HE NEUTRINO ICECUBE · High energy neutrino astronomy with IceCube: towards the detection of neutrinos from Gamma Ray Bursts (GRBs)

Periodic Report Summary 1 - HE NEUTRINO ICECUBE (High energy neutrino astronomy with IceCube: towards the detection of neutrinos from Gamma Ray Bursts (GRBs))

The aims of this Marie Curie fellowship are diverse. The ultimate physics goal is the search for the signal of astrophysical neutrinos emitted from Gamma-ray bursts (GRBs), one of the prime candidates for the emission of charged particle high-energy cosmic rays. A possible detection would solve the question of the origin of these cosmic rays, which remained open for more than a century. Further aims are, on the one hand, a central role within the IceCube collaboration for the researcher, Dr Andreas Groß. On the other hand, a very wide, almost complete, knowledge in the field of neutrino astronomy is desired. IceCube has two detection channels, long tracks of muons generated in charged current interactions of muon neutrinos and the cascade channel, more point-like emissions generated in charged current interactions of electron (or tau) neutrinos and in neutral current interactions of all flavors. During this fellowship, the focus is on the technically more challenging cascade channel, complementary to previous work on muon neutrinos. The work during the fellowship aims for improvements in reconstruction and analysis of the cascade channel, in order to make fully use of this detection channel. The improvement in reconstruction and data analysis achieved then should be used for the search for GRB neutrinos. Role within the IceCube collaboration: As planned in the proposal, Andreas Groß maintained the role as Amanda detector coordinator. The activities as Amanda coordinator included the deployment to the geographical South Pole leading calibration and maintenance efforts for Amanda in November 2008. During the review period, in its last year of operation, Amanda reached the largest period of high quality data taking since its completion in 2000. The successful operation of Amanda as low-energy subdetector of IceCube allowed for the proof of principle for the enhancement towards relatively low particle energies (below a few TeV). This paved the way for the DeepCore subdetecor, a dedicated infill array placed at a better location in the centre of IceCube, which uses the same technology as IceCube. The construction of DeepCore started January 2009. As a result, the IceCube collaboration decided to decommission Amanda in May 2009. With this time, the responsibility for the Amanda subdetector ended. After the closure of Amanda, the goal of a central role within the IceCube collaboration has been reached in a different way. The coordination of reconstruction, simulation and data quality as part of IceCube maintenance and operation was taken over in June 2009. One essential part of this coordination is to organise the processing of data collected by IceCube after they have been transferred to the Northern hemisphere. This so-called offline processing is a common activity for the IceCube collaboration where a large set of particle event reconstruction is added to allow for a better interpretation of the collected data. Scripts have been redesigned to make this processing more robust and resource efficient. Research activity: The focus was set on the reconstruction of electron neutrino induced events, so-called cascades. Previously unused photomultiplier signal hits without a close partner hit on the same detector-string (so-called SLC hits) were studied to improve separation of neutrino-induced signal from background from cosmic ray-induced air showers. The different time-evolution of signal and background was used to develop further topological variables discriminating between signal and background events. As event rates for background rates are orders of magnitude higher than for signal, an improved discrimination of signal from background is essential to enhance IceCube's capabilities. The ultimate goal is to use these methods in an analysis for electron neutrino signal from GRBs. Final physics results are expected during the integration phase of the project.

Data: CORDIS, © European Union