LXI. <i>The laws of deflexion of a particles through large angles</i>

Geiger, H.; Marsden, E.

doi:10.1080/14786440408634197

Cited by 189 publications

(78 citation statements)

References 4 publications

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“…No trecho "Na figura 4-2 mostramos um arranjo típico que ele [Rutherford] e seus colaboradores utilizaram para estudar o espalhamento de partículas alfa ao atravessar folhas delgadas de várias substâncias" [15], os autores deixam transparecer que o experimento foi feito também por Rutherford. Entretanto, o papel (fundamental) do físico foi a análise dos resultados; a Geiger e Marsden coube a execução, o tratamento dos dados e a publicação do experimento [16,17].…”

Section: Modelos Atômicosunclassified

Consequências das descontextualizações em um livro didático: uma análise do tema radioatividade

Cordeiro

Peduzzi

2013

Rev. Bras. Ensino Fís.

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Na década de 1980, Chevallard investigou as transformações sofridas pelo conhecimento científico para se tornar ensinável, chamando esse processo de Transposição Didática. Em livros textos de ciências, em geral, esse processo envolve a apresentação de conteúdos organizados de forma lógica, sem preocupações com as origens histórico-filosóficas do contexto de geração desses conhecimentos. Essa didática descontextualizadora, além de propagar equívocos sobre a natureza da ciência e do trabalho científico,é falha também quando, inadvertidamente, faz uso de conceitos estranhos ao quadro conceitual de origem em que são abordados determinados assuntos, utilizando a história da ciência como mero conteúdo introdutório. Nesse trabalho analisa-se a transposição didática da radioatividade em um livro usado em disciplinas de estrutura da matéria e afins, na formação de professores e futuros cientistas. Palavras-chave: transposição didática, história da ciência, radioatividade, livro didático.In the 1980s, Chevallard investigated the transformations of the scientific knowledge to become teachable, and called this process "Didactic Transposition". In science textbooks, this process generally involves the logic organization of contents, which removes the concepts from their historical and philosophical origins. This outof-context didactics, besides giving rise to mistaken images of the nature of science and the scientific inquiry, fails as well when it inadvertently uses some concepts foreign to the original conceptual background, taking the history of science as merely introductory content. In this paper, the didactic transposition of radioactivity, which is present in a textbook widely used in disciplines such as the structure of matter, for future teachers and scientists, is analyzed. Keywords: didactic transposition, history of science, radioactivity, textbook. IntroduçãoO livro didáticoé a principal fonte de consulta de professores e estudantes, em qualquer nível de ensino. Ao descrever o que denominou de período de ciência normal, o físico e filósofo da ciência Thomas Kuhn [1] faz referência aos livros didáticos como elementos típicos do período, que "expõem o corpo das teorias aceitas, ilustram muitas ou todas as suas aplicações bem sucedidas e comparam essas aplicações com observações e experimentos exemplares". Para Kuhn, os livros são essenciais para transmitiràs novas gerações os conhecimentos aceitos e compartilhados pela comunidade científica.Preocupado com a forma pela qual o conhecimentó e disseminado nos manuais didáticos e na prática docente, Yves Chevallard analisou os processos sofridos pelo conhecimento científico para tornar-se conhecimento escolar, mostrando a distinção fundamental entre seu produto final -em suas palavras, os saberes a ensinar e ensinado -e a matéria-prima, o saber sábio. Sua análise ficou conhecida como transposição didática [2]. Na comunidade acadêmica de ensino de ciências, a análise ganhou muitos adeptos, e tornou-se referência para uma grande variedade de investigações, tanto nas ciên...

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Section: Modelos Atômicosunclassified

Consequências das descontextualizações em um livro didático: uma análise do tema radioatividade

Cordeiro

Peduzzi

2013

Rev. Bras. Ensino Fís.

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“…Ever since Rutherford, Geiger, and Marsden discovered the atomic nucleus by measuring the distribution of alpha particles scattered from gold foils ( [3], [4], and [5]), scattering experiments have been the method of choice of nuclear and particle physicists to examine the microscopic structure of matter. In the mid-1950s, a series of experiments led by Robert Hofstadter at Stanford established electron scattering as a powerful technique for exploring nuclear structure( [6], [7], [8]).…”

Section: Elastic En Scattering: Formalismmentioning

confidence: 99%

Recoil Polarization Measurements of the Proton Electromagnetic Form Factor Ratio to High Momentum Transfer

