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Jelena Maricic | Drexel university, Philadelphia | USA

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New face of LBNE

The news is up. We had election results announced for the spokesperson for the Long Baseline Neutrino Experiment at DUSEL. This is the first time I witnessed proper elections. Three excellent candidates, extremely dedicated to the project. They came up with their vision and how they see project priorities and future.  It was interesting to tune into scientific elections. I am sure that all three will lead this longterm collaboration (read: results not likely before 2020) at some point or another. In the end collaborators decided for Bob Svoboda from UC Davis and I wish him good luck.

It is an unbeleivable challenge keeping motivated, dedicated collaboration for a decade at least. The physics promise is unsurpassed, but it is a long way getting there. We all want to know if  the lepton CP-violation phase is large enough to fit in the answer to matter dominance that we observe.  We all want to know which neutrino mass is the heaviest, but again, it is a long way getting there. Everyone would love to see some of the relic supernova neutrinos, of even a real supernova blast, but the road is long with a lot of hurdless.

So, in the meantime we concentrate on more down to Earth questions – some fun like choosing a more exciting name for the LBNE. Vote counting is underway between:

Neutrino Galactic Observatory and Long baseline Detector

Black hills Illinois Supernova, Oscillation, and Nucleon decay detector

Homestake Neutrino Detector

Which one do you like?

There are planty of technical design questions (a lot of fun too)  such as how one efficiently calibrates a 100 kton detector (size of just 1 of three modules!)?  What are the things that must be calibrated if we want to reliably answer above mentioned physics questions?

Generally, one can never calibrate too much to  better understand detector data, but what is the minimum, we wonder?

Since we will use water (most likely), it needs to be transparent – by hundreds of meters ! So there should be away that water clarity is checked regularly. Do organisms tend to grow in water?  Of course. Do they make water blurry?  Probably. So elaborate water purification system will be designed.

We may add gadolinium to water to get powerful neutron tagging ability (which I would really like to see happen since it opens doors for various several  MeV level physics). Will Gd stay in water? How do we put it back in after purification of everything else? We need to care about environment as well. So, more open questions…

On top of that we will need to get accurate timing and charge gain calibration for around 150,000 photomultiplier tubes (PMTs). Even at the speed of 10 per minute it would take a full month just for that (assume normal working days). We need to be clever.

And finally the part that I really like is calibrating detector energy scale – namely, when we gather all the PMT signals, we go back and figure out the energy of particle interaction that caused the signal. It is sort of like a detective game. We know when each PMT produced the signal and how big was it and then we trace back and figure out what particles and at what energy caused the signal and where in the detector it took place. Fun! As real detectives we first use the known (facts) which is calibration and based on it, figure out the unknown  which are all the other data collected from the PMTs. The first option for calibration are muons – they come in all energies from various direction, but it an uncontrolled fashion and no independent cross-check of their energy. One can build small accelerator and get fast electron of know energies to study detector nergy response. Part that we have started looking into are radioactive sources. Because it turns out that most of typical radioactive sources produce gammas and or other particles up to several MeV, but nothing above 10 MeV. And it is this reion of 10-20 MeV that would be really nice to understand well for supernova neutrnos. And getting a nice neutrino spectrum of fresh supernova would indeed be precious. So we started looking into fission fragments and if anything can be done with it. We may end up with some quite exsotic radioactive sources. Will keep you posted.