Calculation of the Doppler broadening of the electron-positron annihilation radiation in defect-free bulk materials

Ghosh, V.J.; Alatalo, M.; Asoka‐Kumar, P.; Nielsen, B.; Lynn, Kelvin G.; Kruseman, A.C.; Mijnarends, P.E.

doi:10.1103/physrevb.61.10092

Cited by 70 publications

(52 citation statements)

References 31 publications

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“…Up to p e − ∼ 15 × 10 −3 m e the main contribution to the annihilation comes from electrons in the 5d shell, beyond that point 4f electrons dominate, while the contribution of the high momentum core electrons becomes relevant only for p e − ≳ 40 × 10 −3 m e where, however, the annihilation probability is suppressed below 10 . Accordingly, we find that a good fit to the experimental and calculated distributions [41] can be obtained with the sum of just three terms: 3. The positron annihilation probability as a function of the target electron momentum for tungsten (figure adapted from Ref.…”

Section: Effects Of Target Electrons Velocitiesmentioning

confidence: 99%

“…The positron annihilation probability as a function of the target electron momentum for tungsten (figure adapted from Ref. [41]). The blue crosses represent experimental points, while the red dashed line is the result of the calculation method adopted in [41].…”

Section: Effects Of Target Electrons Velocitiesmentioning

confidence: 99%

“…[41]). The blue crosses represent experimental points, while the red dashed line is the result of the calculation method adopted in [41]. The green dot-dashed line corresponds to the fit given by the function in Eq.…”

Section: Effects Of Target Electrons Velocitiesmentioning

confidence: 99%

“…In Fig. 3 (adapted from [41]) a large set of experimental points for 74 W is represented with blue crosses. The red dashed line represents a theoretical calculation performed in the same paper.…”

Section: Effects Of Target Electrons Velocitiesmentioning

confidence: 99%

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Resonant production of dark photons in positron beam dump experiments

et al. 2018

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Positrons beam dump experiments have unique features to search for very narrow resonances coupled superweakly to e þ e − pairs. Due to the continued loss of energy from soft photon bremsstrahlung, in the first few radiation lengths of the dump a positron beam can continuously scan for resonant production of new resonances via e þ annihilation off an atomic e − in the target. In the case of a dark photon A 0 kinetically mixed with the photon, this production mode is of first order in the electromagnetic coupling α, and thus parametrically enhanced with respect to the Oðα 2 Þe þ e − → γA 0 production mode and to the Oðα 3 ÞA 0 bremsstrahlung in e − -nucleon scattering so far considered. If the lifetime is sufficiently long to allow the A 0 to exit the dump, A 0 → e þ e − decays could be easily detected and distinguished from backgrounds. We explore the foreseeable sensitivity of the Frascati PADME experiment in searching with this technique for the 17 MeV dark photon invoked to explain the 8 Be anomaly in nuclear transitions.

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Section: Effects Of Target Electrons Velocitiesmentioning

confidence: 99%

Section: Effects Of Target Electrons Velocitiesmentioning

confidence: 99%

Section: Effects Of Target Electrons Velocitiesmentioning

confidence: 99%

Section: Effects Of Target Electrons Velocitiesmentioning

confidence: 99%

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Resonant production of dark photons in positron beam dump experiments

et al. 2018

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“…The function model was determined from a qualitative analysis of the experimental data and published theoretical results [7,8]. Positron annihilation with band electrons was fi tted by three arcs of parabola and one gaussian along the…”

Section: Model Functionmentioning

confidence: 99%

Study of the electron-positron annihilation coincidence peak two-dimensional pofile

et al. 2004

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Positron annihilation radiation profi le in aluminum was observed with a pair of Ge detectors in coincidence. 22 Na was used as a source of positron and the two-dimensional gamma energy spectrum was fi tted using a model function. Annihilation components of positron at rest with conduction band, 1s, 2s, and 2p electrons were observed. The in-flight positron annihilation was also observed. The model function also took into account the detector response function, relative effi ciency corrections and the gamma backscattering. Coincidences involving a combination of Compton effect, pileup, ballistic defi cit, and pulse shaping problems were treated as well.

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Characterization of Lattice Defects in Refractory Metal High‐Entropy Alloy HfNbTaTiZr by Means of Positron Annihilation Spectroscopy

Čı́žek

Vlasák

Melikhova

2022

Physica Status Solidi (a)

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Lattice defects in refractory metal high‐entropy alloy HfNbTaTiZr are investigated using positron lifetime spectroscopy combined with coincidence Doppler broadening (CDB) spectroscopy. Annealing of HfNbTaTiZr alloy at 1000 °C results in full recovery of defects and formation of single‐phase random solid solution characterized by the bulk positron lifetime of 141 ps. This value is in accordance with the theoretical estimation. Quenching of the alloy from high temperature prevents recovery of thermally equilibrium vacancies and enables to retain a high concentration of vacancies in the sample at ambient temperature. For single vacancies in the HfNbTaTiZr alloy, a characteristic positron lifetime of 212 ps is measured, which is significantly shorter than the value estimated by theoretical calculations. It indicates that there is considerable ion relaxation around vacancies. The CDB spectroscopy investigations reveal that vacancies in HfNbTaTiZr alloy are not distributed randomly but are preferentially coupled with Hf solutes.

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Calculation of the Doppler broadening of the electron-positron annihilation radiation in defect-free bulk materials

Cited by 70 publications

References 31 publications

Resonant production of dark photons in positron beam dump experiments

Resonant production of dark photons in positron beam dump experiments

Study of the electron-positron annihilation coincidence peak two-dimensional pofile

Characterization of Lattice Defects in Refractory Metal High‐Entropy Alloy HfNbTaTiZr by Means of Positron Annihilation Spectroscopy

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