2026-09-20T11:34:57Zhttps://dspace.mit.edu/server/oai/requestoai:dspace.mit.edu:1721.1/838132022-01-13T07:54:07Zcom_1721.1_7582com_1721.1_7581col_1721.1_131024
Peter Fisher.
Balakrishnan, Purnima Parvathy
Massachusetts Institute of Technology. Department of Physics.
Massachusetts Institute of Technology. Department of Physics
2014-01-09T19:57:50Z
2014-01-09T19:57:50Z
2013
http://hdl.handle.net/1721.1/83813
865478286
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (page 49).
The DarkLight experiment is searching for a dark force carrier, the A' boson, and hopes to measure its mass with a resolution of approximately 1 MeV/c 2 . This mass calculation requires precise reconstruction to turn data, in the form of hits within the detector, into a particle track with known initial momentum. This thesis investigates the appropriateness of the Billoir optimal fit to reconstruct helical, low-energy lepton tracks while accounting for multiple scattering, using two separate track parameterizations. The first method approximates the track as a piecewise concatenation of parabolas in three-dimensions, and (wrongly) assumes that the y and z components of the track are independent. When tested using simulated data, this returns a track which geometrically fits the data. However, the momentum extracted from this geometrical representation is an order of magnitude higher than the true momentum of the track. The second method approximates the track as a piecewise concatenation of helical segments. This returns a track which geometrically fits the data even better than the parabolic parameterization, but which returns a momentum which depends on the seeds to the algorithm. Some further work must be done to modify this fitting method so that it will reliably reconstruct tracks.
by Purnima Parvathy Balakrishnan.
S.B.
49 pages
eng
Massachusetts Institute of Technology
M.I.T. theses are protected by
copyright. They may be viewed from this source for any purpose, but
reproduction or distribution in any format is prohibited without written
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http://dspace.mit.edu/handle/1721.1/7582
Physics.
Studies of optimal track-fitting techniques for the DarkLight experiment
Thesis
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<Abstract>The DarkLight experiment is searching for a dark force carrier, the A' boson, and hopes to measure its mass with a resolution of approximately 1 MeV/c 2 . This mass calculation requires precise reconstruction to turn data, in the form of hits within the detector, into a particle track with known initial momentum. This thesis investigates the appropriateness of the Billoir optimal fit to reconstruct helical, low-energy lepton tracks while accounting for multiple scattering, using two separate track parameterizations. The first method approximates the track as a piecewise concatenation of parabolas in three-dimensions, and (wrongly) assumes that the y and z components of the track are independent. When tested using simulated data, this returns a track which geometrically fits the data. However, the momentum extracted from this geometrical representation is an order of magnitude higher than the true momentum of the track. The second method approximates the track as a piecewise concatenation of helical segments. This returns a track which geometrically fits the data even better than the parabolic parameterization, but which returns a momentum which depends on the seeds to the algorithm. Some further work must be done to modify this fitting method so that it will reliably reconstruct tracks.</Abstract>
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