Search for invisible decays of the Higgs boson at √ s = 13 TeV
File(s)
Author(s)
Milosevic, Vukasin
Type
Thesis
Abstract
A search for invisibly decaying Higgs bosons using proton-proton collision data
collected by the CMS experiment at √
s = 13 TeV is presented. For the first time,
this search is performed using the complete dataset collected during the Run 2 phase
of operation, corresponding to total integrated luminosity of 137.1 fb−1
.
In 2017 and 2018, to supplement the traditional trigger strategy based on the
presence of missing transverse energy, a new dedicated trigger based on the Vector
Boson Fusion jet topology was introduced. Its motivation, implementation and subsequent usage is described in detail. This addition further enhanced the sensitivity
to the Vector Boson Fusion production mechanism by allowing for a new analysis
category focused around previously inaccessible phase space.
A combination with the study focusing on the 2016 data is performed. No deviations from the Standard Model have been observed and the final result is reported in
the form of a 95 % Confidence Level upper limit on the Br(H→inv). The overall result of the measurement using the 2017 and 2018 data yields an observed (expected)
Br(H→inv) < 15 % (13 %), while the full Run 2 limit stands at Br(H→inv) < 15 %
(12 %). When interpreted in terms of dark matter searches, this result can be used
to provide 90% Confidence Level upper limits on the spin-independent dark matternucleon scattering cross section. Lastly, a study of projected sensitivity of this
study for the conditions provided by the future upgrades of the CMS experiment is
also presented. The projected limit for the total integrated luminosity of 3000 fb−1
is placed, from the perspective of the CMS experiment, at Br(H→inv) < 3.8 %,
while a combined result from the ATLAS and CMS experiments is expected to yield
Br(H→inv) < 2.5 %.
collected by the CMS experiment at √
s = 13 TeV is presented. For the first time,
this search is performed using the complete dataset collected during the Run 2 phase
of operation, corresponding to total integrated luminosity of 137.1 fb−1
.
In 2017 and 2018, to supplement the traditional trigger strategy based on the
presence of missing transverse energy, a new dedicated trigger based on the Vector
Boson Fusion jet topology was introduced. Its motivation, implementation and subsequent usage is described in detail. This addition further enhanced the sensitivity
to the Vector Boson Fusion production mechanism by allowing for a new analysis
category focused around previously inaccessible phase space.
A combination with the study focusing on the 2016 data is performed. No deviations from the Standard Model have been observed and the final result is reported in
the form of a 95 % Confidence Level upper limit on the Br(H→inv). The overall result of the measurement using the 2017 and 2018 data yields an observed (expected)
Br(H→inv) < 15 % (13 %), while the full Run 2 limit stands at Br(H→inv) < 15 %
(12 %). When interpreted in terms of dark matter searches, this result can be used
to provide 90% Confidence Level upper limits on the spin-independent dark matternucleon scattering cross section. Lastly, a study of projected sensitivity of this
study for the conditions provided by the future upgrades of the CMS experiment is
also presented. The projected limit for the total integrated luminosity of 3000 fb−1
is placed, from the perspective of the CMS experiment, at Br(H→inv) < 3.8 %,
while a combined result from the ATLAS and CMS experiments is expected to yield
Br(H→inv) < 2.5 %.
Version
Open Access
Date Issued
2020-08
Date Awarded
2021-01
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Tapper, Alexander
Sponsor
President's Scholarship
Publisher Department
Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)