properties; confinement is dominant in low-energy scales but, as energy increases, asymptotic freedom becomes dominant. -
Advanced Information on the Nobel Prize in Physics, 5 October 2004
Advanced information on the Nobel Prize in Physics, 5 October 2004 Information Department, P.O. Box 50005, SE-104 05 Stockholm, Sweden Phone: +46 8 673 95 00, Fax: +46 8 15 56 70, E-mail: [email protected], Website: www.kva.se Asymptotic Freedom and Quantum ChromoDynamics: the Key to the Understanding of the Strong Nuclear Forces The Basic Forces in Nature We know of two fundamental forces on the macroscopic scale that we experience in daily life: the gravitational force that binds our solar system together and keeps us on earth, and the electromagnetic force between electrically charged objects. Both are mediated over a distance and the force is proportional to the inverse square of the distance between the objects. Isaac Newton described the gravitational force in his Principia in 1687, and in 1915 Albert Einstein (Nobel Prize, 1921 for the photoelectric effect) presented his General Theory of Relativity for the gravitational force, which generalized Newton’s theory. Einstein’s theory is perhaps the greatest achievement in the history of science and the most celebrated one. The laws for the electromagnetic force were formulated by James Clark Maxwell in 1873, also a great leap forward in human endeavour. With the advent of quantum mechanics in the first decades of the 20th century it was realized that the electromagnetic field, including light, is quantized and can be seen as a stream of particles, photons. In this picture, the electromagnetic force can be thought of as a bombardment of photons, as when one object is thrown to another to transmit a force. -
The Strong and Weak Senses of Theory-Ladenness of Experimentation: Theory-Driven Versus Exploratory Experiments in the History of High-Energy Particle Physics
[Accepted for Publication in Science in Context] The Strong and Weak Senses of Theory-Ladenness of Experimentation: Theory-Driven versus Exploratory Experiments in the History of High-Energy Particle Physics Koray Karaca University of Wuppertal Interdisciplinary Centre for Science and Technology Studies (IZWT) University of Wuppertal Gaußstr. 20 42119 Wuppertal, Germany [email protected] Argument In the theory-dominated view of scientific experimentation, all relations of theory and experiment are taken on a par; namely, that experiments are performed solely to ascertain the conclusions of scientific theories. As a result, different aspects of experimentation and of the relation of theory to experiment remain undifferentiated. This in turn fosters a notion of theory- ladenness of experimentation (TLE) that is too coarse-grained to accurately describe the relations of theory and experiment in scientific practice. By contrast, in this article, I suggest that TLE should be understood as an umbrella concept that has different senses. To this end, I introduce a three-fold distinction among the theories of high-energy particle physics (HEP) as background theories, model theories and phenomenological models. Drawing on this categorization, I contrast two types of experimentation, namely, “theory-driven” and “exploratory” experiments, and I distinguish between the “weak” and “strong” senses of TLE in the context of scattering experiments from the history of HEP. This distinction enables to identify the exploratory character of the deep-inelastic electron-proton scattering experiments— performed at the Stanford Linear Accelerator Center (SLAC) between the years 1967 and 1973—thereby shedding light on a crucial phase of the history of HEP, namely, the discovery of “scaling”, which was the decisive step towards the construction of quantum chromo-dynamics (QCD) as a gauge theory of strong interactions. -
Sensitivity Physics. D KAONS, Or
A PERIODICAL OF PARTICLE PHYSICS WINTER 1995 VOL. 25, NUMBER 4 Editors RENE DONALDSON, BILL KIRK Contributing Editor MICHAEL RIORDAN Editorial Advisory Board JAMES BJORKEN, GEORGE BROWN, ROBERT N. CAHN, DAVID HITLIN, JOEL PRIMACK, NATALIE ROE, ROBERT SIEMANN Illustrations page 4 TERRY ANDERSON Distribution CRYSTAL TILGHMAN The Beam Line is published quarterly by the Stanford Linear Accelerator Center, PO Box 4349, Stanford, CA 94309. Telephone: (415) 926-2585 INTERNET: [email protected] FAX: (415) 926-4500 Issues of the Beam Line are accessible electronically on uayc ou the World Wide Web at http://www.slac.stanford.edu/ pubs/beamline/beamline.html SLAC is operated by Stanford University