Opened Box

Well, the big moment is about to arrive. More than a decade ago, the LSND collaboration shook up the particle physics world by announcing a neutrino (actually, antineutrino) oscillation result whose interpretation requires physics beyond the standard model. As I wrote in a previous entry, I am on MiniBooNE which has been working on a blind analysis to confirm or refute the LSND result for the past ten years. We have been pushing very hard to "open the box" and see what the answer is for quite a while and it has finally happened.

Our box opening procedure was a four step process in which each step was designed to reveal enough information that we could decide if things were working correctly, but not enough information to tell us the answer. Thus blindness was preserved until the final step. Our procedure was designed so that if a problem were to be found in one of the early steps, we could stop the procedure and try to fix the problem, before starting over again. Doing that would be OK as long as we did not reveal any information about the contents of the box.

Today at Fermilab, our first oscillation result will finally be announced, and tomorrow I will give a seminar on the result myself here at Imperial. I can't say what the answer is yet, so you'll have to come to my seminar to find out!

As an interesting side note, we did have to stop the box opening procedure and start over again, so it was a very good thing that we had this procedure. We attempted a box opening in February, over the weekend when I wrote my blind analysis blog entry, and discovered a reason to abort the process and regroup. But a full entry about that will have to wait until the result is announced to the world. Right now, I have to complete my seminar!

Blind Analysis

I'm a member of the MiniBooNE collaboration, and we are doing a blind analysis in our search for neutrino oscillations. The idea is that we wish to prevent biasing ourselves before we complete the analysis of the data. We are doing a "closed box" blind analysis, which means that we sequester the events that appear to be signal-like and do not perform any analyses on them before the analysis chain is complete.

Our analysis is a search for electron neutrino events in a muon neutrino beam, which is the signature of neutrino oscillations seen by the LSND experiment. We are performing the experiment to confirm or rule out the LSND neutrino oscillation result. Effectively, the blind analysis means that we use other data samples, like the muon neutrino data and cosmic muon decay electron events, to understand our event reconstruction and analysis algorithms. We do not use electron neutrino events that might come from neutrino oscillations in the development of the analysis, but only after the algorithms are complete. We are currently in the final stages of the analysis, and are hoping to open the box soon, although we have been saying that for a while!

We chose to do a blind analysis for many reasons, but one of the key reasons is that the LSND result, if it is due to oscillations, would be inconsistent with the Standard Model's prediction of only three families of neutrinos. Thus, the LSND result has huge ramifications if it is confirmed and we deemed it necessary to use the most strict methods in our search for these oscillations.

As a MiniBooNE collaborator, I am often asked if we will see a signal, which is to say: do I think the LSND signal is real? I've come to realize I don't care if we see a signal. All that matters to me is getting it right. Frankly, I think it would be scientifically irresponsible for me to hold a strong opinion about it one way or the other. I think that the beauty of science comes from the idea that Nature can reveal her secrets if we ask the right questions and are open to the answers. Approaching this analysis with a strong bias one way or the other would be tantamount to closing one's mind to a certain type of answer, and to me that would be a failure.

A lot of people in the field feel that the signal is false, and that we will rule out LSND-type oscillations, with almost religious conviction. It belies their bias in what should be an objective pursuit. I think part of it stems from the saga of the 17 keV neutrino. In that case the scientific method was vindicated (although I am sure that there was plenty of subjective chatter amongst the participants, especially at conferences) but I think the experience left a lot of people in the field uncomfortable with new and different experimental results in neutrino physics. We will shortly learn whether or not the LSND result was a false alarm, or whether Nature is a lot more complex than we thought.

And I can't wait to know the answer, whatever it might be!