Week+of+10-22+to+10-28

October 22nd
Today Jeremiah, Grace, Jason, John and I arrived at QuarkNet at 3:45. Dr. L gave us a little physics lesson, teaching us about the equation E^2 = m^2 + p^2, and how it was derived from E=mc^2. He also discussed the relationship between kinetic energy and velocity, KE=.5mv^2. We then dove into looking at some ManyEyes graphs as a group on the projector. We looked at the relationship between Mass and Energy, particularly at the way they change between parent rest frame and the full view. In the parent rest frame, the graph E vs M was a perfect line with a slope of 1, but when we switched the graph out of the parent rest frame and just graphed E vs M, we got the graph below. The line with a slope of 1 was still present, but now it turned into more of a limit, rather than an exact trend. This is because from the parent rest frame, momentum is always 0 because the particles go in opposite directions from the parent particle, so E = m according to the equation E^2 = m^2 + p^2. Outside of the parent rest frame, though, E can be greater than m, it just cannot be smaller than m. Two interesting groups that are present in this graph are cosmic rays and z bosons. The cosmic rays, as we have stated before, have a mass of 40 GeV or greater. As we can see on this graph, at 40 GeV, there is a stark change from the limit sort of phenomenon to much more of a line, suggesting that the momentum of cosmic rays is 0. The z bosons are the group of particles around 90 GeV that have E greater than those that fall on the line. Dr. L then spent some time explaining to Jason the process of cutting the graphs in the e-lab histogram tool, and the benefits of using this tool to analyze trends. We further showed the way the cosmic rays begin to show up on the graph above. We also discussed the impossibility of cosmic rays traveling straight through the earth, including in our discussion the huge difference between the distance from the surface to the edge of the atmosphere and the diameter of the earth. We then dove into the seemingly impossible theory that distances become shorter at extremely high speeds, and that distance is actually a function of velocity. We cannot see this, because the relationship is essentially constant at the speeds that we see, but at the speeds things like neutrinos travel at, this relationship begins to happen. This was discovered when people discovered that no matter what the physical situation, the speed of light is the speed of light, and light never travels faster than the speed of light. This seems like an impossibility, but experimental evidence has proven it. Another product of this theory is that photons don't experience time or distance because they have no mass and they travel at the upper limit of speed. We left QuarkNet at 5:30

October 24th
Today Jason and I arrived at QuarkNet around 3:45. Now that we got the extensive physics lesson from Dr. L, we have more substantial knowledge that could be used for figuring out what the interesting graphs we found mean. One graph I will start attempting to explain is the graph of E1 parent rest frame vs. M, shown below.

This graph is simple enough, so it seems fitting that I should begin by tackling this one. If one does not pay close enough attention to it, it may appear to be a graph of a variable against itself, because the autoscaling of ManyEyes has caused it to look just like those graphs. But, in fact, it is not. All the data on this graph conform exactly to the line y=0.5x. That is what caught my eye with this graph. When I paid more attention to the variables, it made sense. If the line is y=0.5x, that means that E1(PRF)=0.5M. That is to say, Energy of product 1 from the perspective of the parent particle is exactly half the value of the mass of the parent particle. This makes complete sense, because at the point of the collision, the momentum is 0, so E=M. Given that the collision provides a perfect split, that means half the energy would be given to each particle, and this energy value would also be half the mass. Next I decided to analyze the graph of pt1 parent rest frame vs. pt1, shown below. In this graph, the points of small mass and small momentum values are clearly scattered, and the higher mass particles concentrate around the line y=x. One interesting feature of this graph is that the trend appears to start exactly when the pt1 from the parent rest frame equals 20. This may be a feature of cosmic rays we have not seen yet: their total momentum in the detector is 20 or greater. After a good amount of me confusing myself trying to interpret this graph, an explanation of pt from Dr. L made many things a lot clearer. He corrected my misconception that it was 3 dimensional. The 3 dimensional momentum value is p3d resultant. On the other hand, pt is the 2 dimensional measurement of the momentums in the x and y directions, and ignores the z direction. Additionally, he brought some clarity to the reason that cosmic rays would cause the detector to always think the pt was the same from the outside view as from the view of the parent rest frame. My understanding is that, since there is not actually a parent particle and because of the way the detector processes the data, it is almost as if it creates an artificial parent particle whose perspective will inevitably parallel the outer view. I am not 100% confident about my understanding of this one, but I feel as if it is a problem of me communicating the explanation properly rather than a fundamental problem in my understanding of the situation. Dr. L also explained the peculiarity of our data set. He discussed how scientists have discovered that cosmic rays can be cut from a data set in a couple different ways. First of all, if precise times were kept as part of the data set, a cut could be performed that would very effectively remove most, if not all, of the cosmic rays because particles that were not registered at the precise time the products of the collision should have been registered could be removed. Another way to cut out the cosmic rays is by getting rid of all the particles that didn't ever go through the point where the collision would occur. Apparently the person who put together the dimuon data set failed to effectively utilize these methods, even though he claimed he did. So, the cosmic rays were a surprising and entertaining discovery when the QuarkNet folks found them in the data. Dr. L and I had a long discussion about how I would move forward in the class in the coming months. It appears that the path I am most likely headed down is to break off from the data analysis side and go into MATLAB programming once I finish with my descriptions of the 10 interesting graphs. In MATLAB, hopefully I will be able to go pretty quickly through the basics, since I have substantial programming experience already. We discussed the possibility of creating small tools to assist the data analysis along the way. The big hope, though, would be that by some point in the second semester I would get to a high enough level of MATLAB understanding that I could begin to digest the complex GUI tool created by CMS scientists and possibly work on perfecting and expanding it. I left QuarkNet today at 5:50.