title: Precision measurement of the hydrogen 1S-2S frequency via a 920-km fiber link.
abstract: We have measured the frequency of the extremely narrow 1S-2S two-photon transition in atomic hydrogen using a remote cesium fountain clock with the help of a 920 km stabilized optical fiber. With an improved detection method we obtain f(1S-2S)=2466 061 413 187 018 (11)  Hz with a relative uncertainty of 4.5×10(-15), confirming our previous measurement obtained with a local cesium clock [C. G. Parthey et al., Phys. Rev. Lett. 107, 203001 (2011)]. Combining these results with older measurements, we constrain the linear combinations of Lorentz boost symmetry violation parameters c((TX))=(3.1±1.9)×10(-11) and 0.92c((TY))+0.40c((TZ))=(2.6±5.3)×10(-11) in the standard model extension framework [D. Colladay, V. A. Kostelecký, Phys. Rev. D. 58, 116002 (1998)].
authors.affiliation: Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany.
authors.forename: Arthur
authors.initials: A
authors.lastname: Matveev
authors.affiliation: Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany.
authors.forename: Christian G
authors.initials: CG
authors.lastname: Parthey
authors.affiliation: Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Predehl
authors.affiliation: Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany.
authors.forename: Janis
authors.initials: J
authors.lastname: Alnis
authors.affiliation: Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany.
authors.forename: Axel
authors.initials: A
authors.lastname: Beyer
authors.affiliation: Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany.
authors.forename: Ronald
authors.initials: R
authors.lastname: Holzwarth
authors.affiliation: Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Udem
authors.affiliation: Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Wilken
authors.affiliation: Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany.
authors.forename: Nikolai
authors.initials: N
authors.lastname: Kolachevsky
authors.affiliation: LNE-SYRTE, Observatoire de Paris, 61 avenue de l'Observatoire, 75014 Paris, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Abgrall
authors.affiliation: LNE-SYRTE, Observatoire de Paris, 61 avenue de l'Observatoire, 75014 Paris, France.
authors.forename: Daniele
authors.initials: D
authors.lastname: Rovera
authors.affiliation: Laboratoire Kastler-Brossel, CNRS, 75231 Paris, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Salomon
authors.affiliation: LNE-SYRTE, Observatoire de Paris, 61 avenue de l'Observatoire, 75014 Paris, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Laurent
authors.affiliation: Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany.
authors.forename: Gesine
authors.initials: G
authors.lastname: Grosche
authors.affiliation: Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany.
authors.forename: Osama
authors.initials: O
authors.lastname: Terra
authors.affiliation: Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Legero
authors.affiliation: Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany.
authors.forename: Harald
authors.initials: H
authors.lastname: Schnatz
authors.affiliation: Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Weyers
authors.affiliation: Department of Physics and Astronomy, University of South Carolina, Columbia, South Carolina 29208, USA.
authors.forename: Brett
authors.initials: B
authors.lastname: Altschul
authors.affiliation: Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany.
authors.forename: Theodor W
authors.initials: TW
authors.lastname: Hänsch