A first measurement of the 1-jettiness event shape observable $\tau_1^b$ in neutral-current deep inelastic scattering is presented.
For the measurement, the equivalence of $\tau_1^b$ to the DIS thrust observable defined in the Breit frame is utilised.
The data were taken by the H1 experiment at HERA from 2003 to 2007 at a centre of mass energy of $\sqrt{s}=319~\text{GeV}$. The data amount to an integrated luminosity of $351.6~\text{pb}^{-1}$.
The triple-differential cross sections are
presented as a function of the 1-jettiness $\tau^1_b$, the
virtuality of the exchanged boson $Q^2$ and the inelasticity of the event $y$.
The data exhibit a sensitivity to the strong coupling constant and to resummation and hadronisation effects, as well as to the parton distribution functions of the proton. The data are compared to selected predictions.