Off-campus UMass Amherst users: To download campus access dissertations, please use the following link to log into our proxy server with your UMass Amherst user name and password.

Non-UMass Amherst users: Please talk to your librarian about requesting this dissertation through interlibrary loan.

Dissertations that have an embargo placed on them will not be available to anyone until the embargo expires.

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Physics

Year Degree Awarded

2018

Month Degree Awarded

February

First Advisor

Carlo Dallapiccola

Second Advisor

Ben Brau

Third Advisor

Michael Ramsey-Musolf

Fourth Advisor

Grant Wilson

Subject Categories

Elementary Particles and Fields and String Theory

Abstract

A search for long-lived, massive particles decaying into dimuon pairs, in 32.9 fb-1 of data analyzed from the ATLAS detector is presented. Two signal models are considered: GGM SUSY, where the long lived particle mass is between 300-1000 GeV, and the dark photon model, where the ZD mass is between 20-60 GeV. An excess over the predicted background is observed in the GGM channel, however the angular/kinematic distributions of the excess vertices are consistent with a detec- tor/conditions related issue. A modified selection is used for the GGM channel which increases the signal sensitivity. 95% confidence level (CL) upper limits on the signal cross sections times branching fraction are set as a function of cτ for both benchmark models. The cτ limits for the GGM channel extend from 2.57-1050 cm, and the cτ limit for the ZD channel extends from 0.32-1572 cm. 95% CL upper limits on the ZD cross section are also set in the coupling-cτ plane, for a range of BF(H→ ZDZD).

Share

COinS