Wednesday, July 7, 2010

Day 2 at CERN: Beginning the quest

Today I got up a bit later than the day before, being overtired from getting lost when biking and from a long day with interrupted sleep (plus jetlag). After morning breakfast and some reading, I took a very long walk (about 45 min) to the nearest bus stop to take me to CERN (I chose not to bike today since I was to be going off somewhere else at the end of the day and would want to have my bike available at my hotel for Wed).

I got myself a sim card and had some books shipped back to the States to lighten the load I am carrying (those two books weigh at least 6-7 kg, I would say) since I have little use for them here and also so that I could bring back some other stuff. Then , I continued with my appointment making and preparation for two meetings.

My first meeting was with the outreach coordinator of ALICE (A Large Ion Collider Experiment). Since I could get most of the usual description of ALICE from the internet and the numerous publications they’ve put out, I used this chance instead to find out about details that don ‘t usually get published in press releases, coffee table books and even history and sociology of physics books. I pressed her on the epistemological interest involved in the experiment conducted and the how and what really is entailed in the differentiation between old and new physics. Dr Despina Chatzifotiadou, an experimental physicist of Greek origins, was pretty forthcoming with her answers. She wanted to know how much about the physics I was aware of, and in particular, if I have a clear image in my mind as to how experiments are set-up and performed. We went a little into the history of CERN and how ALICE came into being just to enable one to understand how the division of labor is set-up (I would have to do more research into this area) based on interest and needs. I learnt more about the history of the involvement of different research groups coming from different parts of the world , including Dr Chatzifotiadou’s involvement via the Bologna group that were involved in the invention of the device and method for calculating the time of flight at the point of beam generation to the point of collision, and thus an understanding of how groups insert themselves through the value they could bring to the experiment by way of innovative way of doing physics and through the funding they could bring in to the advancement of the larger projects. We didn’t get to tackle too much the philosophical questions as to whether a scientific framework is merely erroneous or incomplete when faced with rather complicated and highly convoluted mathematical explanations. However, she concedes that many experimental physicists do not always quite understand the mathematical innovations that the theoreticians have. Many theoreticians do not necessarily work long-term or have a consistent relationship with the different experimental groups, for that depends much on their interests and how they see the ongoing experiments as providing empirical proofs to their mathematical visions. I also had a better understanding as to what ‘offline’ weeks or meetings entailed: they refer to the analysis performed on data ‘offline,’ that is data that are not continuously fed in by the machines. During this time, the accelerator physicists could spend time dealing with whatever performance issues that may get in the way of optimal production of the physics. I find it fascinating that there is a sort of division between the ‘physics’ and the ‘performance’ but this is certainly something I will mention later in relating my meeting with one of the members of the CMS (Compact Muon Solenoid) group. Another thing that may be of interest to note is how cosmic rays are used as ‘natural’ particles for the calibration and checking on the ‘health’ of the apparatuses before the proton beams are generated. Due to the fact that ALICE is the only collider-detector that deals with heavy ions (I will be attending a talk on this tomorrow), silicon trackers are used as they more able to retain the trace-information left behind by the collisions between ions. Of course, at this point, much of the collision performed are proton-proton types though they are attempting to work their way up the generation in the Standard Model. We also had a small discussion on rivalry between groups when it came to accessing data but I will not go into this here at the moment.

At my meeting with the PFG (Prompt-Forward Group) that specializes in ICHEP certification (which is to certified the quality of the results obtained in the detectors), there was much concentration on the clarity of the crystals used for the detection and counting of the different constituents of the matter that went through (particularly the calorimetric calibrations of the EM and the hadrons). There are of course much discussion and arguments on what constitute as methods for obtaining data of highest quality. Some of this data may come out of crystals that are considered as being able to detect high quality traces by masking those that are leading to a lot of channel noise. Everyone is concerned about how the various hardware and software used are impacting the quality of the data received, and everyone certainly wants to maximize the channels available to obtain the highest quality data.

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