On the Decay Process of Positive and Negative Mesons

Conversi, M.; Pancini, E.; Piccioni, O.

doi:10.1103/physrev.68.232

Cited by 61 publications

(11 citation statements)

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“…Since its discovery in the forties [1], nuclear muon capture (NMC) has been a probe par excellence for both weak interaction studies and exploring nuclear dynamics [2]. In the context of QCD, the nucleus provides a new vacuum, wherein quark and gluon condensates can have entirely different values from those in the free hadrons [3], thereby opening the possibility of nuclear renormalization of the hadronic weak couplings [4].…”

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confidence: 99%

Inclusive muon capture in light nuclei

et al. 1998

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We study total muon capture rates in light (A ∼ 6-18) nuclei, taking into account renormalizations of the nuclear vector and axial vector strengths. We estimate the influence in the results of uncertainties of the spin-isospin interaction parameter g ′ and nuclear densities. A few of these reactions are theoretical benchmarks for physics involving searches for neutrino oscillations. New experiments in muon capture in several targets are suggested, in the light of some discrepancies with theory, crudeness of some experimental results and relevance to neutrino physics.

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confidence: 99%

Inclusive muon capture in light nuclei

et al. 1998

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“…Experiments designed to perform these searches are also sensitive to muon decays where new particles like Goldstone and pseudo-Goldstone bosons are produced. The muon, the first particle to be studied with modern particle physics techniques in the pioneering work by Conversi, Pancini and Piccioni [3], still provides one of the best playgrounds for the development of fundamental physics.…”

Section: Discussionmentioning

confidence: 99%

“…Since the discovery of the muon in the cosmic ray radiation [1], the study of the properties and decays of this particle contributed to build and test the Standard Model (SM) of particle physics. Although this particle was initially identified as the mesotron proposed by Yukawa [2] in its theory of strong interactions, this interpretation was discarded by the experiments conducted by Conversi, Pancini and Piccioni in the years 1940s [3,4], which marked the birth of particle physics both from an experimental and theoretical point of view. Soon after, Hincks and Pontecorvo [5] started to look for the µ + → e + γ decay, and the missing observation of photons among the muon decay products demonstrated that it could not be considered just as an excited state of the electron.…”

Section: Introductionmentioning

confidence: 99%

Experimental searches for muon decays beyond the Standard Model

Renga

2019

Reviews in Physics

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The study of muon properties and decays played a crucial role in the early years of particle physics and contributed over decades to build and consolidate the Standard Model. At present, searches for muon decays beyond the Standard Model are performed by exploiting intense beams of muons, and plans exist to upgrade the present facilities or build new ones, which would open new prospects for the quest of new physics in this sector. In this paper I review the present status of the search for muon decays beyond the Standard Model, with a special attention to the most conventional muon lepton flavor violation experiments, but also considering more exotic scenarios and future outlooks. Experimental techniques for muon decay studiesAs already mentioned, the muon was discovered and firstly studied in the cosmic ray radiation. A significative step forward in the study of its properties and decay modes was performed when pion beam became available in the years 1950s. Pions can be stopped in a target and the muons produced in their decays can be studied. Finally, the first muon beams were delivered in the years 1970s.Muon beams are usually produced starting from a proton beam impinging on a target and producing pions. Pions decaying in the target itself produce muons that can be collected and transported by a beam line toward the experimental areas where the detectors are installed. The most intense continuous muon beams in the world [10,11] are currently delivered at the Paul Scherrer Institut (PSI), in Villigen (CH). A 2 mA current of protons of 590 MeV kinetic energy from the PSI Ring Cyclotron hits two different graphite targets where, in total, ∼ 18% of the protons are stopped, the rest being preserved to serve a downstream neutron spallation source. The two targets serve different beam lines. In order to get an intense, pure and monoenergetic muon beam, particles with momentum p ∼ 28 MeV/c are selected, corresponding to muons emitted by pions decaying at rest. It happens when the pion decays right on the surface of the production target (surface muons). The beam can be further purified by selecting particles with a given velocity (and hence a given mass) by means of a Wien filter, a superposition of orthogonal electric (E) and magnetic (B) fields through which only particles with the desired velocity v = E/B go straight, while others are removed by collimators. Beams with up to a few 10 8 surface muons per second can be currently delivered at PSI.In the Ring Cyclotron at PSI protons travel in bunches with a repetition rate of about 50 MHz. The pion lifetime (∼ 26 ns) is large enough to spoil the time structure of the beam and make a practically continuous muon beam. For some applications, pulsed beams are instead necessary. For instance, the Delivery Ring at Fermilab (Batavia, USA) used for the Mu2e experiment [12] provides protons in bunches separated in time by 1695 ns. They hit a target and produce muons that mostly arrive to the experimental apparatus within a few hundred ns. After about 700 ns and before the nex...

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“…No período 1943−1946, esses italianos realizaram uma série de experimentos em Roma, onde mediram com grande precisão a vida-média dos mésotrons, encontrando (2,33 ± 0,15) microssegundo [25,26], como também estudaram a absorção desses mésotrons na matéria [27,28].…”

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70 Years of π-Meson with César Lattes

Tavares¹

2018

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Início da pesquisa em Física Moderna no Brasil Hideki Yukawa e a hipótese da força nuclear Descoberta do mésotron na radiação cósmica Início da carreira científica de Lattes (1943-1946) A motivação que levou Lattes a Bristol (Inglaterra) As emulsões Ilford e a competição nas alturas Donald Perkins e o méson-π negativo Conversi, Pancini e Piccioni: mésotrons negativos não são os mésons de Yukawa A grande descoberta: desintegração méson → mésotron (π → µ) A maratona de 1947: Lattes em Chacaltaya Desintegração π → µé confirmada Resumo das investigaçẽs sobre mésons em altitudes de montanha Divulgação e visita de César Lattes a Niels Bohr Os cíclotrons da Universidade da Califórnia (Berkeley) na década de 1930 Os CALUTRONS e a bomba sobre Hiroshima O cíclotron de 184 polegadas em Berkeley Motivação de Lattes para ir a Berkeley Lattes a caminho de Berkeley Produção de píons em colisões núcleo-núcleo Mésons-π − no cíclotron de 184 polegadas do UCRL (Berkeley) 1948: pioneirismo de Lattes na detecção de píons negativos artificiais Ampla divulgação pela imprensa e nos meios científicos Detecção de píons positivos no cíclotron de 184 polegadas Primeiras medidas de massa dos píons e múons Desdobramentos imediatos e alcance dos feitos de César Lattes Epílogo Bibliografia Geral e Referências citadas Agradecimento Sobre o autor Apêndice A: Como píons são produzidos em colisões núcleo-núcleo Apêndice B: Ganhadores do Prêmio Nobel mencionados neste artigo

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On the Decay Process of Positive and Negative Mesons

Cited by 61 publications

References 4 publications

Inclusive muon capture in light nuclei

Inclusive muon capture in light nuclei

Experimental searches for muon decays beyond the Standard Model

70 Years of π-Meson with César Lattes

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