under contract with the U.S. Department of Energy. The opinions of the authors do not necessarily reflect the policy of the Stanford Linear Accelerator Center. Cover: Martin Perl (left) and Frederick Reines (center) receive the 1995 Nobel Prize in physics from His Majesty the King of Sweden at the awards ceremony last December. (Photograph courtesy of Joseph Peri) Printed on recycled paper tj) . CONTENTS FEATURES "We conclude that the signature e-/. events cannot be explained either by the production and decay of any presently known particles 4 Discovery of the Tau or as coming from any of the well- THE ROLE OF MOTIVATION & understood interactions which can TECHNOLOGY IN EXPERIMENTAL conventionally lead to an e and a PARTICLE PHYSICS gu in the final state. A possible ex- One of this year's Nobel Prize in physics planation for these events is the recipients describes the discovery production and decay of a pair of of the tau lepton in his 1975 new particles, each having a mass SLAC experiment. -
James Chadwick and E.S
What is the Universe Made Of? Atoms - Electrons Nucleus - Nucleons Antiparticles And ... http://www.parentcompany.com/creation_explanation/cx6a.htm What Holds it Together? Gravitational Force Electromagnetic Force Strong Force Weak Force Timeline - Ancient 624-547 B.C. Thales of Miletus - water is the basic substance, knew attractive power of magnets and rubbed amber. 580-500 B.C. Pythagoras - Earth spherical, sought mathematical understanding of universe. 500-428 B.C. Anaxagoras changes in matter due to different orderings of indivisible particles (law of the conservation of matter) 484-424 B.C. Empedocles reduced indivisible particles into four elements: earth, air, fire, and water. 460-370 B.C. Democritus All matter is made of indivisible particles called atoms. 384-322 B.C. Aristotle formalized the gathering of scientific knowledge. 310-230 B.C. Aristarchus describes a cosmology identical to that of Copernicus. 287-212 B.C. Archimedes provided the foundations of hydrostatics. 70-147 AD Ptolemy of Alexandria collected the optical knowledge, theory of planetary motion. 1214-1294 AD Roger Bacon To learn the secrets of nature we must first observe. 1473-1543 AD Nicholaus Copernicus The earth revolves around the sun Timeline – Classical Physics 1564-1642 Galileo Galilei - scientifically deduced theories. 1546-1601, Tycho Brahe accurate celestial data to support Copernican system. 1571-1630, Johannes Kepler. theory of elliptical planetary motion 1642-1727 Sir Isaac Newton laws of mechanics explain motion, gravity . 1773-1829 Thomas Young - the wave theory of light and light interference. 1791-1867 Michael Faraday - the electric motor, and electromagnetic induction, electricity and magnetism are related. electrolysis, conservation of energy. -
Twenty Five Years of Asymptotic Freedom
TWENTY FIVE YEARS OF ASYMPTOTIC FREEDOM1 David J. Gross Institute For Theoretical Physics, UCSB Santa Barbara, California, USA e-mail: [email protected] Abstract On the occasion of the 25th anniversary of Asymptotic Freedom, celebrated at the QCD Euorconference 98 on Quantum Chrodynamics, Montpellier, July 1998, I described the discovery of Asymptotic Freedom and the emergence of QCD. 1 INTRODUCTION Science progresses in a much more muddled fashion than is often pictured in history books. This is especially true of theoretical physics, partly because history is written by the victorious. Con- sequently, historians of science often ignore the many alternate paths that people wandered down, the many false clues they followed, the many misconceptions they had. These alternate points of view are less clearly developed than the final theories, harder to understand and easier to forget, especially as these are viewed years later, when it all really does make sense. Thus reading history one rarely gets the feeling of the true nature of scientific development, in which the element of farce is as great as the element of triumph. arXiv:hep-th/9809060v1 10 Sep 1998 The emergence of QCD is a wonderful example of the evolution from farce to triumph. During a very short period, a transition occurred from experimental discovery and theoretical confusion to theoretical triumph and experimental confirmation. In trying to relate this story, one must be wary of the danger of the personal bias that occurs as one looks back in time. It is not totally possible to avoid this. Inevitably, one is fairer to oneself than to others, but one can try. -
In Leon's Company, It Seemed That Anything Might Be Possible
