A bound on the natural width of the Higgs boson CMS has improved the constraints on the Higgs width, a fundamental property of this unique new particle, by more than two orders of magnitude. Nearly two years after its discovery, there is much to learn about the Higgs boson observed by the CMS and ATLAS collaborations at CERNs Large Hadron Collider. At the annual Rencontres de Moriond meeting, CMS presented improved limits on the natural width of the Higgs boson, a parameter related to the lifetime of the particle and crucial to understanding its nature. The Heisenberg Uncertainty Principle implies that the energy, and thus the mass as well, of all unstable particles must have an uncertainty, which is inversely proportional to their lifetime. This uncertainty is quantified by the particles natural width, which characterises the range of masses with which a particle is observed. In the Standard Model, the Higgs boson is expected to be very narrow: its width is roughly 4 MeV, a good 30,000 times smaller than the central mass of approximately 125 GeV. The width of the Higgs boson is a very important parameter, for it is determined from the strength with which it interacts with all particles, including those that may exist but which we have not observed yet! The width is usually determined from the distribution of masses observed. In this case, however, the expected width is much smaller than the experimental resolution of the mass measurement. As an example, in events with a Higgs boson decaying to two Z bosons, the masses reconstructed are shown in Figure 1. The Higgs boson signal, in red, appears over a range of values, which is dominated by the precision of the experimental measurement, and not the width of the Higgs boson. The best bound one could obtain directly from the Higgs peak in the data was that the width was less than 3.4 GeV. Read more at: phys.org/news/2014-04-bound-natural-width-higgs-boson.html#jCp
Posted on: Sun, 06 Apr 2014 07:54:23 +0000
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