Puckett

2010

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The electromagnetic form factors of the nucleon characterize the effect of its internal structure on its response to an electromagnetic probe as studied in elastic electronnucleon scattering. These form factors are functions of the squared four-momentum transfer Q 2 between the electron and the proton. The two main classes of observables of this reaction are the scattering cross section and polarization asymmetries, both of which are sensitive to the form factors in different ways. When considering large momentum transfers, double-polarization observables offer superior sensitivity to the electric form factor. This thesis reports the results of a new measurement of the ratio of the electric and magnetic form factors of the proton at high momentum transfer using the recoil polarization technique. A polarized electron beam was scattered from a liquid hydrogen target, transferring polarization to the recoiling protons. These protons were detected in a magnetic spectrometer which was used to reconstruct their kinematics, including their scattering angles and momenta, and the position of the interaction vertex. A proton polarimeter measured the polarization of the recoiling protons by measuring the azimuthal asymmetry in the angular distribution of protons scattered in CH 2 analyzers. The scattered electron was detected in a largeacceptance electromagnetic calorimeter in order to suppress inelastic backgrounds. The measured ratio of the transverse and longitudinal polarization components of the scattered proton is directly proportional to the ratio of form factors G AcknowledgmentsThis thesis would not have been possible without the support and efforts of many, many people. It would be impossible to give all due credit to all of the individual efforts that went into designing, planning, staging, and executing this experiment, and the subsequent analysis of the data. Therefore, any omissions from the following acknowledgments are in no way meant to diminish those contributions.I would like to thank the members of the GEp-III collaboration whose tireless efforts made experiments E04-108 and E04-019 a success. This includes the spokespeople; Ed Brash, Mark Jones, Charles Perdrisat and Vina Punjabi, and the other outstanding physicists involved in the core collaboration. I thank Frank Wesselmann for his successful leadership of the testing, installation, commissioning and operation of the Focal Plane Polarimeter, and his significant contribution to the data analysis in the form of the event decoding and tracking software for the FPP drift chambers. I thank Mark Jones for his encyclopedic knowledge of experimental Hall C and for his outsized contribution to making the various parts of the experiment work together as a whole, and for being called upon more often than not to troubleshoot problems with the experiment as they occurred. Mark's many important contributions to the data analysis included the optimization of the HMS reconstruction coefficients. Much of what I have learned about the actual hands-on require...

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“…dQ2dv-~ 2Wl(Q ,v)sm 2 + W2 (Q 2 ,v)cos 2 2 ], (3) in terms of the two unknown "structure functions" wl and w2. scalar functions that describe the hadronic electromagnetic current.…”

Section: B Cross Section and Structure Functionsmentioning

confidence: 99%

“…This means that the only relevant 4-vectors at the hadronic vertex are p and q, and the only Lorentz-invariant quantities are q 2 and p · q (and p 2 = MJ.). While isolating the hadronic vertex is a productive move toward understanding the scattering process, experimentally it is imp_ortant to note that these quantities can be measured 3 ' < using only the initial and final muons:…”

Section: A Kinematicsmentioning

confidence: 99%

Measurement of the nucleon structure function in iron using 215- and 93-GeV muons

Meyers¹,

Clark

Johnson

et al. 1986

Phys. Rev. D

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We have measured the inclusive deep inelastic scattering of muons on nucleons in iron using beams of 93 and 215GeV muons. To perform this measurement, we have built and operated the Multimuon Spectrometer (MMS) in the muon beam at Fermilab. Using the known form of the radiativelycorrected electromagnetic cross section, we extract the struc- A. KinematicsThe Feynman diagram for deep inelastic lepton-hadron scattering in the lowest order of QED is shown in Fig. 1, together with a summary of our kinematical notation. To this order, the process is described as the exchange of one virtual photon. QED allows us to calculate unambiguously what happens at the leptonic (upper) vertex. The goal of our experiment is to uncover what happens in the region surrounding the hadronic vertex.We will be studying inclusive scattering, p.N -+ p.X, with no reference to any particular hadronic final state. This means that the only relevant 4-vectors at the hadronic vertex are p and q, and the only Lorentz-invariant quantities are q 2 and p · q (and p 2 = MJ.). While isolating the hadronic vertex is a productive move toward understanding the scattering process, experimentally it is imp_ortant to note that these quantities can be measured 3 ' < using only the initial and final muons:Q 2 = -q 2 = 4EE'sin 2 ~. where E, E', and 9 are the initial and final muon energies and the muon scattering angle as measured in the laboratory frame (the target rest frame). Terms containing the lepton mass have been neglected. Another useful quantity is the invariant mass of the hadronic final state: W 2 = (p + q) 2 = MJ. + 2MNv-Q 2 • The elastic limit is W 2 = MJ. or Q 2 = 2MNV. Resonances appear at fixed W 2 near this limit. Figure 2 shows the region of the Q 2 -v plane accessible to inelastic scattering at fixed incident energy E.It is convenient to describe another set of variables that are Q 2 and v scaled by their maximum values, neglecting lepton masses:v = Q 2 j2MNE = xy. B. Cross section and structure functionsBy demanding Lorentz covariance and gauge invariance we can translate 7 • 8 the diagram of Fig. 1 directly into an expression for the spin-averaged inclusive cross section:dQ2dv-~ 2Wl(Q ,v)sm 2 + W2 (Q 2 ,v)cos 2 2 ], (3) in terms of the two unknown "structure functions" wl and w2. scalar functions that describe the hadronic electromagnetic current. We treat the incident muon as a source of virtual photons and write the cross section as where T and L refer to transversely and longitudinally polarized virtual ph'?tons and K is a flux factor. Defining R = uL/uT we can eliminate W 1 in favor of R in the cross section Eq. 3. The advantages of this substitution will be described in the next section where it is shown that for some cases of interest R is expected to be small. For now we record the cross section in its new form, The approximate form comes from taking the Bjorken limit where energies (E,Q 2 ,v)-+ oo with x and y-finite. 10 In the kinematic region covered by our data, making such an approximation has a maximum effect of < ! % on our ...

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LXI. The laws of deflexion of a particles through large angles

Cited by 189 publications

References 4 publications

Consequências das descontextualizações em um livro didático: uma análise do tema radioatividade

Consequências das descontextualizações em um livro didático: uma análise do tema radioatividade

Recoil Polarization Measurements of the Proton Electromagnetic Form Factor Ratio to High Momentum Transfer

Measurement of the nucleon structure function in iron using 215- and 93-GeV muons

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