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Title of Journal: Nuovo Cimento A 19651970

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Abbravation: Il Nuovo Cimento A (1965-1970)

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Springer Berlin Heidelberg

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DOI

10.1016/0091-6749(78)90462-1

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1826-9869

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Primakoff effect and πSuperscript0/Superscript

Authors: G Bellettini C Bemporad P L Braccini L Foà
Publish Date: 2015/12/28
Volume: 40, Issue: 4, Pages: 1139-1170
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Abstract

The results of an experiment to measure the π0 lifetime via the inverse decay process “Primakoff effect” are presented The coherent photoproduction of neutral pions in the reaction γ+Pb→π0+Pb has been measured with very high angular resolution with a π0 detector containing 10 independent counting channels at the two mean energies 950 and 1000 MeV using the bremsstrahlung beam of the Frascati electron synchrotron The angular distributions show a characteristic bumping around the forward direction giving conclusive evidence for the existence of the Primakoff effect The results are interpreted in terms of two amplitudesthe electromagnetic and the nuclear oneadding up coherently to give the overall coherent crosssection Such a crosssection is expressed in terms of four unknown parameters the lifetime τ the phase δ between the electromagnetic and nuclear amplitude the strengthC of the nuclear amplitude and the nuclear radiusR0 Neutralpion reabsorption inside nuclear matter is taken into account and a χ2 analysis of the data is done in terms of τ δC andR The best fit τ value is 073±0105·10−16s Systematic errors as well as the sensitivity of the results to the model used to interpret the data are extensively discussed and conservatively taken into accountPresentiamo i risultati di un esperimento volto a misurare la vita media del π0 tramite il processo inverso al decadimento «effetto Primakoff» Abbiamo misurato con alta risoluzione angolare la fotoproduzione coerente di mesoni neutri nella reazione γ+Pb→π0+Pb alle due energie medie di 950 e 1000 MeV usando un rivelatore di π0 contenente 10 canali indipendenti di conteggio Le distribuzioni angolari hanno un caratteristico picco anteriore che dà la prova conclusiva dellesistenza delleffetto Primakoff Abbiamo interpretato i risultati in termini di due ampiezze—quella elettromagnetica e quella nucleare—che si sommano coerentemente per dare la sezione durto coerente complessiva Questa sezione durto si esprime in funzione di quattro parametri incogniti la vita media τ la fase δ fra la ampiezza elettromagnetica e lampiezza nucleare lintensitàC della ampiezza nucleare ed il raggioR del nucleo Abbiamo tenuto conto del riassorbimento dei pioni neutri nella materia nucleare ed abbiamo eseguito una analisi del χ2 dei dati in funzione di τδC eR Il valore di bestfit di τ è 073±0105·10−16s Discutiamo per esteso gli errori sistematici e la sensibilità dei risultati al modello usato per interpretare i dati e ne teniamo conto con buon margine di sicurenzza

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Other Papers In This Journal:
  1. Second-order phase transitions in three dimensions
  2. Projector in constrained quantum dynamics
  3. Pion inclusive distribution at cosmic-ray energies and comparison with ISR data
  4. Analysis of the reaction π + p → ρ 0 Δ ++ at 11.7 GeV/c incident momentum
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  6. A new approach to heavy-ion fusion
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  9. Surface waves in pion-proton elastic scattering
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  14. Doppler shift attenuation measurements on 57 Fe and 57 Co
  15. Charge radii of nucleons
  16. Regge poles with kinematic cuts in pion photoproduction
  17. Existence of solutions of partial-wave dispersion relations and singular N/D equations
  18. SU 9 «composite» symmetry and weak interactions
  19. Small-angle scattering and absorption of 3.0 GeV/c antiprotons in nuclear emulsion
  20. The spectrum of b $$\bar c$$ , t $$\bar c$$ and t $$\bar b$$ ; bound states in the two-step potential model
  21. The sequential light-particle emission in peripheral heavy-ion collisions. A theoretical approach
  22. Energy gain of spherical shell targets ablatively imploded by thermal radiation
  23. Finite-energy sum rules on hyperbolas. — II
  24. K X-ray spectrum of Na excited by photons
  25. Singular-value decomposition of the nucleon-nucleon reactance matrix
  26. Inelastic π - 3 He interaction at 180 MeV 3 He interaction at 180 MeV
  27. Mechanism of particle production in nucleon-nucleon interactions at very high energies
  28. 852 keV first-forbidden beta transition in 115 Cd g
  29. Natural orbital calculations of nucleon momentum distributions
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  31. Two-variable crossing-symmetric expansion of the ππ scattering amplitude and low-energy parameter sum rules
  32. Reduction of complex electromagnetic fields to the irreducible representations of the inhomogeneous Lorentz group
  33. Investigation of the 149 Sm (n, α) 146 Nd reaction induced by fast neutrons
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  35. The $$\bar K$$ N system near thresholdsystem near thresholdСистема $$\bar K$$ N вблиэи порогавблиэи порога
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  39. Absorption corrections for the double peripheral model
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  43. Heavy-ion reactions with nucleon transfer
  44. Vertex functions and form factors for conformal spin-1/2 systems
  45. Baryon properties in chiral models
  46. Nuclear models and the hypernuclear interaction
  47. A χ 2 -test to study the α 1 , α 2 , α 3 convergence for high-precision LEP data, having in mind the SUSY threshold
  48. A study of the low-mass part of the (Kππ) system in the reaction K − p→K − pπ + π − at 8.25 GeV/c
  49. A homological approach to parametric Feynman integrals
  50. Once more on the role of the bound-state wave function in the leptonic decays of light hadrons
  51. Dynamical fission and transitional mechanisms in medium-mass heavy-ion reactions
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  53. Direct reconstruction of the pp scattering matrix below 500 MeV, an attempt
  54. Alternative interaction between spinor and Yang-Mills fields
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  58. A new approach to conformal invariant field theories
  59. Effective trajectories in the presence of Regge cuts
  60. π—-p interactions at 650 MeV
  61. Composite gauge fields from nonlinear realizations
  62. Approximate saturation of the algebra of axial currents
  63. A general treatment of current algebra
  64. Piecewise analyticity of S -matrix elements and nonlocal interactions
  65. The deck model for nucleon diffraction dissociation at very high energies
  66. Deformation and interaction energies in statistical multifragmentation
  67. Strings and fields
  68. Bound states of the two-dimensional O N model at finite temperatures
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  71. Off-energy-shell phase shifts in potential scattering
  72. A boundary-condition model for the P 33 pion-nucleon state
  73. O 4 invariance of a Bethe-Salpeter equation
  74. Tests for general models of deep inelastic lepton scattering
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  77. Nonstatistical structures in 12 C( 14 N, 4 He) 22 Na reaction
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  79. Fully-symmetric dual models and Lorentz invariance
  80. A temporarily free SU 6 gauge field theory model for strong interactions
  81. Inclusive and exclusive cross-sections in K − p interactions at 14.3 GeV/c
  82. Parafermion representations of the lie-algebra chain O 7 ⊃ G 2 ⊃ SU 3
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  106. Semi-relativistic equation for quark-antiquark systems
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  108. Gross features of pionization and fragmentation
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