Martin Lewis Perl (June 24, 1927 – September 30, 2014) was an American chemical engineer and physicist who won the Nobel Prize in Physics in 1995 for his discovery of the tau lepton .
23-692: The Oscillation Project with Emulsion-tRacking Apparatus ( OPERA ) was an instrument used in a scientific experiment for detecting tau neutrinos from muon neutrino oscillations . The experiment is a collaboration between CERN in Geneva , Switzerland , and the Laboratori Nazionali del Gran Sasso (LNGS) in Gran Sasso , Italy and uses the CERN Neutrinos to Gran Sasso (CNGS) neutrino beam . The process started with protons from
46-509: A few millimetres of the collision. Hence Perl and his coworkers did not detect the tau directly, but rather discovered anomalous events where they detected either an electron and a muon, or a positron and an antimuon: We have discovered 64 events of the form for which we have no conventional explanation. The need for at least two undetected particles was shown by the inability to conserve energy and momentum with only one. However, no other muons, electrons, photons, or hadrons were detected. It
69-590: A graduate student in physics in 1950. He received his Ph.D. from Columbia University in 1955, where his thesis advisor was I.I. Rabi . Perl's thesis described measurements of the nuclear quadrupole moment of sodium , using the atomic beam resonance method that Rabi had won the Nobel Prize in Physics for in 1944. Following his Ph.D., Perl spent 8 years at the University of Michigan , where he worked on
92-409: A muon neutrino beam. On 6 June 2012, OPERA announced the observation of a second tau neutrino event. On 26 March 2013, the experiment caught for the third time a muon neutrino oscillating into a tau neutrino during travel from CERN to LNGS . The fourth one was found in 2014, and the fifth was seen in 2015. In September 2011, OPERA researchers observed muon neutrinos apparently traveling faster than
115-420: A neutrino interaction and its corresponding brick are tagged in real time by the scintillators and spectrometers. These bricks are extracted from the walls asynchronously with respect to the beam for film development, scanning and for the topological and kinematic search of tau decays. In total, five tau neutrinos were detected. On 31 May 2010, OPERA researchers observed the first tau neutrino candidate event in
138-555: Is an elementary particle similar to the electron, with negative electric charge and a spin of 1 ⁄ 2 , but with 3477 times the mass. Together with the electron , the muon , and the three neutrinos , it is classified as a lepton . The tau was first detected in a series of experiments between 1974 and 1977 by Perl with his colleagues at the SLAC - LBL group. Their equipment consisted of SLAC 's then-new e – e colliding ring, called SPEAR , and
161-605: The Department of Energy 's Office of Science , the National Science Foundation , and the National Institute of Standards and Technology . He died after a heart attack at Stanford University Hospital on September 30, 2014, at the age of 87. His son, Jed Perl , is an author and art critic for The New Republic . The tau lepton (τ, also called the tau particle, tauon or simply tau)
184-465: The LBL magnetic detector. They could detect and distinguish between leptons, hadrons and photons . SPEAR was able to collide electrons and positrons at higher energies than had previously been possible, initially at up to 4.8 GeV and eventually at 8 GeV, energies high enough to lead to the production of a tau/antitau pair. The tau has a lifetime of only 2.9 × 10 s and so these particles decayed within
207-747: The Standard Model (i.e., it was observed 12 years before the discovery of the Higgs boson in 2012). Martin Lewis Perl Perl was born in New York City, New York. His parents, Fay (née Resenthal), a secretary and bookkeeper, and Oscar Perl, a stationery salesman who founded a printing and advertising company, were Jewish immigrants to the US from the Polish area of Russia . Perl
230-593: The Super Proton Synchrotron (SPS) at CERN being fired in pulses at a carbon target to produce pions and kaons . These particles decay to produce muons and neutrinos . The beam from CERN was stopped on 3 December 2012, ending data taking, but the analysis of the collected data has continued. OPERA, in Hall C of the Gran Sasso underground labs, was built in 2003–2008. The taus resulting from
253-512: The speed of light . In February and March 2012, OPERA researchers blamed this result on a loose fibre optic cable connecting a GPS receiver to an electronic card in a computer. On 16 March 2012, a report announced that an independent experiment in the same laboratory, also using the CNGS neutrino beam, but this time the ICARUS detector found no discernible difference between the speed of a neutrino and
