LHC Lecture/Paper – Page 5

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The Large Hadron Collider (continued)

Transverse Mass: The transverse mass of an event can be thought of in very simple terms as how heavy an event is. Transverse mass is calculated by adding up the mass and transverse momenta of all particles produced in a collision.
Transverse Sphericity: The sphericity of an event is a measure of how close the spread of energy in the event is to a sphere in shape. An event that appears to be completely smoothly distributed in three dimensions is spherical and has a sphericity of 1. An event that is clumpy and irregular is closer to having sphericity 0.
Centrality: This is similar to sphericity, but is more a measure of how much of the ‘event’ is contained within the central part of the detector. By the ‘central’ part of the detector we mean the disk (ATLAS is cylindrical) that passes through the collision point.
Electromagnetic Fraction: The ATLAS energy detectors are called calorimeters, and there are two types of calorimeter. One of them is designed to measure the energy of particles, which, interact via the electromagnetic force, and the other is designed to measure the energy of particles, which interact ‘hadronically’ via the strong nuclear force. The electromagnetic fraction is calculated by dividing the energy detected in the electromagnetic calorimeter by the total energy detected.
Missing Energy Fraction: ATLAS is designed to be able to detect pretty much any kind of particle. A neutrino, however, is not directly detectable by any part of ATLAS. This funny little particle refuses to interact with anything. Billions of them are passing through your body as you read this, mostly coming from the sun. They will fly right through planet earth without even noticing it is there. The only way we can detect neutrinos with ATLAS is to look at the spread of detectable energy in the detector and try to balance it according to the laws of conservation of energy and momentum. We calculate the amount of energy carried by the neutrino(s) produced in a collision and subsequent particle decays and divide this by the total detectable energy in an event.

One challenge I had with trying to map the data to a reasonable correlate of my instrument parameters was that the hadronization process occurs so rapidly that the detectors cannot capture the timing. Upon discovering this I considered abandoning the project because it seemed there was no way to reasonably represent the events without such fundamental information. However, after further consideration, it was decided that the data that was provided could be in part mapped to the timing pfields of the score even though it was not an actual aspect of the timing relationships. Though this constraint was unexpected, it actually worked out quite nicely.

I proceeded to organize eight columns and almost three thousand rows of data into the beginnings of a score by using a spreadsheet. When possible, I chose parameters of the LHC data that seemed to resemble the parameters of the Csound instrument when mapping it to the score. So for instance, the Transverse Mass seemed to most directly correlate to amplitude. Sphericity seemed to be a spatial parameter and so was used in determining aspects of the panning.

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