Coincident air shower measurements with IceCube and IceTop

IceCube observes high energy ($\gtrsim$ 500 GeV) muons produced in cosmic ray air showers which are often in time-coincidence with surface data from IceTop. This unique data has been used in various previous analyses of cosmic rays. IceCube's main cosmic ray mass composition analysis, for example, relies on coincident events and the comparison of deep muon and surface energy. This analysis is constrained to events that are contained in IceTop to get a reliable primary energy estimate with existing air shower reconstruction techniques. Thereby, a large fraction of air shower events is discarded, especially from large inclinations above zenith angles of approximately $\theta$ $\simeq$ 30${}^{\circ }$. We will present a new approach for the reconstruction of in-time coincident events in IceCube and IceTop. It uses events contained in the deep in-ice detector together with information from the surface array at the same time. It will be shown that this method generally improves the resolution of air shower reconstructions. Moreover, accounting for the in-ice information allows reconstruction of events which are far outside of the IceTop surface array. This enables studying events from zenith angles up to roughly $\theta$ $\simeq$ 60${}^{\circ }$ and significantly improves the statistics of successfully reconstructed air shower events. It will be shown that this new technique significantly extends the IceTop acceptance for air shower measurements towards low and high energies.