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Linear Polarimetry with γe+e Conversions

LLR, Ecole polytechnique & CNRS/IN2P3, 91128 Palaiseau, France
Academic Editors: Emmanouil Angelakis, Markus Boettcher and Jose L. Gómez
Galaxies 2017, 5(4), 72; https://doi.org/10.3390/galaxies5040072
Received: 25 September 2017 / Revised: 22 October 2017 / Accepted: 25 October 2017 / Published: 1 November 2017
(This article belongs to the Special Issue Polarised Emission from Astrophysical Jets)
γ -rays are emitted by cosmic sources by non-thermal processes that yield either non-polarized photons, such as those from π 0 decay in hadronic interactions, or linearly polarized photons from synchrotron radiation and the inverse-Compton up-shifting of these on high-energy charged particles. Polarimetry in the MeV energy range would provide a powerful tool to discriminate among “leptonic” and “hadronic” emission models of blazars, for example, but no polarimeter sensitive above 1 MeV has ever been flown into space. Low-Z converter telescopes such as silicon detectors are developed to improve the angular resolution and the point-like sensitivity below 100 MeV. We have shown that in the case of a homogeneous, low-density active target such as a gas time-projection chamber (TPC), the single-track angular resolution is even better and is so good that in addition the linear polarimetry of the incoming radiation can be performed. We actually characterized the performance of a prototype of such a telescope on beam. Track momentum measurement in the tracker would enable calorimeter-free, large effective area telescopes on low-mass space missions. An optimal unbiased momentum estimate can be obtained in the tracker alone based on the momentum dependence of multiple scattering, from a Bayesian analysis of the innovations of Kalman filters applied to the tracks. View Full-Text
Keywords: gamma-ray astronomy; gamma-ray polarimetry; pair conversion; time projection chamber; gas detector; optimal methods; Kalman filter; Bayesian method gamma-ray astronomy; gamma-ray polarimetry; pair conversion; time projection chamber; gas detector; optimal methods; Kalman filter; Bayesian method
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MDPI and ACS Style

Bernard, D. Linear Polarimetry with γe+e Conversions. Galaxies 2017, 5, 72. https://doi.org/10.3390/galaxies5040072

AMA Style

Bernard D. Linear Polarimetry with γe+e Conversions. Galaxies. 2017; 5(4):72. https://doi.org/10.3390/galaxies5040072

Chicago/Turabian Style

Bernard, Denis. 2017. "Linear Polarimetry with γe+e Conversions" Galaxies 5, no. 4: 72. https://doi.org/10.3390/galaxies5040072

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