Observation and Measurements of the Higgs Boson with the H->WW(*)->lvlv Decay.

High Energy Physics;ATLAS;LHC;Higgs Boson;Physics;Science;Physics

Long, Jonathan DavidZhu, Junjie ;

University of Michigan

关键词: High Energy Physics;    ATLAS;    LHC;    Higgs Boson;    Physics;    Science;    Physics;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/113573/longjon_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

A summary is presented of the observation of the Higgs boson decaying into a pair of W bosons and measurements of its properties using the H-->WW(*)-->lvlv channel with the ATLAS detector at the Large Hadron Collider.Up to 4.5 fb-1 of data collected at center-of-mass energy 7 TeV and 20.3 fb-1 at 8 TeV are used.An excess over the background only expectation is observed at 6.1 standard deviations with 5.8 expected.This corresponds to a measured signal strength, the ratio of the measured to expected cross section times branching ratio, for a Standard Model Higgs boson with mH=125.36 GeV of mu=1.09 +0.16 -0.15 (stat.) +0.17 -0.14 (syst.).The measured signal strengths for the gluon fusion and vector boson fusion production modes are mu_ggF=1.02 +0.19 -0.19 (stat.) +0.22 -0.18 (syst.) and mu_VBF=1.27 +0.44 -0.40 (stat.) +0.30 -0.21 (syst.) respectively.The presence of vector boson fusion production is tested using the ratio of these signal strengths resulting in evidence for vector boson fusion production at the level of 3.2 standard deviations.This analysis is projected to have an uncertainty on the signal strength of 14 % at the end of the Large Hadron Collider running with 300 fb-1 and 10 % at the end of the High Luminosity LHC running with 3000 fb-1, assuming no improvements on the current theoretical uncertainties on the signal.The WW final state is also used to determine the off-shell Higgs boson production signal strength in the mass range above 2mW.Using the CLs method, a 95 % confidence level upper limit of 17.2 is placed on the off-shell signal strength, assuming a gg-->WW background k-factor equal to that of the gg-->H-->WW signal.The ratio of off-shell signal strength to on-shell strength can be interpreted as a measurement of the Higgs boson total decay width assuming the relevant Higgs boson couplings are independent of the production energy scale.Combining the H-->WW and H-->ZZ on- and off-shell analyses, the observed (expected) 95 % confidence level upper limit on the Higgs boson total width is22.7 (33.0) MeV.