In Leon’s company, it seemed that anything might be possible Chris Quigg email:[email protected] Theoretical Physics Department Fermi National Accelerator Laboratory P.O. Box 500, Batavia, Illinois 60510 USA 5 January 2020 FERMILAB-PUB-20-001-T Memorial sessions celebrated Leon Lederman, Helen Edwards, and Burton Richter at the April 2019 Meeting of the American Physical Society in Denver. In the session entitled Honoring Leon Lederman, Sally Dawson gave an overview of Leon’s scientific career, Marge Bardeen reviewed his work in science education, and I spoke of his years as Fermilab Director. Presentation materials for all three sessions are archived at http://j.mp/31mNkHA. This essay is drawn from my lecture; my slides can be found at https://bit.ly/2QJ7Jmw. Leon Lederman in 1983. (Fermilab Creative Services) In 1978, Leon Lederman put aside a promising career in experimental physics that had spanned three decades to accept the appointment as Director of Fermilab—the Enrico Fermi National Accelerator Laboratory. Leon was tied to Fermilab even before it existed. He had discov- ered early in life that if he took himself seriously, others were likely 1 L. M. Lederman, “The Truly National to take him seriously as well. As the community pondered a new ac- Laboratory (TNL),” in Super-High- Energy Summer Study, Brookhaven celerator in the 100-GeV and above range, Leon delivered a manifesto Report No. BNL-AADD-6 (1963), pp. for what he called a Truly National Laboratory.1 8–11. He gave voice to a complaint of university users that they had not been treated justly at Berkeley and Brookhaven, where the very powerful in-house groups would—according to Leon—consume all the prime beam time for themselves, and only then distribute scraps among the sorry supplicants from Columbia University and other institutions. -
STANFORD Anniversary Time Accelerator Summer School
George A. Key worth, Science Adviser to President Reagan and Director of the President's Office of Science and Technology Policy, speaking at the SLAC anniversary — 'a deep personal pleasure to pay tribute to the powerful impact this excellent laboratory has had on the world's science'. very much on top of the prediction for b c, and an upper limit of 9 per cent is obtained for the ratio b -> u/b -> c. By studying how the results depend on the mass of the u quark hadrons, the CLEO group finds that the results are insensitive to masses below about 1 GeV. Upper limits for the ratio of branching ratios of 9 per cent are obtained by the CLEO group from both their muon and their elec tron spectra. These three measurements estab lish that the b quark decays predo Robert Hofstadter in his Nobel prize enormously useful to particle phy minately into c quarks, rather than u winning study of the structure of the sics and has spawned nearly 20 ma quarks. This results in a significant proton, and finally to the beginnings chines of increasing size. The most improvement of our knowledge of of the Two Mile Linac with the an prolific has been SPEAR, a ring built the parameters of the six-quark mod nouncement of support for the pro at SLAC in 1972. Richter shared the el. With the larger data samples that ject by President Eisenhower in Nobel prize of 1976 for his work in will become available, is should be 1957. the discovery of the charmed quark possible to measure the b u frac SLAC Director Pief Panofsky con and the development of this new tion from the lepton spectrum. -
Making History
Making history The International Symposium on the History of Particle Physics, held at the Stanford Linear Accelerator Center (SLAC) from 24-27 June, and entitled 'The Rise of the Standard Model' brought together science historians and philosophers as well as particle physicists. Left to right, Science philosopher Michael Redhead of Cambridge, Symposium co-chairman and science historian Lillian Hoddeson of Illinois, and science historian Robert Seidel of Los Alamos. While the Standard Model is still the unchallenged picture of modern particle physics, a recent international symposium showed how it nevertheless goes back long enough to have become science history. The International Symposium on the History of Particle Physics, held at the Stanford Linear Accelerator Center (SLAC) from 24-27 June, and entitled The Rise of the Standard Model' attracted a wide audience - teachers, sociologists and science historians as well as physicists. The list of speakers included nine Nobel prizewinners. Under the imaginative guidance of scientist and science writer Michael Riordan of SLAC and physics historian Lillian Hoddeson of Illinois, Perl); the