Studies of optimal track-fitting techniques for the DarkLight experiment

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.

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Physics.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2013

Author dc:creator

• Balakrishnan, Purnima Parvathy

Advisor dc:contributor.advisor

• Peter Fisher.

• Physics.

Statement dc:rights

• 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 permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/83813

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/83813