From KAREN wiki

• Description

The IceCube Neutrino Detector is a neutrino telescope currently under construction at the South Pole. Like its predecessor, the Antarctic Muon And Neutrino Detector Array (AMANDA), IceCube is being constructed in deep Antarctic ice by deploying thousands of spherical optical sensors (photomultiplier tubes, or PMTs) at depths between 1,450 and 2,450 meters. The sensors are deployed on "strings" of sixty modules each, into holes in the ice melted using a hot water drill.

The main goal of the experiment is to detect neutrinos in the high energy range, spanning from 10¹¹eV to about 10²¹ eV. The neutrinos are not detected themselves. Instead, the rare instance of a collision between a neutrino and an atom within the ice is used to deduce the kinematical parameters of the incoming neutrino.

IceCube has been under construction for several years now, with new IceCube strings and sensitive modules being deployed each summer. In 2008 the detector was half its designed size. It consisted of 40 IceCube strings (IC40) with with a total 2400 optical sensors. Even though it's under construction, each year IceCube is able to take useful physics data. This is the data which we use to search for astrophysical neutrinos. At Canterbury we are using the IC40 data to search for electron type neutrinos. Neutrinos exist in three types, or flavours, called electron, muon, and tau neutrinos. At Canterbury the focus is the search for electron type neutrinos interacting in IceCube. The search is made difficult by the fact that most of the events in the detector are caused by muons, a heavy electron-type particle, which outnumber the electron neutrino events by a factor of 10⁶. To suppress this large muon background the data is passed through several levels of filters. Each filter is designed to cut out as much of the muon background as possible while retaining as much of the electron neutrino signal as possible. At each level some of the signal is lost but a significantly larger percentage of the background is cut out. The filtering algorithms exploit the differences in signature in the detector between the muon events and the electron neutrino events. Muon background events, Figure 1, appear as elongated tracks in the detector while electron signal events, Figure 2, appear as spherical distributions of light in the detector.

A low level of filtering is done online at the South Pole. The IC40 detector triggered approximately at 1 kHz. Since most of the events which will cause the detector to trigger and read data will be background muons produced in the atmosphere, a series of online filters are run to decide which events are worth saving for further study. Approximately 36.9 GB/day of data was stored after this online filter stage. This data consisted of events likely due to all three types of neutrino flavours. The electron neutrino filtered data at this level was 5.2 GB/day. All the filtered data at this level is transferred daily, via a satellite uplink, to the IceCube data warehouse at the University of Wisconsin in Madison. By this stage the data has effectively gone through two levels of filtering, namely the detector trigger decisions and the online filter. The next level of filtering, level 3, is the one for which this KAREN travel funding was sought.

The IceCube group at UC, lead by Dr Jenni Adams, and the group at the Deutsches Elektronen-Synchrotron (DESY) in Zeuthen, Germany, are interested in searching for electron neutrino events. Throughout the first half of 2009 the two groups, which form part of the larger electron neutrino working group in IceCube, collaborated on strategies to further filter the data. This level 3 filtering would make cuts on the data based on the energy of the events and on a combination of direction of incidence and goodness of fit of each event to the location of an electron neutrino that could produce the event. In September 2009 Dr Suruj Seunarine and post-graduate student Stephanie Hickford travelled to DESY to collaborate on the final stages of the filtering algorithm and code. Stephanie PhD thesis project is on the search for electron neutrino events in IC40. The visit was hosted by Prof. Dr. Hermann Kolanoski of DESY. The level 3 filtering is being done on the clusters at DESY and the filtered data is to be moved to back to Madison for IceCube collaboration use and to UC for use by the UC IceCube group.

• Contacts

Dr Suruj Seunarine

• How does this project use KAREN?

The work at UC routinely involves transfer of IceCube data between the data warehouse in Madison, Wisconsin, and Canterbury. This involves transferring both detector data and Monte Carlo simulated data. Though routine transfer of data my involve smaller chunks of data, on the order of a few to a hundred GB, availability of KAREN has impacted greatly on our work in that the turn over time between fetching some data, designing and testing filters and retrieving further data has been greatly reduced. Apart from analysis of physics data, our work has also involved detector verification and detector calibration, both of which required data from the warehouse at Madison. In early 2009 we also transferred approximately 4TB of of IceCube verification data, via grid ftp, from Canterbury to Madison.

Regarding the level 3 data from the current project at DESY, the filtering of that data is still ongoing as of the time of writing this report. The filter study period took longer than projected because of complications involved in including data from AMANDA (Antarctic Muon And Neutrino Detector Array) in the filter stream. AMANDA is the precursor experiment to IceCube and in 2008 AMANDA was running in coincidence with IceCube 40. Understanding how to combine the data from both experiments in the level 3 filtering was not trivial. However the level 3 filtering is now proceeding at DESY, with about 1.8TB, or 10% of the data filtered. We have already moved some of it to Madison and we will soon move it to Canterbury.

• University of Canterbury IceCube Group

Dr Jenni Adams (Senior Lecturer, Principal Investigator), Dr Andreas Gross (Marie Curie Post Doctoral Fellow), Stephanie Hickford (PhD student), Kahae Han (PhD student), Sarah Bouckoms (MSc student), Dr Suruj Seunarine (Adjunct Fellow UC; Lecturer, UWI)

• Acknowledgement

We are thankful that Dr Vladimir Mencl posses the infinite patience and good will necessary to allow ordinary physicists to become grid enabled.