upsilon at Fermilab in 1977 detectors for colliding beam the symposium traced the and the subsequent elucidation of the machines. beginnings and evolution of the fifth quark (Leon Lederman); CP But the Standard Model is a theory, Standard Model - the twin picture violation at Brookhaven in 1963 albeit not of the most elegant kind. which rather brutally pairs the (James Cronin); neutrino beams in The theoretical side was covered by electroweak unification of the early 1960s (Mel Schwartz); Makoto Kobayashi (mixing in a six- electromagnetism and weak neutral currents at CERN in 1973 quark picture), Martinus Veltman and interactions on one hand with the (Don Perkins); weak-electromagnetic Gerard't Hooft (the momentous quantum chromodynamics field interference at SLAC in 1979 realization that the electroweak theory of quarks and gluons on the (Charles Prescott); baryon and theory is renormalizable, allowing other. -
Sam Treiman Was Born in Chicago to a First-Generation Immigrant Family
NATIONAL ACADEMY OF SCIENCES SAM BARD TREIMAN 1925–1999 A Biographical Memoir by STEPHEN L. ADLER Any opinions expressed in this memoir are those of the author and do not necessarily reflect the views of the National Academy of Sciences. Biographical Memoirs, VOLUME 80 PUBLISHED 2001 BY THE NATIONAL ACADEMY PRESS WASHINGTON, D.C. Courtesy of Robert P. Matthews SAM BARD TREIMAN May 27, 1925–November 30, 1999 BY STEPHEN L. ADLER AM BARD TREIMAN WAS a major force in particle physics S during the formative period of the current Standard Model, both through his own research and through the training of graduate students. Starting initially in cosmic ray physics, Treiman soon shifted his interests to the new particles being discovered in cosmic ray experiments. He evolved a research style of working closely with experimen- talists, and many of his papers are exemplars of particle phenomenology. By the mid-1950s Treiman had acquired a lifelong interest in the weak interactions. He would preach to his students that “the place to learn about the strong interactions is through the weak and electromagnetic inter- actions; the problem is half as complicated.’’ The history of the subsequent development of the Standard Model showed this philosophy to be prophetic. After the discovery of parity violation in weak interactions, Treiman in collaboration with J. David Jackson and Henry Wyld (1957) worked out the definitive formula for allowed beta decays, taking into account the possible violation of time reversal symmetry, as well as parity. Shortly afterwards Treiman embarked with Marvin Goldberger on a dispersion relations analysis (1958) of pion and nucleon beta decay, a 3 4 BIOGRAPHICAL MEMOIRS major outcome of which was the famed Goldberger-Treiman relation for the charged pion decay amplitude. -
Hep-Th/0111196V1 21 Nov 2001 Ltv Da Novn Lc Oe N Aaerztoso Standard- Idea Described
SLAC–PUB–9063 November 2001 Emergent Gauge Bosons∗ James Bjorken Stanford Linear Accelerator Center Menlo Park, CA 94025 [email protected] Abstract The old idea that the photon is a Goldstone boson emergent from a spontaneously broken theory of interacting fermions is revisited. It is conjectured that the gauge- potential condensate has a vacuum expectation value which is very large, perhaps the GUT/Planck momentum scale, but that the magnitude of the effective potential which generates it is very small, so small that in the limit of vanishing cosmological constant it would vanish. In this way, the threat of unacceptably large observable, noncovariant residual effects is mitigated. The linkage of these ideas to other spec- ulative ideas involving black holes and parametrizations of Standard-Model coupling constants is also described. arXiv:hep-th/0111196v1 21 Nov 2001 Contributed to the 4th Workshop “What Comes beyond the Standard Model?” Bled, Slovenia July 17–27, 2001 ∗Work supported by Department of Energy contract DE–AC03–76SF00515. 1 Introduction It is a pleasure to write this note on the occasion of Holger Bech Nielsen’s 60th birthday celebration. It will deal with very speculative matters, most of which down through the years have benefitted by interactions with him. Holger Bech is one of few with whom I find it fruitful to even discuss such things. Not only has he been always receptive, but most importantly he has reacted thoughtfully and critically, instead of the commonplace reaction of indifference. The subject matter discussed below is actually of common interest: whether gauge bosons such as the photon may be regarded as emergent degrees of freedom.