New level of precision achieved in combined measurements of Higgs boson couplings

phys.org | 7/12/2018 | Staff
joyy (Posted by) Level 3
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The Higgs boson, discovered at the Large Hadron Collider (LHC) in 2012, has a singular role in the Standard Model of particle physics. Most notable is the Higgs boson's affinity to mass, which can be likened to the electric charge for an electric field: the larger the mass of a fundamental particle, the larger the strength of its interaction, or "coupling," with the Higgs boson. Deviations from these predictions could be a hallmark of new physics in this as-yet little-explored part of the Standard Model.

Higgs boson couplings manifest themselves in the rate of production of the Higgs boson at the LHC, and its decay branching ratios into various final states. These rates have been precisely measured by the ATLAS experiment at CERN, using up to 80 fb–1 of data collected at a proton-proton collision energy of 13 TeV from 2015 to 2017. Measurements were performed in all of the main decay channels of the Higgs boson: to pairs of photons, W and Z bosons, bottom quarks, taus, and muons. The overall production rate of the Higgs boson was measured to be in agreement with Standard Model predictions, with an uncertainty of 8%. The uncertainty is reduced from 11% in the previous combined measurements released last year.

Measurements - Production - Modes - Standard - Model

The measurements are broken down into production modes (assuming Standard Model decay branching ratios), as shown in Figure 1. All four main production modes have now been observed at ATLAS with a significance of more than 5 standard deviations: the long-established gluon-gluon fusion mode, the recently-observed associated production with top-quark pair, and last-remaining weak boson fusion mode, presented today by...
(Excerpt) Read more at: phys.org
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