title: Table-top laser-based source of femtosecond, collimated, ultrarelativistic positron beams.
abstract: The generation of ultrarelativistic positron beams with short duration (τ(e+) ≃ 30  fs), small divergence (θ(e+) ≃ 3  mrad), and high density (n(e+) ≃ 10(14)-10(15)  cm(-3)) from a fully optical setup is reported. The detected positron beam propagates with a high-density electron beam and γ rays of similar spectral shape and peak energy, thus closely resembling the structure of an astrophysical leptonic jet. It is envisaged that this experimental evidence, besides the intrinsic relevance to laser-driven particle acceleration, may open the pathway for the small-scale study of astrophysical leptonic jets in the laboratory.
authors.affiliation: School of Mathematics and Physics, The Queen's University of Belfast, BT7 1NN Belfast, United Kingdom.
authors.forename: G
authors.initials: G
authors.lastname: Sarri
authors.forename: W
authors.initials: W
authors.lastname: Schumaker
authors.forename: A
authors.initials: A
authors.lastname: Di Piazza
authors.forename: M
authors.initials: M
authors.lastname: Vargas
authors.forename: B
authors.initials: B
authors.lastname: Dromey
authors.forename: M E
authors.initials: ME
authors.lastname: Dieckmann
authors.forename: V
authors.initials: V
authors.lastname: Chvykov
authors.forename: A
authors.initials: A
authors.lastname: Maksimchuk
authors.forename: V
authors.initials: V
authors.lastname: Yanovsky
authors.forename: Z H
authors.initials: ZH
authors.lastname: He
authors.forename: B X
authors.initials: BX
authors.lastname: Hou
authors.forename: J A
authors.initials: JA
authors.lastname: Nees
authors.forename: A G R
authors.initials: AG
authors.lastname: Thomas
authors.forename: C H
authors.initials: CH
authors.lastname: Keitel
authors.forename: M
authors.initials: M
authors.lastname: Zepf
authors.forename: K
authors.initials: K
authors.lastname: Krushelnick