A remeasurement of the Panofsky ratio

Spuller, J.; Berghofer, D.; Hasinoff, M.; MacDonald, R.; Measday, D.F.; Salomon, M.; Suzuki, Tatsuo; Poutissou, J. M.; Poutissou, R.; Lee, J.K.P.

doi:10.1016/0370-2693(77)90449-x

Cited by 114 publications

(43 citation statements)

References 6 publications

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“…[2,3] but is proportional to oq x o2 which has a vanishing matrix element here. We neglect the very small contributions of b and p mesons in Fig.…”

Section: Mmentioning

confidence: 99%

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Role of heavy meson exchange in near thresholdNN→dπ

Horowitz

1993

Phys. Rev. C

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The total cross section for NN~der very near threshold is calculated in a simple distorted wave impulse approximation including one-body, pion rescattering, and sigma and omega meson exchange current (MEC) contributions. Calculations with MEC are in good agreement with recent TRIUMF measurements while calculations without MEC are signi6. cantly smaller. Thus the MEC mechanism, which was proposed to explain a large enhancement in the pp~pp7r cross section, is consistent with NN~der data. PACS number(s): 13.75.Cs, 21.30. +y

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“…[2,3] but is proportional to oq x o2 which has a vanishing matrix element here. We neglect the very small contributions of b and p mesons in Fig.…”

Section: Mmentioning

confidence: 99%

“…This result can be explained by a cr meson exchange current (MEC) which enhances both the axial charge and s-wave pion production [2,3]. This could have important implications for our understanding of pion production and absorption reactions and axial MEC.…”

Section: Introductionmentioning

confidence: 99%

Role of heavy meson exchange in near thresholdNN→dπ

Horowitz

1993

Phys. Rev. C

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“…Here r B = 222.56 fm is the Bohr radius in π − p, Q 0 = 0.142 fm −1 is the cms momentum of the π 0 , P = 1.546 ± 0.009 is the Panofsky ratio of π − p → π 0 n to π − p → γ n [13]. The correction parameter δ contains, among others, isospin symmetry breaking effects, calculated within the framework of ChPT [14].…”

Section: Pion Nucleon Interactionmentioning

confidence: 99%

Determination of the hadronic width of the ground state in pionic hydrogen

Hirtl

2009

Hyperfine Interact

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In a new high-precision experiment at the Paul Scherrer Institut (PSI), the hadronic shift (ε 1s ) and width ( 1s ) of the ground state of pionic hydrogen, which are directly connected to the pion-nucleon isospin scattering lengths, were remeasured (PSI-Experiment R-98-01 Gotta et al. 1998). The results can be confronted with recent work of effective field theories defined in the low-energy limit of quantum chromodynamics (QCD), such as, e. g., chiral perturbation theory (ChPT). In addition, 1s is connected to the pion-nucleon coupling constant f πN . A precisely known value for f πN allows an accurate determination of the Goldberger-Treiman discrepancy, which constitutes a measure of chiral symmetry breaking. This contribution is mainly devoted to describe a method for an accurate extraction of the hadronic width from the π − H data.

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“…The π o → γγ background therefore prohibits a measurement of double radiative capture at large opening angles and endangers the measurement at small opening angles due to the finite resolution of the detector system. Since the branching ratio for charge exchange is much larger in hydrogen (0.607 ± 0.004 [29]) than deuterium ((1.45 ± 0.19) × 10 −4 [32]) the π o → γγ background is more worrisome in hydrogen than in deuterium. Herein we denote the real γ-γ coincidences from π o → γγ decay as the "π o background".…”

Section: Experimental Challengesmentioning

confidence: 99%

Double radiative pion capture on hydrogen and deuterium and the nucleon's pion cloud

et al. 2007

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We report measurements of double radiative capture in pionic hydrogen and pionic deuterium. The measurements were performed with the RMC spectrometer at the TRIUMF cyclotron by recording photon pairs from pion stops in liquid hydrogen and deuterium targets. We obtained absolute branching ratios of (3.02 ± 0.27(stat.) ± 0.31(syst.)) × 10 −5 for hydrogen and (1.42 ± 0.09 0.12 (stat.) ± 0.11(syst.)) × 10 −5 for deuterium, and relative branching ratios of double radiative capture to single radiative capture of (7.68 ± 0.69(stat.) ± 0.79(syst.)) × 10 −5 for hydrogen and (5.44 ± 0.34 0.46 (stat.) ± 0.42(syst.))×10 −5 for deuterium. For hydrogen, the measured branching ratio and photon energy-angle distributions are in fair agreement with a reaction mechanism involving the annihilation of the incident π − on the π + cloud of the target proton. For deuterium, the measured branching ratio and energyangle distributions are qualitatively consistent with simple arguments for the expected role of the spectator neutron. A comparison between our hydrogen and deuterium data and earlier beryllium and carbon data reveals substantial changes in the relative branching ratios and the energy-angle distributions and is in agreement with the expected evolution of the reaction dynamics from an annihilation process in S-state capture to a bremsstrahlung process in P-state capture. Lastly, we comment on the relevance of the double radiative process to the investigation of the charged pion polarizability and the in-medium pion field.

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A remeasurement of the Panofsky ratio

Cited by 114 publications

References 6 publications

Role of heavy meson exchange in near thresholdNN→dπ

Role of heavy meson exchange in near thresholdNN→dπ

Determination of the hadronic width of the ground state in pionic hydrogen

Double radiative pion capture on hydrogen and deuterium and the nucleon's pion cloud

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