CMS+Project

toc =Introduction= For our first project, we looked at different graphs of data to determine whether or not there were cosmic rays in the data. Using two websites, many eyes and e-lab, we were able to cut out data and look at histograms and scatter plots of the "maybe" cosmic rays. The website many eyes was used for looking at different scatter plots, and the website e-lab used histograms to look at the data. Alex, Grace, Jason, and Jeremiah used both websites to gather information on the cosmic rays, but they were assigned to one website to argue their points for cosmic rays. Alex and Grace will write about many eyes, while Jason and Jeremiah will write about e-lab. We are hoping that the final results will be the same for both websites so that we can say we spotted cosmic rays in the CMS detector.

=Many Eyes= Because cosmic rays originate in space and live only a short time, the only way they can be picked up by the detector is to take the shortest path in - vertically through the ground to the top of the detector. This trajectory is represented by Eta values near 0, a Phi 1 value near -pi/2 (roughly -1.57), and a Phi 2 value near pi/2 (roughly 1.57). To illustrate this, and to explain why we need both Eta measurements and Phi measurements, I took a couple pictures on the 3D view of the CMS detector. This first one shows the perspective from which eta 1 and 2 are measured.



They would be measured away from the vertical line in the center of this snapshot. Thus, any eta measurement actually contains an entire plane that is a slice across the diameter of the detector that looks something like this following picture.



This entire circular plane is contained in an eta value, so a data point with eta 0 could actually be a particle that went laterally across the detector, for example in a horizontal line across the center of this circle. This would not be consistent with a cosmic ray, so we need phi in order to further narrow down our search. Also, cosmic rays have the highest energy of all the particles picked up by the detector, and at the scale on which the events in the CMS Detector occur, this means they also have the largest mass. In order the begin to isolate these particles that have the qualities discussed above, ManyEyes is a fantastic tool. It is restricted to showing scatter plots, but provides great variability in the scatter plots it is capable of showing. Every category of data taken down in the detector is available to be plotted as x-axis, y-axis, or dot size, so trends can be tracked in a number of different ways using ManyEyes. I started to isolate the cosmic rays by setting the dot size to reflect the mass of the particle to isolate and draw attention to the larger and more energetic particles. The next step was to then isolate the particles based on the Eta and Phi values. I looked at Eta 1 vs. Eta 2 (Figure 1) and Phi 1 vs. Phi 2 (Figure 2) to see where the heaviest particles concentrated in each coordinate system. On Eta 1 vs. Eta 2, the heaviest particles concentrate around 0 on both axes. On Phi 1 vs. Phi 2, they concentrate at around pi/2 (about 1.57) on Phi 2 and negative pi/2 (about -1.57) on Phi 1.



To further isolate the group of particles that fit the characteristics for cosmic rays, I plotted the mass as the x-axis in addition to having the size of the dots be set to the mass. ManyEyes offers a control+click function for highlighting a group of points. Those points can then be tracked across graphs with various axes as they stay highlighted after an axis change. The following picture shows the original set of points I chose that were near Eta 1 of 0 on the Eta 1 vs. Mass graph, with a box around the particles of higher mass, beginning at 40 GeV where the pattern appears to change. The next graph shows where the group of points selected above moved as the y-axis was changed from Eta 1 to Eta 2. ==

From this image, it appears that the particles heavier than 40 GeV have both Eta 1 and Eta 2 near 0, whereas the particles of smaller mass that had an Eta 1 near 0 have scattered values of Eta 2.

Now it is pretty clear that our group of selected points is full of cosmic rays, and the last check we have to ensure that our particles fit our predictions is the Phi values. In order to make this last check, I used the same set of selected points and switched the Y axis to Phi 1 and then Phi 2 in order to see if the seemingly vertical trajectory noted in the Eta coordinates was truly vertical or not. I hoped to see that the selected points would concentrate around positive and negative pi/2 (1.57) on Phi 2 and Phi 1, respectively, in order to show that the 40+ GeV particles were coming in vertically through the highest point in the detector. The following pictures are Phi 2 vs. Mass (left) and Phi 1 vs. Mass (right).

As I had hoped, the more massive particles that held interest as potential cosmic rays concentrated Phi 2 of pi/2 (1.57) and Phi 1 of -pi/2 (-1.57). Given that the selected particles have the high mass that would be expected of cosmic rays, and they flew into the detector on the trajectory cosmic rays would be expected to enter on, I am very confident that the group of particles I selected that is 40+ GeV is clearly a group consisting mostly of cosmic rays. Thanks to ManyEyes, we were able to discover this group of particles by tracking it across many categories of data. =media type="file" key="Screencast Vdeo 2.swf" width="662" height="662"=

I went through the data settings and displayed the data for the muons measured in Mass, Eta, and Phi. Looking first at Eta, because the bin width was originally set to 10, I figured that it would be better to decrease the bin width to a much smaller value to get more precise readings. After lowering the bin width to around .1 instead of ten, I was able to see many more precise readings of data. Also, because cosmic rays enter the detector from almost straight overhead, I cut the graph to eliminate the other data that would not likely contain cosmic rays. As I found in the graphs above on ManyEyes, cosmic rays gather around -.2 to .2. Because of this, I cut the graph to focus only on this region. The histogram that I was able to configure is shown below. Notice that there are a great deal of particles that are observable in this range. It is here that cosmic rays are observable using Eta on a histogram. Adjusting the bin width basically just shows how precise the histogram will display the data. By changing the bin width to a smaller value, it will create a separate bar in increments at that value. This helped me to understand much more how to manipulate the graphs. The next histogram I looked at was Phi. This histogram further shows the evidence for the cosmic rays in the data. Like in Eta, the graphs on ManyEyes are consistent to the histograms that we see here. The cosmic rays gather around a Phi value of 1.57, which makes sense, as this is pi/2, or essentially straight overhead. Looking at the graph for Phi, there were two noticeable peaks. These peaks occurred at 1.57 and -1.57. This means that the points at this moment are probably cosmic rays, entering straight through the detector. After I found these consistencies in observations, I looked at the histogram of the mass. There were a few noticeable points about the graph. When I looked at ManyEyes and learned to highlight the points, I determined that there were patterns at a mass of 40 GeV. In the histogram, there is a separation between the particles. The cosmic rays begin at 40 GeV, and the lower mass particles that are meant to take place in the detector all have scattered, lower masses under 30. This points to the notion that the cosmic rays have masses greater than 40 GeV, as confirmed earlier in ManyEyes.

=CMS e-Lab= []

=Data sets for Excel=
 * 1K** dimuon data file **with** **Lorentz** transformation

**10K without Lorentz** Transformation


 * 100k** DIMUONfromCMS **without Lorentz** Transformation


 * Next**: 100K dimuon with Lorentz:

=3-D display tools:= =[]= []