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Studies of Cathode Strip Chamber longevity, comparing Ar+CO2 gas mixtures with fractions of 5%, 2%, and 0% CF4, were performed using several small cathode strip prototype chambers. In each trial, a localized source of radiation was used to irradiate up to an accumulated charge of about 300 mC/cm. Additionally, longevity of a uniformly irradiated prototype operating with 2% CF4 was studied at the CERN Gamma Irradiation Facility GIF++. Post-hoc analysis of the chamber electrodes using spectroscopy techniques was also done.

A summary of the methods used to make a precision measurement of the Higgs boson mass is presented. The final mass value for the Higgs boson is measured to be $m_{\rm H} = 125.26 \pm 0.21\ \mathrm{GeV}$. This analysis considers the $\mathrm{H} \rightarrow \mathrm{Z}\mathrm{Z} \rightarrow 4\ell$ channel ($\ell = e, \mu$), using proton-proton collision data collected in 2016 corresponding to an integrated luminosity of $35.9\ \mathrm{fb}^{-1}$ at $\sqrt{s} = 13$ TeV by the CMS experiment at the LHC. A mass constraint is imposed on the invariant mass of the two leptons coming from the mostly on-shell Z boson to refit the lepton momenta and, hence, improve the measurement of the Higgs boson mass, per-event. The mass of the Higgs boson is extracted using a three-dimensional likelihood fit, which uses three observables per-event: (1) the refitted four-lepton invariant mass ($m'_{4\ell}$), (2) the refitted four-lepton mass uncertainty (${\mathcal D}'_{\rm mass}$), and (3) a matrix element-based kinematic discriminant (${\mathcal D}^{\rm kin}_{\rm bkg}$)., Comment: Talk presented at the 2019 Meeting of the Division of Particles and Fields of the American Physical Society (DPF2019), July 29 - August 2, 2019, Northeastern University, Boston, C1907293