The Upsilon Particle
Calculating Invariant Mass Through Particle Decay
Anna Garcia and Kaylee Young12/19/2016
Abstract
Although scientists have already come to a consensus on the invariant mass of the Upsilon meson, we decided to search for further evidence of an it an attempt to gain a better understanding of the particle. With information provided by the CMS detector at the LHC, we were able to analyze the collisions that occurred and the peaks in the graphs that formed. We came to the conclusion that the invariant mass is roughly 9.46 GeV/c^2.
Introduction
The upsilon particle, represented by the Greek letter Y, is a meson composed of two quarks, one bottom quark and one anti-bottom quark. It has no antiparticle. It is electromagnetically neutral and is a vector meson, with odd parity and a total spin of 1. Like most mesons, it is not a highly stable particle. It decays into a muon and an antimuon pair, but is relatively long-lived for a vector meson, giving it a lifetime of 1.21 x 10^-20 seconds. The upsilon was discovered in 1977 at Fermilab, and was the first experimental detection of the fifth quark type, beyond up, down, strange, and charm quarks. Its officially calculated mass is approximately 9.46 GeV/c^2, nearly ten times larger than a proton.
Procedures
In order to understand the information that the CMS provides for us it was vital to first research how the CMS works. This allowed us to come to a better understanding of how it is designed, the intense energy it creates, and the ways it tracks collisions and particle movement. Once we were competenet in the CMS's functions, we were able to look past at the other e-lab functions. The CMS e-Lab holds the data collected from the Large Hadron Collider at CERN so we were able to come to more in depth conclusions using the graphs created. Utilizing this data, we can confirm the calibration of the experiment as well as the calculated mass of the upsilon particle.
Results
The graphs below give evidence of the accurate calculations of the upsilon mass, as conducted by the CMS accelerator. Each of the graphs gives a mass approximately between 9.35 and 9.5 GeV/c^2, with the accuracy increasing with smaller bin sizes.
Figures
Discussion and Conclusions
Using the data from the CMS detector, we see that in the graphs there is a high peak around 2 GeV/c^2, which then slopes downward but is interrupted by another smaller peak around 9.5 GeV/c^2. This second peak is evidence of the collisions that produced upsilon particles, as the official mass of the particles is approximately 9.46 GeV/c^2. The first, higher peak can be attributed to the J/Psi meson, which requires less energy to be created and thus occurs more often. We can also tell that the graph with the data from two global muon masses gives a higher peak than that with a single global muon mass, reflecting the fact that the upsilon decays into a muon/antimuon pair. Each of the peaks showed that the approximate invariate mass is around 9.43 GeV/c^2. This suggests that the
Bibliography
"Discovery of the Bottom Quark, Upsilon." Fermilab History and Archives Project. Fermilab, 1977. Web. 19 Dec. 2016.
"The Upsilon Particle." Hadrons, Baryons, Mesons. N.p., n.d. Web. 19 Dec. 2016.
"The Upsilon System." The Upsilon System. Cornell Laboratory for Accelerator-Based Sciences and Education, n.d. Web. 19 Dec. 2016.