TeVPA 2018

Gas active targets: a window to high-energy gamma-ray polarimetry with conversions to e+e-; experimental demonstration with the HARPO TPC (time projection chamber) prototype.

28 Aug 2018, 15:45

1h

LVH, Luisenstraße 58, 10117 Berlin

Board: GR03

Poster (A0 portrait) Gamma-rays Poster Session and Coffee Break

Speaker

Dr Denis Bernard (LLR, CNRS/IN2P3)

Description

gamma-ray astronomy is polarization-blind as no significant polarimetry of a cosmic source has been performed since the [OSO-8 measurement on the Crab nebula][1] in the X-ray band. gamma-ray polarimetry would enable to [tag the curvature-synchrotron radiation transition in pulsars][2], to [decipher leptonic from hadronic radiation models for blazars][3] .. and [much more][4]. We [demonstrated][5] that with a low-density homogeneous active target such as a gas TPC (time projection chamber), the single-track angular resolution is so good after a low radiation-length thickness that polarimetry should be possible with gamma conversions to e+e- pairs. **With a TPC prototype in a gamma-ray beam, we demonstrated experimentally the effective polarimetry with an excellent polarization-asymmetry dilution** [AstroPart. Phys. 97 (2018) 10][6]. Spin-offs of interest to the community: An analytical analysis of the single-track angular resolution with an optimal tracking à la Kalman, an optimal method to measure a track momentum in a non-magnetic tracker from the analysis of the deflections due to multiple scattering ([Kalman][7] helping [Molière][8]), interest to silicon-detector based telescopes (Fermi-LAT, AGILE, e-ASTROGAM, AMEGO) [NIM A 867 (2017) 182][9]. An exact Monte carlo event generator of the five-dimensional (5D) Bethe-Heitler differential cross section (polarized or not, nuclear or triplet conversion, pure QED or with electron cloud screening) and strictly energy-momentum conserving, [to appear in NIM A][10]. Good hope of a deployment of the G4BetheHeitler5DModel physics model in the 10.5beta Geant4 release at the end of June 2018. [1]: http://dx.doi.org/10.1086/182648 [2]: http://inspirehep.net/record/1641719 [3]: http://inspirehep.net/record/1242827 [4]: https://inspirehep.net/record/1498288 [5]: http://inspirehep.net/record/1242601 [6]: https://inspirehep.net/record/1606056 [7]: http://inspirehep.net/record/259509 [8]: http://zfn.mpdl.mpg.de/data/Reihe_A/10/ZNA-1955-10a-0177.pdf [9]: https://inspirehep.net/record/1605726 [10]: https://doi.org/10.1016/j.nima.2018.05.021

Presentation materials

Poster

poster.pdf