Quantum Diaries

I am just back from an exciting week in Boston.  If you read my last post you would know that the Double Chooz far detector has been filled, and is streaming real data.  Last week we held an analysis meeting at MIT to begin organizing analysis tasks.  This meeting was primarily attended by graduate students and post-docs, and there was an emphasis on helping students get familiar with the tools necessary for accessing and studying the data.

One important reason to get start looking at the data is check that the detector is behaving as we expect.  We have seen a few cases in which this was not true, but so far the problems have been minor.

Since this was the first time I was being exposed to the Double Chooz data and software, I learned a lot.  I began by trying to identify muons from cosmic rays in our data.  Muons are like heavy electrons, and are produced in the upper atmosphere when high energy protons collide with the nuclei in our atmosphere.  Since the muons are relatively long lived they can survive the descent and pass through our detector.  For reasons I wont dwell on, identifying these in our data are important because they can lead to other backgrounds which we must understand for the experiment to be successful.  I was able to identify muon events in the data, and was able to confirm that the rate of these events was what we expected.

There is still so much work to be done, and so much to be learned, but excitement is in the air for our collaboration.

My next post will include an update on LBNE.  We have a collaboration meeting at UCLA in a couple of weeks, and we should hear about some pretty major decisions. Cheers.

At about 2:00AM in Chooz, France, a dedicated group of physicists finished filling the Double Chooz far detector with the neutrino detecting liquid scintillator.  The filling procedures were carefully executed over the last two months and everyone is very excited to be past this stage.  As a quick reminder, the Double Chooz detectors are concentric cylinders made of acrylic.  Each tank is filled with a different kind of liquid, and so special care needs to be taken in order to ensure that each tank is filled simultaneously.  Even a small difference in the liquid levels could put enough pressure on the acrylic cylinders to crack them.

Special thanks is owed to our filling team on site, and to those collaborators who helped monitor the detector remotely while our filling team slept.

There are many more installations needed for the detector to be fully functional, but this is an exciting step forward!

I recently passed the last last exam of my life (unless something unexpected happens), and it got me thinking about all of the exams I have had to take over my lifetime.

The first exam I have a memory from is a spelling test in the first grade.  In fact, I don’t so much remember a particular test, but I remember that I did well on one and my teacher invited me and the other top scorers to have lunch with her at the big table. This was much more exciting for a first grader that it would be now, and trust me it did not happen to me very often.  Since then the number of exams I have had to take is probably easily over a thousand, an idea which is a bit mind boggling.

Another funny thing about exams is that they seem to keep getting more important.  The first important exam for most people is probably the SAT which has some leverage in getting accepted to a college, and the in college you have Midterms and Finals to worry about.  If you are like me and want to get a Ph.D. you then have to go take two GRE exams, one general, and one in your field.  Once in graduate school the Midterms and Finals get even harder, and then you are typically asked to pass a written exam in your field.  This is usually do or die, except that most schools give the students a couple of tries to pass.  It took me two tries to pass that test in my department.

Finally we come to the last test which for us is an oral exam where you stand in front of a committee of five faculty and present to them your research topic while they grill you in an attempt to flush out any and all misunderstandings.  Thankfully I passed this test, and have now advanced to candidacy, a distinction which has no real affect on my day to day life, but is important for the university.

Now it is time for a little rest and relaxation to recover from all of these exams.

Me in our lab with the 10" and 20" PMTs.

Last week a group of LBNE collaborators, myself included, met by phone to discuss issues related to the photomultiplier tubes (PMT) we would use in the large water Cherenkov detector option.  Without getting into details, a PMT can be thought of as a single pixel in a camera, and we look at the brightness of light that each PMT sees to discern a signal.  We are lucky to have collaborators who are also on the Super-K experiment in Japan which is very similar to what we are talking about building.  One important difference is that Super-K uses much bigger PMTs.  The Super-K PMTs have a diameter of 20 inches (50cm) and one candidate we are considering for LBNE are half that size, 10 inches in diameter.  In general, the larger PMTs will see more light than a smaller one, but in our case, the smaller PMTs are actually more efficient, and so it is not so clear cut.

An important thing to know is how much better or worse the 10inch PMTs are compared to the 20 inch ones.  We can try to answer that question by compiling all of the data we have on each PMT and comparing, but there are a lot of uncertainties in that comparison.  During the discussion we decided that we should try to compare these PMTs in a real lab experiment with the same light source.  Coincidentally, there was only one collaborating institution that had one of each tube … us! So, I got volunteered to do this test, and we need the answer ASAP.

We had to make a number of modifications to our testing lab to accommodate the larger PMT, but we were able to make it work and are in the process of taking data.

Hello Quantum Diaries.  My Name is John Felde, and I am a new blogger.  I am a Graduate Student at the University of California, Davis studying neutrino oscillations.  Since these blogs are meant to reflect the daily life of particle physicists I thought I would introduce UC Davis in my first post.  It is my impression that outside of Northern California, UC Davis is not really all that well known by the general public, mostly since we don’t have a good football team.  In the physics community we are more well known given our involvement in CDF at Fermilab, and CMS at the LHC.  Here is a little bit about my town, and university.

UC Davis was founded in 1905 as an extension of UC Berkeley offering farming and agricultural related degrees.  In 1959 UC Davis was formally established as an independent campus of the University of California system.  Now, the university if made up of 4 colleges and 6 professional schools offering 102 undergraduate majors, and 82 graduate programs.  In 2009 the student enrollment reached 32,153.  Fortunately, UC Davis has the largest campus of the UC’s with 5,300 acres (1 acre ~ 4,000 m^2).

One of many bike circles on campus.

Physics Building (Background) and Undergraduate Physics Labs (Foreground)

The city of Davis has a population of ~65,000.  It has never been clear to me how, or if, students are counted, but it goes without saying that the University is an integral part of the community.  Davis is well know for being bicycle friendly, and was names the best cycling town in 2006 by Bicycling Magazine.  In 2009 Davis was chosen to host the U.S. Bicycling Hall of Fame.  The college town aspect of Davis makes it unique among neighboring cities.  Residents boast the highest level of education in California with greater than 60% having completed a four-year degree.

I also very much enjoy the location of Davis.  We are situated at the northern end of the Central Valley of California, within about 2 hours of both San Fransisco, and the Sierra Nevada Mountains.  This makes our area special in that at certain times of the year one could actually ski in the morning, and surf in the afternoon, if they were so inclined.

Well, there is a little bit about where I do my work.  There is some exciting news the Double Chooz and LBNE collaborations which I look forward to sharing with you all in the near future.