FINDING+COSMIC+RAYS

=GROUP.= To start off with some ideas on how to find cosmic rays, we first need to consider what cosmic rays are. Here are some background knowledge questions that you need to think about before beginning the search for cosmic rays in the CMS. 1. What exactly is a cosmic ray? 2. What are Z/W particles 3. Thinking of how the Detector is brought underground, why can cosmic rays interfere with the data?

9/23/12 @http://www-958.ibm.com/software/data/cognos/manyeyes/visualizations/cms-dimuon-data-derived-from-an-ed Above is the website we will be using to find the cosmic rays

Here is what we have to do. I think we have both this week and next week to do it, but it was not as difficult as I thought it would be. All we have to do is look at graphs in either one or two websites that I will give you and look for Cosmic Rays in the events. Cosmic Rays are muons that come from outer space, and they come almost straight down into the earth's atmosphere or a little bit at an angle. We are looking for Cosmic Rays in the events because they are giving us more information than we want to see, if that makes sense. Because there are particles colliding in the detector, we don't want stuff coming in from the surroundings and adding particles to the system. Hopefully that made sense. If I didn't explain that well just email me and let me know so that I can think of a better way. But I will send you the two websites once I figure out how to find cosmic rays in the data, and then I will give you some hints on how to find them. As an overview, here are some labels you will see in the graphs: px1 and px2: These are the momentums (P) of the two particles that come out of the collision we are looking at. It is in the x axis direction. py1 and py2: This is the momentum in the y axis direction pz1 and pz2: This is the momentum in the z axis direction pt1 and pt2: This is the transverse mass momentum (we don't have to know this just yet for what we are doing so I can explain this later)

There are a couple other terms in the graphs that are important. These are E and M. E stands for the total energy of the particles, and M stands for the total mass. They can be split up into E1 and E2 and M1 and M2 for the the two particles the collision makes.

Now there are two ways of measuring the angles for the CMS detector. There is eta, which is looking at the detector if you were standing on the x axis, and phi, which is looking at the Detector as if you are inside (straight on from the z axis)

-Group: Here are some graphs that you should be looking at while on many eyes for finding cosmic rays. Using what you know about Eta, Phi, energy and mass, explain where the cosmic rays are along with how you know.

PHI
Phi1 vs M

Phi2 vs M

ETA
-Now that we know that the phi works (explain how we know using information on how cosmic rays come in from the atmosphere and how phi is measured in the detector) look at another angle.

Eta2 vs. M

Eta1 vs. M

-Looking at Eta, why is it that one value is negative while the other is positive?

-Play around with many eyes and find out how to find the cosmic rays in some other graphs. GOOD LUCK :)

After looking at Many Eyes, its now time to turn and look at a new website. the e-lab site gives us a unique way of looking at the cosmic rays. These histograms show the number of events shown for a certain setting. I have three settings that I found useful to look at while playing around with the site. Eta, Phi, and the Mass were used in the Dimuon set to examine the particle events. E-lab was entirely new to me, so it took me a while to get used to the interface. To start off, I changed the bin width on eta to .1 to get a better idea of what the peaks were in the graph. After doing so, I cut the data from -.2 to.2 to see the angle at which cosmic rays come in. After cutting the data, it became clear in Phi that there were two peaks coming in at -1.57 and 1.57. This confirmed the cosmic rays because we know that pi/2 is the upper and lower angle in phi, and so we knew that the particles were back to back and coming in "straight down" from space. From the mass (GeV) set I saw the sudden spikes starting at 40 GeV. This is very important because we can see where exactly the mass of the back to back particles start off. Cosmic Rays seem to have a cut off point around 40 GeV, which is important to continuing our search for cutting out the cosmic rays. Below are some of the graphs from the e-lab.

Eta (cut)

Phi (cut) From looking at Phi, we see the two peaks. It is very positive to see that the two peaks are at 1.57 and -1.57. This means that the particles are coming in at the top and passing down to the bottom of the detector. Making the cut in eta makes it clear that there are cosmic rays in the data set.

Mass (cut) The mass (measured in GeV) plot above shows how there is a dead spot from 15 to 40 GeV, and then a random spike of peaks. Using this data we can assume that the limit for the mass of a Cosmic Ray particle is around 40 GeV.