Neutral Currents: a Perfect Experimental Discovery
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CERN Courier September 2013 Anniversary Image courtesy of: National High Magnetic Field Laboratory (NHMFL), Neutral currents: A perfect Florida State University, Tallahassee, FL SuperPower® 2G HTS Wire State-of-the-art second-generation high temperature superconductor (2G HTS) wire – the enabling component for experimental discovery many energy-efficient and power dense devices, each of which can benefit from unique wire specifications. We offer three variations of wire, each for distinct devices: Advanced Pinning (AP) Cable (CF) formulation – Fault Current Limiter (FCL) formulation – superior enhanced performance at geometry – based on a thicker Forty years after the observation of weak performance at a range of around 77K and in very low (100 micron), highly resistive temperatures from 77K to field for cable and other similar Hastelloy® substrate, with the neutral currents at CERN, Luciano Maiani as low as 4K and in various applications option to vary the thickness of refl ects on their impact. magnetic fields for motors, the silver cap layer suitable for generators and other high-field these grid protection devices magnetics In a seminar at CERN on 19 July 1973, Paul Musset of the Gar- Contact us today about our Quick Ship program gamelle collaboration presented the fi rst direct evidence of weak Offering expert engineering & coil winding services neutral currents. They had discovered events in which a neutrino Fig. 1. A hadronic neutral current event, where the interaction of scattered from a hadron (proton or neutron) without turning into a the neutrino from the left produces three secondary particles, all 450 Duane Ave. ■ Schenectady, NY 12304 ■ USA Inc. Tel: 518-346-1414 ■ Fax: 518-346-6080 muon (fi gure 1) – the signature of a hadronic weak neutral current. clearly identifi able as hadrons, as they interact with other nuclei www.superpower-inc.com ■ [email protected] superior performance. powerful technology. In addition they had one leptonic event characterized by a single in the liquid. There is no charged lepton. electron track (fi gure 2). A month later, Gerald Myatt presented the results on a global stage at the 6th International Symposium on Elec- tron and Photon Interactions at High Energies in Bonn. By then, two papers detailing the discovery were in the offi ces ofPhysics Letters and were published together on 3 September. A few days later, the Key Physics Books from CRC Press results were presented in Aix-en-Provence at the International Euro- 100 Years of Superconductivity Particle and Astroparticle Physics physics Conference on High-Energy Particle Physics, where they Horst Rogalla & Peter H. Kes Utpal Sarkar were aired as part of a large programme of events for the public. Emphasizing key developments in the early 1950s and 1960s, this This book discusses group and field theories, summarizes the Earlier in May, Luciano Maiani was with Nicola Cabibbo at their book looks at how superconductivity started to permeate society standard model of particle physics, and includes some extensions university in Rome when Ettore Fiorini visited, bringing news of and how most of today’s applications are based on the innovations to the model, such as neutrino masses and CP violation. The book of those years. It also explores the genuine revolution that occurred explores grand unified theories, supersymmetry, the general theory what the Gargamelle collaboration had found in photographs of neu- with the discovery of high temperature superconductors. of relativity, higher dimensional theories of gravity, and superstring trino interactions in the huge heavy-liquid bubble chamber at CERN. ISBN 978-1-4398-4946-0 |£66.99 | 2011 theory. The main problem facing the collaboration was to be certain that the ISBN 978-1-58488-931-1 | £69.99 | 2007 XAFS for Everyone events were from neutrinos and not from neutrons that were liber- Scott Calvin The Standard Model and Beyond ated in interactions in the material surrounding the bubble chamber This text provides a practical, thorough guide to x-ray absorption Paul Langacker (CERN Courier September 2009 p25). Fiorini described how the Fig. 2. The fi rst leptonic neutral current event. An antineutrino fine-structure (XAFS) spectroscopy for both novices and seasoned The Standard Model and Beyond presents an advanced introduction practitioners from a range of disciplines. Cartoon characters and to the physics and formalism of the standard model and other researchers had overcome this in their analysis, one of the important coming from the left knocks an electron forwards, creating a easy-to-follow illustrations introduce multiple viewpoints without non-abelian gauge theories. It provides a solid background for factors being the size of Gargamelle. “He explained that the secret characteristic shower of electron–positron pairs. distracting from the main narrative. understanding supersymmetry, string theory, extra dimensions, was the volume,” Maiani recalls, “which could kill the neutron back- ISBN 978-1-4398-7863-7 | £63.00 | 2013 dynamical symmetry breaking, and cosmology. ISBN 978-1-4200-7906-7 | £52.99 | 2009 ground.” Maiani at least was convinced that the collaboration had For Maiani, the theoretical steps began in 1962 with his colleague Particle and Particle Systems observed neutral currents. It was a turning point along the road to Cabibbo’s work that restored universality in weak interactions. The Characterization Gauge Theories in Particle Physics: A Practical today’s Standard Model of particles and their interactions, he says. problem that Cabibbo had resolved concerned an observed difference Small-Angle Scattering (SAS) Applications Introduction, Fourth Edition - 2 Volume set Weak neutral currents, which involve no exchange of electric in the strength of weak decays of strange particles compared with Wilfried Gille Ian J.R. Aitchison & Anthony J.G. Hey This book is aimed at those scientists using small-angle scattering The fourth edition of this bestselling two-volume set continues to charge between the particles concerned, are the manifestation of the muons and neutrons. His solution, formulated before the proposal of for the study of densely packed systems, an area where there has provide a fundamental introduction to advanced particle physics exchange of the neutral vector boson, Z, which mediates the weak quarks, was based on a weak current parameterized by a single angle been considerable progress due to new mathematical models. It while incorporating substantial new experimental results, especially interaction together with the charged bosons, W±. The discovery of – later known as the Cabibbo angle. will be essential reading for material scientists, physicists, in the areas of CP violation and neutrino oscillations. nano-scientists and crystallographers. ISBN 978-1-58488-931-1 | £69.99 | 2007 these neutral currents in 1973 was crucial experimental support for During the next 10 years, not only did the concept of quarks as ISBN 978-1-4665-8177-7 | £89.00 | December 2013 the unifi cation of electromagnetic and weak interactions in elec- fundamental particles emerge but other elements of today’s Stand- troweak theory. This theory – for which Sheldon Glashow, Abdus ard Model developed, too. In 1970, for example, Maiani, Glashow SAVE 20% when you order online and enter Promotional Code JKM23 Salam and Steven Weinberg received the Nobel Prize in Physics in and Iliopoulos put forward a model that involved a fourth quark, FREE standard shipping when you order online. ▲ 1979 – became one of the pillars of the Standard Model. charm, to deal correctly with divergences in weak-interaction 53 p52.indd 1 12/08/2013 15:18 CERNCOURIER www. V OLUME 5 3 N UMBER 7 S EPTEMBER 2 0 1 3 CERN Courier September 2013 Anniversary The two papers from the 23 September 1973 issue of Physics Letters together NEW VERSIONS showed that FOR SILICON100V PHOTO MULTIPLIERS Gargamelle had discovered weak neutral currents. ・NHS, EHS, VHS modules ・NIM, Eurocassette and VME ・ resolution voltage set/meas 0.5 mV ・ ripple and noise typ. 1mVp-p theory. Their idea was based on a simple analogy between the weak ・ 24 bit ADC / 20 bit DAC hadronic and leptonic currents. As their paper stated, the model Physicists meet the public at Aix featured “a remarkable symmetry between leptons and quarks” – ・ 4 / 6 / 8 / 12 / 16 / 32 channel versions and this brought the neutral currents of the electroweak unifi cation During the week of the Aix Conference more attention than usual was given of Weinberg and Salam into play in the quark sector. One important to the need for communication with non-physicists. A plenary session was implication was a large suppression of strangeness-changing neu- held on “Popularizing High Energy Physics” and on several evenings “La tral currents through what became known as the GIM mechanism. Physique dans la Rue” events were organized in the town centre. Maiani now says that at this point no one was talking in terms One evening saw a more classical presentation of information with www.iseg-hv.com/100V of a standard theory, even though many of the elements were there talks by Louis Leprince-Ringuet (on the beauties of pure research), – charm, intermediate vector bosons and the Brout-Englert-Higgs Bernard Gregory (on the role of fundamental science and its pioneering AH0513B_PPG-LTD_Nanopositioners_193x125_Layout 1 5/8/2013+49.351.26996-0 11:03 AM Page 1 | www.iseg-hv.com mechanism for electroweak-symmetry breaking. However, per- role in international collaboration) and Valentine Telegdi (on the intricate ceptions began to change around 1972 with the work of Gerardus subject of neutral currents). More than 600 people heard these talks, no 11 10 Aerotech nanopositioners provide the nanometer- ’t Hooft and Martinus Veltman, who showed that electroweak doubt attracted particularly by the well known television personality of 9 8 7 level linear accuracy and sub-arc-second rotary Leprince-Ringuet. 6 theory could be self-consistent through renormalization (CERN Aerotech Nanopositioners 5 4 Position (nm) accuracy required for today’s leading research, ● CERN Courier October 1973 pp297–298 (extract).