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Freya Blekman | USLHC | USA

Read Bio

A box is a good thing. I hope

Tuesday, May 27th, 2008

http://www.ignorancia.org/ )

Like most other large particle physics experiments, CMS has a lot of management structure, physicists who effectively are just managers. As you can see these organizational charts are usually represented with a lot of inter-connected boxes. Which is why positions like this are sometimes referred to as boxes. Most of the important boxes, like the spokesman, our representative to the rest of the world, are elected by the collaboration. In the case of mere lower convenors, a team of wise senior physicists typically just finds you worthy, then nominates you and if you accept you have the job. Particularly for post-doctoral researchers these positions are quite coveted, as it proves (if you do your job well) that you have some form of leadership capabilities, one of the alleged requirements for a tenure track job.

Today is a special day for me, as I have accepted to help run the CMS pixel detector software group for a year (at least). I find this all highly exciting, as I suspect I will be learning a lot in this time, not only about our detector but also about how particle physics experiments, or at least CMS, are run behind the scenes. I even have a title, as I now am a Detector Performance Group convenor for the CMS pixel offline software. My own acronym and a box to put it on, whoo whoo! Essentially the title means that I have to make sure the software that is used to analyze and reconstruct pixel data is in a good state. And that means keeping track of all different actitivities that go on in the development, making sure things stay up to date, etc. And that means… guess what: meetings.

So, I got my little (and yes this really is quite a minute) box. I wonder what’s next. I suspect many more meetings.

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What data?

Thursday, May 15th, 2008

This week has been very eventful for me. For one thing CMS had a very successful global run where we collected so many cosmic ray events that we decided to give ourselves a weekend off, but at the same time we were also doing a Computing Challenge (which Ken can surely write about) to test that we can ship the LHC data around as quickly as it arrives (and do some basic operations on it). For now we were using fake (so simulated) data for the latter, as even though the cosmic run was successful, the data volume was no way near what we expect once we get collisions.

So how did those activities affect me? Well, I am responsible for the databases and software that ensures we can read out the CMS pixel detector. This meant I had to check that the pixel data was coming out of the cosmic run (it was) and that the simulated pixel data was correct so the the people responsible for analyzing the data can check that their software works. Which effectively meant being the first person to look at all data. Of course simulated data is something we have been dealing with for the last few years, so at least from the pixel side there was not much excitement there. However, I was really looking forward to looking at the first *real* hits coming from a pixel detector in the real system.

To give you some ideas of things that you have to deal with in these matters let me explain the configuration in the cosmic run. As the CMS pixel detector can only be installed once the CMS beam pipe (the part of the accelerator that goes through the CMS detector) is installed, we instead connected only a small part of the pixel detector to the readout electronics. This small part we call the Pixel In a Box (PIB, in CMS you need to have an acronym for your activity. It almost seems you do not get taken seriously otherwise). In a few weeks we will have a real detector installed, it is ready and we’re keeping it at a random cleanroom at CERN for now (and the other half of it in Zuerich) but the beam pipe needs to be ready first. The PIB was connected to the entire system just like the real pixel detector would be, and taking data just like the rest of the detector. Of course a small pixel detector (it’s about 10 square inches of active material in total) does not find many cosmic rays so this really was just a exercise in cooperating with the rest of the detector. Still, exciting and definitely a new phase.

The pixel in a box run was a success, data was taken and it very quickly arrived at the lowest level grid analysis facilities (the CERN tier zero) where the responsible expert (read: me) took a look at it. And then the trouble started. There was nothing in the data! Of course the first step is to prove I wasn’t doing something wrong myself, but a few days and many discussions with the other experts later it turned out that…. the PIB was supposed to create no data. Actually the PIB was set up in such a way that all pixels were turned off. In some sense it is a good thing that I could prove this but some way or another it just does not feel the same as when you get actual data out.

I now try to comfort myself by telling myself that at least I proved I could see there was no data before someone standing next to the PIB could see there was no data. But it still is a bit disappointing.

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Cables and headscarves (or lack thereof)

Monday, May 5th, 2008

Yesterday I returned from a three-day trip to Ankara, Turkey. The Turkish Atomic Energy Agency (TAEK) were kind enough to invite me to give tutorials on the CMS offline reconstruction software. I’ve been teaching these tutorials for a few years now, and really enjoy it as teaching is something I don’t do much of being at CERN (and I actually enjoy it, it must be in my genes with all the teachers in my family!) and it is always great to see people pick up things and make them their own. This time particularly I jumped at the invitation as I had never been to Turkey and love traveling. Actually, I think travel and seeing the world is one of the extra perks you get as a particle physicist. Also, I managed to get some nice snaps while I was there, but unfortunately I have mislaid the cable I use to connect my camera to my computer so I will have to disappoint you by not showing any photos. At least not until I’ve found my cable.

However, what I was amazed by, was the response I received from some otherwise sensible friends and colleagues, who were quite concerned for me and worried for my safety. I already was aware that Turkey is a very modern country, and definitely with (at least) one foot in Europe, but I actually received the baffling question (twice!) whether I would have to wear a vail or head scarf while I was there. So let me hereby confirm: In Ankara, Turkey people are very modern and are very proud (and aware) of that too. To break some more stereotypes, I had wonderful Turkish wine, pizza with ham and definitely did not wear a head scarf, and neither did most other women. In some sense I think some western countries could learn something from the Turkish about gender biases in science and how to fix them, as in Turkey around 40 percent of physicists are female! I was very impressed by the smart, enthusiastic, young people who were doing their Ph.D.s there, it was all in all an excellent experience.

But OK, lets not all move to Turkey at once, the country’s physicists have to do their work with a lot less resources than in the US or the European CERN member states. With a small science budget it is difficult to contribute significanctly to the collaboration, or send many people to CERN. No presence at CERN means that until the LHC is in a stable running state that means you will always hear things much later, and can not really contribute to the exciting times we are in at CERN now, particularly the commissioning of the detectors. I suppose that trips like this also remind me how fortunate I am to work with the people and the resources I have available, it really is a privilege.

(un)Fortunately for me, the aforementioned commissioning of the CMS pixel detector continued while I was helping our Turkish collaborators getting up to speed with the software. So this (Sunday) morning I spent some time catching up with my normal work and preparing the database that contains cabling information that will be needed for our run that will start Monday morning. This will be a very exciting time for the pixel community, as we will try to run the pixel detector (or at least a small component of it, for now) in combination with the rest of the CMS experiment. I hope the run goes well, I’m confident the CMS pixel cable information is in place. Now if I could only find my camera cable!

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