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#1732772871769276-561: The tau ( τ ) , it forms the third generation of leptons , hence the name tau neutrino . Its existence was immediately implied after the tau particle was detected in a series of experiments between 1974 and 1977 by Martin Lewis Perl with his colleagues at the SLAC – LBL group. The discovery of the tau neutrino was announced in July 2000 by the DONUT collaboration (Direct Observation of
299-679: The Nu Tau). In 2024, the IceCube Neutrino Observatory published findings of seven astrophysical tau neutrino candidates. The DONUT experiment from Fermilab was built during the 1990s to specifically detect the tau neutrino. These efforts came to fruition in July ;2000, when the DONUT collaboration reported its detection. The tau neutrino is last of the leptons, and is the second most recent discovered particle of
322-472: The detection of the neutrino ". In 1996 he published Reflections on Experimental Science , which consists of "comments, scientific reprints, reflections, and a memoir ...". He joined University of Liverpool as a visiting professor. He served on the board of advisors of Scientists and Engineers for America , an organization focused on promoting sound science in American government. In 1996, he received
345-437: The interaction of tau neutrinos are observed in "bricks" of photographic films ( nuclear emulsion ) interleaved with lead sheets. Each brick weighs 8.3 kg; the two OPERA supermodules contain 150,000 bricks arranged into parallel walls interleaved with plastic scintillator counters. Each supermodule is followed by a magnetic spectrometer for momentum and charge identification of penetrating particles. During data collection,
368-526: The mass and spin of the tau. The symbol τ was derived from the Greek τρίτον ( triton , meaning "third" in English), since it was the third charged lepton discovered. Perl won the Nobel Prize in 1995 jointly with Frederick Reines . The prize was awarded "for pioneering experimental contributions to lepton physics". Perl received half "for the discovery of the tau lepton" while Reines received his share "for
391-649: The opportunity to start planning experimental work in this area when he moved in 1963 to the Stanford Linear Accelerator Center (SLAC), then being built in California . He was particularly interested in understanding the muon : why it should interact almost exactly like the electron but be 206.8 times heavier, and why it should decay through the route that it does. Perl chose to look for answers to these questions in experiments on high-energy charged leptons . In addition, he considered
414-415: The physics of strong interactions , using bubble chambers and spark chambers to study the scattering of pions and later neutrons on protons . While at Michigan, Perl and Lawrence W. Jones served as co-advisors to Samuel C. C. Ting , who earned the Nobel Prize in Physics in 1976. Seeking a simpler interaction mechanism to study, Perl started to consider electron and muon interactions. He had
437-516: The possibility of finding a third generation of lepton through electron- positron collisions. Perl is one of the 20 American recipients of the Nobel Prize in Physics to sign a letter addressed to President George W. Bush in May 2008, urging him to "reverse the damage done to basic science research in the Fiscal Year 2008 Omnibus Appropriations Bill" by requesting additional emergency funding for
460-460: The speed of light. In May 2012, the Gran Sasso experiments BOREXINO, ICARUS, LVD and OPERA all measured neutrino velocity with a short-pulsed beam, and obtained agreement with the speed of light, showing that the original OPERA result was mistaken. Finally in July 2012, the OPERA collaboration updated their results. After the instrumental effects mentioned above were taken into account, it was shown that
483-413: The speed of neutrinos is consistent with the speed of light. This was confirmed by a new, improved set of measurements in May 2013. 42°28′N 13°34′E / 42.46°N 13.57°E / 42.46; 13.57 Tau neutrino The tau neutrino or tauon neutrino is an elementary particle which has the symbol ν τ and zero electric charge . Together with
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#1732772871769506-678: Was a 1948 chemical engineering graduate of Brooklyn Polytechnic Institute (now known as NYU-Tandon ) in Brooklyn. After graduation, Perl worked for the General Electric Company , as a chemical engineer in a factory producing electron vacuum tubes. To learn about how the electron tubes worked, Perl signed up for courses in atomic physics and advanced calculus at Union College in Schenectady, New York , which led to his growing interest in physics, and eventually to becoming
529-480: Was proposed that this event was the production and subsequent decay of a new particle pair: This was difficult to verify, because the energy to produce the τ τ pair is similar to the threshold for D meson production. Work done at DESY -Hamburg, and with the Direct Electron Counter (DELCO) at SPEAR , subsequently confirmed the discovery and established
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